2
votes
1answer
152 views

CMAC vs HMAC security strength

From the perspective of a Birthday Paradox attack, isn't it true that CMAC based on AES-128 is weaker than HMAC-SHA-1? The attack on CMAC-AES-128 requires about $2^{64}$ operations whereas the same ...
10
votes
1answer
579 views

Security of N bit HMAC

Lets say that I am using 128 bit HMAC. How many operations are needed to find a "non secure" message. Is a birthday attack possible?