Research On Identity-based Signcryption Scheme

Signcryption is a technology that combined of encryption and signature, this technology not only achieve the confidentiality of encryption, but also provide unforgeability and non-repudiation of signature algorithm. Comparing with the traditional method ‘first signature then encryption algorithm’, signcryption saves the memory space of system and greatly enhance the computational efficiency, its an ideal choice of the network environment who need meet the requirements of confidentiality and authentication. Multi-signcryption is a special type of signcryption which the number of signcrypters is more than one, it can be used to this case that a message needs to be signed then encrypted before transport in network environment. Generalized signcryption has flexible features, it can achieve signature, encryption and signcryption in a single cryptographic module.The main contributions of this thesis include:(1) There are two security risks be found in an efficient and secure identity-based multi-signcryption scheme in standard model: 1) Private key of user can be forged by any unauthorized person who pretend the PKG; 2)The ciphertext information of multi-signcryption can also be forged by unauthorized people. It gives the proof of the existence of these two security risks.(2) To propose an efficient identity-based multi-signcryption scheme in standard mode, then prove the security in standard model, analyze the computational efficiency of the new scheme,compare with proposed schemes which has high computational efficiency, when the number of signcrypters is nn)1((29), the new scheme reduce by n-1 exponentiation.(3) To propose a new identity-based generalized signcryption program. Prove the security of this scheme from all aspects, then compare the algorithm with proposed schemes which has high computational efficiency. The results show that, the new scheme reduce the numbers of computation of the pairing and scalar multiplication. Present an application example of the scheme,and describe the process of applying the program in mail system.