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25
A Probabilistic PolyTime Framework for Protocol Analysis
, 1998
"... We develop a framework for analyzing security protocols in which protocol adversaries may be arbitrary probabilistic polynomialtime processes. In this framework, protocols are written in a form of process calculus where security may be expressed in terms of observational equivalence, a standard rel ..."
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Cited by 114 (7 self)
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We develop a framework for analyzing security protocols in which protocol adversaries may be arbitrary probabilistic polynomialtime processes. In this framework, protocols are written in a form of process calculus where security may be expressed in terms of observational equivalence, a standard relation from programming language theory that involves quantifying over possible environments that might interact with the protocol. Using an asymptotic notion of probabilistic equivalence, we relate observational equivalence to polynomialtime statistical tests and discuss some example protocols to illustrate the potential of this approach.
Symmetric Encryption in a Simulatable DolevYao Style Cryptographic Library
 In Proc. 17th IEEE Computer Security Foundations Workshop (CSFW
, 2004
"... Recently we solved the longstanding open problem of justifying a DolevYao type model of cryptography as used in virtually all automated protocol provers under active attacks. The justification was done by defining an ideal system handling DolevYaostyle terms and a cryptographic realization wi ..."
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Cited by 58 (17 self)
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Recently we solved the longstanding open problem of justifying a DolevYao type model of cryptography as used in virtually all automated protocol provers under active attacks. The justification was done by defining an ideal system handling DolevYaostyle terms and a cryptographic realization with the same user interface, and by showing that the realization is as secure as the ideal system in the sense of reactive simulatability. This definition encompasses arbitrary active attacks and enjoys general composition and propertypreservation properties. Security holds in the standard model of cryptography and under standard assumptions of adaptively secure primitives.
Probabilistic PolynomialTime Equivalence and Security Analysis
 IN PROC. WORLD CONGRESS ON FORMAL METHODS, VOLUME 1708 OF LNCS
, 1999
"... We use properties of observational equivalence for a probabilistic process calculus to prove an authentication property of a cryptographic protocol. The process calculus is a form of calculus, with probabilistic scheduling instead of nondeterminism, over a term language that captures probabili ..."
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Cited by 52 (12 self)
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We use properties of observational equivalence for a probabilistic process calculus to prove an authentication property of a cryptographic protocol. The process calculus is a form of calculus, with probabilistic scheduling instead of nondeterminism, over a term language that captures probabilistic polynomial time. The operational semantics of this calculus gives priority to communication over private channels, so that the presence of private communication does not affect the observable probability of visible actions. Our definition of observational equivalence involves asymptotic comparison of uniform process families, only requiring equivalence to within vanishing error probabilities. This definition differs from previous notions of probabilistic process equivalence that require equal probabilities for corresponding actions; asymptotics fit our intended application and make equivalence transitive, thereby justifying the use of the term "equivalence." Our security proof uses a series of lemmas about probabilistic observational equivalence that may well prove useful for establishing correctness of other cryptographic protocols.
A probabilistic polynomialtime calculus for analysis of cryptographic protocols
 Electronic Notes in Theoretical Computer Science
, 2001
"... We prove properties of a process calculus that is designed for analyzing security protocols. Our longterm goal is to develop a form of protocol analysis, consistent with standard cryptographic assumptions, that provides a language for expressing probabilistic polynomialtime protocol steps, a spec ..."
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Cited by 44 (8 self)
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We prove properties of a process calculus that is designed for analyzing security protocols. Our longterm goal is to develop a form of protocol analysis, consistent with standard cryptographic assumptions, that provides a language for expressing probabilistic polynomialtime protocol steps, a specification method based on a compositional form of equivalence, and a logical basis for reasoning about equivalence. The process calculus is a variant of CCS, with bounded replication and probabilistic polynomialtime expressions allowed in messages and boolean tests. To avoid inconsistency between security and nondeterminism, messages are scheduled probabilistically instead of nondeterministically. We prove that evaluation of any process expression halts in probabilistic polynomial time and define a form of asymptotic protocol equivalence that allows security properties to be expressed using observational equivalence, a standard relation from programming language theory that involves quantifying over possible environments that might interact with the protocol. We develop a form of probabilistic bisimulation and use it to establish the soundness of an equational proof system based on observational equivalences. The proof system is illustrated by a formation derivation of the assertion, wellknown in cryptography, that ElGamal encryption’s semantic security is equivalent to the (computational) Decision DiffieHellman assumption. This example demonstrates the power of probabilistic bisimulation and equational reasoning for protocol security.
A cryptographically sound security proof of the NeedhamSchroederLowe publickey protocol
 JOURNAL ON SELECTED AREAS IN COMMUN.
, 2004
"... We present a cryptographically sound security proof of the wellknown NeedhamSchroederLowe publickey protocol for entity authentication. This protocol was previously only proved over unfounded abstractions from cryptography. We show that it is secure against arbitrary active attacks if it is imp ..."
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Cited by 33 (14 self)
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We present a cryptographically sound security proof of the wellknown NeedhamSchroederLowe publickey protocol for entity authentication. This protocol was previously only proved over unfounded abstractions from cryptography. We show that it is secure against arbitrary active attacks if it is implemented using standard provably secure cryptographic primitives. Nevertheless, our proof does not have to deal with the probabilistic aspects of cryptography and is hence in the scope of current automated proof tools. We achieve this by exploiting a recently proposed DolevYaostyle cryptographic library with a provably secure cryptographic implementation. Besides establishing the cryptographic security of the NeedhamSchroederLowe protocol, our result exemplifies the potential of this cryptographic library and paves the way for the cryptographically sound verification of security protocols by automated proof tools.
Cryptographically Sound Theorem Proving
 In Proc. 19th IEEE CSFW
, 2006
"... We describe a faithful embedding of the DolevYao model of Backes, Pfitzmann, and Waidner (CCS 2003) in the theorem prover Isabelle/HOL. This model is cryptographically sound in the strong sense of reactive simulatability/UC, which essentially entails the preservation of arbitrary security proper ..."
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Cited by 26 (7 self)
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We describe a faithful embedding of the DolevYao model of Backes, Pfitzmann, and Waidner (CCS 2003) in the theorem prover Isabelle/HOL. This model is cryptographically sound in the strong sense of reactive simulatability/UC, which essentially entails the preservation of arbitrary security properties under active attacks and in arbitrary protocol environments. The main challenge in designing a practical formalization of this model is to cope with the complexity of providing such strong soundness guarantees. We reduce this complexity by abstracting the model into a sound, lightweight formalization that enables both concise property specifications and efficient application of our proof strategies and their supporting proof tools. This yields the first toolsupported framework for symbolically verifying security protocols that enjoys the strong cryptographic soundness guarantees provided by reactive simulatability/UC. As a proof of concept, we have proved the security of the NeedhamSchroederLowe protocol using our framework.
A cryptographically sound DolevYao style security proof of the OtwayRees protocol
 In Proc. 9th European Symposium on Research in Computer Security (ESORICS
, 2004
"... We present the first cryptographically sound DolevYaostyle security proof of a comprehensive electronic payment system. The payment system is a slightly simplified variant of the 3KP payment system and comprises a variety of different security requirements ranging from basic ones like the impossibi ..."
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Cited by 24 (10 self)
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We present the first cryptographically sound DolevYaostyle security proof of a comprehensive electronic payment system. The payment system is a slightly simplified variant of the 3KP payment system and comprises a variety of different security requirements ranging from basic ones like the impossibility of unauthorized payments to more sophisticated properties like disputability. We show that the payment system is secure against arbitrary active attacks, including arbitrary concurrent protocol runs and arbitrary manipulation of bitstrings within polynomial time if the protocol is implemented using provably secure cryptographic primitives. Although we achieve security under cryptographic definitions, our proof does not have to deal with probabilistic aspects of cryptography and is hence within the scope of current proof tools. The reason is that we exploit a recently proposed DolevYaostyle cryptographic library with a provably secure cryptographic implementation. Together with composition and preservation theorems of the underlying model, this allows us to perform the actual proof effort in a deterministic setting corresponding to a slightly extended DolevYao model. 1.
A Computational Interpretation of DolevYao Adversaries
 in Proc. of 3rd Int. Workshop on Issues in the Theory of Security (WITS’03
, 2003
"... The Dolev{Yao model is a simple and useful framework in which to analyze security protocols, but it assumes an extremely limited adversary. It is unclear if the results of this model would remain valid were the adversary to be given additional power. In this work, we show that there exist situat ..."
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Cited by 15 (1 self)
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The Dolev{Yao model is a simple and useful framework in which to analyze security protocols, but it assumes an extremely limited adversary. It is unclear if the results of this model would remain valid were the adversary to be given additional power. In this work, we show that there exist situations in which DolevYao adversary can be viewed as a valid abstraction of all realistic adversaries. We do this in two steps: 1. We translate the allowed behaviors of the DolevYao adversary into the computational model, an alternate framework with a very powerful adversary.
Computationally sound secrecy proofs by mechanized flow analysis
 In Proc. 13th CCS
, 2006
"... A large body of work exists for machineassisted analysis of cryptographic protocols in the formal (DolevYao) model, i.e., by abstracting cryptographic operators as a free algebra. In particular, proving secrecy by typing has shown to be a salient technique as it allowed for elegant and fully autom ..."
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Cited by 13 (2 self)
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A large body of work exists for machineassisted analysis of cryptographic protocols in the formal (DolevYao) model, i.e., by abstracting cryptographic operators as a free algebra. In particular, proving secrecy by typing has shown to be a salient technique as it allowed for elegant and fully automated proofs, often