Study And Design On Some Kinds Of Proxy Signature Schemes

Delegation of signing right is a common issue in real life. Proxy signature which is actually a special kind of digital signature provides a solution to such an issue. In this thesis, we discuss some classical proxy signatures and analyze their security in details. Several new proxy signature schemes are proposed. The major contributions of the paper are as follows:1. Strong forward security concept is introduced due to the problem of "afterward security" in forward secure signature schemes. A formal definition of strong forward secure proxy signature is given by combining strong forward security and proxy signature. Based on the definition and different proxy secret key generation protocols, two kinds of strong forward secure signature schemes are constructed, which meet the properties of strong forward secure proxy signatures.2. A proxy blind signature scheme based on the variation of DSA blind signature is proposed. A new multi-proxy blind multi-signature is designed with a combination of multi-proxy multi-signature and proxy blind signature based on the variation of DSA blind signature as well. The new schemes satisfy the basic properties of proxy signature and blind signature.3. Non-designated proxy signature proposed by Lee et al is not secure because the original signer can forge proxy signatures on behalf of the proxy signer. Thus, strong unforgeability can't be achieved. For this reason, this paper gives an improved scheme which solves the security problem of the original one. Then the improved scheme may be applied to mobile agent which ensures the secure transactions in a hostile environment.