Secure partial secret key issuing in Certificateless Public Key Infrastructure

Despite many advantages of Identity-based Public Key Cryptography (ID-PKC) in removing the certificates of public key over traditional Public Key Infrastructure (PKI), there are some problems related to key escrow property and the need for a secure channel to transmit the private key to the user. A Certificateless Public Key Cryptography (CL-PKC) retains the efficiency of ID-PKC while it solves the key escrow problem and does not need a certificate. The requirement of the infrastructure of the CL-PKC is to transmit the partial key to the user. Therefore, a partial key issuing mechanism is needed to deliver the partial key to the user through a secure channel. In this paper, a new algorithm for partial private key transmission is proposed which uses a simple blinding technique and user chosen secret value to eliminate secure channel problem. The proposed scheme is secure under the hardness assumption of Diffie-Hellman problem.