Patent ID: 8526602
Filing Date: 2013-09-03
Classification: H04L

Abstract:
1. An adjustment-value-attached block cipher apparatus, comprising: a computer processor; an encryption section performing encryption by using a block cipher system; an input section accepting plaintext, an adjustment value and instruction information which indicates a first cipher processing operation or a second cipher processing operation; and a generation section using the computer processor to divide the adjustment value into a first adjustment value and into a second adjustment value, encrypt the first adjustment value using the encryption section to generate a cipher for offset, determine an offset value on the basis of the cipher for offset and the second adjustment value, determine the sum of the offset value and the plaintext, and encrypt the sum using the encryption section to generate a first ciphertext when the instruction information indicates the first cipher processing operation, and encrypt the plaintext using the encryption section to generate second ciphertext when the instruction information indicates the second cipher processing operation; wherein the generation section fixes the least significant bit of the first adjustment value to 0 and fixes the least significant bit of the plaintext used in the second cipher processing to 1 so that the first adjustment value is different from the plaintext used in the second cipher processing operation.