The Research On Digital Signature Scheme And Its Digital Sequential Multisignature Scheme

The digital signature is one of main researches in modern cryptography, and it cannot be substituted by other techniques in information security, including authentication,data integrity, and non-repudiation. Digital signatures have many applications in military electronic commerce and electronic government,etc.In this dissertation, the theories and algorithms of specialized digital signature are studied based on many research works of a lot of academicians and experts. and four digital signature schemes are proposed: A new threshold and confirmer digital signature scheme, A threshold signature scheme for group communicationswithout a shared distribution center, A new cryptosystem and digital signature scheme based on ElGamal cryptosystem, A new digital multisignature scheme based on schnorr digital signature.In this paper,a new threshold and confirmer signature scheme is proposed by using the idea of multiplication secret sharing and famous public key cryptosystem RSA.It is the first time that threshold and confirmer are combined in a digital signature scheme.The idea of zero-knowledge proof also is used in the confirming and denying protocol.The new scheme is secure under condition of intractability assumption of quadric remain and the security of RSA. the new scheme can control the diffusion of the validity of the signature and prevent the signer from denying the disadvantageous signature to protect the benefit of verifier.The new scheme is efficient and can be applied to justice-subscribe of electronic contract.In this paper,we shall propose a (t,n) threshold signature with (k,l) threshold-shared verification to be used in a group-oriented cryptosystem without a shared distribution center (SDC).In this scheme,any t participants can represent a group (signing group) to sign a message ,and any k participants can represent another another group (verifying group) to verify the signature .We need no SDC to distribute the public and private keys to all the participants in the two group.Hence,our scheme is more practical in real-world application and more efficient than its predecessors in terms of communication and computationa; complexity as well as storage.Although existing ElGmal digital signature that has been proved is an effective user authentication scheme ,it also has limitations that are lower efficiency and lower security.The new user authentication scheme based on ElGamal digital signature scheme is presented in the paper,which avoids modual contradictorily operation and enables a authentication system to validate a user's identity without exposing the user's secret information .Thus the scheme has very high efficiency and security class.Finally,this paper presents a new digital sequential multisignature scheme based on the Schnorr scheme.This paper points out that they are especially efficient to sequential multisignature generation.Moreover the authors prove that it is as secure as the Schnorr scheme against passive attacks by using the computational complexity theory.