ENCRYPTION DEVICE, ENCRYPTION SYSTEM, ENCRYPTION METHOD AND ENCRYPTION PROGRAM

摘要

The objective of the present invention is to make encrypted communication possible even if encryption keys for a one-time pad cipher (Vernam cipher) are insufficient. A one-time pad encryption unit encrypts communication data by way of a one-time pad cipher to generate encrypted data, using portions of a one-time pad encryption key stored in a one-time pad encryption key storage unit in order. A block encryption unit encrypts the communication data by way of a block cipher to generate encrypted data using a block encryption key stored in a block encryption key storage unit. An encryption control unit controls whether to encrypt the communication data with the one-time pad encryption unit or to encrypt with the block encryption unit depending upon the remaining number of bits of the one-time pad encryption key stored in the one-time pad encryption key storage unit.