The concept of partially blind signatures was first introduced by Abe and Fujisaki. Subsequently, in work by Abe and Okamoto, a provably secure construction was proposed along with a formalised definition for partially blind schemes. The construction was based on a witness indistinguishable protocol described by Cramer et al. and utilises a blind Schnorr signature scheme. This paper investigate...

A blind signature scheme is a cryptographic protocol for obtaining a signature from a signer such that the signer’s view of the protocol cannot be linked to the resulting message signature pair. In this paper we have proposed two blind signature schemes using braid groups. The security of given schemes depends upon conjugacy search problem in Braid groups.

Blind signatures provide a mechanism for achieving privacy and anonymity whereby a user gets the signer to sign a message of his choice without the signer learning the content of the message, nor linking message/signature request pairs when he sees the final signature. In this paper, we construct a blind signature that requires minimal interaction (two moves) between the user and the signer, an...

Multi-proxy signature allows the original signer delegate his singing power to a group of proxy signers. Blind proxy-signature allows the user to obtain a signature of a message from several signers in a way that each signer learns neither the message nor the resulting signature. Plenty of multi-proxy signature and blind multisignature schemes have been proposed under the certificate-based (CA-...

A proxy blind signature scheme is combination of two signature schemes particularly proxy signature and blind signature. In this signature scheme the original signer delegate his/her signing authority to some other entity named proxy signer. The proxy signer signs the documents or messages, but he cannot be able to find any link between the blind signature and the identity of the signature requ...

In 2003, Hwang et al. proposed a new blind signature based on the RSA cryptosystem. The Extended Euclidean algorithm is employed in their proposed scheme. They claimed that the proposed scheme was untraceable and it could meet all requirements of a blind signature. However, we find that the signer can still trace the blind signature applicant in some cases. Thus, we present the security flaw of...

In this paper, we propose a provably secure group-oriented blind (t, n) threshold signature scheme, which is the first scheme whose security is proved to be equivalent to the discrete logarithm problem in the random oracle model. Based on the scheme, any t out of n signers in a group can represent the group in signing blind threshold signatures, which can be used in anonymous digital e-cash sys...

In a proxy signature scheme, a potential signer delegates his signing capability to a proxy entity, who signs a message on behalf of the original signer. All the proposals of proxy signature schemes made until now have been based on Schnorr's signature scheme. Threshold versions of these schemes have also been proposed, in which the power of the proxy signer is distributed among a group of play...

Proxy signature schemes have been invented to delegate signing rights. The paper proposes a new concept of Identify Based Strong Bi-Designated Verifier threshold proxy signature (ID-SBDVTPS) schemes. Such scheme enables an original signer to delegate the signature authority to a group of ‘n’ proxy signers with the condition that ‘t’ or more proxy signers can cooperatively sign messages on behal...

Braids groups provide an alternative to number theoretic public cryptography and can be implemented quite efficiently. The paper proposes five signature schemes: Proxy Signature, Designated Verifier, Bi-Designated Verifier, Designated Verifier Proxy Signature And Bi-Designated Verifier Proxy Signature scheme based on braid groups. We also discuss the security aspects of each of the proposed sch...