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727
DiffieHellman Key Distribution Extended to Group Communication
, 1996
"... Ever since 2party DiffieHellman key exchange was first proposed in 1976, there have been efforts to extend its simplicity and elegance to a group setting. Notable solutions have been proposed by Ingemarsson et al. (in 1982) and Burmester/Desmedt (in 1994). In this paper, we consider a class of pro ..."
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Cited by 252 (10 self)
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Ever since 2party DiffieHellman key exchange was first proposed in 1976, there have been efforts to extend its simplicity and elegance to a group setting. Notable solutions have been proposed by Ingemarsson et al. (in 1982) and Burmester/Desmedt (in 1994). In this paper, we consider a class of protocols that we call natural extensions of DiffieHellman to the nparty case. After demonstrating the security of the entire class based on the intractability of the DiffieHellman problem we introduce two novel and practical protocols and compare them to the previous results. We argue that our protocols are optimal with respect to certain aspects of protocol complexity. 1 Introduction It has been almost twenty years since DiffieHellman (DH) 2party key exchange was first proposed in [1]. In the meantime, there have been many attempts to extend its elegance and simplicity to the group setting. The main motivating factor is the increasing popularity of various types of groupware application...
Signature schemes and anonymous credentials from bilinear maps
, 2004
"... We propose a new and efficient signature scheme that is provably secure in the plain model. The security of our scheme is based on a discretelogarithmbased assumption put forth by Lysyanskaya, Rivest, Sahai, and Wolf (LRSW) who also showed that it holds for generic groups and is independent of th ..."
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Cited by 235 (25 self)
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We propose a new and efficient signature scheme that is provably secure in the plain model. The security of our scheme is based on a discretelogarithmbased assumption put forth by Lysyanskaya, Rivest, Sahai, and Wolf (LRSW) who also showed that it holds for generic groups and is independent of the decisional DiffieHellman assumption. We prove security of our scheme under the LRSW assumption for groups with bilinear maps. We then show how our scheme can be used to construct efficient anonymous credential systems as well as group signature and identity escrow schemes. To this end, we provide efficient protocols that allow one to prove in zeroknowledge the knowledge of a signature on a committed (or encrypted) message and to obtain a signature on a committed message.
Key Agreement in Dynamic Peer Groups
 IEEE Transactions on Parallel and Distributed Systems
, 2000
"... As a result of the increased popularity of grouporiented applications and protocols, group communication occurs in many different settings: from network multicasting to application layer tele and videoconferencing. Regardless of the application environment, security services are necessary to provi ..."
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Cited by 212 (18 self)
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As a result of the increased popularity of grouporiented applications and protocols, group communication occurs in many different settings: from network multicasting to application layer tele and videoconferencing. Regardless of the application environment, security services are necessary to provide communication privacy and integrity. This paper considers the problem of key agreementindynamic peer groups. (Key agreement, especially in a group setting, is the steeping stone for all other security services.) Dynamic peer groups require not only initial key agreement (IKA) but also auxiliary key agreement (AKA) operations such as member addition, member deletion and group fusion. We discuss all group key agreement operations and present a concrete protocol suite, CLIQUES, which offers complete key agreement services. CLIQUES is based on multiparty extensions of the wellknown DiffieHellman key exchange method. The protocols are efficient and provably secure against passiveadversari...
Efficient proofs that a committed number lies in an interval
, 2000
"... Abstract. Alice wants to prove that she is young enough to borrow money from her bank, without revealing her age. She therefore needs a tool for proving that a committed number lies in a specific interval. Up to now, such tools were either inefficient (too many bits to compute and to transmit) or in ..."
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Cited by 174 (0 self)
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Abstract. Alice wants to prove that she is young enough to borrow money from her bank, without revealing her age. She therefore needs a tool for proving that a committed number lies in a specific interval. Up to now, such tools were either inefficient (too many bits to compute and to transmit) or inexact (i.e. proved membership to a much larger interval). This paper presents a new proof, which is both efficient and exact. Here, “efficient ” means that there are less than 20 exponentiations to perform and less than 2 Kbytes to transmit. The potential areas of application of this proof are numerous (electronic cash, group signatures, publicly verifiable secret encryption, etc...). 1
Secure Distributed Key Generation for DiscreteLog Based Cryptosystems
, 1999
"... Abstract. Distributed key generation is a main component of threshold cryptosystems and distributed cryptographic computing in general. Solutions to the distributed generation of private keys for discretelog based cryptosystems have been known for several years and used in a variety of protocols an ..."
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Cited by 168 (4 self)
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Abstract. Distributed key generation is a main component of threshold cryptosystems and distributed cryptographic computing in general. Solutions to the distributed generation of private keys for discretelog based cryptosystems have been known for several years and used in a variety of protocols and in many research papers. However, these solutions fail to provide the full security required and claimed by these works. We show how an active attacker controlling a small number of parties can bias the values of the generated keys, thus violating basic correctness and secrecy requirements of a key generation protocol. In particular, our attacks point out to the places where the proofs of security fail. Based on these findings we designed a distributed key generation protocol which we present here together with a rigorous proof of security. Our solution, that achieves optimal resiliency, can be used as a dropin replacement for key generation modules as well as other components of threshold or proactive discretelog based cryptosystems.
An Efficient Offline Electronic Cash System Based On The Representation Problem
, 1993
"... We present a new offline electronic cash system based on a problem, called the representation problem, of which little use has been made in literature thus far. Our system is the first to be based entirely on discrete logarithms. Using the representation problem as a basic concept, some technique ..."
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Cited by 151 (3 self)
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We present a new offline electronic cash system based on a problem, called the representation problem, of which little use has been made in literature thus far. Our system is the first to be based entirely on discrete logarithms. Using the representation problem as a basic concept, some techniques are introduced that enable us to construct protocols for withdrawal and payment that do not use the cut and choose methodology of earlier systems. As a consequence, our cash system is much more efficient in both computation and communication complexity than previously proposed systems. Another
Pseudonym Systems
, 1999
"... Pseudonym systems allow users to interact with multiple organizations anonymously, using pseudonyms. The pseudonyms cannot be linked, but are formed in such a way that a user can prove to one organization a statement about his relationship with another. Such statement is called a credential. Previou ..."
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Cited by 149 (10 self)
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Pseudonym systems allow users to interact with multiple organizations anonymously, using pseudonyms. The pseudonyms cannot be linked, but are formed in such a way that a user can prove to one organization a statement about his relationship with another. Such statement is called a credential. Previous work in this area did not protect the system against dishonest users who collectively use their pseudonyms and credentials, i.e. share an identity. Previous practical schemes also relied very heavily on the involvement of a trusted center. In the present paper we give a formal definition of pseudonym systems where users are motivated not to share their identity, and in which the trusted center's involvement is minimal. We give theoretical constructions for such systems based on any oneway function. We also suggest an efficient and easy to implement practical scheme. This is joint work with Ronald L. Rivest and Amit Sahai.
CoercionResistant Electronic Elections
 In WPES ’05
, 2002
"... We introduce a model for electronic election schemes that involves a more powerful adversary than in previous work. In particular, we allow the adversary to demand of coerced voters that they vote in a particular manner, abstain from voting, or even disclose their secret keys. We define a scheme ..."
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Cited by 148 (0 self)
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We introduce a model for electronic election schemes that involves a more powerful adversary than in previous work. In particular, we allow the adversary to demand of coerced voters that they vote in a particular manner, abstain from voting, or even disclose their secret keys. We define a scheme to be coercion resistant if it is impossible for the adversary to determine whether a coerced voter complies with the demands. Furthermore, we relax the requirements made in some previous proposals from an untappable channel to only requiring the existence of an anonymous channel.
Proving in ZeroKnowledge that a Number is the Product of Two Safe Primes
, 1998
"... This paper presents the first efficient statistical zeroknowledge protocols to prove statements such as: A committed number is a pseudoprime. ..."
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Cited by 142 (15 self)
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This paper presents the first efficient statistical zeroknowledge protocols to prove statements such as: A committed number is a pseudoprime.
The gapproblems: a new class of problems for the security of cryptographic schemes
 Proceedings of PKC 2001, volume 1992 of LNCS
, 1992
"... Abstract. This paper introduces a novel class of computational problems, the gap problems, which can be considered as a dual to the class of the decision problems. We show the relationship among inverting problems, decision problems and gap problems. These problems find a nice and rich practical ins ..."
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Cited by 140 (11 self)
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Abstract. This paper introduces a novel class of computational problems, the gap problems, which can be considered as a dual to the class of the decision problems. We show the relationship among inverting problems, decision problems and gap problems. These problems find a nice and rich practical instantiation with the DiffieHellman problems. Then, we see how the gap problems find natural applications in cryptography, namely for proving the security of very efficient schemes, but also for solving a more than 10year old open security problem: the Chaum’s undeniable signature.