Patent ID: 6985582
Filing Date: 2006-01-10
Classification: H04L

Abstract:
1. An encryption/decryption unit for encrypting a plaintext into a ciphertext and/or decrypting a ciphertext into a plaintext, comprising: first encryption/decryption means for performing an encryption or decryption process; first substitution means for performing data substitution of an output from said first encryption/decryption means according to a predetermined permutation table; second encryption/decryption means for performing an encryption or decryption process for an output from said first substitution means; second substitution means for performing data substitution of an output from said second encryption/decryption means according to a predetermined permutation table; third encryption/decryption means for performing an encryption or decryption process for an output from said second substitution means; key generating means for generating intermediate keys respectively supplied to said first, second, and third encryption/decryption means and said first and second substitution means; and said first and second substitution means functioning to perform identity conversion when the intermediate key generated by said key generating means contains predetermined data; wherein said key generating means comprises: dividing means for dividing key data K of a predetermined number of bits into a plurality of data and storing the divided data into respective register; expanded permutation means for reading out the divided key data from the respective registers and effecting an expanded permutation on the divided key data; DES-SS key schedule means for generating intermediate keys K DES key schedule means for generating an intermediate key K substitution schedule means for generating intermediate keys KK