A Threshold Blind Digital Signature Scheme Using Elliptic Curve Dlog-Based Cryptosystem

Abstract

In a (t,n) threshold Blind Digital signature scheme, only t or more users can generate a group signature on behalf of the entire group in a cryptographically secure manner. Such signatures require that a signer be able to sign a document without knowing its contents. Moreover, should the signer ever see the document/signature pair, he should not be able to determine when or for whom he signed it. By using blind digital signature, we can design protocols for secure distributed electronic banking, and secure online voting with multiple voting centers. In this paper, a blind threshold signature scheme based on elliptic curve discrete logarithm problem has been proposed. The proposed scheme provides high level of secrecy for small key sizes compared to the threshold signature schemes based on discrete logarithm problem (DLP) over a finite field or an integer factorization problem (IFP). Moreover, our proposed scheme has moderate timings, and timing do not vary significantly with changing the key size which reflects the suitability of the proposed scheme for applications where the devices are resource constrained such as mobile phones, PDAs, and sensor nodes.