Construction of Certificateless Proxy Signcryption Scheme From CMGs

As a cryptography primitive for secure data transmission, certificateless proxy signcryption (CLPS) allows an original signcrypter to entrust his signing authority to a proxy signcrypter for signing specified message on his behalf. In this paper, we combine CLPS with cyclic multiplication groups (CMGs) to construct a new certificateless proxy signcryption scheme from CMGs (CMGs-CLPSS). CMGs-CLPSS will receive significant attention because it simplifies the traditional public key cryptosystem (PKC) and solves the key escrow issue suffered by identity-based public key cryptosystem (IB-PKC). In CMGs-CLPSS, an encrypted message can only be decrypted by a designated receiver who is also responsible for verifying the message; moreover, if a later dispute over repudiation occurs, the designated receiver can readily announce ordinary CLPS for public verification without any extra computation effort. CMGs-CLPSS is proved to have the indistinguishability under adaptive chosen-ciphertext attacks (IND-CCA2 security) and existential unforgeability under adaptive chosen-message attacks (UF-CMA security) in the random oracle model. CMGs-CLPSS outperforms the existing schemes on the basis of computational complexity and is suitable for applications in digital contract signing and online proxy auction, and so on.