In 2004, Abe et al. proposed a threshold signerambiguous signature scheme from variety of keys. Their scheme is a generalized case of the ring signature scheme, and it allows the key types to be based the trapdoor one-way permutations (TOWP) or sigma-protocols including Schnorr’s signature scheme. However, the signed message is public for all, which may result in disputes. In this paper, we pre...

We show how the Fiat-Shamir transform can be used to convert three-move identification protocols into two-tier signature schemes (a primitive we define) with a proof of security that makes a standard assumption on the hash function rather than modeling it as a random oracle. The result requires security of the starting protocol against concurrent attacks. We can show that numerous protocols hav...

One-time signature (OTS) offer a viable alternative to public key-based digital signatures. OTS security is typically based only on the strength of the underlying one-way function and does not depend on the conjectured difficulty of some mathematical problem. Although many OTS methods have been proposed in the past, no solid foundation exists for judging their efficiency or optimality. This pap...

We present an attack against a code-based signature scheme based on the Lyubashevsky protocol that was recently proposed by Song, Huang, Mu, Wu and Wang (SHMWW). The private key in SHMWW contains columns coming part from identity matrix random matrix. existence of two types leads to strong bias distribution set bits produced signatures. Our exploits such recover bunch collected provide theoreti...

A group signature scheme allows any member of a potentially large group to sign on behalf of the group. Group signatures are anonymous and unlinkable. Only a designated group manager can co-relate signatures and/or reveal the identity of the actual signer. At the same time, no one (including a group manager) can misattribute a valid signature. In this paper we construct a very eecient and prova...

In this paper, we construct a strongly unforgeable ID-based signature scheme without random oracles. The signature size of our scheme is smaller than that of other schemes based on varieties of the Diffie–Hellman problem or the discrete logarithm problem. The security of the scheme relies on the difficulty to solve three problems related to the Diffie–Hellman problem and a one-way isomorphism.

One of the central lines of cryptographic research is identifying the weakest assumptions required for the construction of secure primitives. In the context of group signatures the gap between what is known to be necessary (one-way functions) and what is known to be sufficient (trapdoor permutations) is quite large. In this paper, we provide the first step towards closing this gap by showing th...