ENCRYPTION DEVICE, DECRYPTION DEVICE, ENCRYPTION METHOD, DECRYPTION METHOD, AND COMPUTER PROGRAM

摘要

Disclosed is an encryption device that, without introducing a state variable or increasing random number length, can increase performance in information leakage prevention relating to plaintext when there has been a random number collision. The encryption device is provided with: a random number generation unit that generates random numbers; a first encryption unit that generates an intermediate ciphertext by performing either equal-length encryption or additive encryption on plaintext that has been input; a second encryption unit that generates a ciphertext by performing the processing that was not performed by the aforementioned first encryption unit from among equal-length encryption or additive encryption on the aforementioned intermediate ciphertext; and a ciphertext output unit that outputs the aforementioned ciphertext and the random number used in the aforementioned additive encryption.