A Practical Key Issuing Scheme in Identity-based Cryptosystem

Secure key issuing in identity-based public key cryptosystems is a challenging task due to the inherent drawback of key escrow and the requirement for secure channel between the private key generator (PKG) and users. In this paper we propose a practical key issuing scheme. User registers at a local registration authority in off-line manner local registration authority signs and delivers authenticated user's information to multiple PKGs in batch manner The master key is generated by PKGs based on secure distributed key generation protocol, which solves the key escrow problem. The secure channel between the user and the PKGs are not needed by using blinding technique. The proposed scheme is more efficient than those of existing key issuing schemes and the security is proved under random oracle model.