[tor-bugs] #8897 [Tor]: Faster curve25519 implementation for ntor

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#8897: Faster curve25519 implementation for ntor
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 Reporter:  nickm                                |          Owner:  nickm
     Type:  enhancement                          |         Status:
 Priority:  Medium                               |  needs_revision
Component:  Tor                                  |      Milestone:  Tor:
 Severity:  Normal                               |  unspecified
 Keywords:  tor-relay, performance, ntor,        |        Version:
  026-triaged-0, 027-triaged-1-in, pre028-patch  |     Resolution:
Parent ID:  #9662                                |  Actual Points:
  Sponsor:                                       |         Points:  large
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Comment (by yawning):

 So, some researchers went and did an AVX2 Curve25519 implementation.

 http://link.springer.com/chapter/10.1007/978-3-319-22174-8_18?no-
 access=true (Paywall)

 Having read the paper, when they say "slight" they mean it (a few percent
 over djb's amd64 assembly), and their code isn't available.  Their work
 should be applicable to AVX512 but since that's still Xeon only even with
 Skylake, I'm inclined to also leave this to a "if we get really desperate"
 sort of thing.

 (Key generation gets more of a boost, but we already have faster code
 there.)

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/8897#comment:28>
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