Two Proxy Signature Schemes With Additional Properties

A digital signature scheme is analogous to the traditional handwriting signature. Since it achieves unforgeability, integrity and non-repudiation, digital signature plays an important role in E-commerce and E-government. With the development of the digital signature, recently a large number of digital signatures with additional properties have appeared (e.g. blind signature, identity-based signature, threshold signature, group signature, multi-signature and proxy signature). The main goal of the thesis is to study blind proxy multi-signature. This new kind of signature could overcome the limitation that a blind proxy signature could not be on behalf of more than one original signer, the security and efficiency are analyzed as well.Recently forward security has received a significant attention and has been extensively researched in the cryptographic community. A forward secure proxy blind signature scheme is proposed combining the concept of forward secure with proxy blind signature. By introducing the mechanism of key evolving, even if the malicious attacker can intrude the system at some period, he can not forge the proxy blind signature in the precious periods. The author prove that the scheme satisfies the security of general proxy blind signature schemes and forward security.