UMAC (cryptography)

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In cryptography, a universal hashing message authentication code, or UMAC, is a message authentication code (MAC) calculated using universal hashing, which involves choosing a hash function from a class of hash functions according to some secret (random) process and applying it to the message. The resulting digest or fingerprint is then encrypted to hide the identity of the hash function that was used. A variation of the scheme was first published in 1999.^[1] As with any MAC, it may be used to simultaneously verify both the data integrity and the authenticity of a message. In contrast to traditional MACs, which are serializable, a UMAC can be executed in parallel. Thus, as machines continue to offer more parallel-processing capabilities, the speed of implementing UMAC can increase.^[1]

A specific type of UMAC, also commonly referred to just as "UMAC", is described in an informational RFC published as RFC 4418 in March 2006. It has provable cryptographic strength and is usually substantially less computationally intensive than other MACs. UMAC's design is optimized for 32-bit architectures with SIMD support, with a performance of 1 CPU cycle per byte (cpb) with SIMD and 2 cpb without SIMD. A closely related variant of UMAC that is optimized for 64-bit architectures is given by VMAC, which was submitted to the IETF as a draft in April 2007 (draft-krovetz-vmac-01) but never gathered enough attention to be approved as an RFC.