SECRET KEY GENERATING METHOD, CIPHERING METHOD, AND CIPHERED COMMUNICATION METHOD

摘要

PROBLEM TO BE SOLVED: To provide a ciphered communication method with ID-NIKS, which is robust to a random-number substitution attack and an extended loop attack. SOLUTION: A center 1 uses specific information (ID information) of respective entities and asymmetrical matrixes which are obtained by dividing a secret symmetrical matrix and unique to the entities, and random-number vectors which correspond to the asymmetrical matrixes and unique to the entities to generate secret keys unique to the entities by the asymmetrical matrixes and send them to the respective entities. At this time, the sum of those random- number vectors is not a zero vector. Each entity generates a common key which is needed for ciphering and deciphering by using an (n)-nomial theorem (n>=3) using its unique secret key and an open key based upon the specific information (ID information) on the opposite side and the sum of the weight of the open key.