Two Digital 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 proxy blind multi-signature. Through the analysis of a scheme presented by Lu, we propose two new efficient schemes, the security and efficiency are analyzed as well.Digital signcryption is a new kind of digital signature which integrates public key encryption and signature simultaneously in a logic step. Now signcryption attracts many cryptologists' interests due to its merits. In the thesis we propose a multi-receiver identity-based proxy signcryption from bilinear pairings. The security and efficiency analysis are also provided.