CIPHER SYSTEM, ENCRYPTION METHOD, DECRYPTION METHOD, AND PROGRAM

摘要

A cipher system according to one embodiment comprises an encryption device which encrypts plaintext into ciphertext, wherein the encryption device is characterized by comprising: a first encryption means which uses a first secret key and generates first information obtained by encrypting the plaintext by means of an encryption function of a prescribed block encryption; a second encryption means which uses a second secret key and generates second information obtained by encrypting a preset adjustment value by means of the encryption function; and a third encryption means which uses the first secret key, and generates the ciphertext obtained by encrypting, by means of the encryption function, a calculation result of exclusive OR for every bit of the first information and the second information.