[tor-dev] [proposal] Post-Quantum Secure Hybrid Handshake Based on NewHope
yawning at schwanenlied.me
Thu May 19 18:40:25 UTC 2016
On Thu, 19 May 2016 17:21:47 +0000
Deirdre Connolly <durumcrustulum at gmail.com> wrote:
> Not sure if this has been noted before on this thread, but the
> BoringSSL team is working on something very similar:
Skimming the code:
* The protocol level stuff is not useful at all because the sort of
problems that need to be solved (or changes) with the Tor
wire protocol for any sort of PQ handshake are rather different than
"just adding another TLS key exchange mechanism".
* Their hybrid construct is unauthenticated (handled separately by TLS,
with a signature), and is `X25519SharedSecret | NHSharedSecret`,
passed into a KDF.
* They have their own special snowflake newhope variant (The code is
based on the `ref` version, with Google copyrights bolted on top),
functional changes are:
* CTR-AES128 instead of SHAKE is used to sample `a` (same
algorithm, doesn't have the sampling optimization or attempt to
hide the rejection sampling timing variation).
* SHA256 is used instead of SHA3-256 to generate `mu` from `nu`.
* RAND_bytes() is called for noise sampling instead of using
ChaCha20 or CTR-AES256.
I don't find these changes to be particularly interesting. Any
system where using AES-CTR like this makes sense will benefit more
from using a vectorized NTT/reconciliation.
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