A new efficient strong proxy signcryption scheme based on a combination of hard problems

Proxy signcryption scheme is the combination of proxy signature and encryption. In this paper we propose a new proxy signcryption scheme which has the following advantages as compared to the previous schemes: (1) It is based on a combination of hard problems: integer factorization problem (IFP), discrete logarithm problem (DLP), Diffie-Hellman problem (DHP), and irreversibility of a one-way hash function (OWHF). This combination achieves a strong security level. (2) It provides non-repudiation and public verifiability for both the original signcrypter and the proxy signcrypter. (3) It provides forward secrecy. (4) It provides proxy-protection against the original signcrypter. (5) It doesn´t require a secure channel between the original signcrypter and the proxy signcrypter. (6) With all these advantages the proposed scheme is efficient.