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Universally composable security: A new paradigm for cryptographic protocols
, 2013
"... We present a general framework for representing cryptographic protocols and analyzing their security. The framework allows specifying the security requirements of practically any cryptographic task in a unified and systematic way. Furthermore, in this framework the security of protocols is preserved ..."
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Cited by 611 (34 self)
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We present a general framework for representing cryptographic protocols and analyzing their security. The framework allows specifying the security requirements of practically any cryptographic task in a unified and systematic way. Furthermore, in this framework the security of protocols is preserved under a general protocol composition operation, called universal composition. The proposed framework with its securitypreserving composition operation allows for modular design and analysis of complex cryptographic protocols from relatively simple building blocks. Moreover, within this framework, protocols are guaranteed to maintain their security in any context, even in the presence of an unbounded number of arbitrary protocol instances that run concurrently in an adversarially controlled manner. This is a useful guarantee, that allows arguing about the security of cryptographic protocols in complex and unpredictable environments such as modern communication networks.
NonMalleable Cryptography
 SIAM Journal on Computing
, 2000
"... The notion of nonmalleable cryptography, an extension of semantically secure cryptography, is defined. Informally, in the context of encryption the additional requirement is that given the ciphertext it is impossible to generate a different ciphertext so that the respective plaintexts are related. ..."
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Cited by 447 (22 self)
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The notion of nonmalleable cryptography, an extension of semantically secure cryptography, is defined. Informally, in the context of encryption the additional requirement is that given the ciphertext it is impossible to generate a different ciphertext so that the respective plaintexts are related. The same concept makes sense in the contexts of string commitment and zeroknowledge proofs of possession of knowledge. Nonmalleable schemes for each of these three problems are presented. The schemes do not assume a trusted center; a user need not know anything about the number or identity of other system users. Our cryptosystem is the first proven to be secure against a strong type of chosen ciphertext attack proposed by Rackoff and Simon, in which the attacker knows the ciphertext she wishes to break and can query the decryption oracle on any ciphertext other than the target.
Security and Composition of Multiparty Cryptographic Protocols
 JOURNAL OF CRYPTOLOGY
, 1998
"... We present general definitions of security for multiparty cryptographic protocols, with focus on the task of evaluating a probabilistic function of the parties' inputs. We show that, with respect to these definitions, security is preserved under a natural composition operation. The definitions f ..."
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Cited by 389 (18 self)
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We present general definitions of security for multiparty cryptographic protocols, with focus on the task of evaluating a probabilistic function of the parties' inputs. We show that, with respect to these definitions, security is preserved under a natural composition operation. The definitions follow the general paradigm of known definitions; yet some substantial modifications and simplifications are introduced. The composition operation is the natural `subroutine substitution' operation, formalized by Micali and Rogaway. We consider several standard settings for multiparty protocols, including the cases of eavesdropping, Byzantine, nonadaptive and adaptive adversaries, as well as the informationtheoretic and the computational models. In particular, in the computational model we provide the first definition of security of protocols that is shown to be preserved under composition.
Optimistic fair exchange of digital signatures
 IEEE Journal on Selected Areas in Communications
, 1998
"... Abstract. We present a new protocol that allows two players to exchange digital signatures over the Internet in a fair way, so that either each player gets the other’s signature, or neither player does. The obvious application is where the signatures represent items of value, for example, an elect ..."
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Cited by 239 (10 self)
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Abstract. We present a new protocol that allows two players to exchange digital signatures over the Internet in a fair way, so that either each player gets the other’s signature, or neither player does. The obvious application is where the signatures represent items of value, for example, an electronic check or airline ticket. The protocol can also be adapted to exchange encrypted data. The protocol relies on a trusted third party, but is “optimistic, ” in that the third party is only needed in cases where one player attempts to cheat or simply crashes. A key feature of our protocol is that a player can always force a timely and fair termination, without the cooperation of the other player. 1
On the Composition of ZeroKnowledge Proof Systems
 SIAM Journal on Computing
, 1990
"... : The wide applicability of zeroknowledge interactive proofs comes from the possibility of using these proofs as subroutines in cryptographic protocols. A basic question concerning this use is whether the (sequential and/or parallel) composition of zeroknowledge protocols is zeroknowledge too. We ..."
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Cited by 190 (14 self)
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: The wide applicability of zeroknowledge interactive proofs comes from the possibility of using these proofs as subroutines in cryptographic protocols. A basic question concerning this use is whether the (sequential and/or parallel) composition of zeroknowledge protocols is zeroknowledge too. We demonstrate the limitations of the composition of zeroknowledge protocols by proving that the original definition of zeroknowledge is not closed under sequential composition; and that even the strong formulations of zeroknowledge (e.g. blackbox simulation) are not closed under parallel execution. We present lower bounds on the round complexity of zeroknowledge proofs, with significant implications to the parallelization of zeroknowledge protocols. We prove that 3round interactive proofs and constantround ArthurMerlin proofs that are blackbox simulation zeroknowledge exist only for languages in BPP. In particular, it follows that the "parallel versions" of the first interactive proo...
BlackBox Concurrent ZeroKnowledge Requires (almost) Logarithmically Many Rounds
 SIAM Journal on Computing
, 2002
"... We show that any concurrent zeroknowledge protocol for a nontrivial language (i.e., for a language outside BPP), whose security is proven via blackbox simulation, must use at least ~ \Omega\Gamma/10 n) rounds of interaction. This result achieves a substantial improvement over previous lower bound ..."
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Cited by 85 (6 self)
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We show that any concurrent zeroknowledge protocol for a nontrivial language (i.e., for a language outside BPP), whose security is proven via blackbox simulation, must use at least ~ \Omega\Gamma/10 n) rounds of interaction. This result achieves a substantial improvement over previous lower bounds, and is the first bound to rule out the possibility of constantround concurrent zeroknowledge when proven via blackbox simulation. Furthermore, the bound is polynomially related to the number of rounds in the best known concurrent zeroknowledge protocol for languages in NP (which is established via blackbox simulation).
Resettable ZeroKnowledge
 In 32nd STOC
, 1999
"... We introduce the notion of Resettable ZeroKnowledge (rZK), a new security measure for cryptographic protocols which strengthens the classical notion of zeroknowledge. In essence, an rZK protocol is one that remains zero knowledge even if an adversary can interact with the prover many times, eac ..."
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Cited by 71 (7 self)
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We introduce the notion of Resettable ZeroKnowledge (rZK), a new security measure for cryptographic protocols which strengthens the classical notion of zeroknowledge. 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 him to use the same random tape.
Universal Composition with Joint State
, 2002
"... We propose a new composition operation for cryptographic protocols, called universal composition with joint state, and demonstrate sufficient conditions for when the new operation preserves security. In contrast with existing composition operations, where the instances of the composed protocols are ..."
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Cited by 61 (5 self)
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We propose a new composition operation for cryptographic protocols, called universal composition with joint state, and demonstrate sufficient conditions for when the new operation preserves security. In contrast with existing composition operations, where the instances of the composed protocols are assumed to have completely disjoint local states, the new operation allows the composed protocols to have some amount of joint state (and, in particular, joint randomness) while still guaranteeing strong composability properties.
Magic Functions
, 1999
"... We consider three apparently unrelated fundamental problems in distributed computing, cryptography and complexity theory and prove that they are essentially the same problem. ..."
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Cited by 55 (0 self)
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We consider three apparently unrelated fundamental problems in distributed computing, cryptography and complexity theory and prove that they are essentially the same problem.
On Deniability in the Common Reference String and Random Oracle Model
 In proceedings of CRYPTO ’03, LNCS series
, 2003
"... Abstract. We revisit the definitions of zeroknowledge in the Common Reference String (CRS) model and the Random Oracle (RO) model. We argue that even though these definitions syntactically mimic the standard zeroknowledge definition, they loose some of its spirit. In particular, we show that there ..."
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Cited by 52 (5 self)
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Abstract. We revisit the definitions of zeroknowledge in the Common Reference String (CRS) model and the Random Oracle (RO) model. We argue that even though these definitions syntactically mimic the standard zeroknowledge definition, they loose some of its spirit. In particular, we show that there exist a specific natural security property that is not captured by these definitions. This is the property of deniability. We formally define the notion of deniable zeroknowledge in these models and investigate the possibility of achieving it. Our results are different for the two models: – Concerning the CRS model, we rule out the possibility of achieving deniable zeroknowledge protocols in “natural ” settings where such protocols cannot already be achieved in plain model. – In the RO model, on the other hand, we construct an efficient 2round deniable zeroknowledge argument of knowledge, that preserves both the zeroknowledge property and the proof of knowledge property under concurrent executions (concurrent zeroknowledge and concurrent proofof knowledge). 1