In this paper, we present a privacy-protecting off-line electronic cash system which is fair, that is, the transactions are (potentially) traceable by a trusted authority but anonymous otherwise. Our scheme, based on a modification of Brands’restrictive blind signature scheme [2], is significantly more efficient than that of [11], while offering the same functionalities (off-line trusted author...

In a (t, n) designated verifier threshold proxy signature scheme, an original signer can delegate his/her signing power to n proxy signers such that any t or more out of n proxy signers can sign messages on behalf of the original signer but t− 1 or less of the proxy signers cannot generate a valid proxy signature. Of course, the signature is issued for a designated receiver and therefore only t...

In a proxy signature scheme, a potential signer delegates his capabilities to a proxy signer, who can sign documents on behalf of him. The recipient of the signature verifies both identities: that of the delegator and that of the proxy signer. There are many proposals of proxy signature schemes, but security of them has not been considered in a formal way until the appearance of [2, 8]. If the ...

We analyse the legal requirements that digital signature schemes have to fulfil to achieve the Statutory Trust granted by the EU electronic signature laws (“legally equivalent to hand-written signatures”). Legally, we found that the possibility to detect subsequent changes is important for the Statutory Trust. However, detectability was neither adequately nor precisely enough defined in the tec...

As modern cryptographic schemes rely their security on the secrecy of the private keys used in them, exposing such keys results in a total loss of security. In fact, attackers have been developing various techniques to seize the secret keys rather than to cryptanalyze the underlying cryptographic primitives. Digital signature schemes, which are widely employed in many applications, are not an e...

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 distribu...

Proxy signatures are very useful tools when one needs to delegate his/her signing capability to other party. After Mambo et al.’s first scheme was announced, many proxy signature schemes and various types of proxy signature schemes have been proposed. Due to the various applications of the bilinear pairings in cryptography, there are many IDbased signature schemes have been proposed. In this pa...

The threshold proxy signature scheme allows the original signer to delegate a signature authority to the proxy group member to cooperatively sign message on behalf of an original signer. In this paper, we also propose a new scheme which includes the features and benefits of the RSA scheme which is a popular security technique. Also, we will evaluate a security of undeniable threshold proxy sign...

In this paper, we survey all related threshold signature schemes and classify them with different properties. In order to compare them with different properties, we image there is an ideal threshold signature scheme which satisfies all requirements of threshold signature schemes. Based on this ideal threshold signature, readers can easily to understand what the next generation of threshold sign...