We say that an encryption scheme or a signature scheme provides anonymity when it is infeasible to determine which user generated a ciphertext or a signature. To construct the schemes with anonymity, it is necessary that the space of ciphertexts or signatures is common to each user. In this paper, we focus on the techniques which can be used to obtain this anonymity property, and propose a new ...

Bellare, Boldyreva, Desai, and Pointcheval [1] recently proposed a new security requirement of the encryption schemes called “keyprivacy.” It asks that the encryption provide (in addition to privacy of the data being encrypted) privacy of the key under which the encryption was performed. Incidentally, Rivest, Shamir, and Tauman [2] recently proposed the notion of ring signature, which allows a ...

Email phishing attacks are one of today’s most common and costly forms of digital identity theft, where an adversary tricks a user into revealing their personal information by impersonating an established company. Such attacks could be mitigated with digitally-signed emails, if these signatures did not: (1) destroy the traditional repudiability of email, and (2) require the unrealistic, widespr...

Group signatures, which allow users of a group to anonymously produce signatures on behalf of the group, are an important cryptographic primitive for privacy-enhancing applications. Over the years, various approaches to enhanced anonymity management mechanisms, which extend the standard feature of opening of group signatures, have been proposed. In this paper we show how pairing-based group sig...

This paper introduces two designs to enhance the Boneh and Freemans linearly homomorphic signature over binary fields, to overcome the limitations to implement homomorphic signatures to the real world scenario due to the heavy calculation and under multiple signers setting for a message. Based on our concurrent work on classification on lattice-based trapdoor functions in SCIS 2017, we modify s...

In 2004, Abe et al. proposed a threshold signer-ambiguous 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 on 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...

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...

In this work, we initially study the necessary properties and security requirements of Ring Confidential Transaction (RingCT) protocol deployed in the popular anonymous cryptocurrency Monero. Firstly, we formalize the syntax of RingCT protocol and present several formal security definitions according to its application in Monero. Based on our observations on the underlying (linkable) ring signa...

This article concerned on the study of signature submanifolds for curves under Lie group actions SE(2), SA(2) and for surfaces under SE(3). Signature submanifold is a regular submanifold which its coordinate components are differential invariants of an associated manifold under Lie group action, and therefore signature submanifold is a key for solving equivalence problems.