| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a method by which, at the time of encrypting a plaintext, the head block of a cypher text is prevented from being used for a key to a cryptanalysis thereof, and the plaintext and the cypher text are identical in their length. <P>SOLUTION: An encryption device 10 derives an exchange block number m indicating a block number of a block to be interchanged with a head block from a common key K by a predetermined algorithm, and interchanges a head block (P1) in a plaintext (P1, ..., Pn) with a plaintext block (Pm) corresponding to the exchange block number m prior to the encryption of the plaintext (P1, ..., Pn). <P>COPYRIGHT: (C)2013,JPO&INPIT |
