Patent ID: 7783037

Claim:
A system adapted to perform the Rijndael inverse cipher, comprising: a security processor comprising: a forward key schedule component adapted to receive a cipher key and compute a last Nk round keys for a sequence of blocks of ciphertext; an inverse key schedule component operatively coupled to the forward key schedule component and adapted to utilize the last Nk round keys of the forward key schedule component to generate a sequence of round keys of an inverse key schedule at appropriate clock cycles and repeatedly for respective Nb-word blocks for the sequence of blocks of ciphertext; and an inverse cipher component operatively coupled to the inverse key schedule component which computes repeatedly for respective Nb-word blocks using the round keys to produce a sequence of blocks of plaintext from the sequence of blocks of ciphertext, the forward key schedule component locked upon receipt of a cipher key and unlocked after the last Nk round keys have been computed; and memory configured to store plaintext output from the inverse cipher component.