Cryptology ePrint Archive: Report 2013/472

Partially blind password-based signatures using elliptic curves

Kristian Gjøsteen

Abstract: Password-based signatures allow a user who can only remember a password to create digital signatures with the help of a server, without revealing the messages to be signed to the server.

Certain applications require the ability to disclose part of the message to the server. We define partially blind password-based signatures and construct a scheme based that we prove secure, based on a novel computational problem related to computing discrete logarithms.

Our scheme is based on Nyberg-Rueppel signatures. We give a variant of Nyberg-Rueppel signatures that we prove secure based on our novel computational problem.

Unlike previous password-based signature schemes, our scheme can be instantiated using elliptic curve arithmetic over small prime fields. This is important for many applications

Category / Keywords: public-key cryptography / digital signatures, Nyberg-Rueppel

Date: received 1 Aug 2013

Contact author: kristian gjosteen at math ntnu no

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Version: 20130803:051518 (All versions of this report)

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