Patent ID: 8265273

Claim:
An encryption circuit which generates encrypted text from plain text using a key, said encryption device comprising: a random number generation circuit which generates a random number; a randomized input data generation circuit which receives the plain text, and generates randomized input data that is obtained by adding, to input data that is obtained by performing predetermined processing on the plain text using the key, a predetermined input mask value determined depending on the random number; a first randomized inverse element data generation circuit which receives the randomized input data generated by said randomized input data generation circuit and the input mask value, and generates randomized output data that is obtained by adding, to an inverse element of the input data in a predetermined first finite field, an output mask value that is an inverse element of the received input mask value in the first finite field; and an output data processing circuit which receives the randomized output data generated by said first randomized inverse element data generation circuit, and generates the encrypted text from the received randomized output data.