Towards a Constrained-based Verification of Parameterized Cryptographic Protocols

International audienceAlthough many works have been dedicated to standard protocols like Needham-Schroeder very few address the more challenging class of group protocol s. We present a synchronous model for group protocols, that generalizes standard protocol models by permitting unbounded lists inside messages. In this extended model we propose a correct and complete set of inference rules for checking security properties in presence of an active intruder for the class of well-tagged protocols. Our inference system generalizes the ones that are implemented in several tools for a bounded number of sessions and fixed size lists in message. In particular when applied to protocols whose specification does not contain unbounded lists our inference system provides a decision procedure for secrecy in the case of a fixed number of sessions

Formal Models and Techniques for Analyzing Security Protocols: A Tutorial

International audienceSecurity protocols are distributed programs that aim at securing communications by the means of cryptography. They are for instance used to secure electronic payments, home banking and more recently electronic elections. Given The financial and societal impact in case of failure, and the long history of design flaws in such protocol, formal verification is a necessity. A major difference from other safety critical systems is that the properties of security protocols must hold in the presence of an arbitrary adversary. The aim of this paper is to provide a tutorial to some modern approaches for formally modeling protocols, their goals and automatically verifying them

Selecting Theories and Nonce Generation for Recursive Protocols

In recent years, formal methods have been developed to analyze and verify cryptographic protocols. We will focus on protocols that rely on iteration or recursion. These protocols typically use special security tokens - such as numbers used only once, called nonces, or keys generated by a principal - to achieve their security assertions. The recursion depth of the computations in such protocols and thus the number of fresh tokens occurring in a run of a protocol is not explicitly bounded by the protocol's description. Therefore, we need a mechanism to provide the protocol's principals with the ability to generate an unbounded number of fresh tokens. In this report we will extend the model of selecting theories introduced by Truderung - in this model recursive protocols can be analyzed in the presence of a Dolev-Yao intruder. We will present an extended model that allows the principals to generate fresh tokens, and we will show decidability with respect to a bounded number of sessions. In the proof, attacks on such protocols will be represented by a special graph structure introduced by Truderung called ADAG; we will prove our decidability result by bounding the size of ADAGs. In the protocol model and in the ADAGs the modeling of fresh tokens will be based on an infinite set of constants in the signature

Verification of Security Protocols with Lists: from Length One to Unbounded Length

International audienceWe present a novel, simple technique for proving secrecy properties for security protocols that manipulate lists of unbounded length, for an unbounded number of sessions. More specifically, our technique relies on the Horn clause approach used in the automatic verifier ProVerif: we show that if a protocol is proven secure by our technique with lists of length one, then it is secure for lists of unbounded length. Interestingly, this theorem relies on approximations made by our verification technique: in general, secrecy for lists of length one does not imply secrecy for lists of unbounded length. Our result can be used in particular to prove secrecy properties for group protocols with an unbounded number of participants and for some XML protocols (web services) with ProVerif

Analysis of security protocols as open systems

We propose a methodology for the formal analysis of security protocols. This originates from the observation that the verification of security protocols can be conveniently treated as the verification of open systems, i.e. systems which may have unspecified components. These might be used to represent a hostile environment wherein the protocol runs and whose behavior cannot be predicted a priori. We define a language for the description of security protocols, namely Crypto-CCS, and a logical language for expressing their properties. We provide an effective verification method for security protocols which is based on a suitable extension of partial model checking. Indeed, we obtain a decidability result for the secrecy analysis of protocols with a finite number of sessions, bounded message size and new nonce generation

Modeling and Analysis of Advanced Cryptographic Primitives and Security Protocols in Maude-NPA

Tesis por compendio[ES] La herramienta criptográfica Maude-NPA es un verificador de modelos especializado para protocolos de seguridad criptográficos que tienen en cuenta las propiedades algebraicas de un sistema criptográfico. En la literatura, las propiedades criptográficas adicionales han descubierto debilidades de los protocolos de seguridad y, en otros casos, son parte de los supuestos de seguridad del protocolo para funcionar correctamente. Maude-NPA tiene una base teórica en la rewriting logic, la unificación ecuacional y el narrowing para realizar una búsqueda hacia atrás desde un patrón de estado inseguro para determinar si es alcanzable o no. Maude-NPA se puede utilizar para razonar sobre una amplia gama de propiedades criptográficas, incluida la cancelación del cifrado y descifrado, la exponenciación de Diffie-Hellman, el exclusive-or y algunas aproximaciones del cifrado homomórfico. En esta tesis consideramos nuevas propiedades criptográficas, ya sea como parte de protocolos de seguridad o para descubrir nuevos ataques. También hemos modelado diferentes familias de protocolos de seguridad, incluidos los Distance Bounding Protocols or Multi-party key agreement protocolos. Y hemos desarrollado nuevas técnicas de modelado para reducir el coste del análisis en protocolos con tiempo y espacio. Esta tesis contribuye de varias maneras al área de análisis de protocolos criptográficos y muchas de las contribuciones de esta tesis pueden ser útiles para otras herramientas de análisis criptográfico.[CAT] L'eina criptografica Maude-NPA es un verificador de models especialitzats per a protocols de seguretat criptogràfics que tenen en compte les propietats algebraiques d'un sistema criptogràfic. A la literatura, les propietats criptogràfiques addicionals han descobert debilitats dels protocols de seguretat i, en altres casos, formen part dels supòsits de seguretat del protocol per funcionar correctament. Maude-NPA te' una base teòrica a la rewriting lògic, la unificació' equacional i narrowing per realitzar una cerca cap enrere des d'un patró' d'estat insegur per determinar si es accessible o no. Maude-NPA es pot utilitzar per raonar sobre una amplia gamma de propietats criptogràfiques, inclosa la cancel·lació' del xifratge i desxifrat, l'exponenciacio' de Diffie-Hellman, el exclusive-or i algunes aproximacions del xifratge homomòrfic. En aquesta tesi, considerem noves propietats criptogràfiques, ja sigui com a part de protocols de seguretat o per descobrir nous atacs. Tambe' hem modelat diferents famílies de protocols de seguretat, inclosos els Distance Bounding Protocols o Multi-party key agreement protocols. I hem desenvolupat noves tècniques de modelització' de protocols per reduir el cost de l'analisi en protocols amb temps i espai. Aquesta tesi contribueix de diverses maneres a l’àrea de l’anàlisi de protocols criptogràfics i moltes de les contribucions d’aquesta tesi poden ser útils per a altres eines d’anàlisi criptogràfic.[EN] The Maude-NPA crypto tool is a specialized model checker for cryptographic security protocols that take into account the algebraic properties of the cryptosystem. In the literature, additional crypto properties have uncovered weaknesses of security protocols and, in other cases, they are part of the protocol security assumptions in order to function properly. Maude-NPA has a theoretical basis on rewriting logic, equational unification, and narrowing to perform a backwards search from an insecure state pattern to determine whether or not it is reachable. Maude-NPA can be used to reason about a wide range of cryptographic properties, including cancellation of encryption and decryption, Diffie-Hellman exponentiation, exclusive-or, and some approximations of homomorphic encryption. In this thesis, we consider new cryptographic properties, either as part of security protocols or to discover new attacks. We have also modeled different families of security protocols, including Distance Bounding Protocols or Multi-party key agreement protocols. And we have developed new protocol modeling techniques to reduce the time and space analysis effort. This thesis contributes in several ways to the area of cryptographic protocol analysis and many of the contributions of this thesis can be useful for other crypto analysis tools.This thesis would not have been possible without the funding of a set of research projects. The main contributions and derivative works of this thesis have been made in the context of the following projects: - Ministry of Economy and Business of Spain : Project LoBaSS Effective Solutions Based on Logic, Scientific Research under award number TIN2015-69175-C4-1-R, this project was focused on using powerful logic-based technologies to analyze safety-critical systems. - Air Force Office of Scientific Research of United States of America : Project Advanced symbolic methods for the cryptographic protocol analyzer Maude-NPA Scientific Research under award number FA9550-17-1-0286 - State Investigation Agency of Spain : Project FREETech: Formal Reasoning for Enabling and Emerging Technologies Scientific I+D-i Research under award number RTI2018-094403-B-C32Aparicio Sánchez, D. (2022). Modeling and Analysis of Advanced Cryptographic Primitives and Security Protocols in Maude-NPA [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/190915Compendi

Constraints-based Verification of Parameterized Cryptographic Protocols.

Cryptographic protocols are crucial for securing electronic transactions. The confidence in these protocols can be increased by the formal analysis of their security properties. Although many works have been dedicated to standard protocols like Needham-Schroeder very few address the more challenging class of group protocols. We present a synchronous model for group protocols, that generalizes standard protocol models by permitting unbounded lists inside messages. In this extended model we propose a correct and complete set of inference rules for checking security properties in presence of an active intruder for the class of Well-Tagged protocols. We prove that the application of these rules on a constraint system terminates and that the normal form obtained can be checked for satisfiability. Therefore, we present here a decision procedure for this class