cryptography - HMAC security - Is the security of the HMAC based on SHA-1 affected by the collisions attacks on SHA-1? -

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is security of hmac based on sha-1 affected collisions attacks on sha-1?

the security implications of hmac described in detail in security section of the rfc. in nutshell, strong attack indeed required before security of hmac threatened; existing collision attacks on sha-1 don't constitute such. hmac designed make attacks difficult, , ordinary collision attacks won't suffice:

the security of message authentication mechanism presented here depends on cryptographic properties of hash function h: resistance collision finding (limited case initial value secret , random, , output of function not explicitly available attacker), , message authentication property of compression function of h when applied single blocks (in hmac these blocks partially unknown attacker contain result of inner h computation and, in particular, cannot chosen attacker).

i recommend reading whole section; goes more detail attacks would suffice break hmac, , how effort required.


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