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Also, you shouldn't use a different hash algorithm for HMAC than for other hashing, because that increases the amount of security-critical code you have, which
by a1369209993 8y ago
Also, you shouldn't use a different hash algorithm for HMAC than for other hashing, because that increases the amount of security-critical code you have, which directly increases the chance that there's a bug in your security-critical code.
- tptacek 8y agoIt's pretty unlikely that you're going to have a bug in your SHA1 and SHA2 cores, for whatever that's worth to you. Virtually nobody implements them by hand.
- kbwt 8y agoAnecdotally I know of one very popular application that has a bug in their SHA-1 implementation causing it to effectively only perform a single round.
- wolf550e 8y agoWould that make it only interoperable with itself, and not have the security a correct implementation of SHA1 provides? Is it a security bug (i.e. is there anything worth stealing by breaking their not-quite-SHA1-hash)?
- kbwt 8y agoThe application is using a proprietary client/server protocol, so it already lacks lacks any kind of interoperability. In this specific case, it's unclear whether the bug has direct security implications. The broken SHA-1 is used on some user-controlled data that gets XORed onto the server's decryption of a user-specified payload before being passed into an RC4 key schedule. It's certainly plausible that this might produce a server-assisted privacy compromise of other users' sessions.