Privacy breach has become a major dispute in online transactions. In such a system, users give their personal information to get the service and that users' personal information may get wide spread across several organizations. Hence, there is a need for privacy protection. Private credentials offer authentication and authorization based on the traits possessed by a user not on the identity of the user. In this paper, we present a private credentials system that uses Schnorr Blind Signature based on elliptic curves. Elliptic curve defined over a prime field is chosen and ECDLP i. e. , Elliptic Curve Discrete Logarithm Problem is the basis for the system. The properties of randomness, unlinkability, unforgability are preserved. The performance and storage space requirement of our system are compared with that of the cryptographic techniques that use discrete logarithm.

1. Joseph H. Silverman, "The Arithmetic of Elliptic Curves", Graduate Texts of Mathematics, Vol. 106, Springer-Verlag 1986.
2. Randhir Kumar, Akash Anil, "Implementation of Elliptical Curve Cryptography", International Journal of Computer Science Issues, Vol. 8, Issue 4, No 2, July 2011.
3. W. Stallings, "Cryptography and Network Security principles and practice", Published by Prentice Hall, 2006.
4. A. Glenn, I. Goldberg, F. Legare, A. Stiglic, "A Description of Protocols for Private Credentials", Published by Zero-Knowledge Systems Inc. , 2001, pp. 1-10.
5. A. Lysyanskaya, R. Rivest, A. Sahai, and S. Wolf, "Pseudonym Systems", Selected Areas in Cryptography, H. Heys and C. Adams, Eds. , Springer Verlag, 1999, vol. 1758, Lecture Notes in Computer Science, pp. 184-199.
6. S. Brands, "Private Credentials", Published by Zero-Knowledge Systems Inc. , 2000, pp. 1- 25.
7. Aditi Athavale, Kuldip Singh, Sandeep Sood, "Design of a Private Credentials Scheme Based on Elliptic Curve Cryptography", First International Conference on Computational Intelligence, Communication Systems and Networks, 2009.
8. D. Chaum, "Blind signatures for untraceable payment", Advances in cryptology, CRYPTO'82, Lect. Notes Computer Science, Published by Springer-Verlag, 1998, pp. 199-203.
9. M. Chang, I. Chen, I. Wu, Y. Yeh, "Schnorr Blind Signature Based on Elliptic Curves", Asian Journal of Information Technology, Published by Grace Publication Network, 2003, pp. 130 -134.
10. Fuh-Gwo Jeng, Tzer-Long Chen, Tzer-Shyong Chen, "An ECC-Based Blind Signature Scheme", Journal of Networks, Vol. 5 , August 2010.

Elliptic Curve Cryptography Private Credentials Schnorr Blind Signature