tor/changes/replay-firstpart

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o Minor features (security):
- Check for replays of the public-key encrypted portion of an
INTRODUCE1 cell, in addition to the current check for replays of
the g^x value. This prevents a possible class of active attacks
by an attacker who controls both an introduction point and a
rendezvous point, and who uses the malleability of AES-CTR to
alter the encrypted g^x portion of the INTRODUCE1 cell. We
think that these attacks is infeasible (requiring the attacker
to send on the order of zettabytes of altered cells in a short
interval), but we'd rather block them off in case there are any
classes of this attack that we missed. Reported by dvorak.