Apparatus for implementing a symmetric block ciphering algorithm without the complementation property

摘要

An implementation of a security algorithm such as DES is provided that overcomes the complementarity weaknesses provided by conventional implementations. In a DES implementation, a cryptographic processor (10) applies the DES algorithm to a data block. The DES processor includes a first input port (14) for receiving the data block (X), a second input port (12) for receiving a cryptographic key (K), and an output port (15) for outputting the data block after encryption. A nonlinear function (20, 22, 24) that does not have complementarity is applied to at least one of the ports. The nonlinear function can comprise a lookup table, which could be advantageously derived from a DES S-Box. IMAGE