[tor-bugs] #25576 [Core Tor/Tor]: Fix non-standard use of keccak in v3 hidden service code

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#25576: Fix non-standard use of keccak in v3 hidden service code
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 Reporter:  isis                                 |          Owner:  (none)
     Type:  defect                               |         Status:  new
 Priority:  Medium                               |      Milestone:  Tor:
                                                 |  unspecified
Component:  Core Tor/Tor                         |        Version:  Tor:
                                                 |  0.3.0.1-alpha
 Severity:  Normal                               |     Resolution:
 Keywords:  cryptography, crypto, tor-hs,        |  Actual Points:
  handshakes                                     |
Parent ID:                                       |         Points:
 Reviewer:                                       |        Sponsor:
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Comment (by cypherpunks):

 Although it is a non-standard use and KMAC is better for Keccak, an HMAC
 not using a Merkle-Damgård hash in this case is not a big deal, according
 to [https://crypto.stackexchange.com/questions/15782/how-secure-would-
 hmac-sha3-be Cryptography] on StackExchange:

 >Thus, the claimed security level of HMAC-SHA3 is the same as the overall
 maximum attainable security level for HMAC, or any other deterministic
 iterated MAC construction, with the same effective internal state size.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/25576#comment:1>
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