Recently, I needed to automatically check the copyright status of a set of The Internet Movie database (IMDB) entries, to figure out which one of the movies they refer to can be freely distributed on the Internet. This proved to be harder than it sounds. IMDB for sure list movies without any copyright protection, where the copyright protection has expired or where the movie is lisenced using a permissive license like one from Creative Commons. These are mixed with copyright protected movies, and there seem to be no way to separate these classes of movies using the information in IMDB. First I tried to look up entries manually in IMDB, Wikipedia and The Internet Archive, to get a feel how to do this. It is hard to know for sure using these sources, but it should be possible to be reasonable confident a movie is "out of copyright" with a few hours work per movie. As I needed to check almost 20,000 entries, this approach was not sustainable. I simply can not work around the clock for about 6 years to check this data set. I asked the people behind The Internet Archive if they could introduce a new metadata field in their metadata XML for IMDB ID, but was told that they leave it completely to the uploaders to update the metadata. Some of the metadata entries had IMDB links in the description, but I found no way to download all metadata files in bulk to locate those ones and put that approach aside. In the process I noticed several Wikipedia articles about movies had links to both IMDB and The Internet Archive, and it occured to me that I could use the Wikipedia RDF data set to locate entries with both, to at least get a lower bound on the number of movies on The Internet Archive with a IMDB ID. This is useful based on the assumption that movies distributed by The Internet Archive can be legally distributed on the Internet. With some help from the RDF community (thank you DanC), I was able to come up with this query to pass to the SPARQL interface on Wikidata:

SELECT ?work ?imdb ?ia ?when ?label
WHERE
 
  ?work wdt:P31/wdt:P279* wd:Q11424.
  ?work wdt:P345 ?imdb.
  ?work wdt:P724 ?ia.
  OPTIONAL  
        ?work wdt:P577 ?when.
        ?work rdfs:label ?label.
        FILTER(LANG(?label) = "en").
   
 

If I understand the query right, for every film entry anywhere in Wikpedia, it will return the IMDB ID and The Internet Archive ID, and when the movie was released and its English title, if either or both of the latter two are available. At the moment the result set contain 2338 entries. Of course, it depend on volunteers including both correct IMDB and The Internet Archive IDs in the wikipedia articles for the movie. It should be noted that the result will include duplicates if the movie have entries in several languages. There are some bogus entries, either because The Internet Archive ID contain a typo or because the movie is not available from The Internet Archive. I did not verify the IMDB IDs, as I am unsure how to do that automatically. I wrote a small python script to extract the data set from Wikidata and check if the XML metadata for the movie is available from The Internet Archive, and after around 1.5 hour it produced a list of 2097 free movies and their IMDB ID. In total, 171 entries in Wikidata lack the refered Internet Archive entry. I assume the 70 "disappearing" entries (ie 2338-2097-171) are duplicate entries. This is not too bad, given that The Internet Archive report to contain 5331 feature films at the moment, but it also mean more than 3000 movies are missing on Wikipedia or are missing the pair of references on Wikipedia. I was curious about the distribution by release year, and made a little graph to show how the amount of free movies is spread over the years: I expect the relative distribution of the remaining 3000 movies to be similar. If you want to help, and want to ensure Wikipedia can be used to cross reference The Internet Archive and The Internet Movie Database, please make sure entries like this are listed under the "External links" heading on the Wikipedia article for the movie:

*  Internet Archive film id=FightingLady 
*  IMDb title id=0036823 title=The Fighting Lady 

Please verify the links on the final page, to make sure you did not introduce a typo. Here is the complete list, if you want to correct the 171 identified Wikipedia entries with broken links to The Internet Archive: Q1140317, Q458656, Q458656, Q470560, Q743340, Q822580, Q480696, Q128761, Q1307059, Q1335091, Q1537166, Q1438334, Q1479751, Q1497200, Q1498122, Q865973, Q834269, Q841781, Q841781, Q1548193, Q499031, Q1564769, Q1585239, Q1585569, Q1624236, Q4796595, Q4853469, Q4873046, Q915016, Q4660396, Q4677708, Q4738449, Q4756096, Q4766785, Q880357, Q882066, Q882066, Q204191, Q204191, Q1194170, Q940014, Q946863, Q172837, Q573077, Q1219005, Q1219599, Q1643798, Q1656352, Q1659549, Q1660007, Q1698154, Q1737980, Q1877284, Q1199354, Q1199354, Q1199451, Q1211871, Q1212179, Q1238382, Q4906454, Q320219, Q1148649, Q645094, Q5050350, Q5166548, Q2677926, Q2698139, Q2707305, Q2740725, Q2024780, Q2117418, Q2138984, Q1127992, Q1058087, Q1070484, Q1080080, Q1090813, Q1251918, Q1254110, Q1257070, Q1257079, Q1197410, Q1198423, Q706951, Q723239, Q2079261, Q1171364, Q617858, Q5166611, Q5166611, Q324513, Q374172, Q7533269, Q970386, Q976849, Q7458614, Q5347416, Q5460005, Q5463392, Q3038555, Q5288458, Q2346516, Q5183645, Q5185497, Q5216127, Q5223127, Q5261159, Q1300759, Q5521241, Q7733434, Q7736264, Q7737032, Q7882671, Q7719427, Q7719444, Q7722575, Q2629763, Q2640346, Q2649671, Q7703851, Q7747041, Q6544949, Q6672759, Q2445896, Q12124891, Q3127044, Q2511262, Q2517672, Q2543165, Q426628, Q426628, Q12126890, Q13359969, Q13359969, Q2294295, Q2294295, Q2559509, Q2559912, Q7760469, Q6703974, Q4744, Q7766962, Q7768516, Q7769205, Q7769988, Q2946945, Q3212086, Q3212086, Q18218448, Q18218448, Q18218448, Q6909175, Q7405709, Q7416149, Q7239952, Q7317332, Q7783674, Q7783704, Q7857590, Q3372526, Q3372642, Q3372816, Q3372909, Q7959649, Q7977485, Q7992684, Q3817966, Q3821852, Q3420907, Q3429733, Q774474

Here's what happened in the Reproducible Builds effort between Sunday October 15 and Saturday October 21 2017:

• The Tails project published a report on how they made their ISO images reproducible.
• dpkg 1.19.0 was uploaded, including support for:
  • Ordering the "unused substitution" warnings to prevent superfluous differences between logs of package builds on the Reproducible Builds test framework. (#870221)
  • A new Build-Kernel-Version field in .buildinfo files that can be generated with a new dpkg-genbuildinfo --always-include-kernel option. (#873937)

Past events

• On Saturday 21st October, Holger Levsen presented at All Systems Go! in Berlin, Germany on reproducible builds. A video recording is available already.

Upcoming events

• On Tuesday 24th October, Chris Lamb will present at All Things Open 2017 in Raleigh, NC, USA.
• On Wednesday 25th October, Holger Levsen will present at the Open Source Summit Europe in Prague, Czech Republic.
• On Saturday 28th October, Chris Lamb will present at freenode.live in Bristol, UK.
• From October 31st November 2nd we will be holding the 3rd Reproducible Builds summit in Berlin, Germany. If you are working in the field of reproducible builds, you should definitely attend. Please see our public invitation mail and contact us if you have any questions.

New York University sessions A three week session will be held at New York University to work on reproducibilty issues in conjunction with the reproducible builds community. Students from the Application Security course will be working for two weeks to work on the reproducible builds effort.

• On Tuesday 24th Oct Ed Maste from FreeBSD will be presenting some reproducible builds work for students.
• On From Tuesday 24th of October to Monday 7th of November students will work on fixing reproducibility issues brought up by the community. A milestone presentation will be held by Santiago Torres-Arias and Preston Moore.
• On Tuesday 7th November Holger Levsen will join the NYU team to wrap up the work.

Packages reviewed and fixed, and bugs filed

• Adrian Bunk:
  • #878883 filed against stoken.
  • #878896 filed against liquidsoap.
  • #878980 filed against belenios.
  • #879042 filed against tuxpaint-config.
  • #879223 filed against websockify.
• Chris Lamb:
  • #878707 filed against python-amqp (randomness in documentation).
  • #878708 filed against geographiclib (build paths).
  • #879169 filed against live-build (timestamps).
• Gilles Filippini:
  • #878818 filed against ovito.

The following reproducible builds-related NMUs were accepted:

• Chris Lamb:
  • gerstensaft (#777414)
  • miniupnpd (#860266)
  • rest2web (#833438)

Patches sent upstream:

• Bernhard M. Wiedemann:
  • singularity (tar+gz)
  • redis (date)
  • tbb (date)
  • nested (sort)
  • nested (date)

Reviews of unreproducible packages 41 package reviews have been added, 119 have been updated and 54 have been removed in this week, adding to our knowledge about identified issues. 2 issue types were removed as they were fixed:

• too_much_input_for_diff
• docbook_to_man_one_byte_delta

Weekly QA work During our reproducibility testing, FTBFS bugs have been detected and reported by:

• Aaron M. Ucko (1)
• Adrian Bunk (49)
• Anthony DeRobertis (1)
• Daniel Schepler (1)
• Gilles Filippini (1)
• James Cowgill (1)
• Matthias Klose (1)
• Matthias Klumpp (1)
• Nobuhiro Iwamatsu (1)

diffoscope development

• Ximin Luo:
  • Tentative support for for parallel diffs

strip-nondeterminism development Version 0.039-1 was uploaded to unstable by Chris Lamb. It included contributions already covered by posts of the previous weeks, including:

• Chris Lamb:
  • Clojure considers the .class file to be stale if it shares the same timestamp of the .clj. We thus adjust the timestamps of the .clj to always be younger. (#877418)
  • dh_strip_nondeterminism: Log which handler processed a file. (#876140)
  • bin/strip-nondeterminism: Print a warning in --verbose mode if no canonical time specified.
  • Use HTTPS URI in debian/watch.

reprotest development

• Ximin Luo:
  • Hopefully fix the autopkgtest tests
• Santiago Torres-Arias:
  • An Arch Linux User Repository package for reprotest has been created.]

tests.reproducible-builds.org

• Holger Levsen:
  • Install rustc on Jenkins for the reproducible-html-build-path-prefix-map-spec job.
• Mattia Rizzolo:
  • health_check: Include the running kernel version when reporting multiple kernel installed in /boot.

Website updates

• Holger Levsen:
  • Berlin 2017:
    • add Qubes OS to participating projects
    • Add NetBSD and EdgeBSD to participating projects
    • Add repeatr.io to participating projects
    • Add disclaimer why only so few projects are listed
    • Add link to Google maps and name the 2nd next subway station on a different line
    • Add first 4 participating projects

Misc. This week's edition was written by Bernhard M. Wiedemann, Chris Lamb, Holger Levsen, Santiago Torres & reviewed by a bunch of Reproducible Builds folks on IRC & the mailing lists.

Today it s my first day working at the Wikimedia Foundation, the non-profit foundation behind well-known projects like Wikipedia and others. This is a full-time, remote job as part of the Wikimedia Cloud Services team, as Operations Engineer. I will be working with modern infrastructure/hosting technologies such as OpenStack and Kubernetes to provide support to the Wikimedia movement and community. All contributors of the movement that provide value to the Wikimedia movement are welcome to use our resources. The recruitment process took several months and was really challenging, 6 or 7 interviews with different people with, of course, heavy technical checks. The Wikimedia Foundation has been always in my radar due to 2 facts:

1. They serve a very relevant mission, commited to freedom of knowledge, community colaboration, focusing in the benefit that this provides to the society.
2. They have a huge infrastructure/technological deployment which, among other things, allows Wikipedia to be one of the TOP5-TOP10 websites.

This new job is a big challenge for me and I m a bit nervous. I feel like this is a big step forward in my professional career and I will try to do my best :-) My new email address is aborrero@wikimedia.org. You can find me in IRC freenode as well, nick arturo. Great times ahead! :-)

Review: Algorithms to Live By, by Brian Christian & Tom Griffiths

Publisher:	Henry Holt and Company
Copyright:	April 2016
ISBN:	1-62779-037-3
Format:	Kindle
Pages:	255

Another read for the work book club. This was my favorite to date, apart from the books I recommended myself. One of the foundations of computer science as a field of study is research into algorithms: how do we solve problems efficiently using computer programs? This is a largely mathematical field, but it's often less about ideal or theoretical solutions and more about making the most efficient use of limited resources and arriving at an adequate, if not perfect, answer. Many of these problems are either day-to-day human problems or are closely related to them; after all, the purpose of computer science is to solve practical problems with computers. The question asked by Algorithms to Live By is "can we reverse this?": can we learn lessons from computer science's approach to problems that would help us make day-to-day decisions? There's a lot of interesting material in the eleven chapters of this book, but there's also an amusing theme: humans are already very good at this. Many chapters start with an examination of algorithms and mathematical analysis of problems, dive into a discussion of how we can use those results to make better decisions, then talk about studies of the decisions humans actually make... and discover that humans are already applying ad hoc versions of the best algorithms we've come up with, given the constraints of typical life situations. It tends to undermine the stated goal of the book. Thankfully, it in no way undermines interesting discussion of general classes of problems, how computer science has tackled them, and what we've learned about the mathematical and technical shapes of those problems. There's a bit less self-help utility here than I think the authors had intended, but lots of food for thought. (That said, it's worth considering whether this congruence is less because humans are already good at this and more because our algorithms are designed from human intuition. Maybe our best algorithms just reflect human thinking. In some cases we've checked our solutions against mathematical ideals, but in other cases they're still just our best guesses to date.) This is the sort of a book where a chapter listing is an important part of the review. The areas of algorithms discussed here are optimal stopping, explore/exploit decisions (when to go with the best thing you've found and when to look for something better), sorting, caching, scheduling, Bayes's rule (and prediction in general), overfitting when building models, relaxation (solving an easier problem than your actual problem), randomized algorithms, a collection of networking algorithms, and finally game theory. Each of these has useful insights and thought-provoking discussion of how these sometimes-theoretical concepts map surprisingly well onto daily problems. The book concludes with a discussion of "computational kindness": an encouragement to reduce the required computation and complexity penalty for both yourself and the people you interact with. If you have a computer science background (as I do), many of these will be familiar concepts, and you might be dubious that a popularization would tell you much that's new. Give this book a shot, though; the analogies are less stretched than you might fear, and the authors are both careful and smart about how they apply these principles. This book passes with flying colors a key sanity check: the chapters on topics that I know well or have thought about a lot make few or no obvious errors and say useful and important things. For example, the scheduling chapter, which unsurprisingly is about time management, surpasses more than half of the time management literature by jumping straight to the heart of most time management problems: if you're going to do everything on a list, it rarely matters the order in which you do it, so the hardest scheduling problems are about deciding what not to do rather than deciding order. The point in the book where the authors won my heart completely was in the chapter on Bayes's rule. Much of the chapter is about Bayesian priors, and how one's knowledge of past events is a vital part of analysis of future probabilities. The authors then discuss the (in)famous marshmallow experiment, in which children are given one marshmallow and told that if they refrain from eating it until the researcher returns, they'll get two marshmallows. Refraining from eating the marshmallow (delayed gratification, in the psychological literature) was found to be associated with better life outcomes years down the road. This experiment has been used and abused for years for all sorts of propaganda about how trading immediate pleasure for future gains leads to a successful life, and how failure in life is because of inability to delay gratification. More evil analyses have (of course) tied that capability to ethnicity, with predictably racist results. I have kind of a thing about the marshmallow experiment. It's a topic that reliably sends me off into angry rants. Algorithms to Live By is the only book I have ever read to mention the marshmallow experiment and then apply the analysis that I find far more convincing. This is not a test of innate capability in the children; it's a test of their Bayesian priors. When does it make perfect sense to eat the marshmallow immediately instead of waiting for a reward? When their past experience tells them that adults are unreliable, can't be trusted, disappear for unpredictable lengths of time, and lie. And, even better, the authors supported this analysis with both a follow-up study I hadn't heard of before and with the observation that some children would wait for some time and then "give in." This makes perfect sense if they were subconsciously using a Bayesian model with poor priors. This is a great book. It may try a bit too hard in places (applicability of the math of optimal stopping to everyday life is more contingent and strained than I think the authors want to admit), and some of this will be familiar if you've studied algorithms. But the writing is clear, succinct, and very well-edited. No part of the book outlives its welcome; the discussion moves right along. If you find yourself going "I know all this already," you'll still probably encounter a new concept or neat explanation in a few more pages. And sometimes the authors make connections that never would have occurred to me but feel right in retrospect, such as relating exponential backoff in networking protocols to choosing punishments in the criminal justice system. Or the realization that our modern communication world is not constantly connected, it's constantly buffered, and many of us are suffering from the characteristic signs of buffer bloat. I don't think you have to be a CS major, or know much about math, to read this book. There is a lot of mathematical details in the end notes if you want to dive in, but the main text is almost always readable and clear, at least so far as I could tell (as someone who was a CS major and has taken a lot of math, so a grain of salt may be indicated). And it still has a lot to offer even if you've studied algorithms for years. The more I read of this book, the more I liked it. Definitely recommended if you like reading this sort of analysis of life. Rating: 9 out of 10

Here s my weekly report for week 42 of 2017. In this week I have replaced my spacebar, failed to replace a HDD and begun the process to replace my YubiKey.

Debian Eariler in the week I blogged about powerline-taskwarrior . There is a new upstream version available that includes the patches I had produced for Python 2 support and I have filed #879225 to remind me to package this. The state of emscripten is still not great, and as I don t have the time to chase this up and I certainly don t have the time to fix it myself, I ve converted the ITP for csdr to an RFP. As I no longer have the time to maintain map.debian.net, I have released this domain name and published the sources behind the service.

• Bugs opened: #879225

Tor Project There was a request to remove the $ from family fingerprint on Atlas. These actually come from Onionoo and we have decided to fix this in Onionoo, but I did push a small fix for Atlas this week that makes sure that Atlas doesn t care if there are $ prefixes or not. I requested that a Trac component be created for metrics-bot. I wrote a seperate post about metrics-bot. I also attended the weekly metrics team meeting.

• Bugs opened: #23926, #23929, #23933, #23934, #23935, #23936, #23937, #23938, #23939, #23941

Sustainability I believe it is important to be clear not only about the work I have already completed but also about the sustainability of this work into the future. I plan to include a short report on the current sustainability of my work in each weekly report. I have not had any free software related expenses this week. The current funds I have available for equipment, travel and other free software expenses remains 60.52. I do not believe that any hardware I rely on is looking at imminent failure. I do not find it likely that I ll be travelling to Cambridge for the miniDebConf as the train alone would be around 350 and hotel accomodation a further 600 (to include both me and Ana).

Like each month, here comes a report about the work of paid contributors to Debian LTS. Individual reports In August, about 170 work hours have been dispatched among 13 paid contributors. Their reports are available:

• Antoine Beaupr did 7h (out of 15.75h allocated, thus keeping 8.75h for October).
• Ben Hutchings did 12 hours (out of 15h allocated + 6 extra hours, thus keeping 9 extra hours for October).
• Brian May did 10 hours.
• Chris Lamb did 15.75 hours.
• Emilio Pozuelo Monfort did 27 hours (out of 15.75 hours allocated + 12.75 hours remaining, thus keeping 1.5 hours for October).
• Guido G nther did 10 hours (out of 11h allocated, thus keeping one hour for October).
• Hugo Lefeuvre did 15h.
• Lucas Kanashiro did 5 hours.
• Markus Koschany did 15.75 hours.
• Ola Lundqvist did 13.5h (out of 7h allocated + 7 extra hours, thus keeping 0.5 extra hours for October).
• Rapha l Hertzog did 10.5 hours (out of 12h allocated, thus keeping 1.5 hours for October).
• Roberto C. Sanchez did 10 hours (out of 15.75 hours allocated + 9 hours remaining, thus keeping 14.75 extra hours for October).
• Thorsten Alteholz did 15.75 hours.

Evolution of the situation The number of sponsored hours is the same as last month. But we have a new sponsor in the pipe. The security tracker currently lists 52 packages with a known CVE and the dla-needed.txt file 49. The number of packages with open issues decreased slightly compared to last month but we re not yet back to the usual situation. Thanks to our sponsors New sponsors are in bold.

• Platinum sponsors:
• TOSHIBA (for 24 months)
• GitHub (for 15 months)
• Gold sponsors:
• The Positive Internet (for 40 months)
• Blablacar (for 39 months)
• Linode (for 29 months)
• Babiel GmbH (for 18 months)
• Plat Home (for 18 months)
• Silver sponsors:
• Domeneshop AS (for 40 months)
• Universit Lille 3 (for 39 months)
• Trollweb Solutions (for 37 months)
• Nantes M tropole (for 34 months)
• Dalenys (for 30 months)
• Univention GmbH (for 25 months)
• Universit Jean Monnet de St Etienne (for 25 months)
• Sonus Networks (for 19 months)
• maxcluster GmbH (for 13 months)
• Exonet B.V. (for 9 months)
• Leibniz Rechenzentrum (for 3 months)
• Bronze sponsors:
• David Ayers IntarS Austria (for 40 months)
• Evolix (for 40 months)
• Offensive Security (for 40 months)
• Seznam.cz, a.s. (for 40 months)
• Freeside Internet Service (for 39 months)
• MyTux (for 39 months)
• Intevation GmbH (for 37 months)
• Linuxhotel GmbH (for 37 months)
• Daevel SARL (for 36 months)
• Bitfolk LTD (for 34 months)
• Megaspace Internet Services GmbH (for 34 months)
• NUMLOG (for 34 months)
• Greenbone Networks GmbH (for 33 months)
• WinGo AG (for 33 months)
• Ecole Centrale de Nantes LHEEA (for 29 months)
• Sig-I/O (for 27 months)
• Entr ouvert (for 24 months)
• Adfinis SyGroup AG (for 22 months)
• GNI MEDIA (for 16 months)
• Laboratoire LEGI UMR 5519 / CNRS (for 16 months)
• Quarantainenet BV (for 16 months)
• RHX Srl (for 13 months)
• Bearstech (for 8 months)
• LiHAS (for 7 months)
• People Doc (for 4 months)
• Catalyst IT Ltd

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Today, Gammu 1.38.5 has been released. After long period of bugfix only releases, this comes with several new noteworthy features. The biggest feature probably is that SMSD can now handle USSD messages as well. Those are usually used for things like checking remaining credit, but it's certainly not limited to this. This feature has been contributed thanks to funding on BountySource. You can read more information in the release announcement.

Filed under: Debian English Gammu

Narabu is a new intraframe video codec, from the Japanese verb narabu ( ), which means to line up or be parallel. Let me first state straight up that Narabu isn't where I hoped it would be at this stage; the encoder isn't fast enough, and I have to turn my attention to other projects for a while. Nevertheless, I think it is interesting as a research project in its own right, and I don't think it should stop me from trying to write up a small series. :-) In the spirit of Leslie Lamport, I'll be starting off with describing what problem I was trying to solve, which will hopefully make the design decisions a lot clearer. Subsequent posts will dive into background information and then finally Narabu itself. I want a codec to send signals between different instances of Nageru, my free software video mixer, and also longer-term between other software, such as recording or playout. The reason is pretty obvious for any sort of complex configuration; if you are doing e.g. both a stream mix and a bigscreen mix, they will naturally want to use many of the same sources, and sharing them over a single GigE connection might be easier than getting SDI repeaters/splitters, especially when you have a lot of them. (Also, in some cases, you might want to share synthetic signals, such as graphics, that never existed on SDI in the first place.) This naturally leads to the following demands:

• Intraframe-only; every frame must be compressed independently. (This isn't strictly needed for all use cases, but is much more flexible, and common in any kind of broadcast.)
• Need to handle 4:2:2 color, since that's what most capture sources give out, and we want to transmit the raw signals as much as possible. Fairly flexible in input resolution (divisible by 16 is okay, limited to only a given set of resolutions is not).
• 720p60 video in less than one CPU core (ideally much less); the CPU can already pretty be busy with other work, like x264 encoding of the finished stream, and sharing four more inputs at the same time is pretty common. What matters is mostly a single encode+decode cycle, so fast decode doesn't help if the encoder is too slow.
• Target bitrates around 100-150 Mbit/sec, at similar quality to MJPEG (ie. 45 dB PSNR for most content). Multiple signals should fit into a normal GigE link at the same time, although getting it to work over 802.11 isn't a big priority.
• Both encoder and decoder robust to corrupted or malicious data; a dropped frame is fine, a crash is not.
• Does not depend on uncommon or expensive hardware, or GPUs from a specific manufacturer.
• GPLv3-compatible implementation. I already link to GPLv3 software, so I don't have a choice here; I cannot link to something non-free (and no antics with dlopen(), please).

There's a bunch of intraframe formats around. The most obvious thing to do would be to use Intel Quick Sync to produce H.264 (intraframe H.264 blows basically everything else out of the sky in terms of PSNR, and QSV hardly uses any power at all), but sadly, that's limited to 4:2:0. I thought about encoding the three color planes as three different monochrome streams, but monochrome is not supported either. Then there's a host of software solutions. x264 can do 4:2:2, but even on ultrafast, it gobbles up an entire core or more at 720p60 at the target bitrates (mostly in entropy coding). FFmpeg has implementations of all kinds of other codecs, like DNxHD, CineForm, MJPEG and so on, but they all use much more CPU for encoding than the target. NDI would seem to fit the bill exactly, but fails the licensing check, and also isn't robust to corrupted or malicious data. (That, and their claims about video quality are dramatically overblown for any kinds of real video data I've tried.) So, sadly, this leaves only really one choice, namely rolling my own. I quickly figured I couldn't beat the world on CPU video codec speed, and didn't really want to spend my life optimizing AVX2 DCTs anyway, so again, the GPU will come to our rescue in the form of compute shaders. (There are some other GPU codecs out there, but all that I've found depend on CUDA, so they are NVIDIA-only, which I'm not prepared to commit to.) Of course, the GPU is quite busy in Nageru, but if one can make an efficient enough codec that one stream can work at only 5% or so of the GPU (meaning 1200 fps or so), it wouldn't really make a dent. (As a spoiler, the current Narabu encoder isn't there for 720p60 on my GTX 950, but the decoder is.) In the next post, we'll look a bit at the GPU programming model, and what it means for how our codec needs to look like on the design level.

It has been ages that I haven t updated the MegaUpdate package for Kobo. Now that a new and seemingly rather bug-free and quick firmware release (4.6.9995) has been released, I finally took the time to update the whole package to the latest releases of all the included items. The update includes all my favorite patches and features: Kobo Start Menu, koreader, coolreader, pbchess, ssh access, custom dictionaries, and some side-loaded fonts. So what are all these items:

• firmware (thread): the basic software of the device, shipped by Kobo company
• Metazoa firmware patches (thread): fix some layout options and functionalities, see below for details.
• Kobo Start Menu (V08, update 5b thread): a menu that pops up before the reading software (nickel) starts, which allows to start alternative readers (like koreader) etc.
• KOreader (koreader-nightly-20171004, thread): an alternative document reader that supports epub, azw, pdf, djvu and many more
• pbchess and CoolReader (2017.10.14, thread): a chess program and another alternative reader, bundled together with several other games
• kobohack (web site): I only use the ssh server
• ssh access (old post: makes a full computer from your device by allowing you to log into it via ssh
• custom dictionaries (thread): this fix updates dictionaries from the folder customdicts to the Kobo dictionary folder. For creating your own Japanese-English dictionary, see this blog entry
• side-loaded fonts: GentiumBasic and GentiumBookBasic, Verdana, DroidSerif, and Charter-eInk

Install procedure Download Mark6 Kobo GloHD firmware: Kobo 4.6.9995 for GloHD Mega update: Kobo-4.6.9995-combined/Mark6/KoboRoot.tgz Mark5 Aura firmware: Kobo 4.6.9995 for Aura Mega update: Kobo-4.6.9995-combined/Mark5/KoboRoot.tgz Mark4 Kobo Glo, Aura HD firmware: Kobo 4.6.9995 for Glo and AuraHD Mega update: Kobo-4.6.9995-combined/Mark4/KoboRoot.tgz Latest firmware Warning: Sideloading or crossloading the incorrect firmware can break/brick your device. The link below is for Kobo GloHD ONLY. The first step is to update the Kobo to the latest firmware. This can easily be done by just getting the latest firmware from the links above and unpacking the zip file into the .kobo directory on your device. Eject and enjoy the updating procedure. Mega update Get the combined KoboRoot.tgz for your device from the links above and put it into the .kobo directory, then eject and enjoy the updating procedure again. After this the device should reboot and you will be kicked into KSM, from where after some time of waiting Nickel will be started. If you consider the fonts too small, select Configure, then the General, and add item, then select kobomenuFontsize=55 and save. Remarks to some of the items included The full list of included things is above, here are only some notes about what specific I have done.

• Metazoa firmware patches Included patches from the Metazoa firmware patches:

  Custom left & right margins
  Fix three KePub fullScreenReading bugs
  Change dicthtml strings to micthtml
  Default ePub monospace font (Courier)
  Custom reading footer style
  Dictionary pop-up frame size increase
  Increase The Cover Size In Library
  Increasing The View Details Container
  New home screen increasing cover size
  Reading stats/Author name cut when the series is showing bug fix 
  New home screen subtitle custom font
  Custom font to Collection and Authors names
  

  If you need/want different patches, you need to do the patching yourself.
• kobohack-h Kobohack (latest version 20150110) originally provided updated libraries and optimizations, but unfortunately it is now completely outdated and using it is not recommended for the library part. I only include the ssh server (dropbear) so that connections to the Kobo via ssh.
• ssh fixes See the detailed instructions here, the necessary files are already included in the mega upload. It updates the /etc/inittab to run also /etc/init.d/rcS2, and this one again starts the inetd server and run user supplied commands in /mnt/onboard/run.sh which is where your documents are.
• Custom dictionaries The necessary directories and scripts are already included in the above combined KoboRoot.tgz, so nothing to be done but dropping updated, fixed, changed dictionaries into your Kobo root into the directory customdict. After this you need to reboot to get the actual dictionaries updated. See this thread for more information. The adaptions and script mentioned in this post are included in the mega update.

WARNINGS If this is the first time you install this patch, you to fix the password for root and disable telnet. This is an important step, here are the steps you have to take (taken from this old post):

1. Turn on Wifi on the Kobo and find IP address
   Go to Settings Connect and after this is done, go to Settings Device Information where you will see something like
IP Address: 192.168.1.NN
   (numbers change!)
2. telnet into your device
   telnet 192.168.1.NN
   it will ask you the user name, enter root (without the quotes) and no password
3. (ON THE GLO) change home directory of root
   edit /etc/passwd with vi and change the entry for root by changing the 6th field from: / to /root (without the quotes). After this procedure the line should look like
   root::0:0:root:/root:/bin/sh
   don t forget to save the file
4. (ON THE GLO) create ssh keys for dropbear
   [root@(none) ~]# mkdir /etc/dropbear
[root@(none) ~]# cd /etc/dropbear
[root@(none) ~]# dropbearkey -t dss -f dropbear_dss_host_key
[root@(none) ~]# dropbearkey -t rsa -f dropbear_rsa_host_key
5. (ON YOUR PERSONAL COMPUTER) check that you can log in with ssh
   ssh root@192.168.1.NN
   You should get dropped into your device again
6. (ON THE GLO) log out of the telnet session (the first one you did)
   [root@(none) ~]# exit
7. (ON THE GLO) in your ssh session, change the password of root
   [root@(none) ~]# passwd
   you will have to enter the new password two times. Remember it well, you will not be easily able to recover it without opening your device.
8. (ON THE GLO) disable telnet login
   edit the file /etc/inetd.conf.local on the GLO (using vi) and remove the telnet line (the line starting with 23).
9. restart your device

The combined KoboRoot.tgz is provided without warranty. If you need to reset your device, don t blame me!

Here's what happened in the Reproducible Builds effort between Sunday October 8 and Saturday October 14 2017: Upcoming events

• On Saturday 21st October, Holger Levsen will present at All Systems Go! in Berlin, Germany on reproducible builds.
• On Tuesday 24th October, Chris Lamb will present at All Things Open 2017 in Raleigh, NC, USA on reproducible builds.
• On Wednesday 25th October, Holger Levsen will present at the Open Source Summit Europe in Prague, Czech Republic on reproducible builds.
• From October 31st - November 2nd we will be holding the 3rd Reproducible Builds summit in Berlin. If you are working in the field of reproducible builds, you should totally be there. Please contact us if you have any questions! Quoting from the public invitation mail:

  These dates are inclusive, ie. the summit will be 3 full days from "9 to 5".
  Best arrive on Monday October 30th and leave on the evening of Thursday, 3rd
  at the earliest.
  Meeting content
  ===============
  The exact content of the meeting is going to be shaped by the
  participants, but here are the main goals:
   - Update & exchange about the status of reproducible builds in various
     projects.
   - Establish spaces for more strategic and long-term thinking than is possible
     in virtual channels.
   - Improve collaboration both between and inside projects.
   - Expand the scope and reach of reproducible builds to more projects.
   - Brainstorming / Designing several things, eg:
    - designing tools enabling end-users to get the most benefits from
      reproducible builds.
    - design of back-ends needed for that.
   - Work together and hack on solutions.
  There will be a huge variety of topics to be discussed. To give a few
  examples:
  - continuing design and development work on .buildinfo infrastructure
  - build-path issues everywhere
  - future directions for diffoscope, reprotest & strip-nondeterminism
  - reproducing signed artifacts such as RPMs
  - discussing formats and tools we can share
  - sharing proposals for standards and documentation helpful to spreading the
    reproducible effort
  - and many many more.
  Please think about what you want discuss, brainstorm & learn about at this
  meeting!
  Schedule
  ========
  Preliminary schedule for the three days:
  9:00 Welcome and breakfast
  9:30 Meeting starts
  12:30 Lunch
  17:00 End of the official schedule
  Gunner and Beatrice from Aspiration will help running the meeting. We will
  collect your input in subsequent emails to make the best of everyone's time.
  Feel free to start thinking about what you want to achieve there. We will also
  adjust topics as the meeting goes.
  Please note that we are very likely to spend large parts of the meeting away
  from laptops and closer to post-it notes. So make sure you've answered any
  critical emails *before* Tuesday morning! :)
  

Reproducible work in other projects Pierre Pronchery reported that that he has built the foundations for doing more reproducibility work in NetBSD. Packages fixed Upstream bugs and patches:

• Bernhard M. Wiedemann:
  • qutim used RANDOM which is unpredictable and unreproducible.
  • dpdk used locale-dependent sort.

Reproducibility non-maintainer uploads in Debian:

• Chris Lamb:
  • mailfront for bugs #777431 & #847020.
  • plib-doc for bugs #778971 & #557676.
  • ipsvd for bugs #777417 & #846890.
• Holger Levsen
  • keyutils for bug #828681.

QA fixes in Debian:

• Adrian Bunk:
  • #878329 filed against sonic-visualiser.
  • #878333 filed against tree-puzzle.

Reviews of unreproducible packages 6 package reviews have been added, 30 have been updated and 37 have been removed in this week, adding to our knowledge about identified issues. Weekly QA work During our reproducibility testing, FTBFS bugs have been detected and reported by:

• Adrian Bunk (40)
• Eric Valette (1)
• Markus Koschany (1)

diffoscope development

• Ximin Luo:
  • Containers: diff the metadata of containers in one central location in the code, so that deep-diff works between all combinations of different container types. This lets us finally close #797759.
  • Tests: add a complete set of cases to test all pairs of container types.
• Chris Lamb:
  • Temporarily skip the test for ps2ascii(1) in ghostscript > 9.21 which now outputs text in a slightly different format.
  • UI wording improvements.

reprotest development Version 0.7.3 was uploaded to unstable by Ximin Luo. It included contributions already covered by posts of the previous weeks, as well as new ones:

• Ximin Luo:
  • Add a --env-build option for testing builds under different sets of environment variables. This is meant to help the discussion over at #876055 about how we should deal with different types of environment variables in a stricter definition of reproducibility.
  • UI and logging tweaks and improvements.
  • Simplify the _shell_ast module and merge it into shell_syn.

Misc. This week's edition was written by Ximin Luo, Chris Lamb and Holger Levsen & reviewed by a bunch of Reproducible Builds folks on IRC & the mailing lists.

Confession time: I started making these posts (eons ago) because a close friend did as well, and I enjoyed reading them. But the main reason why I continue is because the primary way I have to keep track of the books I've bought and avoid duplicates is, well, grep on these posts. I should come up with a non-bullshit way of doing this, but time to do more elegant things is in short supply, and, well, it's my blog. So I'm boring all of you who read this in various places with my internal bookkeeping. I do try to at least add a bit of commentary. This one will be more tedious than most since it includes five separate Humble Bundles, which increases the volume a lot. (I just realized I'd forgotten to record those purchases from the past several months.) First, the individual books I bought directly: Ilona Andrews Sweep in Peace (sff)
Ilona Andrews One Fell Sweep (sff)
Steven Brust Vallista (sff)
Nicky Drayden The Prey of Gods (sff)
Meg Elison The Book of the Unnamed Midwife (sff)
Pat Green Night Moves (nonfiction)
Ann Leckie Provenance (sff)
Seanan McGuire Once Broken Faith (sff)
Seanan McGuire The Brightest Fell (sff)
K. Arsenault Rivera The Tiger's Daughter (sff)
Matthew Walker Why We Sleep (nonfiction)
Some new books by favorite authors, a few new releases I heard good things about, and two (Night Moves and Why We Sleep) from references in on-line articles that impressed me. The books from security bundles (this is mostly work reading, assuming I'll get to any of it), including a blockchain bundle: Wil Allsop Unauthorised Access (nonfiction)
Ross Anderson Security Engineering (nonfiction)
Chris Anley, et al. The Shellcoder's Handbook (nonfiction)
Conrad Barsky & Chris Wilmer Bitcoin for the Befuddled (nonfiction)
Imran Bashir Mastering Blockchain (nonfiction)
Richard Bejtlich The Practice of Network Security (nonfiction)
Kariappa Bheemaiah The Blockchain Alternative (nonfiction)
Violet Blue Smart Girl's Guide to Privacy (nonfiction)
Richard Caetano Learning Bitcoin (nonfiction)
Nick Cano Game Hacking (nonfiction)
Bruce Dang, et al. Practical Reverse Engineering (nonfiction)
Chris Dannen Introducing Ethereum and Solidity (nonfiction)
Daniel Drescher Blockchain Basics (nonfiction)
Chris Eagle The IDA Pro Book, 2nd Edition (nonfiction)
Nikolay Elenkov Android Security Internals (nonfiction)
Jon Erickson Hacking, 2nd Edition (nonfiction)
Pedro Franco Understanding Bitcoin (nonfiction)
Christopher Hadnagy Social Engineering (nonfiction)
Peter N.M. Hansteen The Book of PF (nonfiction)
Brian Kelly The Bitcoin Big Bang (nonfiction)
David Kennedy, et al. Metasploit (nonfiction)
Manul Laphroaig (ed.) PoC GTFO (nonfiction)
Michael Hale Ligh, et al. The Art of Memory Forensics (nonfiction)
Michael Hale Ligh, et al. Malware Analyst's Cookbook (nonfiction)
Michael W. Lucas Absolute OpenBSD, 2nd Edition (nonfiction)
Bruce Nikkel Practical Forensic Imaging (nonfiction)
Sean-Philip Oriyano CEHv9 (nonfiction)
Kevin D. Mitnick The Art of Deception (nonfiction)
Narayan Prusty Building Blockchain Projects (nonfiction)
Prypto Bitcoin for Dummies (nonfiction)
Chris Sanders Practical Packet Analysis, 3rd Edition (nonfiction)
Bruce Schneier Applied Cryptography (nonfiction)
Adam Shostack Threat Modeling (nonfiction)
Craig Smith The Car Hacker's Handbook (nonfiction)
Dafydd Stuttard & Marcus Pinto The Web Application Hacker's Handbook (nonfiction)
Albert Szmigielski Bitcoin Essentials (nonfiction)
David Thiel iOS Application Security (nonfiction)
Georgia Weidman Penetration Testing (nonfiction)
Finally, the two SF bundles: Buzz Aldrin & John Barnes Encounter with Tiber (sff)
Poul Anderson Orion Shall Rise (sff)
Greg Bear The Forge of God (sff)
Octavia E. Butler Dawn (sff)
William C. Dietz Steelheart (sff)
J.L. Doty A Choice of Treasons (sff)
Harlan Ellison The City on the Edge of Forever (sff)
Toh Enjoe Self-Reference ENGINE (sff)
David Feintuch Midshipman's Hope (sff)
Alan Dean Foster Icerigger (sff)
Alan Dean Foster Mission to Moulokin (sff)
Alan Dean Foster The Deluge Drivers (sff)
Taiyo Fujii Orbital Cloud (sff)
Hideo Furukawa Belka, Why Don't You Bark? (sff)
Haikasoru (ed.) Saiensu Fikushon 2016 (sff anthology)
Joe Haldeman All My Sins Remembered (sff)
Jyouji Hayashi The Ouroboros Wave (sff)
Sergei Lukyanenko The Genome (sff)
Chohei Kambayashi Good Luck, Yukikaze (sff)
Chohei Kambayashi Yukikaze (sff)
Sakyo Komatsu Virus (sff)
Miyuki Miyabe The Book of Heroes (sff)
Kazuki Sakuraba Red Girls (sff)
Robert Silverberg Across a Billion Years (sff)
Allen Steele Orbital Decay (sff)
Bruce Sterling Schismatrix Plus (sff)
Michael Swanwick Vacuum Flowers (sff)
Yoshiki Tanaka Legend of the Galactic Heroes, Volume 1: Dawn (sff)
Yoshiki Tanaka Legend of the Galactic Heroes, Volume 2: Ambition (sff)
Yoshiki Tanaka Legend of the Galactic Heroes, Volume 3: Endurance (sff)
Tow Ubukata Mardock Scramble (sff)
Sayuri Ueda The Cage of Zeus (sff)
Sean Williams & Shane Dix Echoes of Earth (sff)
Hiroshi Yamamoto MM9 (sff)
Timothy Zahn Blackcollar (sff)
Phew. Okay, all caught up, and hopefully won't have to dump something like this again in the near future. Also, more books than I have any actual time to read, but what else is new.

An earlier article showed that private key storage is an important problem to solve in any cryptographic system and established keycards as a good way to store private key material offline. But which keycard should we use? This article examines the form factor, openness, and performance of four keycards to try to help readers choose the one that will fit their needs. I have personally been using a YubiKey NEO, since a 2015 announcement on GitHub promoting two-factor authentication. I was also able to hook up my SSH authentication key into the YubiKey's 2048 bit RSA slot. It seemed natural to move the other subkeys onto the keycard, provided that performance was sufficient. The mail client that I use, (Notmuch), blocks when decrypting messages, which could be a serious problems on large email threads from encrypted mailing lists. So I built a test harness and got access to some more keycards: I bought a FST-01 from its creator, Yutaka Niibe, at the last DebConf and Nitrokey donated a Nitrokey Pro. I also bought a YubiKey 4 when I got the NEO. There are of course other keycards out there, but those are the ones I could get my hands on. You'll notice none of those keycards have a physical keypad to enter passwords, so they are all vulnerable to keyloggers that could extract the key's PIN. Keep in mind, however, that even with the PIN, an attacker could only ask the keycard to decrypt or sign material but not extract the key that is protected by the card's firmware.

Form factor The four keycards have similar form factors: they all connect to a standard USB port, although both YubiKey keycards have a capacitive button by which the user triggers two-factor authentication and the YubiKey 4 can also require a button press to confirm private key use. The YubiKeys feel sturdier than the other two. The NEO has withstood two years of punishment in my pockets along with the rest of my "real" keyring and there is only minimal wear on the keycard in the picture. It's also thinner so it fits well on the keyring. The FST-01 stands out from the other two with its minimal design. Out of the box, the FST-01 comes without a case, so the circuitry is exposed. This is deliberate: one of its goals is to be as transparent as possible, both in terms of software and hardware design and you definitely get that feeling at the physical level. Unfortunately, that does mean it feels more brittle than other models: I wouldn't carry it in my pocket all the time, although there is a case that may protect the key a little better, but it does not provide an easy way to hook it into a keyring. In the group picture above, the FST-01 is the pink plastic thing, which is a rubbery casing I received along with the device when I got it. Notice how the USB connectors of the YubiKeys differ from the other two: while the FST-01 and the Nitrokey have standard USB connectors, the YubiKey has only a "half-connector", which is what makes it thinner than the other two. The "Nano" form factor takes this even further and almost disappears in the USB port. Unfortunately, this arrangement means the YubiKey NEO often comes loose and falls out of the USB port, especially when connected to a laptop. On my workstation, however, it usually stays put even with my whole keyring hanging off of it. I suspect this adds more strain to the host's USB port but that's a tradeoff I've lived with without any noticeable wear so far. Finally, the NEO has this peculiar feature of supporting NFC for certain operations, as LWN previously covered, but I haven't used that feature yet. The Nitrokey Pro looks like a normal USB key, in contrast with the other two devices. It does feel a little brittle when compared with the YubiKey, although only time will tell how much of a beating it can take. It has a small ring in the case so it is possible to carry it directly on your keyring, but I would be worried the cap would come off eventually. Nitrokey devices are also two times thicker than the Yubico models which makes them less convenient to carry around on keyrings.

Open and closed designs The FST-01 is as open as hardware comes, down to the PCB design available as KiCad files in this Git repository. The software running on the card is the Gnuk firmware that implements the OpenPGP card protocol, but you can also get it with firmware implementing a true random number generator (TRNG) called NeuG (pronounced "noisy"); the device is programmable through a standard Serial Wire Debug (SWD) port. The Nitrokey Start model also runs the Gnuk firmware. However, the Nitrokey website announces only ECC and RSA 2048-bit support for the Start, while the FST-01 also supports RSA-4096. Nitrokey's founder Jan Suhr, in a private email, explained that this is because "Gnuk doesn't support RSA-3072 or larger at a reasonable speed". Its devices (the Pro, Start, and HSM models) use a similar chip to the FST-01: the STM32F103 microcontroller. Nitrokey also publishes its hardware designs, on GitHub, which shows the Pro is basically a fork of the FST-01, according to the ChangeLog. I opened the case to confirm it was using the STM MCU, something I should warn you against; I broke one of the pins holding it together when opening it so now it's even more fragile. But at least, I was able to confirm it was built using the STM32F103TBU6 MCU, like the FST-01. But this is where the comparison ends: on the back side, we find a SIM card reader that holds the OpenPGP card that, in turn, holds the private key material and does the cryptographic operations. So, in effect, the Nitrokey Pro is really a evolution of the original OpenPGP card readers. Nitrokey confirmed the OpenPGP card featured in the Pro is the same as the one shipped by the Free Software Foundation Europe (FSFE): the BasicCard built by ZeitControl. Those cards, however, are covered by NDAs and the firmware is only partially open source. This makes the Nitrokey Pro less open than the FST-01, but that's an inevitable tradeoff when choosing a design based on the OpenPGP cards, which Suhr described to me as "pretty proprietary". There are other keycards out there, however, for example the SLJ52GDL150-150k smartcard suggested by Debian developer Yves-Alexis Perez, which he prefers as it is certified by French and German authorities. In that blog post, he also said he was experimenting with the GPL-licensed OpenPGP applet implemented by the French ANSSI. But the YubiKey devices are even further away in the closed-design direction. Both the hardware designs and firmware are proprietary. The YubiKey NEO, for example, cannot be upgraded at all, even though it is based on an open firmware. According to Yubico's FAQ, this is due to "best security practices": "There is a 'no upgrade' policy for our devices since nothing, including malware, can write to the firmware." I find this decision questionable in a context where security updates are often more important than trying to design a bulletproof design, which may simply be impossible. And the YubiKey NEO did suffer from critical security issue that allowed attackers to bypass the PIN protection on the card, which raises the question of the actual protection of the private key material on those cards. According to Niibe, "some OpenPGP cards store the private key unencrypted. It is a common attitude for many smartcard implementations", which was confirmed by Suhr: "the private key is protected by hardware mechanisms which prevent its extraction and misuse". He is referring to the use of tamper resistance. After that security issue, there was no other option for YubiKey NEO users than to get a new keycard (for free, thankfully) from Yubico, which also meant discarding the private key material on the key. For OpenPGP keys, this may mean having to bootstrap the web of trust from scratch if the keycard was responsible for the main certification key. But at least the NEO is running free software based on the OpenPGP card applet and the source is still available on GitHub. The YubiKey 4, on the other hand, is now closed source, which was controversial when the new model was announced last year. It led the main Linux Foundation system administrator, Konstantin Ryabitsev, to withdraw his endorsement of Yubico products. In response, Yubico argued that this approach was essential to the security of its devices, which are now based on "a secure chip, which has built-in countermeasures to mitigate a long list of attacks". In particular, it claims that:

A commercial-grade AVR or ARM controller is unfit to be used in a security product. In most cases, these controllers are easy to attack, from breaking in via a debug/JTAG/TAP port to probing memory contents. Various forms of fault injection and side-channel analysis are possible, sometimes allowing for a complete key recovery in a shockingly short period of time.

While I understand those concerns, they eventually come down to the trust you have in an organization. Not only do we have to trust Yubico, but also hardware manufacturers and designs they have chosen. Every step in the hidden supply chain is then trusted to make correct technical decisions and not introduce any backdoors. History, unfortunately, is not on Yubico's side: Snowden revealed the example of RSA security accepting what renowned cryptographer Bruce Schneier described as a "bribe" from the NSA to weaken its ECC implementation, by using the presumably backdoored Dual_EC_DRBG algorithm. What makes Yubico or its suppliers so different from RSA Security? Remember that RSA Security used to be an adamant opponent to the degradation of encryption standards, campaigning against the Clipper chip in the first crypto wars. Even if we trust the Yubico supply chain, how can we trust a closed design using what basically amounts to security through obscurity? Publicly auditable designs are an important tradition in cryptography, and that principle shouldn't stop when software is frozen into silicon. In fact, a critical vulnerability called ROCA disclosed recently affects closed "smartcards" like the YubiKey 4 and allows full private key recovery from the public key if the key was generated on a vulnerable keycard. When speaking with Ars Technica, the researchers outlined the importance of open designs and questioned the reliability of certification:

Our work highlights the dangers of keeping the design secret and the implementation closed-source, even if both are thoroughly analyzed and certified by experts. The lack of public information causes a delay in the discovery of flaws (and hinders the process of checking for them), thereby increasing the number of already deployed and affected devices at the time of detection.

This issue with open hardware designs seems to be recurring topic of conversation on the Gnuk mailing list. For example, there was a discussion in September 2017 regarding possible hardware vulnerabilities in the STM MCU that would allow extraction of encrypted key material from the key. Niibe referred to a talk presented at the WOOT 17 workshop, where Johannes Obermaier and Stefan Tatschner, from the Fraunhofer Institute, demonstrated attacks against the STMF0 family MCUs. It is still unclear if those attacks also apply to the older STMF1 design used in the FST-01, however. Furthermore, extracted private key material is still protected by user passphrase, but the Gnuk uses a weak key derivation function, so brute-forcing attacks may be possible. Fortunately, there is work in progress to make GnuPG hash the passphrase before sending it to the keycard, which should make such attacks harder if not completely pointless. When asked about the Yubico claims in a private email, Niibe did recognize that "it is true that there are more weak points in general purpose implementations than special implementations". During the last DebConf in Montreal, Niibe explained:

If you don't trust me, you should not buy from me. Source code availability is only a single factor: someone can maliciously replace the firmware to enable advanced attacks.

Niibe recommends to "build the firmware yourself", also saying the design of the FST-01 uses normal hardware that "everyone can replicate". Those advantages are hard to deny for a cryptographic system: using more generic components makes it harder for hostile parties to mount targeted attacks. A counter-argument here is that it can be difficult for a regular user to audit such designs, let alone physically build the device from scratch but, in a mailing list discussion, Debian developer Ian Jackson explained that:

You don't need to be able to validate it personally. The thing spooks most hate is discovery. Backdooring supposedly-free hardware is harder (more costly) because it comes with greater risk of discovery. To put it concretely: if they backdoor all of them, someone (not necessarily you) might notice. (Backdooring only yours involves messing with the shipping arrangements and so on, and supposes that you specifically are of interest.)

Since that, as far as we know, the STM microcontrollers are not backdoored, I would tend to favor those devices instead of proprietary ones, as such a backdoor would be more easily detectable than in a closed design. Even though physical attacks may be possible against those microcontrollers, in the end, if an attacker has physical access to a keycard, I consider the key compromised, even if it has the best chip on the market. In our email exchange, Niibe argued that "when a token is lost, it is better to revoke keys, even if the token is considered secure enough". So like any other device, physical compromise of tokens may mean compromise of the key and should trigger key-revocation procedures.

Algorithms and performance To establish reliable performance results, I wrote a benchmark program naively called crypto-bench that could produce comparable results between the different keys. The program takes each algorithm/keycard combination and runs 1000 decryptions of a 16-byte file (one AES-128 block) using GnuPG, after priming it to get the password cached. I assume the overhead of GnuPG calls to be negligible, as it should be the same across all tokens, so comparisons are possible. AES encryption is constant across all tests as it is always performed on the host and fast enough to be irrelevant in the tests. I used the following:

• Intel(R) Core(TM) i3-6100U CPU @ 2.30GHz running Debian 9 ("stretch"/stable amd64), using GnuPG 2.1.18-6 (from the stable Debian package)
• Nitrokey Pro 0.8 (latest firmware)
• FST-01, running Gnuk version 1.2.5 (latest firmware)
• YubiKey NEO OpenPGP applet 1.0.10 (not upgradable)
• YubiKey 4 4.2.6 (not upgradable)

I ran crypto-bench for each keycard, which resulted in the following:

Algorithm	Device	Mean time (s)
ECDH-Curve25519	CPU	0.036
	FST-01	0.135
RSA-2048	CPU	0.016
	YubiKey-4	0.162
	Nitrokey-Pro	0.610
	YubiKey-NEO	0.736
	FST-01	1.265
RSA-4096	CPU	0.043
	YubiKey-4	0.875
	Nitrokey-Pro	3.150
	FST-01	8.218

There we see the performance of the four keycards I tested, compared with the same operations done without a keycard: the "CPU" device. That provides the baseline time of GnuPG decrypting the file. The first obvious observation is that using a keycard is slower: in the best scenario (FST-01 + ECC) we see a four-fold slowdown, but in the worst case (also FST-01, but RSA-4096), we see a catastrophic 200-fold slowdown. When I presented the results on the Gnuk mailing list, GnuPG developer Werner Koch confirmed those "numbers are as expected":

With a crypto chip RSA is much faster. By design the Gnuk can't be as fast - it is just a simple MCU. However, using Curve25519 Gnuk is really fast.

And yes, the FST-01 is really fast at doing ECC, but it's also the only keycard that handles ECC in my tests; the Nitrokey Start and Nitrokey HSM should support it as well, but I haven't been able to test those devices. Also note that the YubiKey NEO doesn't support RSA-4096 at all, so we can only compare RSA-2048 across keycards. We should note, however, that ECC is slower than RSA on the CPU, which suggests the Gnuk ECC implementation used by the FST-01 is exceptionally fast. In discussions about improving the performance of the FST-01, Niibe estimated the user tolerance threshold to be "2 seconds decryption time". In a new design using the STM32L432 microcontroller, Aurelien Jarno was able to bring the numbers for RSA-2048 decryption from 1.27s down to 0.65s, and for RSA-4096, from 8.22s down to 3.87s seconds. RSA-4096 is still beyond the two-second threshold, but at least it brings the FST-01 close to the YubiKey NEO and Nitrokey Pro performance levels. We should also underline the superior performance of the YubiKey 4: whatever that thing is doing, it's doing it faster than anyone else. It does RSA-4096 faster than the FST-01 does RSA-2048, and almost as fast as the Nitrokey Pro does RSA-2048. We should also note that the Nitrokey Pro also fails to cross the two-second threshold for RSA-4096 decryption. For me, the FST-01's stellar performance with ECC outshines the other devices. Maybe it says more about the efficiency of the algorithm than the FST-01 or Gnuk's design, but it's definitely an interesting avenue for people who want to deploy those modern algorithms. So, in terms of performance, it is clear that both the YubiKey 4 and the FST-01 take the prize in their own areas (RSA and ECC, respectively).

Conclusion In the above presentation, I have evaluated four cryptographic keycards for use with various OpenPGP operations. What the results show is that the only efficient way of storing a 4096-bit encryption key on a keycard would be to use the YubiKey 4. Unfortunately, I do not feel we should put our trust in such closed designs so I would argue you should either stick with 2048-bit encryption subkeys or keep the keys on disk. Considering that losing such a key would be catastrophic, this might be a good approach anyway. You should also consider switching to ECC encryption: even though it may not be supported everywhere, GnuPG supports having multiple encryption subkeys on a keyring: if one algorithm is unsupported (e.g. GnuPG 1.4 doesn't support ECC), it will fall back to a supported algorithm (e.g. RSA). Do not forget your previously encrypted material doesn't magically re-encrypt itself using your new encryption subkey, however. For authentication and signing keys, speed is not such an issue, so I would warmly recommend either the Nitrokey Pro or Start, or the FST-01, depending on whether you want to start experimenting with ECC algorithms. Availability also seems to be an issue for the FST-01. While you can generally get the device when you meet Niibe in person for a few bucks (I bought mine for around \$30 Canadian), the Seeed online shop says the device is out of stock at the time of this writing, even though Jonathan McDowell said that may be inaccurate in a debian-project discussion. Nevertheless, this issue may make the Nitrokey devices more attractive. When deciding on using the Pro or Start, Suhr offered the following advice:

In practice smart card security has been proven to work well (at least if you use a decent smart card). Therefore the Nitrokey Pro should be used for high security cases. If you don't trust the smart card or if Nitrokey Start is just sufficient for you, you can choose that one. This is why we offer both models.

So far, I have created a signing subkey and moved that and my authentication key to the YubiKey NEO, because it's a device I physically trust to keep itself together in my pockets and I was already using it. It has served me well so far, especially with its extra features like U2F and HOTP support, which I use frequently. Those features are also available on the Nitrokey Pro, so that may be an alternative if I lose the YubiKey. I will probably move my main certification key to the FST-01 and a LUKS-encrypted USB disk, to keep that certification key offline but backed up on two different devices. As for the encryption key, I'll wait for keycard performance to improve, or simply switch my whole keyring to ECC and use the FST-01 or Nitrokey Start for that purpose.

---

[The author would like to thank Nitrokey for providing hardware for testing.] This article first appeared in the Linux Weekly News.

I said that I was going to start writing these regularly, so I'm going to stick to it, even when the results are rather underwhelming. One of the goals is to make the time for more free software work, and I do better at doing things that I record. The only piece of free software work for September was that I made rra-c-util compile cleanly with the Clang static analyzer. This was fairly tedious work that mostly involved unconfusing the compiler or converting (semi-intentional) crashes into explicit asserts, but it unblocks using the Clang static analyzer as part of the automated test suite of my other projects that are downstream of rra-c-util. One of the semantic changes I made was that the vector utilities in rra-c-util (which maintain a resizable array of strings) now always allocate room for at least one string pointer. This wastes a small amount of memory for empty vectors that are never used, but ensures that the strings struct member is always valid. This isn't, strictly speaking, a correctness fix, since all the checks were correct, but after some thought, I decided that humans might have the same problem that the static analyzer had. It's a lot easier to reason about a field that's never NULL. Similarly, the replacement function for a missing reallocarray now does an allocation of size 1 if given a size of 0, just to avoid edge case behavior. (I'm sure the behavior of a realloc with size 0 is defined somewhere in the C standard, but if I have to look it up, I'd rather not make a human reason about it.) I started on, but didn't finish, making rra-c-util compile without Clang warnings (at least for a chosen set of warnings). By far the hardest problem here are the Clang warnings for comparisons between unsigned and signed integers. In theory, I like this warning, since it's the cause of a lot of very obscure bugs. In practice, gah does C ever do this all over the place, and it's incredibly painful to avoid. (One of the biggest offenders is write, which returns a ssize_t that you almost always want to compare against a size_t.) I did a bunch of mechanical work, but I now have a lot of bits of code like:

     if (status < 0)
         return;
    written = (size_t) status;
    if (written < avail)
        buffer->left += written;

which is ugly and unsatisfying. And I also have a ton of casts, such as with:

    buffer_resize(buffer, (size_t) st.st_size + used);

since st.st_size is an off_t, which may be signed. This is all deeply unsatisfying and ugly, and I think it makes the code moderately harder to read, but I do think the warning will potentially catch bugs and even security issues. I'm still torn. Maybe I can find some nice macros or programming styles to avoid the worst of this problem. It definitely requires more thought, rather than just committing this huge mechanical change with lots of ugly code. Mostly, this kind of nonsense makes me want to stop working on C code and go finish learning Rust.... Anyway, apart from work, the biggest thing I managed to do last month that was vaguely related to free software was upgrading my personal servers to stretch (finally). That mostly went okay; only a few things made it unnecessarily exciting. The first was that one of my systems had a very tiny / partition that was too small to hold the downloaded debs for the upgrade, so I had to resize it (VM disk, partition, and file system), and that was a bit exciting because it has an old-style DOS partition table that isn't aligned (hmmm, which is probably why disk I/O is so slow on those VMs), so I had to use the obsolete fdisk -c=dos mode because I wasn't up for replacing the partition right then. The second was that my first try at an upgrade died with a segfault during the libc6 postinst and then every executable segfaulted. A mild panic and a rescue disk later (and thirty minutes and a lot of swearing), I tracked the problem down to libc6-xen. Nothing in the dependency structure between jessie and stretch forces libc6-xen to be upgraded in lockstep or removed, but it's earlier in the search path. So ld.so gets upgraded, and then finds the old libc6 from the libc6-xen package, and the mismatch causes immediate segfaults. A chroot dpkg --purge from the rescue disk solved the problem as soon as I knew what was going on, but that was a stressful half-hour. The third problem was something I should have known was going to be an issue: an old Perl program that does some internal stuff for one of the services I ran had a defined @array test that has been warning for eons and that I never fixed. That became a full syntax error with the most recent Perl, and then I fixed it incorrectly the first time and had a bunch of trouble tracking down what I'd broken. All sorted out now, and everything is happily running stretch. (ejabberd, which other folks had mentioned was a problem, went completely smoothly, although I suspect I now have too many of the plugin packages installed and should do a purging.)

FOSDEM is a free software event that offers open source communities a place to meet, share ideas and collaborate. It is renown for being highly developer-oriented and brings together 8000+ participants from all over the world. It is held in the city of Brussels (Belgium). FOSDEM 2018 will take place during the weekend of February 3rd-4th 2018. More details about the event can be found at http://www.fosdem.org Call for Participation The Retrocomputing DevRoom is a first-timer at FOSDEM, with talks about use of older computing hardware and software in modern times. Presentation topics could include but are not limited to:

• Emulation of old systems to run videogames, legacy software, etc
• Open source software emulation/simulation
• Open hardware
• Operating systems/executives for retrocomputers/retrosystems
• Uses of retrocomputing today
• Other retrosystems topics
• Opportunities in retrocomputing
• Round tables

You are not limited to slide presentations, of course. Be creative. However, FOSDEM is an open source conference, therefore we ask you to stay clear of marketing presentations. We are not afraid of technical stuff: devrooms are a place for development teams to meet, discuss, hack and publicly present their project s latest improvements and future directions. If you will have special needs for your talk (e. g. because you will need to plug some sort of a system), please note that clearly in your proposal so that we can provide it. You can use the Wikipedia definition of retrocomputing as a reference definition to see if you talk qualifies, although it is not exclusive: https://en.wikipedia.org/wiki/Retrocomputing Important dates

• 25 Nov 2017: submission deadline for talk proposals
• 15 Dec 2017: announcement of the final schedule
• 4 Feb 2018: Retrocomputing dev room

Useful information Use the FOSDEM Pentabarf tool to submit your proposal: https://penta.fosdem.org/submission/FOSDEM18 If necessary, create a Pentabarf account and activate it. Please reuse your account from previous years if you have already created it. Details on submission:

• In the Person section, provide First name, Last name (in the General tab), Email (in the Contact tab) and Bio ( Abstract field in the Description tab).
• Submit a proposal by clicking on Create event .
• Important! Select the Retrocomputing DevRoom track (on the General tab). If you do not select a track, then nobody, from any track, will look at your submission!
• Provide the title of your talk ( Event title in the General tab).
• Provide a description of the subject of the talk and the intended audience (in the Abstract field of the Description tab)
• Provide a rough outline of the talk or goals of the session (a short list of bullet points covering topics that will be discussed) in the Full description field in the Description tab
• Provide an expected length of your talk in the Duration field, including discussion. The default duration is 30 minutes.

Please note neither FOSDEM nor the Retrocomputing DevRoom will reimburse any expenses you incur Recording of talks The FOSDEM organizers plan to have live streaming and recording fully working, both for remote/later viewing of talks, and so that people can watch streams in the hallways when rooms are full. This requires speakers to consent to being recorded and streamed. If you plan to be a speaker, please understand that by doing so you implicitly give consent for your talk to be recorded and streamed. The recordings will be published under the same license as all FOSDEM content (CC-BY). Contact The Retrocomputing DevRoom is managed by Pau Garcia Quiles (retrocomputing-devroom-manager@fosdem.org). A mailing list of speakers, audience and the curious is available, please subscribe at https://lists.fosdem.org/listinfo/retrocomputing-devroom Hope to hear from you soon! And please forward this announcement.

Here s my weekly report for week 41 of 2017. In this week I have explored some Java 8 features, looked at automatic updates in a few Linux distributions and decided that actually I don t need swap anymore.

Debian The issue that was preventing the migration of the Tasktools Packaging Team s mailing list from Alioth to Savannah has now been resolved. Ana s chkservice package that I sponsored last week has been ACCEPTED into unstable and since MIGRATED to testing.

Tor Project I have produced a patch for the Tor Project website to update links to the Onionoo documentation now this has moved (#23802 ). I ve updated the Debian and Ubuntu relay configuration instructions to use systemctl instead of service where appropriate (#23048 ). When a Tor relay is less than 2 years old, an alert will now appear on Atlas to link to the new relay lifecycle blog post (#23767 ). This should hopefully help new relay operators understand why their relay is not immediately fully loaded but instead it takes some time to ramp up. I have gone through the tickets for Tor Cloud and did not find any tickets that contain any important information that would be useful to someone reviving the project. I have closed out these tickets and the Tor Cloud component no longer has any non-closed tickets (#7763, #8544, #8768, #9064, #9751, #10282, #10637, #11153, #11502, #13391, #14035, #14036, #14073, #15821 ). I ve continued to work on turning the Atlas application into an integrated part of Tor Metrics (#23518 ) and you can see some progress here. Finally, I ve continued hacking on a Twitter bot to tweet factoids about the public Tor network and you can now enjoy some JavaDoc documentation if you d like to learn a little about its internals. I am still waiting for a git repository to be created (#23799 ) but will be publishing the sources shortly after that ticket is actioned.

• Bugs opened: #23799, #23802, #23809, #23830, #23831
• Bugs closed (fixed/wontfix): #7763, #8544, #8768, #9064, #9751, #10282, #10637, #11153, #11502, #13391, #14035, #14036, #14073, #15821, #23048, #23767

Sustainability I believe it is important to be clear not only about the work I have already completed but also about the sustainability of this work into the future. I plan to include a short report on the current sustainability of my work in each weekly report. I have not had any free software related expenses this week. The current funds I have available for equipment, travel and other free software expenses remains 60.52. I do not believe that any hardware I rely on is looking at imminent failure. I d like to thank Digital Ocean for providing me with futher credit for their platform to support my open source work. I do not find it likely that I ll be travelling to Cambridge for the miniDebConf as the train alone would be around 350 and hotel accomodation a further 600 (to include both me and Ana).

Weblate 2.17 has been released today. There are quite some performance improvements, improved search, improved access control settings and various other improvements. Full list of changes:

• Weblate by default does shallow Git clones now.
• Improved performance when updating large translation files.
• Added support for blocking certain emails from registration.
• Users can now delete their own comments.
• Added preview step to search and replace feature.
• Client side persistence of settings in search and upload forms.
• Extended search capabilities.
• More fine grained per project ACL configuration.
• Default value of BASE_DIR has been changed.
• Added two step account removal to prevent accidental removal.
• Project access control settings is now editable.
• Added optional spam protection for suggestions using Akismet.

Update: The bugfix 2.17.1 is out as well, fixing testsuite errors in some setups:

• Fixed running testsuite in some specific situations.
• Locales updates.

If you are upgrading from older version, please follow our upgrading instructions. You can find more information about Weblate on https://weblate.org, the code is hosted on Github. If you are curious how it looks, you can try it out on demo server. You can login there with demo account using demo password or register your own user. Weblate is also being used on https://hosted.weblate.org/ as official translating service for phpMyAdmin, OsmAnd, Turris, FreedomBox, Weblate itself and many other projects. Should you be looking for hosting of translations for your project, I'm happy to host them for you or help with setting it up on your infrastructure. Further development of Weblate would not be possible without people providing donations, thanks to everybody who have helped so far! The roadmap for next release is just being prepared, you can influence this by expressing support for individual issues either by comments or by providing bounty for them.

Filed under: Debian English SUSE Weblate

Dear all, This would be a longish blog post (as most of mine are) compiled over days but as there is so short a time and so much to share. I had previously thought to share beautiful photographs of Ganesh mandals taking out the procession at time of immersion of the idol or the last day of Durga Puja recent events around do not make my mood to share photos at this point in time. I may share some of them in a future blog post or two . Before going further, I would like to offer my sympathies and condolences to people hurt and dislocated in Hurricane Irma , the 2017 Central Mexico Earthquake and lastly the most recent Las Vegas shooting as well as Hurricane Maria in Puerto Rico . I am somewhat nonplussed as to why Americans always want to name, especially hurricanes which destroy people s lives and livelihood built over generations and why most of the hurricanes are named after women. A look at weather.com site unveiled the answer to the mystery. Ironically (or not) I saw some of the best science coverage about Earthquakes or anything scientific reporting and analysis after a long time in mainstream newspapers in India. On another note, I don t understand or even expect to understand why the gunman did what he did 2 days back. Country music AFAIK is one of the most chilled-out kind of music, in some ways very similar to classical Indian singing although they are worlds apart in style of singing, renditions, artists, the way they emote etc. I seriously wish that the gunman had not been shot but caught and reasons were sought about what he did, he did. While this is certainly armchair thinking as was not at the scene of crime, but if a Mumbai Police constable could do it around a decade ago armed only with a lathi could do it, why couldn t the American cops who probably are trained in innumerable ways to subdue people without killing them, did. While investigations are on, I suspect if he were caught just like Ajmal Kasab was caught then lot of revelations might have come up. From what is known, the gentleman was upwardly mobile i.e. he was white, rich and apparently had no reason to have beef with anybody especially a crowd swaying to some nice music, all of which makes absolutely no sense. Indian Economy Slowdown Anyways, back to one of the main reasons of writing this blog post. Few days back, an ex-finance Minister of India Yashwant Sinha wrote what was felt by probably millions of Indians, an Indian Express article called I need to speak up now While there have been many, many arguments made since then by various people. A simple search of I need to speak up would lead to lead to many a result besides the one I have shared above. The only exception I have with the article is the line Forty leading companies of the country are already facing bankruptcy proceedings. Many more are likely to follow suit. I would not bore you but you ask any entrepreneur trying to set up shop in India i.e. ones who actually go through the processes of getting all the licenses for setting up even a small businesses as to the numerous hurdles they have to overcome and laid-back corrupt bureaucracy which they have to overcome. I could have interviewed some of my friends who had the conviction and the courage to set up shop and spent more than half a decade getting all the necessary licenses and approval to set up but it probably would be too specific for one industry or the other and would lead to the same result. Co-incidentally, a new restaurant, leaf opened in my vicinity few weeks before. From the looks it looked like a high-brow, high-priced restaurant hence like many others I did not venture in. After a few days, they introduced south-Indian delicacies like Masala Dosa, Uttapam at prices similar to other restaurants around. So I ventured in and bought some south Indian food to consume between mum and me. Few days later, I became friends with the owner/franchisee and I suggested (in a friendly tone) that why he doesn t make it like a CCD play where many people including yours truly use the service to share, strategize and meet with clients. The CCD joints usually serve coffee and snacks (which are over-priced but still run out pretty fast) but people come as they have chilled-out atmosphere and Wi-Fi access which people need for their smartphones, although the Wi-Fi part may soon become redundant With Reliance Jio making a big play. I also shared why he doesn t add more variety and time (the south Indian items are time-limited) as I see/saw many empty chairs there. Anyways, the shop-owner/franchisee shared his gross costs including salary, stocking, electricity, rent and it doesn t pan out to be serving Rs.80/- dish (roughly a 1US dollar and 25 cents) then serving INR Rs. 400/- a dish (around 6 $USD). One round of INR 400/- + dishes make his costs for the day, around 12 tables were there. It s when they have two full rounds of dishes costing INR 400/- or more that he actually has profits and he is predicting loss for at least 6 months to a year before he makes a rebound. He needs steady customers rather than just walk-ins that will make his business work/click. Currently his family is bearing the costs. He didn t mention the taxes although I know apart from GST there are still some local body taxes that they will have to pay and comply with. There are a multitude of problems for shutting a shop legally as well as they have to again renavigate the bureaucracy for the same. I have seen more than a few retailers downing their shutters for 6-8 months and then either sell it to new management, let go of the lease or simply sell the property to a competitor. The Insolvency and Bankruptcy Code is probably the first proper exit policy for large companies. So the 40 odd companies that Mr. Sinha were talking about were probably sick for a long time. In India, there is also an additional shame of being a failed entrepreneur unlike in the west where Entrepreneurs start on their next venture. As seen from Retailing In India only 3.3% of the population or at the most 4% of the population is directly or indirectly linked with the retail trade. Most of the economy still derives its wealth from the agrarian sector which is still reeling under the pressure from demonetization which happened last year. Al jazeera surprisingly portrayed a truer picture of the effects demonetization had on common citizen than many Indian newspapers did at the time. Because of the South African Debconf, I had to resort to debit cards and hence was able to escape standing in long lines in which many an old and women perished. It is only yesterday that the Government has acknowledged which many prominent Indians have been saying for months now, that we are in a slowdown . Be aware of the terms being used for effect by the Prime Minister. There are two articles which outlines the troubles India is in atm. The only bright spot has been e-commerce which so far has eluded GST although the Govt. has claimed regulations to put it in check. Indian Education System Interestingly, Ravish Kumar has started a series on NDTV where he is showcasing how Indian education sector, especially public colleges have been left to teachers on contract basis, see the first four episodes on NDTV channel starting with the first one I have shared as a hyperlink. I apologize as the series is in Hindi as the channel is meant for Indians and is mostly limited to Northern areas of the Country (mostly) although he has been honest that it is because they lack resources to tackle the amount of information flowing to them. Ravish started the series with sharing information about the U.S. where the things are similar with some teachers needing to sleep in cars because of high-cost of living to some needing to turn to sex-work . I was shocked when I read the guardian article, that is no way to treat our teachers.I went on to read How the American University was Killed following the breadcrumbs along the way. Reading that it seems Indians have been following the American system playbook from the 1980 s itself. The article talks about HMO as well and that seems to have followed here as well with my own experience of hospital fees and drugs which I had to entail a few weeks/month ago. Few years ago, when me and some of my friends had the teaching bug and we started teaching in a nearby municipal school, couple of teachers had shared that they were doing 2-3 jobs to make ends meet. I don t know about others in my group, at least I was cynical because I thought all the teachers were permanent and they make good money only to realize now that the person was probably speaking the truth. When you have to do three jobs to make ends meet from where do you bring the passion to teach young people and that too outside the syllabus ? Also, with this new knowledge in hindsight, I take back all my comments I made last year and the year before for the pathetic education being put up by the State. With teachers being paid pathetically/underpaid and almost 60% teachers being ad-hoc/adjunct teachers they have to find ways to have some sense of security. Most teachers are bachelors as they are poor and cannot offer any security (either male or female) and for women, after marriage it actually makes no sense for them to continue in this profession. I salute all the professors who are ad-hoc in nature and probably will never get a permanent position in their life. I think in some way, thanx to him, that the government has chosen to give 7th pay commisson salary to teachers. While the numbers may appear be large, there are a lot of questions as to how many people will actually get paid. There needs to be lot of vacancies which need to be filled quickly but don t see any solution in the next 2-3 years as well. The Government has taken a position to use/re-hire retired teachers rather than have new young teachers as an unwritten policy. In this Digital India context how are retired teachers supposed to understand and then pass on digital concepts is beyond me when at few teacher trainings I have seen they lack even the most basic knowledge that I learnt at least a decade or two ago, the difference is that vast. I just don t know what to say to that. My own experience with my own mother who had pretty good education in her time and probably would have made a fine business-woman if she knew that she will have a child that she would have to raise by herself alone (along with maternal grand-parents) is testimonial to the fact how hard it is for older people to grasp technology and here I m talking just using the interface as a consumer rather than a producer or someone in-between who has the idea of how companies and governments profit from whatever data is shared one way or the other. After watching the series/episodes and discussing the issue with my mother it was revealed that both her and my late maternal grandfather were on casual/ad-hoc basis till 20-25 years in their service in the defense sector. If Ravish were to do a series on the defense sector he probably would find the same thing there. To add to that, the defense sector is a vital component to a country s security. If 60% of the defense staff in all defense establishments have temporary staff how do you ensure the loyalty of the people working therein. That brings to my mind Ignorance is bliss . Software development and deployment There is another worry that all are skirting around, the present dispensation/government s mantra is minimum government-maximum governance with digital technologies having all solutions which is leading to massive unemployment. Also from most of the stories/incidents I read in the newspapers, mainstream media and elsewhere it seems most software deployments done in India are done without having any system of internal checks and balances. There is no lintian for software to be implemented. Contracts seem to be given to big companies and there is no mention of what prerequisites or conditions were laid down by the Government for software development and deployment and if any checks were done to ensure that the software being developed was in according to government specifications or not. Ideally this should all be in public domain so that questions can be asked and responsibility fixed if things go haywire, as currently they do not. Software issues As my health been not that great, I have been taking a bit more time and depth while filing bugs. #877638 is a good example. I suspect though that part of the problem might be that mate has moved to gtk3 while guake still has gtk-2 bindings. I also reported the issue upstream both in mate-panel as well as guake . I haven t received any response from either or/and upstreams . I also have been fiddling around with gdb to better understand the tool so I can exploit/use this tool in a better way. There are some commands within the gdb interface which seem to be interesting and hopefully I ll try how the commands perform over days, weeks to a month. I hope we see more action on the mate-panel/guake bug as well as move of guake to gtk+3 but that what seemingly seemed like wait for eternity seems to have done by somebody in last couple of days. As shared in the ticket there are lots of things still to do but it seems the heavy lifting has been done but seems merging will be tricky as two developers have been trying to update to gtk+3 although aichingm seems to have a leg up with his 3! branch. Another interesting thing I saw is the below picture. The firefox version I was using to test the site/wordpress-wp-admin was Mozilla Firefox 52.4.0 which AFAIK is a pretty recentish one and people using Debian stretch would probably be using the same version (firefox stable/LTS) rather than the more recent versions. I went to the link it linked to and it gave no indication as to why it thought my browser is out-of-date and what functionality was/is missing. I have found that wordpress support has declined quite a bit and people don t seem to use the forums as much as they used to before. I also filed a few bugs for qalculate. #877716 where a supposedly transitional package removes the actual application, #877717 as the software has moved its repo. to github.com as well as tickets and other things in process and lastly #877733. I had been searching for a calculator which can do currency calculations on the fly (say for e.g. doing personal budgeting for Taiwan debconf) without needing to manually enter the conversion rates and losing something in the middle. While the current version has support for some limited currencies, the new versions promise more as other people probably have more diverse needs for currency conversions (people who do long or short on oil, stocks overseas is just one example, I am sure there are many others) than simplistic mine.
Filed under: Miscellenous Tagged: #American Education System, #bug-filing, #Climate change, #Dignity, #e-commerce, #gtk+3, #gtk2, #Indian Economy 'Slowdown', #Indian Education System, #Insolvency and Bankruptcy Code, #Las Vegas shooting, #Modern Retail in India, #planet-debian, #qalculate, Ad-hoc and Adjunct Professors, wordpress.com

Often, when I mention how things work in the interactive theorem prover [Isabelle/HOL] (in the following just Isabelle ¹) to people with a strong background in functional programming (whether that means Haskell or Coq or something else), I cause confusion, especially around the issue of what is a function, are function total and what is the business with undefined. In this blog post, I want to explain some these issues, aimed at functional programmers or type theoreticians. Note that this is not meant to be a tutorial; I will not explain how to do these things, and will focus on what they mean.

HOL is a logic of total functions If I have a Isabelle function f :: a b between two types a and b (the function arrow in Isabelle is , not ), then by definition of what it means to be a function in HOL whenever I have a value x :: a, then the expression f x (i.e. f applied to x) is a value of type b. Therefore, and without exception, every Isabelle function is total. In particular, it cannot be that f x does not exist for some x :: a. This is a first difference from Haskell, which does have partial functions like

spin :: Maybe Integer -> Bool
spin (Just n) = spin (Just (n+1))

Here, neither the expression spin Nothing nor the expression spin (Just 42) produce a value of type Bool: The former raises an exception ( incomplete pattern match ), the latter does not terminate. Confusingly, though, both expressions have type Bool. Because every function is total, this confusion cannot arise in Isabelle: If an expression e has type t, then it is a value of type t. This trait is shared with other total systems, including Coq. Did you notice the emphasis I put on the word is here, and how I deliberately did not write evaluates to or returns ? This is because of another big source for confusion:

Isabelle functions do not compute We (i.e., functional programmers) stole the word function from mathematics and repurposed it². But the word function , in the context of Isabelle, refers to the mathematical concept of a function, and it helps to keep that in mind. What is the difference?

• A function a b in functional programming is an algorithm that, given a value of type a, calculates (returns, evaluates to) a value of type b.
• A function a b in math (or Isabelle) associates with each value of type a a value of type b.

For example, the following is a perfectly valid function definition in math (and HOL), but could not be a function in the programming sense:

definition foo :: "(nat   real)   real" where
  "foo seq = (if convergent seq then lim seq else 0)"

This assigns a real number to every sequence, but it does not compute it in any useful sense. From this it follows that

Isabelle functions are specified, not defined Consider this function definition:

fun plus :: "nat   nat   nat"  where
   "plus 0       m = m"
   "plus (Suc n) m = Suc (plus n m)"

To a functional programmer, this reads

plus is a function that analyses its first argument. If that is 0, then it returns the second argument. Otherwise, it calls itself with the predecessor of the first argument and increases the result by one.

which is clearly a description of a computation. But to Isabelle, the above reads

plus is a binary function on natural numbers, and it satisfies the following two equations:

And in fact, it is not so much Isabelle that reads it this way, but rather the fun command, which is external to the Isabelle logic. The fun command analyses the given equations, constructs a non-recursive definition of plus under the hood, passes that to Isabelle and then proves that the given equations hold for plus. One interesting consequence of this is that different specifications can lead to the same functions. In fact, if we would define plus' by recursing on the second argument, we d obtain the the same function (i.e. plus = plus' is a theorem, and there would be no way of telling the two apart).

Termination is a property of specifications, not functions Because a function does not evaluate, it does not make sense to ask if it terminates. The question of termination arises before the function is defined: The fun command can only construct plus in a way that the equations hold if it passes a termination check very much like Fixpoint in Coq. But while the termination check of Fixpoint in Coq is a deep part of the basic logic, in Isabelle it is simply something that this particular command requires for its internal machinery to go through. At no point does a termination proof of the function exist as a theorem inside the logic. And other commands may have other means of defining a function that do not even require such a termination argument! For example, a function specification that is tail-recursive can be turned in to a function, even without a termination proof: The following definition describes a higher-order function that iterates its first argument f on the second argument x until it finds a fixpoint. It is completely polymorphic (the single quote in 'a indicates that this is a type variable):

partial_function (tailrec)
  fixpoint :: "('a   'a)   'a   'a"
where
  "fixpoint f x = (if f x = x then x else fixpoint f (f x))"

We can work with this definition just fine. For example, if we instantiate f with ( x. x-1), we can prove that it will always return 0:

lemma "fixpoint (  n . n - 1) (n::nat) = 0"
  by (induction n) (auto simp add: fixpoint.simps)

Similarly, if we have a function that works within the option monad (i.e. Maybe in Haskell), its specification can always be turned into a function without an explicit termination proof here one that calculates the Collatz sequence:

partial_function (option) collatz :: "nat   nat list option"
 where "collatz n =
        (if n = 1 then Some [n]
         else if even n
           then do   ns <- collatz (n div 2);    Some (n # ns)  
           else do   ns <- collatz (3 * n + 1);  Some (n # ns) )"

Note that lists in Isabelle are finite (like in Coq, unlike in Haskell), so this function returns a list only if the collatz sequence eventually reaches 1. I expect these definitions to make a Coq user very uneasy. How can fixpoint be a total function? What is fixpoint ( n. n+1)? What if we run collatz n for a n where the Collatz sequence does not reach 1?³ We will come back to that question after a little detour

HOL is a logic of non-empty types Another big difference between Isabelle and Coq is that in Isabelle, every type is inhabited. Just like the totality of functions, this is a very fundamental fact about what HOL defines to be a type. Isabelle gets away with that design because in Isabelle, we do not use types for propositions (like we do in Coq), so we do not need empty types to denote false propositions. This design has an important consequence: It allows the existence of a polymorphic expression that inhabits any type, namely

undefined :: 'a

The naming of this term alone has caused a great deal of confusion for Isabelle beginners, or in communication with users of different systems, so I implore you to not read too much into the name. In fact, you will have a better time if you think of it as arbitrary or, even better, unknown. Since undefined can be instantiated at any type, we can instantiate it for example at bool, and we can observe an important fact: undefined is not an extra value besides the usual ones . It is simply some value of that type, which is demonstrated in the following lemma:

lemma "undefined = True   undefined = False" by auto

In fact, if the type has only one value (such as the unit type), then we know the value of undefined for sure:

lemma "undefined = ()" by auto

It is very handy to be able to produce an expression of any type, as we will see as follows

Partial functions are just underspecified functions For example, it allows us to translate incomplete function specifications. Consider this definition, Isabelle s equivalent of Haskell s partial fromJust function:

fun fromSome :: "'a option   'a" where
  "fromSome (Some x) = x"

This definition is accepted by fun (albeit with a warning), and the generated function fromSome behaves exactly as specified: when applied to Some x, it is x. The term fromSome None is also a value of type 'a, we just do not know which one it is, as the specification does not address that. So fromSome None behaves just like undefined above, i.e. we can prove

lemma "fromSome None = False   fromSome None = True" by auto

Here is a small exercise for you: Can you come up with an explanation for the following lemma:

fun constOrId :: "bool   bool" where
  "constOrId True = True"
lemma "constOrId = ( _.True)   constOrId = ( x. x)"
  by (metis (full_types) constOrId.simps)

Overall, this behavior makes sense if we remember that function definitions in Isabelle are not really definitions, but rather specifications. And a partial function definition is simply a underspecification. The resulting function is simply any function hat fulfills the specification, and the two lemmas above underline that observation.

Nonterminating functions are also just underspecified Let us return to the puzzle posed by fixpoint above. Clearly, the function seen as a functional program is not total: When passed the argument ( n. n + 1) or ( b. b) it will loop forever trying to find a fixed point. But Isabelle functions are not functional programs, and the definitions are just specifications. What does the specification say about the case when f has no fixed-point? It states that the equation fixpoint f x = fixpoint f (f x) holds. And this equation has a solution, for example fixpoint f _ = undefined. Or more concretely: The specification of the fixpoint function states that fixpoint ( b. b) True = fixpoint ( b. b) False has to hold, but it does not specify which particular value (True or False) it should denote any is fine.

Not all function specifications are ok At this point you might wonder: Can I just specify any equations for a function f and get a function out of that? But rest assured: That is not the case. For example, no Isabelle command allows you define a function bogus :: () nat with the equation bogus () = Suc (bogus ()), because this equation does not have a solution. We can actually prove that such a function cannot exist:

lemma no_bogus: "  bogus. bogus () = Suc (bogus ())" by simp

(Of course, not_bogus () = not_bogus () is just fine )

You cannot reason about partiality in Isabelle We have seen that there are many ways to define functions that one might consider partial . Given a function, can we prove that it is not partial in that sense? Unfortunately, but unavoidably, no: Since undefined is not a separate, recognizable value, but rather simply an unknown one, there is no way of stating that A function result is not specified . Here is an example that demonstrates this: Two partial functions (one with not all cases specified, the other one with a self-referential specification) are indistinguishable from the total variant:

fun partial1 :: "bool   unit" where
  "partial1 True = ()"
partial_function (tailrec) partial2 :: "bool   unit" where
  "partial2 b = partial2 b"
fun total :: "bool   unit" where
  "total True = ()"
  "total False = ()"
lemma "partial1 = total   partial2 = total" by auto

If you really do want to reason about partiality of functional programs in Isabelle, you should consider implementing them not as plain HOL functions, but rather use HOLCF, where you can give equational specifications of functional programs and obtain continuous functions between domains. In that setting, () and partial2 = total. We have done that to verify some of HLint s equations.

You can still compute with Isabelle functions I hope by this point, I have not scared away anyone who wants to use Isabelle for functional programming, and in fact, you can use it for that. If the equations that you pass to fun are a reasonable definition for a function (in the programming sense), then these equations, used as rewriting rules, will allow you to compute that function quite like you would in Coq or Haskell. Moreover, Isabelle supports code extraction: You can take the equations of your Isabelle functions and have them expored into Ocaml, Haskell, Scala or Standard ML. See Concon for a conference management system with confidentially verified in Isabelle. While these usually are the equations you defined the function with, they don't have to: You can declare other proved equations to be used for code extraction, e.g. to refine your elegant definitions to performant ones. Like with code extraction from Coq to, say, Haskell, the adequacy of the translations rests on a moral reasoning foundation. Unlike extraction from Coq, where you have an (unformalized) guarantee that the resulting Haskell code is terminating, you do not get that guarantee from Isabelle. Conversely, this allows you do reason about and extract non-terminating programs, like fixpoint, which is not possible in Coq. There is currently ongoing work about verified code generation, where the code equations are reflected into a deep embedding of HOL in Isabelle that would allow explicit termination proofs.

Conclusion We have seen how in Isabelle, every function is total. Function declarations have equations, but these do not define the function in an computational sense, but rather specify them. Because in HOL, there are no empty types, many specifications that appear partial (incomplete patterns, non-terminating recursion) have solutions in the space of total functions. Partiality in the specification is no longer visible in the final product.

PS: Axiom undefined in Coq This section is speculative, and an invitation for discussion. Coq already distinguishes between types used in programs (Set) and types used in proofs Prop. Could Coq ensure that every t : Set is non-empty? I imagine this would require additional checks in the Inductive command, similar to the checks that the Isabelle command datatype has to perform⁴, and it would disallow Empty_set. If so, then it would be sound to add the following axiom

Axiom undefined : forall (a : Set), a.

wouldn't it? This axiom does not have any computational meaning, but that seems to be ok for optional Coq axioms, like classical reasoning or function extensionality. With this in place, how much of what I describe above about function definitions in Isabelle could now be done soundly in Coq. Certainly pattern matches would not have to be complete and could sport an implicit case _ undefined. Would it help with non-obviously terminating functions? Would it allow a Coq command Tailrecursive that accepts any tailrecursive function without a termination check?

---

1. Isabelle is a metalogical framework, and other logics, e.g. Isabelle/ZF, behave differently. For the purpose of this blog post, I always mean Isabelle/HOL.
2. Isabelle is a metalogical framework, and other logics, e.g. Isabelle/ZF, behave differently. For the purpose of this blog post, I always mean Isabelle/HOL.
3. Let me know if you find such an n. Besides n = 0.
4. Like fun, the constructions by datatype are not part of the logic, but create a type definition from more primitive notions that is isomorphic to the specified data type.

It feels like the past week or two has been very busy, and so I'm looking forward to my "holiday" next month. I'm not really having a holiday of course, my wife is slowly returning to work, so I'll be taking a month of paternity leave, taking sole care of Oiva for the month of November. He's still a little angel, and now that he's reached 10 months old he's starting to get much more mobile - he's on the verge of walking, but not quite there yet. Mostly that means he wants you to hold his hands so that he can stand up, swaying back and forth before the inevitable collapse. Beyond spending most of my evenings taking care of him, from the moment I return from work to his bedtime (around 7:30PM), I've made the Debian Administration website both read-only and much simpler. In the past that site was powered by a lot of servers, I think around 11. Now it has only a small number of machines, which should slowly decrease. I've ripped out the database host, the redis host, the events-server, the planet-machine, the email-box, etc. Now we have a much simpler setup:

• Front-end machine
  • Directly serves the code site
  • Directly serves the SSL site which exists solely for Let's Encrypt
  • Runs HAProxy to route the rest of the requests to the cluster.
• 4 x Apache servers
  • Each one has a (read-only) MySQL database on it for the content.
    • In case of future-compromise I removed all user passwords, and scrambled the email-addresses.
    • I don't think there's a huge risk, but better safe than sorry.
  • Each one runs the web-application.
    • Which now caches each generated page to /tmp/x/x/x/x/$hash if it doesn't exist.
    • If the request is cached it is served from that cache rather than dynamically.

Finally although I'm slowly making progress with "radio stuff" I've knocked up a simple hack which uses an ultrasonic sensor to determine whether I'm sat in front of my (home) PC. If I am everything is good. If I'm absent the music is stopped and the screen locked. Kinda neat. (Simple ESP8266 device wired to the sensor. When the state changes a message is posted to Mosquitto, where a listener reacts to the change(s).) Oh, not final. I've also transfered my mobile phone from DNA.fi to MoiMobile. Which should complete soon, right now my phone is in limbo, active on niether service. Oops.