[tor-dev] Comments on proposal 224 updates
desnacked at riseup.net
Thu Apr 14 10:39:07 UTC 2016
Nick Mathewson <nickm at torproject.org> writes:
> [ text/plain ]
> I'm behind on this! But let me comment on the stuff that got merged recently.
Thanks for the comments!
Please see my branch `prop224-fixes-nickm` for the corresponding fixes.
Feel free to merge it in torspec.git if you feel like it, otherwise I can do it
> "prop224: Remove the MAINT_INTRO feature."
> "prop224: Clarify backwards compatibility sections slightly."
> "prop224: Clarify use of shared random values."
> "prop224: Fix undefined variables in the ntor section."
> Looks ok.
> "prop224: Add missing key expansion section for rendezvous crypto."
> KDF-Tor is a legacy algorithm, and we want to get away from SHA1. We
> don't use KDF-Tor with NTOR. Let's kill it for new use. I'd suggest
> HKDF-SHA256 or SHAKE, both of which we have implemented already.
I'm now using our KDF (i.e. SHAKE256) for the key expansion there.
We don't have a salt value to use for that key expansion, but I think that's OK
because NTOR_KEY_SEED is the result of ntor so it should be unique.
I also changed the interface of our KDF to KDF(m,d) to match the interface of SHAKE256(m,d).
> "prop224: In cells, replace TYPE/LEN/KEY with just TYPE/KEY."
> I'm not sure about this change. If we ever add a third key type, all
> of the cells will be unparseable.
> "prop224: Various improvements."
> There's no point in using HKDF with SHAKE; we should just use SHAKE as the KDF.
Fixed in the crypto commit as well.
Let me know if something is not right and I will fix it up.
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