KEY SHARING METHOD, PRIVATE KEY GENERATING METHOD, COMMON KEY GENERATING METHOD, ENCRYPTION COMMUNICATION METHOD, PRIVATE KEY GENERATOR, COMMON KEY GENERATOR, ENCRYPTION COMMUNICATION SYSTEM AND RECORDING MEDIUM

摘要

PROBLEM TO BE SOLVED: To provide a key sharing method by which both entities can easily share a common key without the need for preliminary communication between both the entities and to provide an encryption communication method and system that can build up the secure ID-NIKS (ID-based non-interactive key sharing scheme) by adopting the key sharing method. SOLUTION: A center 1 maps ID information of each entity onto a point on an elliptic curve and generates a private key of each entity by using a public key being a mapped value and private information of the center 1 itself. Each entity generates a common key used for encryption processing/decoding processing by using its own private key received from the center 1 and the public key being the mapped value resulting from the ID information of a communication opposite party mapped on the elliptic curve. In this case, a pairing defined onto the elliptic curve is utilized.