Research On Multy Banks E-cash Systems Based On Group And Blind Signature Schemes

The development of computers and network technology has led human into informationized society and made e-commerce a top subject of research and application these days. To large extent, the crutial elements of e-commmerce's healthy and sustainable development are the information security techniques such as identity authentication, key transmission, digital signature, and electronic cash. Based on the research of precedents, the paper has systematically explored fields including key exchange authentification, message recovery signature, blind signature, group signature, electronic signature and so forth, and has acheived significant fruits in the course of the research.Firstly, the paper comprehensively analyzes the authentication key agreement and discusses the security and efficiency of two typical categories of authentication key agreements. Furthermore,in order to deal with the Diffen-Hellman-based agreement, it puts forward a universal attack strategy, with which the attacker is able to caculate the user's follow-up sharing key to unsatisfy the security of knowing the conversational key when a certain sharing key of such agreements is disclosed. To solve the problem, a protection strategy to prevent such attacks is analyzed and the author comes up with a modified and revised agreement of single/multi-key exchange. The new agreement inherits the merits of former plans and does not affect the security fo follow-up sharing key even if the share key is exposed. On the other hand, cross-server authentication key exchange remains a thorny obstacle. In addition, the security and efficency of password-based cross-server authentication key exchange agreement is also futher explored with the purpose to propose a secure and efficient agreement on the basis of the original agreement.Secondly, the paper analyzes the constrction and security of message recovery digital signature schemes y and does a lot of research on the security of two latest typical categories of message recovery digital signature agreements,which do not utilize Hash Functions. Two new forgery attacks on digital signature with message recovery are designs respetively and reasons for the forgery attack on schemes are figured out, which both attribute to two new secure schemes of digital signature with message recovery which do not use Hash Functions. While , compared with the old schemes,the efficency of both is equal, the security of the new schemes is improved quite a lot.Thirdly, the construction and security of blind digital signature schemes is analysed as a system and further expound the security of two newly-emerged typial blind signature agreements. The paper accordingly and seperately points out new approaches to handle with forgery attack, homomorphism attack and small exponent attack. Based on the analysis of reasons for being easily attacked, the author works out a new blind digital signature scheme.Fouthly, the author also analyzes the construction and security of group digital schemes and studies the security of two latest typical categories of group signature agreements. Aiming at discrete-logarithm-based group signature schemes, the author designs a new scheme of signature forgery attacke and certificate forgery attack to prove the such signature is insecure. Also, the paper points out several types of different signature and certificate forgery attacks to destroy the group signature with several hypothetic difficulties such as discrete logarithm, polynomials over a large infinite, knowledge proof and so on. Moreover, the author find out that these group signature schemes do not satisfy the needs of unconnectability which the group signature requires. In terms of reasons for the potential security risks, the paper puts up proposals for the future design of new secure group signature.Lastly, the paper systematically analyzes the development and construction of electronic cash and studies the staus quo of its development. Besides, the author,on the basis of the modification of Brands single-face value electronic cash scheme, proposes an effective one with diverse face value through the techniques of identity authentication and digital signature. The scheme makes use of discrete-logarithm-based constricted blind signature schemes to protect the user's privacy and overcome the disadvantage of overloaded calculation with the technology of fair segmentation. The new scheme also enables banks to overcome the differentiation of public key and private key when banks issue cash with diverse face value according to recent off-line electronic cash schemes. With the help of a new method, the author innovates a simple scheme, where the bank is able to issue multi-face- value electronic cash with only one private key.