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...

Ring signatures enable a user to anonymously sign a message on behalf of group of users. In this paper, we propose the first ring signature scheme whose size is O(log2N), where N is the number of users in the ring. We achieve this result by improving Chandran et al.’s ring signature scheme presented at ICALP 2007. Our scheme uses a common reference string and non-interactive zero-knowledge proo...

The concept of ring signature was introduced by Rivest, Shamir and Tauman. This signature is considered to be a simplified group signature from which identity of signer is ambiguous although verifier knows the group to which signer belong. In this paper we introduce a new proxy ring signature scheme.

In this paper, we propose a new primitive called non interactive deniable ring authentication: it is possible to convince a verifier that a member of an ad hoc collection of participants is authenticating a message m without revealing which one and the verifier V cannot convince any third party that the message m was indeed authenticated in a non-interactive way. Unlike the deniable ring authen...

The ring signature is a group signature without a group manager, so that a signer realizes a signature in the name of the group. In some situations it is necessary for a message to be signed by more than one persons. The scheme of the ring signature with divided key is an algorithm which ensures realizing a key signature by a group of k entities from a group of n entities. Because of the way th...

Multivariate Cryptography is one of the main candidates for creating post-quantum cryptosystems. Especially in the area of digital signatures, there exist many practical and secure multivariate schemes. However, there is a lack of more advanced schemes, such as schemes for oblivious transfer and signature schemes with special properties. While, in the last years, a number of multivariate ring s...

The anonymity provided by the threshold ring signature scheme proposed by Bresson et al (Crypto’02) is perfect. However, its complexity is prohibitively large even for relatively small sets of signers. We propose use of threshold schemes based on covering designs that are efficient for large groups of signers. The cost we pay is non-perfect anonymity.

An original digital signature scheme based on action of infinite ring on module is presented. It is assumed that the ring contains an infinite multiplicative monoid. The ring action is defined as monoid elements's action on the module element as an operator. The signature scheme is based on particularly designed one–way functions (OWFs), using a postulated hard problem in monoid action level. T...

We propose a group signature scheme with constant-size public key and signature length that does not require trapdoor. So system parameters can be shared by multiple groups belonging to different organizations. The scheme is provably secure in the formal model recently proposed by Bellare, Shi and Zhang (BSZ04), using random oracle model, Decisional Bilinear Diffie-Hellman and Strong Diffie-Hel...