Directed Threshold Multi – Signature Scheme without SDC.pdf

Directed Threshold Multi – Signature Scheme without SDC * * * Sunder Lal and Manoj Kumar !#$%# Abstract. In this paper, we propose a Directed threshold multisignature scheme without SDC. This signature scheme is applicable when the message is sensitive to the signature receiver; and the signatures are generated by the cooperation of a number of people from a given group of senders. In this scheme, any malicious set of signers cannot impersonate any other set of signers to forge the signatures. In case of forgery, it is possible to trace the signing set. Key words. Digital signature, Directed signatures, Multi-signatures, Threshold- signatures, Lagrange interpolation, discrete logarithm problems. 1. Introduction Digital signature is a cryptographic tool to authenticate electronic communications. Digital signature scheme allows a user with a public key and a corresponding private key to sign a document in such a way that anyone can verify the signature on the document (using her/his public key), but no one can forge the signature on any other document. This self-authentication is required for some applications of digital signatures such as certification by some authority. In most situations, the signer is generally a single person. However, in some cases the message is sent by one organization and requires the approval or consent of several people. In these cases, the signature generation is done by more than one consenting person. A common example of this policy is a large bank transaction, by one organization, which requires