Blind signatures have proved an essential building block for applications that protect privacy while ensuring unforgeability, i.e., electronic cash and electronic voting. One of the oldest, and most efficient blind signature schemes is the one due to Schnorr that is based on his famous identification scheme. Although it was proposed over twenty years ago, its unforgeability remains an open prob...

In this paper we construct a practical group blind signature scheme. Our scheme combines the already existing notions of blind signatures and group signatures. It is an extension of Camenisch and Stadler's Group Signature Scheme 5] that adds the blindness property. We show how to use our group blind signatures to construct an electronic cash system in which multiple banks can securely distribut...

We explicitly describe and analyse blind hierachical identity-based encryption (blind HIBE) schemes, which are natural generalizations of blind IBE schemes [20]. We then uses the blind HIBE schemes to construct: (1) An identity-based blind signature scheme secure in the standard model, under the computational Diffie-Hellman (CDH) assumption, and with much shorter signature size and lesser commu...

We explore the security of blind signatures under aborts where the user or the signer may stop the interactive signature issue protocol prematurely. Several works on blind signatures discuss security only in regard of completed executions and usually do not impose strong security requirements in case of aborts. One of the exceptions is the paper of Camenisch, Neven and shelat (Eurocrypt 2007) w...

Ring signatures allow a signer to anonymously sign a message on behalf of a set of arbitrarily chosen signers called a “ring”. Blind signatures, on the other hand, allow a user to obtain a signature on a message while maintaining the privacy of the message. Blind ring signatures combine properties of both primitives and hence provide a strong notion of anonymity where the privacy of both the id...

Blind signatures have key role in real world applications like e-cash, e-voting etc. The first blind signature was proposed by Chaum under public key infrastructure(PKI) model. The inherent problem in PKI is the certificate management which is overcome by identity(ID) based system. The ID based system is susceptible to key escrow problem. By removing the inherent problems of both PKI and ID bas...

We explore the security of blind signatures under aborts where the user or the signer may stop the interactive signature issue protocol prematurely. Several works on blind signatures discuss security only in regard of completed executions and usually do not impose strong security requirements in case of aborts. One of the exceptions is the paper of Camenisch, Neven and shelat (Eurocrypt 2007) w...

A proxy signature scheme enables a proxy signer to sign messages on behalf of the original signer. In this paper, we demonstrate that a number of discrete logarithm based proxy signature schemes are vulnerable to an original signer’s forgery attack. In this attack, a malicious original signer can impersonate a proxy signer and produce a forged proxy signature on a message. A third party will in...

Based on the anonymity that digital signatures provide to users and messages, digital signatures can be classified as hidden, weak, interactive, or strong blind signatures. The hidden blind signature hides the signed message from the signer’s vision during his interaction with an honest requester. Later on, after revealing the message the signer can easily link the message-signature pair. The h...

This paper introduces the concept of “revocable unlinkability” for unlinkable anonymous signatures and proposes a generalized scheme that modifies the signatures to include revocable unlinkability. Revocable unlinkability provides a condition in which multiple messages signed using an unlinkable anonymous signature are unlinkable for anyone except the unlinkability revocation manager. Noteworth...