Study On The System Of Signcryption

The confidentiality and authentication of the message are the two basic require-ments in secure communication. In the traditional communication process, we achievethem by signature followed by encryption, but the communication cost is relatively highin this way. YuLiang Zheng first proposed the concept of digital signcryption in 1997 ,signcryption as a new cryptographic primitive that simultaneously fulfills both the func-tions of digital signature and public key encryption in a logically single step, and withits computational cost and message expansion rate significantly lower than that requiredby the traditional signature followed by encryption. Therefore, signcryption has broadapplication prospect such as key management, e-cash payment, privacy election etc.In this dissertation, we study further about the construction and security analysisof the signcryption schemes, furthermore, we propose a special scheme by applying theconcept of certificateless public key to blind idea. The results obtained are outlined asfollowed three aspects:(1) We have made improvement to the Hill cryptosystem based on the study of ergodicmatrix and general inverse eigen-problem for matrix , then presented a new Hillcryptosystem with the digital signature function, making the classical Hill cryp-tosystem has the characteristics of signcryption. we described the process of paperdetailedly. And also in this paper, we realized the key exchange protocols based onthe ergodic matrix, which can avoid the re?ex attack. It makes the classic cryp-tosystem developed and applyed more and more.(2) The security of a certificateless signcryption scheme is analyzed,which includes con-fidentiality and unforgeability. It is shown that the it is insecure. It can not resistthe attack of the two types of adversary.In this paper,the course of our attacks weredescribed in detail.(3) Motivated by Baek ???? ????.'s pairing-free certificateless encryption schemes, we pro-posed a pairing-free CLBSC scheme, which is by applying the concept of certificate-less public key to blind idea, and it is more e?cient than all the previous construc- tion.