Blockchain Papers

Ming Zhong

No abstract is available for this record.

Yong-Sork Her, 容碩 許, キョ, ヨウソク, Kouichi Sakurai · 6 authors

In this paper, we propose the absentee e-voting system based on security, completeness and verifiability. We use r-th residue cryptography for homomorphic encryption, ZKIP (Zero-Knowledge interactive proofs), RSA algorithm for the secure absentee e-voting.

HE Mng-xing, Pingzhi Fan

A new multiple secrets sharing scheme, based on the intractability of the discrete logarithm (DL) and the RSA encryption algorithm is presented, in which the participants' shadows remain secret and can be reused, even if all subshadows are made public. Meanwhile, by using a zero-knowledge proof protocol, the validity verification of shadow and subshadow is also provided to prevent both dealer cheating and other participant cheating, and any freely given secrets without pre-computation by dealer can be reconstructed. The scheme can be applied to many areas such as conference key distribution, secure multi-part-computation, threshold signature etc.

Michael O’Donnell

In this paper we examine the role of Identification Protocols in the field of Cryptography. Firstly, the rationale behind the need for Identification Protocols is discussed. Secondly, we examine, in detail, challenge-response protocols, based upon zero-knowledge proofs, that form a subset of Identification Protocols in general. Thirdly, the mathematical tools necessary for the understanding of how these protocols work is given. Finally, we discuss four main Identification Protocols: Fiat-Shamir, Feige-Fiat-Shamir, Schnorr and Guillou- Quisquater. This discussion includes the theory, practical examples and the security aspects of each protocol.

Vanesa Daza, Javier Herranz, Carles Padró, Germán Sáez

In [16], Naor, Pinkas and Reingold introduced schemes in which some groups of servers distribute keys among a set of users in a distributed way. They gave some specic proposals both in the unconditional and in the computational security framework. Their computationally secure scheme is based on the Decisional DiÆe-Hellman Assumption. This model assumes secure communication between users and servers. Furthermore it requires users to do some expensive computations in order to obtain a key. In this paper we modify the model introduced in [16], requiring au-thenticated channels instead of assuming the existence of secure channels. Our model makes the user's computations easier, because most compu-tations of the protocol are carried out by servers, keeping to a more re-alistic situation. We propose a basic scheme, that makes use of ElGamal cryptosystem, and that ts in with this model in the case of a passive ad-versary. We then add zero-knowledge proofs and veriable secret sharing to prevent from the action of an active adversary. We consider general structures (not only the threshold ones) for those subsets of servers that can provide a key to a user and for those tolerated subsets of servers that can be corrupted by the adversary. We nd necessary combinatorial conditions on these structures in order to provide security to our scheme. 1

Magdi El-Soudani, Heba S. El-Refaey, Hebat-Allah M. Mourad

Zero knowledge proofs form an important category in the public key identification protocols, they are depending on number theory. In 1989, Stern announced his protocol which is based on syndrome-decoding problem, he also studied the attacks against this type of problems. In this paper, we propose a broadcasting variant based on the Stern’ s Identification scheme. Broadcasting is applied when there are one prover and many verifiers. In the proposed broadcasting scheme, the prover is communicating with verifiers through a broadcasting channel so he is running the identification session once, which minimizes the time and the communication complexity. We have developed Stern basic scheme to be adequate for broadcasting applications, but the underlying hard problem that the security of Stern identification scheme depends on, is used as it is.

Chun Chen

An interactive zero-knowledge proof based protocol of identification and digital signature is proposed in this paper. The security of protocol is based on large number factorization and security of RSA problems. This protocol can be applied to smart cards. This scheme requires minimal amount of computation and communications information. Compared with Nyang's scheme, the scheme is more likely to win higher security. The k , which is the cycle number in order to achieve zero-knowledge, is smaller than Nyang's. On one cycle, the highest security degree, which the protocol can achieve, is independent of the user's identity. The protocol is versatile enough to be applied to digital signature, multiple digital signature, and (N, T) threshold digital signature.

Takeru Miyazaki

No abstract is available for this record.

Tzafrir Cohen, Joe Kilian, Erez Petrank

No abstract is available for this record.

Taekyoung Kwon

This paper presents a new password authentication and key agreement protocol called AMP in a provable manner. The intrinsic problem with password authentication is a password, associated with each user, has low entropy so that (1) the password is hard to transmit securely over an insecure channel and (2) the password file is hard to protect. Our solution to this complex problem is the amplified password proof idea along with the amplified password file. A party commits the high entropy information and amplifies her password with that information in the amplified password proof. She never shows any information except that she knows it for her proof. Our amplified password proof idea is similar to the zero-knowledge proof in that sense. A server stores amplified verifiers in the amplified password file that is secure against a server file compromise and a dictionary attack. AMP mainly provides the passwordverifier based authentication and the Diffie-Hellman based key agreement, securely and efficiently. AMP is simple and actually the most efficient protocol among the related protocols.

Dae Hun Nyang, Joo Seok Song

We propose a zero-knowledge interactive proof based identification and signature scheme. The protocol is based on Euler's totient function and discrete logarithms over the ring Z/nZ , and can be applied to smart cards. A prover keeps a signed subgroup generator provided by a trusted center as its secret information. Our scheme has symmetricity in the sense that the same computational complexity and the same hardware both for Prover and for Verifier are required. Also, it requires minimal amount of computation and communications for secret information. The protocol is versatile enough to be applicable to digital signature scheme, multiple digital signature scheme and key exchange protocol. We outline those protocols to show the versatility of our protocol.

Taekyoung Kwon

This paper presents a new password authentication and key agreement protocol, AMP, based on the ampli ed password idea. The intrinsic problems with password authentication are the password itself has low entropy and the password le is very hard to protect. We presentthe ampli ed password proof and the ampli ed password le for solving these problems. A party commits the high entropy information and ampli es her password with that information in the amplifed password proof. She never shows any information except that she knows it. Our ampli ed password proof idea is very similar to the zero-knowledge proof in that sense. We adds one more idea � the ampli ed password le for password le protection. Aserver stores the ampli ed veri ers in the ampli ed password le that is secure against a server le compromise and a dictionary attack. AMP mainly provides the password-veri er based authentication and the Di e-Hellman based key agreement, securely and e ciently. AMP is easy to generalize in any other cyclic groups. In spite of those plentiful properties, AMP is actually the most e cient protocol among the related protocols due to the simultaneous multiple exponentiation method. Several variants such as AMPi,AMPn,AMPn+, AMP +,AMP++, and AMPc are also proposed. Among them, AMPn is actually the basic protocol of this paper that describes the ampli ed password proof idea while AMP is the most complete protocol that adds the ampli ed password le. AMPi simply removes the ampli ed password le from AMP.Intheend,wegive a comparison to the related protocols in terms of e ciency. This manuscript is a preliminary version of our paper available from the IACR eprint archive,

David Pointcheval

No abstract is available for this record.

Giovanni Di Crescenzo

No abstract is available for this record.

Vijay Varadharajan, Yi Mu

No abstract is available for this record.

Khanh Quoc Nguyen, Vijay Varadharajan, Yi Mu

This paper presents a technique to speed up practical zero-knowledge cryptographic protocols. We introduce a new technique of batching proofs of knowledge. Its security is analysed and its applicability to some cryptographic protocols is described. The use of the batching technique can significantly reduce the number of online computations required in the proofs and consequently helps to lower the costs associated with the corresponding transactions. This technique is particularly useful for e-commerce related cryptographic protocols.

Markus Jakobsson, Claus-Peter Schnorr

We study the notion of meta-proofs, which, as the name indicates, are proofs about proofs. We employ the notion of meta-proofs to produce a highly efficient oblivous proof of correct exponentiation. It is minimum-knowledge independently of whether the input is valid or not, a property that does not hold for many other protocols (that are zero-knowledge only for valid inputs.) This has direct security implications to multiparty protocols, where the protocols we demonstrate — one interactive and one non-interactive — can be employed to obtain protocol robustness at a low cost. As a result of potential independent interest, we show how to turn any standard discrete log signature scheme into a scheme for proving equality of discrete logarithms. We demonstrate our method using the Schnorr signature scheme.

Ran Canetti, Oded Goldreich, S. Goldwasser, Silvio Micali

We introduce the notion of Resettable Zero-Knowledge (rZK), a new security measure for cryptographic protocols which strengthens the classical notion of zero-knowledge. In essence, an rZK protocol is one that remains zero knowledge even if an adversary can interact with the prover many times, each time resetting the prover to its initial state and forcing it to use the same random tape. Under general complexity assumptions, which hold for example if the Discrete Logarithm Problem is hard, we construct (non-constant round) Resettable Zero-Knowledge proof-systems for NP constant-round Resettable Witness-Indistinguishable proof-systems for NP constant-round Resettable Zero-Knowledge arguments for NP in the public key model: where veriers have fixed, public keys associated with them. In addition to shedding new light on what makes zero knowledge possible (by constructing ZK protocols that use randomness in a dramatically weaker way than before), rZK has great relevance to applications. Firstly, we show that rZK protocols are closed under parallel and

Ransom Richardson, Joe Kilian

No abstract is available for this record.

Gerrit Bleumer

. In this paper, we establish the notion of divertibility as a protocol property as opposed to the existing notion as a language property (see Okamoto, Ohta [OO90]). We give a definition of protocol divertibility that applies to arbitrary 2-party protocols and is compatible with Okamoto and Ohta's definition in the case of interactive zero-knowledge proofs. Other important examples falling under the new definition are blind signature protocols. A su#cient criterion for divertibility is presented and found to be satisfied by many examples of protocols in the literature. The generality of the definition is further demonstrated by examples from protocol classes that have not been considered for divertibility before. We show diverted El-Gamal encryption and diverted Di#e-Hellman key exchange. Keywords: interactive protocol, divertibility, zero-knowledge proof, Fiat-Shamir identification, blind signature, Di#e-Hellman key-exchange, El-Gamal encryption. 1

Liqun Chen

No abstract is available for this record.

Julien P. Stern

No abstract is available for this record.

Matt Blaze, Gerrit Bleumer, Martin J. Strauss

No abstract is available for this record.

Cynthia Dwork, Moni Naor, Amit Sahai

Concurrent executions of a zero-knowledge protocol by a single prover (with one or more verifiers) may leak information and may not be zero-knowledge in toto . In this article, we study the problem of maintaining zero-knowledge.We introduce the notion of an (α, β) timing constraint : for any two processors P 1 and P 2 , if P 1 measures α elapsed time on its local clock and P 2 measures β elapsed time on its local clock, and P 2 starts after P 1 does, then P 2 will finish after P 1 does. We show that if the adversary is constrained by an (α, β) assumption then there exist four-round almost concurrent zero-knowledge interactive proofs and perfect concurrent zero-knowledge arguments for every language in NP . We also address the more specific problem of Deniable Authentication , for which we propose several particularly efficient solutions. Deniable Authentication is of independent interest, even in the sequential case; our concurrent solutions yield sequential solutions without recourse to timing , that is, in the standard model.