20 ms·
If you know the HMAC key, why would you ever need to generate a collision? You can just reevaluate the MAC and replace the old one.
by mckiddy 11y ago
If you know the HMAC key, why would you ever need to generate a collision? You can just reevaluate the MAC and replace the old one.
- tptacek 11y agoYup. "This almost certainly doesn’t have any security impact, but I’m happy(ish) to be proved wrong." There's a few words I'd remove from that sentence, I guess.
- sdevlin 11y agoSNARK REDACTED
- tptacek 11y agoSee this kind of snark is usually what gets 'pbsd to come out of the shadows and smack me down. Your turn this time!
- sarciszewski 11y agoI think it's because you're not wrong here. :D
- jessaustin 11y agoI think the point was that if some dumb protocol were misusing HMAC (and I'm not good enough at thinking about protocols to imagine how it might do so), it could be vulnerable to collisions generated this way.
- tptacek 11y agoThe point of the parent commenter is that a misuse of HMAC that gives attackers knowledge of the key admits much simpler attacks than this.