Abstract: To solve the problems of authenticating the user's identity and distributing the user's private keys in the identity-based encryption(IBE) system, a new scheme for both identity authentication and private key distribution is proposed as a reinforcement for IBE by smartly using the concept of public-key certificate. A trusted third party is employed to transfer trust, and an additional public key is used to set up the secure channel for transmitting the private key. Not only is the number of authentications needed decreased significantly, but the private key distribution problem which has never been dealt with in the original scheme and relating applications is addressed in the new scheme. Based on IBE, we also propose an encryption scheme which has one public key with two corresponding private keys. Both of the private keys can be used for decryption, one of which is escrowed to a trusted third party, the other for non-repudiation signature.

Key words: identity-based encryption, identity authentication, key distribution