This paper first gives out definition of receipt-freeness,and prove necessary and sufficient condition of receipt-freeness. Then by employing homomorphic ElGamal encryption,threshold ElGamal encryption and zero-knowledge proof,this paper designs an efficient electronic voting scheme,which satisfies universal verifiability,receipt-freeness,also eligibility,privacy and so on. Different from the previous protocols,there needs less security requirement on trusted third party in the new scheme,which is more practical.
In this paper, we prove classical coin-flipping secure in the presence of quantum adversaries. The proof uses a recent result of Watrous [Wat09] that allows quantum rewinding for protocols of a certain form. We then discuss two applications. First, the combination of coin-flipping with any non-interactive zero-knowledge protocol leads to an easy transformation from non-interactive zero-knowledge to interactive quantum zero-knowledge. Second, we discuss how our protocol can be applied to a recently proposed method for improving the security of quantum protocols [DFL+09], resulting in an implementation without set-up assumptions. Finally, we sketch how to achieve efficient simulation for an extended construction in the common-reference-string model.
Abstract. In the setting of secure computation, a set of parties wish to securely compute some function of their inputs, in the presence of an adversary. The adversary in question may be static (meaning that it con-trols a predetermined subset of the parties) or adaptive (meaning that it can choose to corrupt parties during the protocol execution and based on what it sees). In this paper, we study two fundamental questions relating to the basic zero-knowledge and oblivious transfer protocol problems: â Adaptive zero-knowledge proofs: We ask whether it is possible to con-struct adaptive zero-knowledge proofs (with unconditional sound-ness). Beaver (STOC 1996) showed that known zero-knowledge proofs are not adaptively secure, and in addition showed how to construct zero-knowledge arguments (with computational soundness). â Adaptively secure oblivious transfer: All known protocols for adap-tively secure oblivious transfer rely on seemingly stronger hardness assumptions than for the case of static adversaries. We ask whether this is inherent, and in particular, whether it is possible to construct adaptively secure oblivious transfer from enhanced trapdoor permu-tations alone. We provide surprising answers to the above questions, showing that achieving adaptive security is sometimes harder than achieving static se-curity, and sometimes not. First, we show that assuming the existence of one-way functions only, there exist adaptive zero-knowledge proofs for all languages in NP. In order to prove this, we overcome the problem that all adaptive zero-knowledge protocols known until now used equivocal commitments (which would enable an all-powerful prover to cheat). Sec-ond, we prove a black-box separation between adaptively secure oblivious transfer and enhanced trapdoor permutations. As a corollary, we derive a black-box separation between adaptively and statically securely obliv-ious transfer. This is the first black-box separation to relate to adaptive security and thus the first evidence that it is indeed harder to achieve security in the presence of adaptive adversaries than in the presence of static adversaries. 1
Remote attestation is an important attribute in trusted computing. One of the purpose of remote attestation is to attest the remote platform is trusty but not revealing the actual identity of the platform. Direct anonymous attestation (DAA) is a kind of scheme which is adopted by Trusted Computing Group in the specification 1.2 to hide the privacy of the platform. But DAA involves various of zero-knowledge proofs and is not efficient to implement. To guarantee the trustworthiness and privacy, we propose a remote anonymous attestation protocol based on ring signature in this paper. We also show that our protocol is secure under the RSA assumption in random oracle model. Furthermore, the attestation protocol does not need the third party and extra zero-knowledge proof, which makes it very efficient in realization.
Nowadays it is widely accepted to formulate the security of a protocol carrying out a given task via the âtrusted-party paradigm,â where the protocol execution is compared with an ideal process where the outputs are computed by a trusted party that sees all the inputs. A protocol is said to securely carry out a given task if running the protocol with a realistic adversary amounts to âemulatingâ the ideal process with the appropriate trusted party. In the Universal Composability (UC) framework the program run by the trusted party is called an ideal functionality. While this simulation-based security formulation provides strong security guarantees, its usefulness is contingent on the properties and correct specification of the ideal functionality, which, as demonstrated in recent years by the coexistence of complex, multiple functionalities for the same task as well as by their âunstableâ nature, does not seem to be an easy task. In this paper we address this problem, by introducing a general methodology for the sound specification of ideal functionalities. First, we introduce the class of canonical ideal functionalities for a cryptographic task, which unifies the syntactic specification of a large class of cryptographic tasks under the same basic template functionality. Furthermore, this representation enables the isolation of the individual properties of a cryptographic task as separate members of the corresponding class. By endowing the class of canonical functionalities with an algebraic structure we are able to combine basic functionalities to a single final canonical functionality for a given task. Effectively, this puts forth a bottom-up approach for the specification of ideal functionalities: first one defines a set of basic constituent functionalities for the task at hand, and then combines them into a single ideal functionality taking advantage of the algebraic structure. In our framework, the constituent functionalities of a task can be derived either directly or, following a translation strategy we introduce, from existing game-based definitions; such definitions have in many cases captured desired individual properties of cryptographic tasks, albeit in less adversarial settings. Our translation methodology entails a sequence of steps that systematically derive a corresponding canonical functionality given a game-based definition, effectively âliftingâ the game-based definition to its composition-safe version. We showcase our methodology by applying it to a variety of basic cryptographic tasks, including commitments, digital signatures, zero-knowledge proofs, and oblivious transfer. While in some cases our derived canonical functionalities are equivalent to existing formulations, thus attesting to the validity of our approach, in others they differ, enabling us to âdebugâ previous definitions and pinpoint their shortcomings.
The selective decommitment problem can be described as follows: assume an adversary receives a number of commitments and then may request openings of, say, half of them. Do the unopened commitments remain secure? Although this question arose more than twenty years ago, no satisfactory answer could be presented so far. We answer the question in several ways: 1. If simulation-based security is desired (i.e., if we demand that the adversary's output can be simulated by a machine that does not see the unopened commitments), then security is not achievable for non-interactive or perfectly binding commitment schemes via black-box reductions to standard cryptographic assumptions. However, we show how to achieve security in this sense with interaction and a non-black-box reduction to one-way permutations. 2. If only indistinguishability of the unopened commitments from random commitments is desired, then security is not achievable for (interactive or non-interactive) perfectly binding commitment schemes, via black-box reductions to standard cryptographic assumptions. However, any statistically hiding scheme does achieve security in this sense. Our results give an almost complete picture when and how security under selective openings can be achieved. Applications of our results include: ⢠Essentially, an encryption scheme must be non-committing in order to achieve provable security against an adaptive adversary. ⢠When implemented with our secure commitment scheme, the interactive proof for graph 3-coloring due to Goldreich et al. becomes zero-knowledge under parallel composition. On the technical side, we develop a technique to show very general impossibility results for black-box proofs.
Endre Bangerter, Jan Camenisch, Stephan Krenn, AhmadâReza Sadeghi ¡ 5 authors
Efficient zero-knowledge proofs of knowledge (ZK-PoK) are basic building blocks of many practical cryptographic applications such as identification schemes, group signatures, and secure multiparty computation. Currently, first applications that essentially rely on ZK-POKs are being deployed in the real world. The most prominent example is Direct Anonymous Attestation (DAA), which was adopted by the Trusted Computing Group (TCG) and implemented as one of the functionalities of the cryptographic chip Trusted Platform Module (TPM). Implementing systems using ZK-PoK turns out to be challenging, since ZK-PoK are, loosely speaking, significantly more complex than standard crypto primitives, such as encryption and signature schemes. As a result, implementation cycles of ZK-PoK are time-consuming and error-prone, in particular for developers with minor or no cryptographic skills. To overcome these challenges, we have designed and implemented a compiler with corresponding languages that given a high-level ZK-PoK protocol specification automatically generates a sound implementation of this. The output is given in form of -protocols, which are the most efficient protocols for ZK-PoK currently known. Our compiler translates ZK-PoK protocol specifications, written in a high-level protocol description language, into Java code or \LaTeX\ documentation of the protocol. The compiler is based on a unified theoretical framework that encompasses a large number of existing ZK-PoK techniques. Within this framework we present a new efficient ZK-PoK protocol for exponentiation homomorphisms in hidden order groups. Our protocol overcomes several limitations of the existing proof techniques.
The abstraction of cryptographic operations by term algebras, called DolevâYao models, is essential in almost all tool-supported methods for proving security protocols. Recently significant progress was made in proving that DolevâYao models offering the core cryptographic operations such as encrypt ion and digital signatures can be sound with respect to actual cryptographic realizations and security definitions. Recent work, however, has started to extend DolevâYao models to more sophisticated operations with unique security features. Zero-knowledge proofs arguably constitute the most amazing such extension. In this paper, we first identify which additional properties a cryptographic (non-interactive) zero-knowledge proof needs to fulfill in order to serve as a computationally sound implementation of symbolic (DolevâYao style) zero-knowledge proofs; this leads to the novel definition of a symbolically-sound zero-knowledge proof system. We prove that even in the presence of arbitrary active adversaries, such proof systems constitute computationally sound implementations of symbolic zero-knowledge proofs. This yields the first computational soundness result for symbolic zero-knowledge proofs and the first such result against fully active adversaries of DolevâYao models that go beyond the core cryptographic operations.
The abstraction of cryptographic operations by term algebras, called Dolev-Yao models, is essential in almost all tool-supported methods for proving security protocols. Recently significant progress was made in proving that Dolev-Yao models offering the core cryptographic operations such as encryption and digital signatures can be sound with respect to actual cryptographic realizations and security definitions. Recent work, however, has started to extend Dolev-Yao models to more sophisticated operations with unique security features. Zero-knowledge proofs arguably constitute the most amazing such extension. In this paper, we first identify which additional properties a cryptographic zero-knowledge proof needs to fulfill in order to serve as a computationally sound implementation of symbolic (Dolev-Yao style) zero-knowledge proofs; this leads to the novel definition of a symbolically-sound zero-knowledge proof system. We prove that even in the presence of arbitrary active adversaries, such proof systems constitute computationally sound implementations of symbolic zero-knowledge proofs. This yields the first computational soundness result for symbolic zero-knowledge proofs and the first such result against fully active adversaries of Dolev-Yao models that go beyond the core cryptographic operations.
We provide the first proof of that for every language L isin NP there exists an O(1)-round computational zero-knowledge argument with polynomial precision for L. Our result assumes that ratio of running-time of any adversary verifier in some same verifier round of any two different executions of the argument is bounded by nalpha, where n is secure parameter and alpha is any predeterminate constant. Such verifiers are called restricted verifiers. Precise zero-knowledge was introduced by Micali and Pass in STOC'06 (They used the term "local zero-knowledge" there.) and they constructed some omega(1)-round polynomial/linear precise zero- knowledge protocols for NP and hence left an open problem how to construct O(1)-round polynomial/linear precise zero-knowledge protocols. By providing a precise simulator for Barak's O(1)-round non-black-box zero-knowledge argument, we prove that the argument is polynomial precise.
Abstract. Statistical zero-knowledge (SZK) properties play an important role in designing cryptographic protocols that enforce honest behavior while maintaining privacy. This paper presents a novel approach for verifying SZK properties, using recently developed techniques based on approximate simulation relations. We formulate statistical indistinguishability as an implementation relation in the Task-PIOA framework, which allows us to express computational restrictions. The implementation relation is then proven using approximate simulation relations. This technique separates proof obligations into two categories: those requiring probabilistic reasoning, as well as those that do not. The latter is a good candidate for mechanization. We illustrate the general method by verifying the SZK property of the well-known identification protocol proposed by Girault, Poupard and Stern. â Supported by the MURI project:DARPA/AFOSR MURI F49620-02-1-0325 grant. 1
The use of quantum correlations to attack security protocols is an important research line deserving growing attention. An important class of cryptographic protocols used as building blocks for several other more complex protocols is zero-knowledge proof systems. One of the properties that zero-knowledge proof systems are assumed to satisfy is that it is impossible for the verifier to show to a third party that he has interacted with the prover (impossibility of transferring proofs). Herein, it is shown how Bell pairs, together with tamper-proofing, can be used to break the impossibility of transferring proofs for an important class of zero-knowledge proof systems.
This paper introduces a novel approach for augmenting attribute-based access control systems in a way that allows them to offer fully anonymous access to resources while at the same time achieving strong accountability guarantees. We assume that users hold attribute certificates and we show how to exploit cryptographic zero-knowledge proofs to allow requesting users to prove that they hold suitable certificates for accessing a resource. In contrast to the commonly taken approach of sending all possibly relevant certificates to the access control system, our approach hence does not release any information to the access control system except for the presence of a set of certificates satisfying the access condition. This constitutes the minimal amount of information that has to be released for coming up with a correct access decision, and our approach is the first to achieve this. Additionally given a trusted third party for identity escrow, we furthermore show that a concise application of zero-knowledge proofs offers the access control system the capability to hold a requesting user accountable for her actions under specific, well-defined conditions. All the employed cryptographic techniques are highly efficient, and an architecture for exploiting our approach in practical scenarios is already in place.
In this thesis,we design a protocol based on Zero-Knowledge Proof to realize the real time secure communication.This protocol is realized through the way of intertactive communication and is also an application of the Zero-Knowledge Proof in identification.The security of this protocol is based on the factorization of large numbers and RSA problems.This protocol can complete the identification with less amount of intetactive communication.