Undeniable Signature Scheme Research Articles

A Zero-knowledge Undeniable Signature Scheme in Non-abelian Group Setting

Recently non-abelian groups have attracted the atten- tion of cryptographers for constructing public-key cryp- tographic protocols. In this paper we use the conju- gacy problem in non-abelian groups to construct a zero- knowledge undeniable signature scheme. a more efficient alternative to well established numeric computations in abelian groups. Where as the secu- rity of cryptographic protocols based on number-theoretic abelian groups are based on the hardness of problems like integer factorization and discrete logarithm, the se- curity of cryptographic protocols based on non-abelian groups are based on the hardness of problems like conju- gacy search, decomposition and root problem. Almost all the undeniable signature schemes constructed so far have been based on the hardness of integer factorization (10) and discrete logarithm problems (6, 7). In this paper, we present a zero-knowledge undeniable signature scheme based on the hardness of the conjugacy problem in non- abelian groups. The outline of the paper is as follows. In Section 2, we describe the preliminaries needed for this paper. A zero-knowledge undeniable signature scheme is given in Section 3. We prove the completeness, soundness and zero-knowledgeness of the protocols also. In Section 4, we suggest some non-abelian groups for the implementation of the above signature scheme. The paper concludes with some general remarks in Section 5.

Certificateless undeniable signature scheme

In this paper, we present the first certificateless undeniable signature scheme. The scheme does not suffer from the key escrow problem, which is inherent in identity based cryptosystems. Also it can avoid the onerous management of certificates. Particularly, by using some cryptographic and mathematical techniques, we guarantee that the scheme’s two component protocols satisfy the properties of zero-knowledge proofs. To address the security issues, we extend security notions of undeniable signatures to the complex certificateless setting, and consider two different types of adversaries. Based on these formally defined security notions, we prove that in the random oracle model, the certificateless undeniable signature scheme is secure in the sense of existential unforgeability under the Bilinear Diffie–Hellman assumption, and is secure in the sense of invisibility under the Decisional Bilinear Diffie–Hellman assumption.

The security of the FDH variant of Chaum's undeniable signature scheme

In this paper, a new kind of adversarial goal called forge-and-impersonate in undeniable signature schemes is introduced. Note that forgeability does not necessarily imply impersonation ability. The security of the full-domain hash (FDH) variant of Chaum's undeniable signature scheme is then classified according to three dimensions, the goal of adversaries, the attacks, and the zero-knowledge (ZK) level of confirmation and disavowal protocols. Each security is then related to some well-known computational problem. In particular, the security of the FDH variant of Chaum's scheme with noninteractive zero-knowledge (NIZK) protocol confirmation and disavowal protocols is proven to be equivalent to the computational Diffie-Hellman (CDH) problem, as opposed to the gap Diffie-Hellman (GDH) problem as claimed by Okamoto and Pointcheval.

A new elliptic curve undeniable signature scheme

A new elliptic curve undeniable signature scheme

Identity based group-oriented undeniable signature scheme

Group-oriented undeniable signature enables any subset of at least t members to represent a group to generate, confirm and disavow a signature. Several schemes were proposed and many of them are not secure. In this paper, we present an identity based (ID-based) group-oriented undeniable signature scheme which is secure in the random oracle model. To the best of authors’ knowledge, our scheme is the first ID-based group-oriented undeniable signature scheme. A great merit of our scheme is that the signature confirmation and disavowal is completely non-interactive: the protocol of the verifier and confirmers is non-interactive and nothing is needed to exchange in between confirmers.

Attack on Han et al.’s ID-based confirmer (undeniable) signature at ACM-EC’03

In ACM conference on electronic commerce (EC'03), Han et al. [Identity-based confirmer signatures from pairings over elliptic curves, in: Proceedings of ACM Conference on Electronic Commerce Citation 2003, San Diego, CA, USA, June 09-12, 2003, pp. 262-263] proposed an ID-based confirmer signature scheme using pairings (the scheme is in fact an ID-based undeniable signature scheme). In this paper, we show that this signature scheme is not secure and the signer can deny any signature, even if it is a valid signature, and any one can forge a valid confirmer signature of a signer with identity ID on an arbitrary message and confirm this signature to the verifier.

Atomic electronic contract protocol based on convertible signature

A new class of atomicity, namely contract atomicity is presented. A new technical strategy based on convertible signature and two-phase commitment is proposed for implementing atomicity of electronic contract protocol. A new atomic contract signing protocol is given nut by using ElGamal-like convertible undeniable signature and commitment of conversion key, and another new atomic contract signing protocol is brought forward by using RSA-based convertible undeniable signature scheme and commitment of conversion key. These two new protocols are proved to be of atomicity, fairness, privacy, non-repudiation.

An efficient undeniable group-oriented signature scheme

Three main methods with favorable security and efficiency can be considered in the design of cryptosystems. These methods are integer factorization systems (of which RSA is the best known example), discrete logarithm systems (such as DSA) and elliptic curve cryptosystems (ECC) [Math. Comput. 48 (1987) 203; Advances in Cryptology-Crypto’85, Springer-Verlag, 1986 p. 417]. The elliptic curve cryptosystem has been applied in this study because of its low computational cost and short key size, which reduces the overheads in a limited-hardware environment. Thus, the elliptic curve constitutes a suitable environment for the cryptosystems. This study improves the undeniable signature scheme [Proceedings of the Eleventh National Conference on Information Security, 2001, p. 331] by reducing its time complexity. Such an improvement makes the proposed scheme more efficient and secure.

Threshold undeniable signature scheme based on conic

Recently, undeniable signature has received a significant attention and has been extensively researched in the cryptographic community. Many undeniable schemes have been proposed. However, most of previous proposed schemes are based on discrete logarithm cryptosystems. In this paper, we present conic analogy of the first undeniable RSA signature scheme proposed by Gennaro, Krawczyk and Rabin at Crypto'97, and propose the first threshold undeniable signature scheme based on conic.

Efficient Undeniable Signature Schemes Based on Ideal Arithmetic in Quadratic Orders

In undeniable signature schemes the correctness or incorrectness of a signature of some message cannot be checked without the agreement of and the interaction with the signer. This is a favorable property for some applications. Well-known undeniable signature schemes presented in the literature will cause operations for the signer which take cubic running time. For a real world implementation, e.g., on a chip card or a web server this might be too inefficient. In this paper, we present new efficient undeniable signature schemes which are constructed over an imaginary quadratic field. We compare our schemes to the only really competitive scheme so far, which is based on RSA. In all signature protocols presented here the signer’s part involving the secret key is always of quadratic complexity, which is much faster in practice than the signer’s part in the RSA-based undeniable signature protocol.

Convertible undeniable signature with subliminal channels

The concept of subliminal channel was first proposed in 1983. After that, many subliminal channel schemes based on digital signatures are proposed. A convertible undeniable signature is an undeniable signature and can be converted to a general digital signature. In this paper, we combine both concepts to propose a new scheme which can embed subliminal channels into a convertible undeniable signature scheme. The proposed scheme keeps all properties of the convertible undeniable signatures and can be used to transmit different subliminal messages to different subliminal receivers. Moreover, the subliminal receivers need not share any secret key with the sender.

New Efficient and Secure Protocols for Verifiable Signature Sharing and Other Applications

Verifiable signature sharing (VΣS) was introduced by Franklin and Reiter in “Eurocrypt '95” (Lecture Notes in Computer Science, Vol. 921, pp. 50–63, Springer-Verlag, Berlin, 1995). VΣS enables the recipient of a digital signature, who is not necessarily the original signer, to share that signature among n proxies so that a subset of them can later reconstruct it. Efficient protocols were also given for RSA, Rabin, ElGamal, Schnorr, and DSS signatures. However, their RSA and Rabin VΣS protocols were subsequently broken and their DSS VΣS lacks a formal proof of security. We present new protocols for RSA, Rabin, and DSS VΣS. Our protocols are efficient and provably secure and can tolerate the malicious behavior of up to half of the proxies. The RSA VΣS scheme is based on a completely novel approach. The recipient of the signature will not share it using conventional secret sharing schemes, but instead will simply encrypt it using a threshold cryptosystem, i.e., a public key whose matching secret key is kept shared at the proxies. She will then also provide the proxies with a proof that the ciphertext indeed contains a signature. The crux of the problem was to design a threshold cryptosystem that would make such a proof efficient. We present several variants of our basic scheme, one of which requires no interaction between the recipient of the signature and the proxies to establish such a proof and one in which the reconstruction of the signature by the proxies is completely non-interactive. The RSA VΣS scheme can be easily adapted to Rabin's signatures. The DSS VΣS scheme is a modified version of the ElGamal VΣS scheme mentioned above which allows for a proof of security. The main application of VΣS is the incorporation of digital cash into multiparty protocols, e.g., cash escrow and secure distributed auctions. Our protocols thus provide simple, efficient, and secure solutions for those applications. Furthermore we believe that some of our techniques are of independent interest. Some of the by-products of our main result are a new threshold cryptosystem, a new undeniable signature scheme, and a way to create binding RSA cryptosystems.

Group-oriented undeniable signature schemes with a trusted center

At Auscrypt ’92, Harn and Yang firstly proposed the concept of group-oriented undeniable signature. Two threshold undeniable signature schemes were devised in their article, where t can be either 1 or n. However, Langford in 1996 showed that the Harn–Yang ( n, n) threshold undeniable signature scheme is not secure enough. In 1996, Lin et al. also proposed a new ( t, n) threshold undeniable signature scheme without a trusted center. Unfortunately, the Langford attack can be applied to Lin et al.’s scheme as well. Thus, the problem of designing a general group-oriented ( t, n) threshold undeniable signature scheme is remained open. The purpose of this article is to propose a ( t, n) threshold undeniable signature scheme, where 1≤ t≤ n. Moreover, the signing policy will be extended to the generalized case, where any authorized subset can sign messages.

Undeniable (t, n)‐threshold signature scheme with cheater identification

We propose an undeniable (t, n) threshold signature scheme with cheater identification. The proposed scheme has the following features: (1) no trusted third party is required for key generation; (2) no additional interactive protocol is required for the generation of the group's public key; (3) any t members can cooperatively sign a message with the assistance of a secure cryptographic module designated by hardware; and (4) the verifier can verify the group signature by only knowing the group's public key; it is not necessary to know the participating signers involved. The proposed scheme also provides capabilities against cheating tricks plotted by signers in the key generation and group signature generation phases.

Convertible Undeniable Signatures

<p>We introduce a new concept called convertible undeniable signature schemes.</p><p>In these schemes, release of a single bit string by the signer turns all of his signatures, which were originally undeniable signatures, into ordinary digital signatures. We prove that the existence of such schemes is implied by the existence of digital signature schemes. Then, looking at the problem more practically, we present a very efficient convertible undeniable signature scheme. This scheme has the added benefit that signatures can also be selectively converted.</p>