Encryption/decryption unit and storage medium

摘要

An encryption/decryption unit includes a first data encryption/decryption section (11) for performing an encryption or decryption process, a first data substitution section (12) for performing data substitution of an output from the first encryption/decryption section according to a predetermined permutation table, a second data encryption/decryption section (13) for performing an encryption or decryption process for an output from the first data substitution section, a second data substitution section (14) for performing data substitution of an output from the second data encryption/decryption section according to a predetermined permutation table, and a third data encryption/decryption section (15) for performing an encryption or decryption process for an output from the second data substitution section.