Method and apparatus for blockwise encryption with each encryption round controlled by an internal state

摘要

An encryption apparatus is constituted by a plurality of rungs of round functions. Each round function (8) comprises internal state storing means (2) for storing an internal state, internal state updating means (3) for updating the internal state stored in the storing means (2), and an F-function (1) for executing an encryption upon receipt of data to be encrypted, an encryption key, and the internal state stored in the internal state storing means (2). The internal state stored in the internal state storing means (2) is updated by the internal state updating means (3) every time the encryption is executed by the F-function (1).