Abstract: 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.

Abstract: The invention provides an apparatus for generating a plurality of sub-keys from a primary key comprising a plurality of data words. The apparatus comprises a shift register for storing the primary key; and a transformation apparatus arranged to perform one or more logical operations on respective data words from the shift register to produce a new data word. The arrangement is such that the new data word is loaded into the shift register, whereupon one of the data words stored in said shift register is shifted out of the shift register, the sub-keys being comprised of one or more of the output data words. The apparatus is particularly suitable for on-the-fly Rijndael decryption Round key calculation. In this context, the invention obviates the need to store the expanded key or to wait until the expanded key is generated from the cipher key before beginning decryption. This removes a latency of at least 10 clock cycles in the operation of the decryption apparatus.

Abstract: One aspect of the invention provides an apparatus for selectably encrypting or decrypting data, the apparatus being arranged to receive a control signal for selecting between encryption and decryption. The apparatus comprises at least one data processing module arranged to perform one or more data encryption or data decryption operations depending on the setting of said control signal, wherein at least part of said data processing module comprises one or more programmable Look-up Tables (LUTs). The apparatus further comprises at least one storage device for storing a first set and a second set of LUT values, the apparatus being arranged to program some or all of said LUTs with said first set of LUT values when said control signal is set to encrypt, and to program some or all of said LUTs with said second set of LUT values when said control signal is set to decrypt. In the preferred embodiment, the apparatus is arranged to implement the Advanced Encryption Standard, or Rijndael, cipher.

Abstract: One aspect of the invention provides a computer useable product co-operable with a circuit synthesis tool for generating a data encryption and apparatus for encrypting a block of plaintext data using a cipher key to produce a block of encrypted data. The product provides a first parameter, programmable by a user, the value of which determines the length of the cipher key. The product is arranged to cause the apparatus to implement a number of encryption rounds, the number of rounds depending on the value of the first parameter. The computer useable product further includes means for implementing a key schedule module for generating, from the cipher key, a number of round keys for use in respective encryption rounds, the number of generated round keys depending on the value of the first parameter. The product preferably takes the form of one or more blocks of HDL (Hardware Description Language) code.

Abstract: A data encryption or decryption apparatus for encrypting or decrypting blocks of data. The apparatus includes a data processing pipeline having at least two pipelined data processing modules each arranged to perform an encryption or decryption operation, in conjunction with a respective sub-key. The apparatus further includes a sub-key generating module for generating a respective sub-key for each data processing module and a sub-key skewing module arranged to provide each sub-key to its respective data processing module. The arrangement is such that the sub-key skewing module synchronises the provision of each sub-key to its respective data processing module with the passage of a data block through the data processing pipeline so that the data block is encrypted or decrypted using sub-keys generated from a common primary key. The apparatus is particularly suitable for use in the implementation of the Data Encryption Standard (DES).