Ciphered message converting device for use in cryptographic system, has message establishing unit producing deciphered message from auxiliary message, and difference between ciphered message and result of conversion of auxiliary message

摘要

The device has a key establishing unit (14) establishing an auxiliary public key that combines with a private key to form keys of an asymmetric encryption system. Message difference establishing unit (16) creates a difference between a ciphered message and a result of conversion of an auxiliary message using the public key. A message establishing unit (18) produces a deciphered message from the difference and the auxiliary message. Independent claims are also included for the following: (A) a message converting process (B) a computer program having program codes for executing a message converting method.