4 ms·
Few thoughts - why MD5 in the example at all? I thought that SHA-2 was the go to for hash functions nowadays. And a question on the timing attack - how real it
by venomsnake 13y ago
Few thoughts - why MD5 in the example at all? I thought that SHA-2 was the go to for hash functions nowadays.
And a question on the timing attack - how real it is? Because in the response time you have a lot of random variables which with the current fast servers will take more time than the calculation itself.
You receive request - how fast it will go trough the loadbalancer is random, then you must read the shared secret, then you must log the request somewhere and the whole hmac calculation is milisecond or less.
- StavrosK 13y agoWith thousands of tries, you can apparently average the noise out pretty effectively, so timing attacks are very possible.
- Dylan16807 13y agoState of the art multiple years ago was 100ns over LAN (aka datacenter). It's something to worry about. Honestly, I'd be extra paranoid and use a construct that hashes the supplied digest an extra time on top of doing a timing-safe comparison.
- tptacek 13y agoSHA2 has the same problems.
- ReidZB 13y agoTo be more accurate, SHA-224, SHA-512/384, and SHA-512/256 don't suffer from length extension attacks. The rest of the SHA2 family (256 and 512) do. Of course, SHA-256 and SHA-512 are more popular than their truncated variants...
- wglb 13y agoSo if the attacker can make a million attempts, don't you think that if the hmac calculation has the most variance of all the other moving parts, that it wont give up the secret?