Strong Designated Verifier Signature Schemes with Undeniable Property and Their Applications

Most of the strong designated verifier signature (SDVS) schemes cannot tell the real signature generator when the signer and the designated verifier dispute on a signature. In other words, most of the SDVS schemes do not have the undeniability property. In this paper, we propose two SDVS schemes which hold the undeniability property, namely, strong designated verifier signature with undeniability property (SDVSUP). Our two schemes are called SDVSUP-1 and SDVSUP-2. In our two SDVSUP schemes, the signer not only can designate a verifier but also can designate an arbiter who can judge the signature when the signer and the designated verifier dispute on the signature. What is more, the judgment procedure can be performed by the arbiter alone without help from the signer or the designated verifier, which increases the judgment efficiency and reduces the complexity of signature confirmation. We also demonstrate a real instance of applying our SDVSUP scheme to electronic bidding system

Classification of Signature-only Signature Models

We introduce a set of criterions for classifying signature-only signature models. By the criterions, we classify signature models into 5 basic types and 69 general classes. Theoretically, 21140 kinds of signature models can be deduced by appropriately combining different general classes. The result comprises almost existing signature models. We also contribute a lot of new signature models. Moreover, we find the three signature models, i.e., group-nominee signature, multi-nominee signature and threshold-nominee signature, are of great importance in light of our classification

Attacks on One Designated Verifier Proxy Signature Scheme

In a designated verifier proxy signature scheme, there are three participants, namely, the original signer, the proxy signer, and the designated verifier. The original signer delegates his or her signing right to the proxy signer, then the proxy signer can generate valid signature on behalf of the original signer. But only the designated verifier can verify the proxy signature. Several designated verifier proxy signature schemes have been proposed. However, most of them were proven secure in the random oracle model, which has received a lot of criticism since the security proofs in the random oracle model are not sound with respect to the standard model. Recently, by employing Water's hashing technique, Yu et al. proposed a new construction of designated verifier proxy signature. They claimed that the new construction is the first designated verifier proxy signature, whose security does not rely on the random oracles. But, in this paper, we will show some attacks on Yu et al.'s scheme. So, their scheme is not secure

Attacks on One Designated Verifier Proxy Signature Scheme

In a designated verifier proxy signature scheme, there are three participants, namely, the original signer, the proxy signer, and the designated verifier. The original signer delegates his or her signing right to the proxy signer, then the proxy signer can generate valid signature on behalf of the original signer. But only the designated verifier can verify the proxy signature. Several designated verifier proxy signature schemes have been proposed. However, most of them were proven secure in the random oracle model, which has received a lot of criticism since the security proofs in the random oracle model are not sound with respect to the standard model. Recently, by employing Water's hashing technique, Yu et al. proposed a new construction of designated verifier proxy signature. They claimed that the new construction is the first designated verifier proxy signature, whose security does not rely on the random oracles. But, in this paper, we will show some attacks on Yu et al.'s scheme. So, their scheme is not secure

CONSTRUCTION OF EFFICIENT AUTHENTICATION SCHEMES USING TRAPDOOR HASH FUNCTIONS

In large-scale distributed systems, where adversarial attacks can have widespread impact, authentication provides protection from threats involving impersonation of entities and tampering of data. Practical solutions to authentication problems in distributed systems must meet specific constraints of the target system, and provide a reasonable balance between security and cost. The goal of this dissertation is to address the problem of building practical and efficient authentication mechanisms to secure distributed applications. This dissertation presents techniques to construct efficient digital signature schemes using trapdoor hash functions for various distributed applications. Trapdoor hash functions are collision-resistant hash functions associated with a secret trapdoor key that allows the key-holder to find collisions between hashes of different messages. The main contributions of this dissertation are as follows: 1. A common problem with conventional trapdoor hash functions is that revealing a collision producing message pair allows an entity to compute additional collisions without knowledge of the trapdoor key. To overcome this problem, we design an efficient trapdoor hash function that prevents all entities except the trapdoor key-holder from computing collisions regardless of whether collision producing message pairs are revealed by the key-holder. 2. We design a technique to construct efficient proxy signatures using trapdoor hash functions to authenticate and authorize agents acting on behalf of users in agent-based computing systems. Our technique provides agent authentication, assurance of agreement between delegator and agent, security without relying on secure communication channels and control over an agent’s capabilities. 3. We develop a trapdoor hash-based signature amortization technique for authenticating real-time, delay-sensitive streams. Our technique provides independent verifiability of blocks comprising a stream, minimizes sender-side and receiver-side delays, minimizes communication overhead, and avoids transmission of redundant information. 4. We demonstrate the practical efficacy of our trapdoor hash-based techniques for signature amortization and proxy signature construction by presenting discrete log-based instantiations of the generic techniques that are efficient to compute, and produce short signatures. Our detailed performance analyses demonstrate that the proposed schemes outperform existing schemes in computation cost and signature size. We also present proofs for security of the proposed discrete-log based instantiations against forgery attacks under the discrete-log assumption

A Certificate-Based Proxy Signature with Message Recovery without Bilinear Pairing

In this paper, we propose the first provable secure certificate-based proxy signature with message recovery without bilinear pairing. The notion of certificate-based cryptography was initially introduced by Gentry in 2003, in order to simplify certificate management in traditional public key cryptography(PKC)and to solve the key escrow problem in identity-based cryptosystems. To date, a number of certificate-based proxy signature(CBPS)schemes from bilinear pairing have been proposed. Nonetheless, the total computation cost of a pairing is higher than that of scalar multiplication(e.g., over elliptic curve group). Consequently, schemes without pairings would be more appealing in terms of efficiency. According to the available research in this regard, our scheme is the first provable secure CBPS scheme with message recovery which is based on the elliptic curve discrete logarithm problem. We prove the security of the presented scheme against existential forgery under adaptive chosen message and ID attacks in the random oracle model. Moreover, the paper will also show how it would be possible to convert this scheme to the CBPS scheme without message recovery. This scheme has more applications in situations with limited bandwidth and power-constrained devices