[tor-dev] RFC-ish: basket2 (aka obfs5)

Yawning Angel yawning at schwanenlied.me
Thu May 12 10:57:43 UTC 2016


So I've been somewhat productive as of late and have been working on
the successor to obfs4.  I have a "oh my god, you wrote how much code,
with no documentation" minimum-viable-product-ish release that appears
to work, though ABSOLUTELY NO ONE SHOULD USE IT YET, because I will
break bridge line/protocol wire compatibility intentionally at least
once before release.

The code: https://git.schwanenlied.me/yawning/basket2 (Really, don't
use it, at all.  I will ignore cries of help, mercilessly mock people
that attempt to chase a moving target, and laugh as I break things).

The documentation: Hahahahahahahahahahahahahahaha (It should be self

A brief overview of the improvements:

 * Client can now negotiate the link padding/delay algorithm at
   handshake time with the server (no more `iat-mode=blah` argument),
   and defaults to something which injects delay.

 * Link cryptography changed to a XChaCha20/Poly1305 construct, with
   AVX2 used for the ChaCha20 when available, and the framing construct
   it self is a lot better designed.

 * Handshake is X25519 + NewHope or X448 + NewHope based (available
   algorithms specified as part of the bridge line), with X25519
   (Elligator2) for authentication.

 * SHA-3/SHAKE are used as the handshake routines.

 * When adding IAT on a burst basis, the code attempts to detect bulk
   data transfer resulting in less delay for large downloads/uploads.

 * Server side buffering reduced by 50% (not sure if that'll stick, I
   need to think about some of this stuff).


 * Implement a "expensive" padding option for bridges that can afford
   to run such a thing. (WTF-Pad, CS-BuFlo, or Tamaraw, not sure yet.
   WTF-Pad is a bit harder to implement than I'd like...)

 * Improve the lightweight padding algorithms instead of using
   what is essentially the same as obfs

 * Finish support for user authentication.

 * Write a formal specification.

 * Debug, debug, debug.

 * Write an AVX2 Poly1305 so it goes faster on boxes that matter (my

 * (Maybe) Write NEON and 32 bit x86 assembly optimized versions of the
   custom crypto, so it runs faster on various low end shit boxes.
   NEON is more important to me than 32 bit Intel (and a low end Atom
   does ChaCha20 at 40 MiB/s or so anyway...).

Anyway, this is sort of a heads up that something like this is in the
works, and is approaching alpha state, though DID I MENTION NOT TO USE

Questions/Comments/Feedback welcome as always.


Yawning Angel
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 819 bytes
Desc: OpenPGP digital signature
URL: <http://lists.torproject.org/pipermail/tor-dev/attachments/20160512/796a9ad3/attachment.sig>

More information about the tor-dev mailing list