Improvement and security analysis about signcryption scheme in electronic commerce

Firstly , the paper presents the advantage of digital signcryption over the traditional signature+encryption method , and describes the four sub-algorithms which compose the digital signcryption scheme.Secondly , it briefly introduces the mathematical basis of the digital signcryption , reviews several existing identity-based digital signcryption schemes under the standard model.It analyses the security of the digital signcryption scheme designed by Yu , and points out that it is insecure when it is attacked by select ciphertext.Thirdly , it gives an improved digital signcryption scheme , and respectively analyses the digital signcryption scheme consisting of four sub-algorithms-the system establish algorithm , the key extraction algorithm , the digital signcryption algorithm and the unsigncryption algorithm.The scheme's security is briefly described through the two aspects of unforgeability under adaptive select message and ciphertext indistinguishability under select ciphertext attack.Finally , the paper compares the efficiency of the improved scheme with other schemes , concluding that the improved scheme is superior at ciphertext size etc , then puts forward plans for future research.