Hi, I have a question regarding the comparison of key fingerprints in the context of TextSecure. According to [1] TextSecure offers the ability for two users to compare fingerprints of their identity key out of band to detect a man in the middle attack. I was wondering why the prekey which was used to start the session is not part of the fingerprint? If the identity key of a user is compromised, prekeys on the server could be replaced with forged ones by an attacker who possesses the complete identity key. The comparison of identity key fingerprints would not be able to detect this. Including the prekey during key comparison would ensure that users know for sure that―even in the presence of compromised identity keys―no one posed as a man in the middle. Am I missing something obvious?
Many thanks in advance for your answers! --- [1] "How secure is TextSecure" [https://eprint.iacr.org/2014/904.pdf] _______________________________________________ Messaging mailing list [email protected] https://moderncrypto.org/mailman/listinfo/messaging
