Abstract:

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.

Key words: digital signature;unsigncryption;digital signcryption;security;efficiency