Researches On Threshold Proxy Signature Schemes And Multi-level Proxy Signature Schemes

Digital signature is an important component part of the Cryptography, It guarantees the information integrity, authenticity and undeniability. According to the different backgrounds, a variety of special digital signatures have been proposed. Digital signatures are applied more deep and extensively.In this paper, we processed a detailed study on threshold proxy signature, proxy multi-signature, multi-level proxy signature. The main work as followings:We carry out an in-depth study on "Cryptanalysis and improvement of nonrepudiable threshold multi-proxy multi-signature scheme with shared verification" which was proposed by Hsu et al. We find two problems, (1) In the proxy signature generation phase, the scheme would leak secret when it is encountered conspiracy attack; (2) In the proxy signature verification phase, assume that at least t out of n verifiers conspire the secret polynomial, anyone of the t verifiers can check the validity of the proxy signature by himself with no help of other verifiers in the next verification. To solve the two problems, an improvement scheme is proposed.A multi-level proxy signature scheme based on discrete logarithm is proposed. We study on the proxy multi-signature and multi-level proxy signature, construct a multi-level proxy signature scheme based on discrete logarithm, and extend to multi-level multi-proxy multi-signature scheme. It is more extensive.A multi-level proxy signature scheme based on Elliptic Curve is proposed. Compared with digital signature based on discrete logarithm and digital signature based on large integer factoring, digital signature based on Elliptic Curve is smaller storage space occupancy, smaller amount of computation and faster processing speed, lower bandwidth requirements higher efficiency. So we apply the method of multi-level multi-proxy multi-signature on Elliptic Curve signature. It made the advantages of the scheme more prominent.