CRYPTOGRAPHIC SYSTEM USING TRIPLE ENCIPHERMENT

摘要

CRYPTOGRAPHIC SYSTEM USING MULTIPLE ENCIPHERMENT Multiple encipherment under the DES algorithm is performed in three steps as an encipher/ decipher/ encipher sequence that gives the increased security of a longer key. The steps each use one of two keys of conventional length. When the two keys are the same, the operation is identical to a single encipherment under one key, and input quantities thus enciphered can be sent to a cryptographic facility that has only a single encipherment capability. The invention maintains compatability between users of multiple encipherment devices and users of single encipherment devices. The invention is particularly useful for enciphering keys and a detailed method and apparatus for this application is described.