Review on multisignature schemes based upon DLP

In digital signature schemes a user is allowed to sign a document by using a public key infrastructure (PKI). For signing a document, the sender encrypts the hash of the document by using his private key. Then, the verifier uses the signer’s public key to decrypt the received signature and to check if it matches the document hash. Generally a digital signature scheme demands only one signer to sign a message so that the validity of the signature can be checked later. But under some situations a group of signers is required to sign a message cooperatively, so that a single verifier or a group of verifiers can check the validity of the given signature. This scheme is known as a multisignature. A multisignature scheme is one of the tools in which plural entities can sign a document more efficiently than they realize it by trivially constructing single signatures. In general, in a multisignature scheme, the total signature size and the verification cost are smaller than those in the trivially constructed scheme. Thus, plural signers can collectively and efficiently sign an identical message. There are different base primitives describing the type of numerical problems upon which the underlying security scheme is based on. In this thesis, some of the most important DLP based multisignature schemes are presented. A categorization between these different existing schemes has been shown, along with their pros and cons

A Multisignature Scheme with Distinguished Signing Authorities

Multisignature is an extension of digital signature, where a group of signers jointly produce a valid signature on a message. Distinguished Signing authorities were first introduced by L.Harn. In Distinguished signing authorities, each of the signers is responsible for only one part of the message rather than the whole message itself. Along with the group of signers, we also have a trusted clerk who verifies the individual signatures and generates the final multisignature. We extensively studied the two existing schemes proposed by Harn and Hwang. Although Hwnag’s scheme overcame all the drawbacks of Harn’s scheme, it has drawbacks like high computational cost and communication overhead. So, we proposed a modification over Hwang’s scheme taking into consideration the signature length, computational complexity of signature generation and the cost of signature verification. The performance evaluation of the proposed scheme was theoretically compared to that of the Hwang’s scheme. Both the schemes are implemented to calculate the signature length and the execution time required for different phases in the multisignature scheme. Hence these implementation results were useful to verify the performance evaluation

A new digital multisignature scheme with distinguished signing authorities

[[abstract]]In 1999, Ham proposed a multisignature scheme with distinguished signing authorities. In Ham's scheme, a malice member easily confuses the signing authorities since individual signatures and multisignatures both generated on the whole document cannot be used as evidence to distinguish the signing authorities. Moreover, Ham' scheme is also not secure against Li et al.'s attack [4]. To provide evidence and remove Li et al.'s attack, a new multisignature scheme with distinguished signing authorities is proposed in this article.[[notice]]補正完畢[[journaltype]]國內[[incitationindex]]SCI[[incitationindex]]E

A New Digital Multisignature Scheme with Distinguished Signing Authorities

[[abstract]]In 1999, Harn proposed a multisignature scheme with distinguished signing authorities. In Harn’s scheme, a malice member easily confuses the signing authorities since individual signatures and multisignatures both generated on the whole document cannot be used as evidence to distinguish the signing authorities. Moreover, Harn’s scheme is also not secure against Li et al.’s attack [4]. To provide evidence and remove Li et al.’s attack, a new multisignature scheme with distinguished signing authorities is proposed in this article