Do You Know The Difference Between HMAC and CMAC?

If you’re into cybersecurity or secure software development, do you know the difference between an HMAC and a CMAC?

HMAC

HMAC is a message authentication code (MAC) that can be used to verify the integrity and authentication of a message. It involves hashing a message with a secret key and thus differs from standard hashing, which is purely a one-way function. As with any MAC, it can be used with a standard hash function, such as MD5 or SHA-1, which results in methods such as HMAC-MD5 or HMAC-SHA-1. Also, as with any hashing function, the strength depends on the quality of the hashing function, and the resulting number of hash code bits. Along with this, the number of bits in the secret key is a factor in the strength of the hash.

The figure below outlines the operation, where the message to be sent is converted with a secret key and the hashing function to an HMAC code. This is then sent with the message. On receipt, the receiver recalculates the HMAC code from the same secret key and the message and checks it against the received version. If they match, it validates both the sender and the message.