Secret crytptographic key is split to reduce work factor

摘要

PROBLEM TO BE SOLVED: To obtain a ciphering system capable of safe communication by deciding a first partial key by means of an authorized person or a corporation and supplying information for enabling the decoding of a ciphered message by means of the acquirement of the first partial key. SOLUTION: The secret key is a random number and is generated at every message in ST10 so as to cipher the message in ST12. The one-way hash of the secret key is generated in ST14 in order to facilitate a suitable section work quantity system. The secret key and a salt are ciphered through the use of the open key of a prescribed receiver. The secret key is divided into at least two partial keys in ST18 so as to permit the authorized person or the corporation to decode the message. The partial keys, the hashed and the whole or a part of solts are ciphered by using the open key in ST20. The ciphered value is transmitted to the receiver together with the ciphered message and the ciphering secret key in ST22. The receiver decodes the ciphering secret key where the secret key is used in ST24.