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What does the author mean about timing attacks on HMACs with Array.equals? Does HMAC leak info and is it subject to timing attacks if you HMAC on both sides bef
by _asummers 9y ago
What does the author mean about timing attacks on HMACs with Array.equals? Does HMAC leak info and is it subject to timing attacks if you HMAC on both sides before doing equality checks? Does he mean for e.g. session cookies?
- spydum 9y agohttps://codahale.com/a-lesson-in-timing-attacks/ https://codahale.com/a-lesson-in-timing-attacks/
- _asummers 9y agoSo okay, if you're using HMAC where the user can provide the HMAC, this would be an issue (like session cookies), but it the user can only provide preimage (as in e.g. encrypting database column and wanting lookup) then this wouldn't be an issue, I don't think.
- bitexploder 9y agoYes. In situations where a hash is modifiable by the user and you do string comparison the issue exists. It isn't solely a problem for MACs.