[tor-bugs] #28837 [Core Tor/Tor]: Use openssl's SHA3 implementations when they are faster.

[Tor Bug Tracker & Wiki]

#28837: Use openssl's SHA3 implementations when they are faster.
-------------------------+-------------------------------------------------
     Reporter:  nickm    |      Owner:  (none)
         Type:           |     Status:  new
  enhancement            |
     Priority:  Medium   |  Milestone:  Tor: 0.4.0.x-final
    Component:  Core     |    Version:  Tor: 0.3.4.9
  Tor/Tor                |   Keywords:  android startup performance
     Severity:  Normal   |  controller
Actual Points:           |  Parent ID:  #28481
       Points:  .3       |   Reviewer:
      Sponsor:           |
  Sponsor8-can           |
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 OpenSSL now has sha3 support.  At least some versions have assembly
 implementations of the keccak core function.  That's our signal to update
 crypto_digest.c to use openssl for sha3.

 This matters for startup, since `keccakf()` is about 10% of our startup
 time when we have a cached directory.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/28837>
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