Blind Signature Schemes using Elliptic Curve Cryptography

Abstract

Blind signature, a special type of digital signature, has been one of the most charming research fields of public key cryptography through which authenticity, data integrity and non-repudiation can be verified. It is a two-party protocol, in which a requester sends a message to a signer to get the signature without revealing the contents of the message to the signer. Elliptic curve cryptography(ECC) is used as an alternative to traditional public-key cryptosystems, and is more suitable for resource-limited environments because of smaller parameter size. The difficult problem in ECC is ECDLP, which is the problem of finding the scalar multiplier knowing the corresponding points on an elliptic curve. Since an ECDLP provides more security as compared to the equivalent other hard problems in public key cryptography, and blind signature ensures anonymity of a user’s message while obtaining a signature from a trusted party, we aim at designing blind signature schemes based upon ECDLP. In this thesis, we present an Elliptic Curve Discrete Logarithm Problem (ECDLP) based blind signature scheme. The proposed scheme is untraceable and proved to be resistant to active attacks. The scheme is also universally verifiable. We compared the performance with some existing scheme and found that, the computational overhead of the proposed scheme is very low. Also we have proposed a certificateless blind signature protocol which is based on elliptic curve cryptography (CLB-ECC). The proposed scheme is proven to be secure against adversaries of two different types. CLB-ECC is efficient in terms of computation compared to other existing conventional schemes. An e-cash framework has also been proposed, which is based on CLB-ECC.