Patent ID: 8085933

Claim:
A cipher system for encrypting plaintext into ciphertext in an encryption direction and for decrypting ciphertext into plaintext in a decryption direction, the cipher system comprising: a cipher; a processor; a first diffuser that, when executed on the processor, provides a first type of diffusion in the encryption direction, wherein, in the first type of diffusion, a change to an input to the first diffuser produces a change to an output from the first diffuser that is larger than the change to the input to the first diffuser; and a second diffuser that, when executed on the processor, provides a second type of diffusion in the encryption direction, wherein, in the second type of diffusion, a change to an input to the second diffuser produces a change to an output from the second diffuser that is smaller than the change to the input to the second diffuser, wherein the first diffuser is provided with input data that is based on plaintext xorred with a sector key, the sector key is derived from a key that comprises a number of bits, the sector key employs a first portion of the number of bits, and the cipher employs a second portion of the number of bits, wherein the second diffuser receives first diffused data from the first diffuser and provides second diffused data to the cipher, and wherein the cipher encrypts the second diffused data into ciphertext.