Patent attributes
A hardware cipher engine encrypts or decrypts a block of input data from a sequence of blocks using a cipher operation where the block of output data depends on the input block's position in the sequence. In a random-access mode of operation, the engine receives a sequence position, receives a block of input data having that position, and outputs a block of output data without outputting data that encrypts, or that decrypts, every block of input data preceding the received position. In some embodiments, the operation is a stream cipher, and the engine generates a sequence of keystream blocks and performs a combining operation between the input block and a keystream block having a corresponding sequence position. In other embodiments, the cipher operation is a block cipher, and the engine generates, but doesn't output, blocks of data that encrypt, or decrypt, one or more blocks preceding the received input block.
