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Reconciling Two Views of Cryptography (The Computational Soundness of Formal Encryption)
, 2000
"... Two distinct, rigorous views of cryptography have developed over the years, in two mostly separate communities. One of the views relies on a simple but effective formal approach; the other, on a detailed computational model that considers issues of complexity and probability. ..."
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Cited by 337 (18 self)
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Two distinct, rigorous views of cryptography have developed over the years, in two mostly separate communities. One of the views relies on a simple but effective formal approach; the other, on a detailed computational model that considers issues of complexity and probability.
Protocol insecurity with finite number of sessions is NPcomplete
 Theoretical Computer Science
, 2001
"... We investigate the complexity of the protocol insecurity problem for a finite number of sessions (fixed number of interleaved runs). We show that this problem is NPcomplete with respect to a DolevYao model of intruders. The result does not assume a limit on the size of messages and supports nonat ..."
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Cited by 152 (13 self)
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We investigate the complexity of the protocol insecurity problem for a finite number of sessions (fixed number of interleaved runs). We show that this problem is NPcomplete with respect to a DolevYao model of intruders. The result does not assume a limit on the size of messages and supports nonatomic symmetric encryption keys. We also prove that in order to build an attack with a fixed number of sessions the intruder needs only to forge messages of linear size, provided that they are represented as dags.
A Model for Secure Protocols and Their Compositions (Extended Abstract)
 IEEE Transactions on Software Engineering
, 1996
"... We give a formal model of protocol security. Our model allows us to reason about the security of protocols, and considers issues of beliefs of agents, time, and secrecy. We prove a composition theorem which allows us to state sufficient conditions on two secure protocols A and B such that they may b ..."
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Cited by 70 (2 self)
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We give a formal model of protocol security. Our model allows us to reason about the security of protocols, and considers issues of beliefs of agents, time, and secrecy. We prove a composition theorem which allows us to state sufficient conditions on two secure protocols A and B such that they may be combined to form a new secure protocol C. Moreover, we give counterexamples to show that when the conditions are not met, the protocol C may not be secure. I. Introduction What does it mean for a protocol to be secure? How can we reason about secure protocols? If we combine two existing protocols into a common protocol, what can we say about the security of the new protocol? This paper develops a family of tools for reasoning about protocol security. We adopt a modelbased approach for defining protocol security properties. This allows us to describe security properties in much greater detail and precision than previous frameworks for reasoning about protocol security. Some of the most a...
Tree Automata With One Memory, Set Constraints and Cryptographic Protocols
"... We introduce a class of tree automata that perform tests on a memory that is updated using function symbol application and projection. The language emptiness problem for this class of tree automata is shown to be in DEXPTIME. ..."
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Cited by 69 (4 self)
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We introduce a class of tree automata that perform tests on a memory that is updated using function symbol application and projection. The language emptiness problem for this class of tree automata is shown to be in DEXPTIME.
Formal Methods for Cryptographic Protocol Analysis: Emerging Issues and Trends
, 2003
"... The history of the application of formal methods to cryptographic protocol analysis spans over 20 years and recently has been showing signs of new maturity and consolidation. Not only have a number of specialized tools been developed, and generalpurpose ones been adapted, but people have begun apply ..."
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Cited by 61 (0 self)
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The history of the application of formal methods to cryptographic protocol analysis spans over 20 years and recently has been showing signs of new maturity and consolidation. Not only have a number of specialized tools been developed, and generalpurpose ones been adapted, but people have begun applying these tools to realistic protocols, in many cases supplying feedback to designers that can be used to improve the protocol’s security. In this paper, we will describe some of the ongoing work in this area, as well as describe some of the new challenges and the ways in which they are being met.
Multiset Rewriting and the Complexity of Bounded Security Protocols
 Journal of Computer Security
, 2002
"... We formalize the DolevYao model of security protocols, using a notation based on multiset rewriting with existentials. The goals are to provide a simple formal notation for describing security protocols, to formalize the assumptions of the DolevYao model using this notation, and to analyze the ..."
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Cited by 57 (6 self)
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We formalize the DolevYao model of security protocols, using a notation based on multiset rewriting with existentials. The goals are to provide a simple formal notation for describing security protocols, to formalize the assumptions of the DolevYao model using this notation, and to analyze the complexity of the secrecy problem under various restrictions. We prove that, even for the case where we restrict the size of messages and the depth of message encryption, the secrecy problem is undecidable for the case of an unrestricted number of protocol roles and an unbounded number of new nonces. We also identify several decidable classes, including a dexpcomplete class when the number of nonces is restricted, and an npcomplete class when both the number of nonces and the number of roles is restricted. We point out a remaining open complexity problem, and discuss the implications these results have on the general topic of protocol analysis.
Open Issues in Formal Methods for Cryptographic Protocol Analysis
 In Proceedings of DISCEX 2000
, 2000
"... The history of the application of formal methods to cryptographic protocol analysis spans nearly twenty years, and recently has been showing signs of new maturity and consolidation. A number of specialized tools have been developed, and others have effectively demonstrated that existing generalpurp ..."
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Cited by 56 (4 self)
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The history of the application of formal methods to cryptographic protocol analysis spans nearly twenty years, and recently has been showing signs of new maturity and consolidation. A number of specialized tools have been developed, and others have effectively demonstrated that existing generalpurpose tools can also be applied to these problems with good results. However, with this better understanding of the field comes new problems that strain against the limits of the existing tools. In this paper we will outline some of these new problem areas, and describe what new research needs to be done to to meet the challenges posed.
Relating Symbolic and Cryptographic Secrecy
 IN PROC. IEEE SYMPOSIUM ON SECURITY AND PRIVACY
, 2004
"... We investigate the relation between symbolic and cryptographic secrecy properties for cryptographic protocols. Symbolic secrecy of payload messages or exchanged keys is arguably the most important notion of secrecy shown with automated proof tools. It means that an adversary restricted to symboli ..."
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Cited by 41 (8 self)
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We investigate the relation between symbolic and cryptographic secrecy properties for cryptographic protocols. Symbolic secrecy of payload messages or exchanged keys is arguably the most important notion of secrecy shown with automated proof tools. It means that an adversary restricted to symbolic operations on terms can never get the entire considered object into its knowledge set. Cryptographic secrecy essentially
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 32 (13 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.
Security properties: two agents are sufficient
 In Research Report LSV0210, Lab. Speci and Veri ENS de
, 2003
"... We consider arbitrary cryptographic protocols and security properties. We show that it is always sufficient to consider a bounded number of agents b (actually b = 2 in most of the cases): if there is an attack involving n agents, then there is an attack involving at most b agents. ..."
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Cited by 31 (4 self)
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We consider arbitrary cryptographic protocols and security properties. We show that it is always sufficient to consider a bounded number of agents b (actually b = 2 in most of the cases): if there is an attack involving n agents, then there is an attack involving at most b agents.