Patent ID: 8218762

Claim:
An encrypting apparatus for performing an encryption process of a common key cipher, the encrypting apparatus comprising: a random number generation device configured to generate a random number; a first route selection device configured to re-array a data string including a plurality of pieces of data and composed of a plurality of extended key mask values for masking extended keys, at random in units of piece of data according to a value of the random number and to output the data string; an extended key operation device configured to generate an exclusive logical OR of a plurality of extended key mask values outputted from the first route selection device, a data string representing the extended keys and an input data string; a second route selection device configured to re-array a data string of the exclusive logical OR including a plurality of pieces of data by performing re-array conversely with the first route selection device in units of piece of data according to the value of the random number and to output the data string; a plurality of non-linear conversion circuits configured to receive the plurality of pieces of data of the data string outputted from the second route selection device, the number of the plurality of non-linear conversion circuits being equal to the number of the plurality of pieces of data, to apply non-linear conversion to the plurality of pieces of data, and to output a data string masked by a plurality of non-linear conversion mask values; and a third route selection device configured to re-array the data string outputted from the plurality of non-linear conversion circuits by performing the same re-array as the first route selection device in units of piece of data according to the value of the random number and to output the data string.