Cryptanalysis And Design Of Signcryption Scheme

With the rapid development of computer networks, both electronic payme- nt and electronic auction are confronted with an urgent security issue, that is, to efficiently realize the authentication and confidentiality of data transmitted. In 1997, Zheng proposed the concept of the signcryption scheme, a public key cryptographic primitive that can simultaneously provide both digital signature and public key encryption functionalities in a valid single logic step. So signcr- yption schemes efficiently realize the authentication and confidentiality of mes- sages. The signcryption schemes require much smaller computational overheads and lower communication costs than traditional"signature-and-then- encrypti- on"approach.Signcryption schemes are investigated and the contributions of the disserta- tion are listed as follows.(1) A new ID-based signcryption scheme is designed by using the bilinear pairing on elliptic curves. The proposed scheme is robust and can provide confidentiality, unforgeability, non-repudiation protections. In the proposed scheme, upon receiving a signcryption message, the receiver can recover the messaage after verifying its validity. So it can prevent the receiver from hostile profiling efficiently. Compared with the existing ID-based signcryption schemes, the new scheme is more efficient in computational complexity and communicat- ion costs. Hence, the authentic- ation and confidentiality of message is realized efficiently.(2) A cryptanalysis of the nonrepudiable proxy multi-signcryption scheme with public verifiability proposed by Yuanju Gan et al. is provided. Some secur- ity drawbacks have been found. The analysis shows that the signcryption scheme does not satisfy the security requirements such as confidentiality, public verifiability and forward security. An improved scheme was proposed to remedy the security drawbacks existing in Gan et al.'s signcrytpion scheme. In addition, the improvement scheme also has the desired features of robustness and forward security. Analysis illustrates that the modified signcryption scheme is efficient and secure.