Galois/Counter Mode Advanced Encryption Standard authenticated encrypted messaging with pre-calculation of round keys

摘要

The Galois/Counter Mode Advanced Encryption Standard (GCM-AES) standard is used for sending encrypted messages with message authentication codes (MAC). The encryption and MAC hashing processes involve multiple rounds, each of which uses a round key derived from an initialising key. The GCM-AES standard proposes creating these keys on the fly to minimise memory requirements. The invention pre-generates and stores B34/B the round keys for the GHASH authentication process B32/B using the AES engine B31/B. This reduces the number of operations that must be performed during the en/decryption cycle.