A new proxy signature scheme based on dual complexities

The vogue of Internet, makes the changes of the people´ s style. Security is one of the key elements of the development of Internet. Digital certification can take the place of identification and verification in virtual world constructed by computer network. MAMBO, USUDA, and OKAMOTO are the pioneers in the research of proxy signature and brings digital signature into a new direction. The original signer can authorize the proxy signers to act as agent via proxy signature scheme without leaking his/her private key. Most of the proposed scheme usually emphasize on the factuality of proxy signature. Some researchers take warrants to enhance the security of proxy signature scheme. The agent may sign many times after one legal authorization until the origin signer changed his/her password or grant periods. The others may need a secure channel to transmit parameters and it decrease practicability. This paper proposes a new proxy signature scheme that can set the grant period without using a warrant or a secure channel. Our scheme is based on the complexity of the discrete logarithm. We also make use of Denning´s time stamp technology to solve the problem of the illegal using of proxy signature by illegal user.