[tor-bugs] #18221 [Tor]: Validate our DH parameters to prevent socat-type fails.

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#18221: Validate our DH parameters to prevent socat-type fails.
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 Reporter:  yawning          |          Owner:
     Type:  enhancement      |         Status:  needs_review
 Priority:  Medium           |      Milestone:  Tor: 0.2.8.x-final
Component:  Tor              |        Version:  Tor: unspecified
 Severity:  Normal           |     Resolution:
 Keywords:  tor-core crypto  |  Actual Points:
Parent ID:                   |         Points:
  Sponsor:                   |
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Comment (by bugzilla):

 > TAP handshake
 It's not ephemeral and has one IIRC "key" for all HSes, or not?
 > less likely
 If an adversary could make a fallback in TLS session, then it'd be
 seamless for the user.
 > Use P-256
 It's not so good as it seems. 256-bit PK is theoretically strong as
 128-bit AES key, but 112-bit can be broken, and the same for 128-bit in
 the near future. And what's then? Urgently disable P-256 fallback from
 P-384?

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/18221#comment:8>
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