Soft Constraint Programming to Analysing Security Protocols

Security protocols stipulate how the remote principals of a computer network should interact in order to obtain specific security goals. The crucial goals of confidentiality and authentication may be achieved in various forms, each of different strength. Using soft (rather than crisp) constraints, we develop a uniform formal notion for the two goals. They are no longer formalised as mere yes/no properties as in the existing literature, but gain an extra parameter, the security level. For example, different messages can enjoy different levels of confidentiality, or a principal can achieve different levels of authentication with different principals. The goals are formalised within a general framework for protocol analysis that is amenable to mechanisation by model checking. Following the application of the framework to analysing the asymmetric Needham-Schroeder protocol, we have recently discovered a new attack on that protocol as a form of retaliation by principals who have been attacked previously. Having commented on that attack, we then demonstrate the framework on a bigger, largely deployed protocol consisting of three phases, Kerberos.Comment: 29 pages, To appear in Theory and Practice of Logic Programming (TPLP) Paper for Special Issue (Verification and Computational Logic

Soft Constraint Programming to Analysing Security Protocols

Security protocols stipulate how remote principals of a computer network should interact in order to obtain specific security goals. The crucial goals of confidentiality and authentication may be achieved in various forms. Using soft (rather than crisp) constraints, we develop a uniform formal notion for the two goals. They are no longer formalised as mere yes/no properties as in the existing literature, but gain an extra parameter, the security level. For example, different messages can enjoy different levels of confidentiality, or a principal can achieve different levels of authentication with different principals. The goals are formalised within a general framework for protocol analysis that is amenable to mechanisation by model checking. Following the application of the framework to analysing the asymmetric Needham- Schroeder protocol, we have recently discovered a new attack on that protocol. We briefly describe that attack, and demonstrate the framework on a bigger, largely deployed protocol consisting of three phases, Kerberos

A Survey of Verification Techniques for Security Protocols

Security protocols aim to allow secure electronic communication despite the potential presence of eavesdroppers. Guaranteeing their correctness is vital in many applications. This report briefly surveys the many formal specification and verification techniques proposed for describing and analysing security protocols

A framework for proving the correctness of cryptographic protocol properties by linear temporal logic

In this paper, a framework for cryptographic protocol analysis using linear temporal logic is proposed. The framework can be used to specify and analyse security protocols. It aims to investigate and analyse the security protocols properties that are secure or have any flaws. The framework extends the linear temporal logic by including the knowledge of participants in each status that may change over the time. It includes two main parts, the Language of Temporal Logic (LTL) and the domain knowledge. The ability of the framework is demonstrated by analysing the Needham-Schroeder public key protocol and the Andrew Secure RPC protocol as examples

Transforming Password Protocols to Compose

Formal, symbolic techniques are extremely useful for modelling and analysing security protocols. They improved our understanding of security protocols, allowed to discover flaws, and also provide support for protocol design. However, such analyses usually consider that the protocol is executed in isolation or assume a bounded number of protocol sessions. Hence, no security guarantee is provided when the protocol is executed in a more complex environment. In this paper, we study whether password protocols can be safely composed, even when a same password is reused. More precisely, we present a transformation which maps a password protocol that is secure for a single protocol session (a decidable problem) to a protocol that is secure for an unbounded number of sessions. Our result provides an effective strategy to design secure password protocols: (i) design a protocol intended to be secure for one protocol session; (ii) apply our transformation and obtain a protocol which is secure for an unbounded number of sessions. Our technique also applies to compose different password protocols allowing us to obtain both inter-protocol and inter-session composition

Transforming Password Protocols to Compose

International audienceFormal, symbolic techniques are extremely useful for modelling and analysing security protocols. They improved our understanding of security protocols, allowed to discover flaws, and also provide support for protocol design. However, such analyses usually consider that the protocol is executed in isolation or assume a bounded number of protocol sessions. Hence, no security guarantee is provided when the protocol is executed in a more complex environment. In this paper, we study whether password protocols can be safely composed, even when a same password is reused. More precisely, we present a transformation which maps a password protocol that is secure for a single protocol session (a decidable problem) to a protocol that is secure for an unbounded number of sessions. Our result provides an effective strategy to design secure password protocols: (i) design a protocol intended to be secure for one protocol session; (ii) apply our transformation and obtain a protocol which is secure for an unbounded number of sessions. Our technique also applies to compose different password protocols allowing us to obtain both inter-protocol and inter-session composition

Composition of Password-based Protocols

International audienceFormal and symbolic techniques are extremely useful for modelling and analysing security protocols. They have helped to improve our understanding of such protocols, allowed us to discover aws, and they also provide support for protocol design. However, such analyses usually consider that the protocol is executed in isolation or assume a bounded number of protocol sessions. Hence, no security guarantee is provided when the protocol is executed in a more complex environment.\par In this paper, we study whether password protocols can be safely composed, even when a same password is reused. More precisely, we present a transformation which maps a password protocol that is secure for a single protocol session (a decidable problem) to a protocol that is secure for an unbounded number of sessions. Our result provides an effective strategy to design secure password protocols: (i) design a protocol intended to be secure for one protocol session; (ii) apply our transformation and obtain a protocol which is secure for an unbounded number of sessions. Our technique also applies to compose different password protocols allowing us to obtain both inter-protocol and inter-session composition

A probabilistic polynomial-time process calculus for the analysis of cryptographic protocols

AbstractWe prove properties of a process calculus that is designed for analysing security protocols. Our long-term goal is to develop a form of protocol analysis, consistent with standard cryptographic assumptions, that provides a language for expressing probabilistic polynomial-time 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 polynomial-time 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 all 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, well-known in cryptography, that El Gamal encryption's semantic security is equivalent to the (computational) Decision Diffie–Hellman assumption. This example demonstrates the power of probabilistic bisimulation and equational reasoning for protocol security

Automated Attack Analysis and Code Generation in a Multi-Dimensional Security Protocol Engineering Framework

A unified, multi-dimensional approach to security protocol engineering is effective for creating cryptographic protocols since it encompasses a variety of design, analysis and implementation techniques, thereby providing a higher level of confidence than individual approaches. SPEAR II, the Security Protocol Engineering and Analysis Resource II is a tool which supports this unified, multi-dimensional approach by offering protocol designers an environment in which to graphically design and analyse security protocols. The premise of this paper is that providing a means of analysing security protocols for attack vulnerabilities that are not detected by static methods, and allowing for the translation of an abstract protocol specification into a correct and secure protocol implementation in the context of a multi-dimensional tool such as SPEAR II, will assist in producing more secure security protocols