Research On Society-Oriented Digital Signature Scheme

The rapid development in computer and network technologies brings in tremendous problems for information security. Cryptography is the fundation of information security, digital signature is one of the main research field of cryptography. It is vital in authentication, data integrity, non-repudiation and so on, which has been used widely in military affairs, electronic commerce, electronic government, etc.With the rapid growth of the science and technology, more and more requires are brought forward, such as how to make the signature occupy the less store resource, the secret key as short as it can be under the ensuring security condition and so on. Lots of researchers have done abundant work in this way, but there are many questions that have not been solving, for example, how to improve the efficiency of multi-signature scheme, how to design some special signatures that can meet the user's special demands, etc. In this dissertation, we give efficiency analysis of some digital signature, and propose some special society-oriented digital signature schemes which can meet the user's special demands. In this research field, the final research achievements are as following:(1) We study the sequential multi-signature scheme (SMSS), especially the implementation and defect of the present sequential multi-signature scheme. There are two methods in the present SMSS, one is every signer independently signs for the message, the final signature is their signature gathering. In this scheme, the length of signature will be increased by multiplying with the increasing number of the signers, which makes the scheme is not practical. The other is all signers sign for the message m cooperatively, thus the first signer A₁ signs for m and send it to the second signer A₂, A₂ verify the validity of the signature at first, then signs for the signature of the signer A₁, until the last signer A_n. In this scheme, the efficiency is very low when the signature algorithm is complex. The essence of multi-signature scheme is that some signers sign for a message. The dissertation designs three SMSS based on Knapsack algorithm, discrete logarithm and Elliptic Curve, which is different from existent SMSS, it can possess all properties of existent SMSS when it only need a signature for a message. What's more, these schemes simplify the procedures among signers, and avoid the cheating by signer efficiently, and conveniently add or delete signer, and reduce the cost of communication.(2) We propose a new digital signature scheme----chain verification digital signature scheme based on the practical application. In this scheme, the verification participators can divide the signature verifier from the chain grantors, the signature verifier cannot verify the validity of the signature until he is authorized by all chain grantors in turn, and any chain grantor (even all chain grantors are collusive) cannot verify the validity of the signature. We respectively design three chain verification digital signature schemes based on Knapsack algorithm, discrete logarithm and Elliptic Curve. What's more, these signature schemes can conveniently add or delete chain grantor and defend the secret key of the chain grantors and signature verifier.(3) Due to the present threshold signature schemes part different privilege groups, the dissertation extends to the more general situation. At first, the threshold signature scheme with special right is proposed, which realized threshold signature among the signers having two different sign rights by using the structures properties of constant coefficients homogeneous linear difference equation. Then we extend this situation to the more general situation, thus extended (t,n) threshold signature scheme. In the scheme, if sign weight of any subset of all signers is not less than t, the subset can gain the valid signature of the message.(4) Analysis are made on the security threats and system flaws of present shared verification signature schemes, and an improved shared verification signature scheme is proposed, namely a shared verification signature scheme with different verification right. Firstly, a new shared verification signature scheme is proposed which has some special characters. Secondly, we propose the shared verification signature scheme, which realizes shared verification among the verifiers having two different verification rights by structures and solution structures of constant coefficients homogeneous linear difference equation. Finally we extend this situation to the more general situation, thus extended (t,n) shared verification signature scheme. In the scheme, if verification weight of any subset of all verifiers is not less than t, the subset can verify the validity signature of the message.To sum up, the dissertation aims at the characteristic of the society-oriented digital signature scheme and flaws of present scheme, and presents improved schemes that can meet the user's special demands. By combining several key techniques of the existing the society-oriented digital signature scheme together, the dissertation researches in depth on how to improve the efficiency of the sequential multi-signature scheme, design threshold signature scheme and shared verification signature scheme that have different signing or verifying right. The dissertation researches in depth on the society-oriented digital signature scheme, it is very significative both in theory and practice.