Data encryption/decryption apparatus

摘要

The present invention concerns in particular the efficient implementation of encryption or decryption rounds of data encryption algorithms, particularly the Rijndael Block Cipher. The invention provides an apparatus for encrypting or decrypting a data block, the apparatus comprising a transformation module and a plurality of shift registers each comprising a sequence of data registers through which data components are shifted in successive operational cycles. At least some of the data registers are associated with a respective selector switch, the setting of which determines whether the associated data register is loaded with a data component from a data register in its respective shift register or with a transformed data component corresponding to its respective shift register. The provision of shift registers and switches affords a significant saving in circuit area. Further, the invention requires a relatively low number of switches (e.g. multiplexers) in the computational data paths and this allows a relatively high throughput to be achieved.