Simon Josefsson: Streamlined NTRU Prime sntrup761 goes to IETF
The OpenSSH project added support for a hybrid Streamlined NTRU Prime post-quantum key encapsulation method
sntrup761 to strengthen their X25519-based default in their version 8.5 released on 2021-03-03. While there has been a lot of talk about post-quantum crypto generally, my impression has been that there has been a slowdown in implementing and deploying them in the past two years. Why is that? Regardless of the answer, we can try to collaboratively change things, and one effort that appears strangely missing are IETF documents for these algorithms.
Building on some earlier work that added X25519/X448 to SSH, writing a similar document was relatively straight-forward once I had spent a day reading OpenSSH and TinySSH source code to understand how it worked. While I am not perfectly happy with how the final key is derived from the sntrup761/X25519 secrets it is a SHA512 call on the concatenated secrets I think the construct deserves to be better documented, to pave the road for increased confidence or better designs. Also, reusing the RFC5656 4 structs makes for a worse specification (one unnecessary normative reference), but probably a simpler implementation. I have published draft-josefsson-ntruprime-ssh-00 here. Credit here goes to Jan Moj of TinySSH that designed the earlier sntrup4591761x25519-sha512@tinyssh.org in 2018, Markus Friedl who added it to OpenSSH in 2019, and Damien Miller that changed it to sntrup761 in 2020. Does anyone have more to add to the history of this work?
Once I had sharpened my xml2rfc skills, preparing a document describing the hybrid construct between the sntrup761 key-encapsulation mechanism and the X25519 key agreement method in a non-SSH fashion was easy. I do not know if this work is useful, but it may serve as a reference for further study. I published draft-josefsson-ntruprime-hybrid-00 here.
Finally, how about a IETF document on the base Streamlined NTRU Prime? Explaining all the details, and especially the math behind it would be a significant effort. I started doing that, but realized it is a subjective call when to stop explaining things. If we can t assume that the reader knows about lattice math, is a document like this the best place to teach it? I settled for the most minimal approach instead, merely giving an introduction to the algorithm, included SageMath and C reference implementations together with test vectors. The IETF audience rarely understands math, so I think it is better to focus on the bits on the wire and the algorithm interfaces. Everything here was created by the Streamlined NTRU Prime team, I merely modified it a bit hoping I didn t break too much. I have now published draft-josefsson-ntruprime-streamlined-00 here.
I maintain the IETF documents on my ietf-ntruprime GitLab page, feel free to open merge requests or raise issues to help improve them.
To have confidence in the code was working properly, I ended up preparing a branch with sntrup761 for the GNU-project Nettle and have submitted it upstream for review. I had the misfortune of having to understand and implement NIST s DRBG-CTR to compute the sntrup761 known-answer tests, and what a mess it is. Why does a deterministic random generator support re-seeding? Why does it support non-full entropy derivation? What s with the key size vs block size confusion? What s with the optional parameters? What s with having multiple algorithm descriptions? Luckily I was able to extract a minimal but working implementation that is easy to read. I can t locate DRBG-CTR test vectors, anyone? Does anyone have sntrup761 test vectors that doesn t use DRBG-CTR? One final reflection on publishing known-answer tests for an algorithm that uses random data: are the test vectors stable over different ways to implement the algorithm? Just consider of some optimization moved one randomness-extraction call before another, then wouldn t the output be different? Are there other ways to verify correctness of implementations?
As always, happy hacking!
I wanted to start using (neo)mutt's sidebar and I wanted a way
of separating groups of mail folders in the list. To achieve
that I interleaved a couple of fake "divider" folder names.
It looks like this:
When I travel for a few days I don t usually
For the soles I may have gone a bit overboard with the vibram claw, but:
As for the finished weight, at 235 g for the pair I thought I could do better, but apparently shoes are considered ultralight if they are around 500 g? Using just one layer of mesh rather than two would probably help, but it would have required a few changes to the pattern, and anyway I don t really to carry them around all day.
I ve also added a loop of fabric (polycotton) to the centre back to be able to hang the slippers to the backpack when wet or dirty; a bit of narrow webbing may have been better, but I didn t have any in my stash.
The 
I hate going out to buy shoes. Even more so I hate buying home shoes, which is what I spend most of my life in, also because no matter what I buy they seem to disintegrate after a season or so. So, obviously, I ve been on a quest to make my own.
As a side note, going barefoot (with socks) would only move the wear issue to the socks, so it s not really a solution, and going bare barefoot on ceramic floors is not going to happen, kaythanksbye.
For the winter I m trying to make knit and felted slippers; I ve had partial success, and they should be pretty easy to mend (I ve just had to do the first mend, with darning and needle felting, and it seems to have worked nicely).
For the summer, I ve been thinking of something sewn, and with the warm season approaching (and the winter slippers needing urgent repairs) I decided it was time to work on them.
I already had a shaped (left/right) pattern for a sole from my hiking sandals attempts (a topic for another post), so I started by drafting a front upper, and then I started to have espadrille feeling and decided that a heel guard was needed.
As for fabric, looking around in the most easily accessible part of the Stash I ve found the nice heavyweight linen I m using for my Augusta Stays, of which I still have a lot and which looked almost perfect except for one small detail: it s very white.
I briefly thought about dyeing, but I wanted to start sewing NOW to test the pattern, so, yeah, maybe it will happen one day, or maybe I ll have patchy dust-grey slippers. If I ll ever have a place where I can do woad dyeing a blue pair will happen, however.
Contrary to the typical espadrillas I decided to have a full lining, and some padding between the lining and the sole, using cotton padding leftovers from my ironing board.
To add some structure I also decided to add a few rows of cording (and thus make the uppers in two layers of fabric), to help prevent everything from collapsing flat.
As for the sole, that s something that is still causing me woes: I do have some rubber sole sheets (see hiking sandals above), but I suspect that they require glueing, which I m not sure would work well with the natural fabric uppers and will probably make repairs harder to do.
In the past I tried to make some crocheted rope soles and they were a big failure: they felt really nice on the foot, but they also self-destroyed in a matter of weeks, which is not really the kind of sole I m looking for.
Now I have some ~ 3 mm twine that feels much harsher on the hands while working it (and would probably feel harsher on the feet, but that s what the lining and padding are for), so I hope it may be a bit more resistant, and I tried to make a braided rope sole.
Of course, I have 
This isn't a book review, although the reason that I am typing this now is
because of a book, You Are Not Alone: from the creator and host of
Griefcast, Cariad Lloyd, ISBN: 978-1526621870 and I include a handful of
quotes from Cariad where there is really no better way of describing things.
Many people experience death for the first time as a child, often relating to a
family pet. Death is universal but every experience of death is unique. One of
the myths of grief is the idea of the Five Stages but this is a
misinterpretation. Denial, Anger, Bargaining, Depression and Acceptance
represent the five stage model of death and have nothing to do with
grief. The five stages were developed from studying those who are
terminally ill, the dying, not those who then grieve for the dead person and
have to go on living without them. Grief is for those who loved the person who
has died and it varies between each of those people just as people vary in how
they love someone. The Five Stages end at the moment of death, grief is what
comes next and most people do not grieve in stages, it can be more like a
tangled knot.
Death has a date and time, so that is why the last stage of the model is
Acceptance. Grief has no timetable, those who grieve will carry that grief for
the rest of their lives. Death starts the process of grief in those who go on
living just as it ends the life of the person who is loved. "Grief eases and
changes and returns but it never disappears.".
I suspect many will have already stopped reading by this point. People do not
talk about death and grief enough and this only adds to the burden of those who
carry their grief. It can be of enormous comfort to those who have carried
grief for some time to talk directly about the dead, not in vague pleasantries
but with specific and strong memories. Find a safe place without distractions
and talk with the person grieving face to face. Name the dead person. Go to
places with strong memories and be there alongside. Talk about the times with
that person before their death. Early on, everything about grief is painful and
sad. It does ease but it remains unpredictable. Closing it away in a box inside
your head (as I did at one point) is like cutting off a damaged limb but
keeping the pain in a box on the shelf. You still miss the limb and eventually,
the box starts leaking.
For me, there were family pets which died but my first job out of university
was to work in hospitals, helping the nurses manage the medication regimen and
providing specialist advice as a pharmacist. It will not be long in that
environment before everyone on the ward gets direct experience of the death of
a person. In some ways, this helped me to separate the process of death from
the process of grief. I cared for these people as patients but these were not
my loved ones. Later, I worked in specialist terminal care units, including
providing potential treatments as part of clinical trials. Here, it was not
expected for any patient to be discharged alive. The more aggressive
chemotherapies had already been tried and had failed, this was about pain
relief, symptom management and helping the loved ones. Palliative care is not
just about the patient, it involves helping the loved ones to accept what is
happening as this provides comfort to the patient by closing the loop.
Grief is stressful. One of the most common 
After my father passed away, I brought home most of the personal items
he had, both at home and at his office. Among many, many (many, many,
many) other things, I brought two of his personal treasures: His photo
collection and a box with the 8mm movies he shot approximately between
1956 and 1989, when he was forced into modernity and got a portable
videocassette recorder.
I have talked with several friends, as I really want to get it all in
a digital format, and while I ve been making slow but steady advances
scanning the photo reels, I was particularly dismayed (even though it
was most expected most personal electronic devices aren t meant to
last over 50 years) to find out the 8mm projector was no longer in
working conditions; the lamp and the fans work, but the spindles won t
spin. Of course, it is quite likely it is easy to fix, but it is
beyond my tinkering abilities and finding photographic equipment
repair shops is no longer easy. Anyway, even if I got it fixed,
filming a movie from a screen, even with a decent camera, is a lousy
way to get it digitized.
But almost by mere chance, I got in contact with my cousin Daniel, ho
came to Mexico to visit his parents, and had precisely brought with
him a 8mm/Super8 movie scanner! It is a much simpler piece of
equipment than I had expected, and while it does present some minor
glitches (i.e. the vertical framing slightly loses alignment over the
course of a medium-length film scanning session, and no adjustment is
possible while the scan is ongoing), this is something
that can be decently fixed in post-processing, and a scanning session
can be split with no ill effects. Anyway, it is quite uncommon a
mid-length (5min) film can be done without interrupting i.e. to join a
splice, mostly given my father didn t just film, but also edited a lot
(this is, it s not just family pictures, but all different kinds of
fiction and documentary work he did).
I acquired some unusual input devices to experiment with, like a CNC control
panel and a bluetooth pedal page turner.
These identify and behave like a keyboard, sending nice and simple keystrokes,
and can be accessed with no drivers or other special software. However, their
keystrokes appear together with keystrokes from normal keyboards, which is the
expected default when plugging in a keyboard, but not what I want in this case.
I'd also like them to be readable via evdev and accessible by my own user.
Here's the udev rule I cooked up to handle this use case: