(A) study on ID-based cryptosystem and key distribution system using different informations

Abstract

In a large-scale communication network, key management is a serious problem in the case where there are many users in the system. The private-key and public-key cryptosystem have difficulties in key management. The concept of an ID_based cryptosystem has been proposed by Shamir as the countermeasure for key management. Tanaka and Tsujii, Itoh have proposed realization schemes of ID_based cryptosystem which are threshold type, that is, if some users conspire, then the system can be insecure. To prevent conspiracy of users, we propose an ID_based cryptosystem using different secret informations for each user and each user``s additional public information which cannot be forged. We also present an ID_based key distribution system similar to the ID_based cryptosystem, and its improved system. The key distribution system has almost the same security as in the case of cryptosystem, and do not require even user``s public additional information.