Research On Designed Confirmer Signatures And Proxy Signatures Scheme

With the fast development of the intelcommunication and internet, digital signature plays an important role in information security, identity authentication, data integrality, undeniability and non-repudiation. Designated-receiver signature scheme and proxy signature scheme are two different types of special signatures. Designated -receiver signature scheme enables the receiver to verify the validity of signature, while proxy signature scheme allows a desinated person, called a proxy signer, to sign on behalf of an original signer. The property and charateristics of these two types of signature make them widely used in electronic business and other fields. However, most designated-receiver signature schemes and proxy signature schemes propoesed at present are not ideal in security and flexibility, which can not meet the need of reality. So it is important to design secure and flexible signature schemes. In this paper, some explorations have been made and several new designated-receiver signature schemes and proxy signature schemes are given respectively.The research approach in this paper is based on the thought that security is the most important standard to evaluate the practical value of a signature scheme and a signature scheme without security will lose the meaning on which it exists, so security should be placed on the first place and then the flexibility is taken into account, when some signature schemes are designed. When the assigned group-receiver signature scheme is designed, its security is established in the difficult question of separate logarithm, as its signature stage is based on Schnorr. The flexibility in application is strengthened through assigning the receiver and confirmer as a group; When we study the proxy blind signature we discovered that a lot of existing proxy blind signature schemes are easy to be attacked by the malicious user in the phase of conversation. In this paper several measures are proposed to strengthen the security of the proxy blind signature to enable it to be applied well in the actual environment; The multiple grade proxy signature is very important in application, but we discovered few researchers had done any research on it and the security and other characteristics of the existing multiple grade proxy signature schemes were not good enough. So in this paper the security of multiple grade proxy signature is redefined and a new strong multiple grade proxy signature is given, whose security is greatly promoted compared with the previous ones and which enable the involver in different grade have a good command of the transferred procedure of the signature. The studies in this paper are conducted focusing on the security of various schemes, therefore they are significant in theory and have good prospect in application.What have been studied in this paper and the main results that the author obtained are as follows:1. Some basic digital signature scheme and their security are analyzed and the possible attacks to digital signature schemes are discussed.2. Designated-verifier signature scheme and the way to construct the designated -verifier signature scheme are introduced. The designated-receiver signature schemes are discussed and two new the designated-receiver signature schemes are presented.3. Several common proxy signature schemes are introduced and their securities are analyzed. A couple of combination between signature schemes and proxy signature scheme are studied. A way of attacking to proxy blind signature scheme in reality is presented and the solution to the attacking problem is given at the same time. On the basis of the designated-receiver signature scheme, two new designated-receiver signature schemes are given in the paper. Finally a new multiple grade proxy signature scheme is given, in which the process of transfer from the signature verifers can be understood clearly and which can be easily applied in reality.