[tor-dev] Post-quantum proposals #269 and #270

[lukep at tutanota.com]

Great to see the community making progress with post-quantum handshakes.
But I'm wondering what's going to happen with Proposals #269 and #270. #269 seems to allow any post-quantum algorithm to be used in the hybrid with NTRUEncrypt and NewHope being specified as two options (presumably other options like SIDH or Mceliece could also be used). #270 is more specific, a hybrid of x25519 and NewHope. NewHope seems to be in the lead but do we want to rule others - so a flexible proposal like #269 might be better. #269 and #270 look as if they would not be compatible with each other so what's the process for deciding between them?

Also see https://eprint.iacr.org/2016/717.pdf, a comparison of attacks on NTRU. It doesn't break NTRU but it does break (some versions of) YASHE which is a FHE scheme based on NTRUEncrypt. In the conclusion it recommends transforming NTRU-like algorithms into ring-LWE like algorithms, and dismissing the former since they are known to be weaker. I still think a flexible protocol rather than all eggs in the NewHope basket is a Good Thing.

-- lukep
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