Formal analysis of cryptographic protocols

Táto diplomová práca sa zaoberá kryptografiou. Popisuje sa jej základné rozdelenie a problémy teórie čísel, ktoré musí riešiť. Taktiež sa zaoberá metódami, ktoré sa použí- vajú k ohodnoteniu formálnej bezpečnosti kryptografických protokolov z matematického hľadiska. Nakoniec sa analyzujú nástroje využívané k automatickému a poloautomatic- kému vyhodnoteniu bezpečnosti kryptografických protokolov. Popisuje sa spôsob práce s týmito nástrojmi a nakoniec sa otestuje bezpečnosť protokolov Kerberos, EKE a protokolov jednosmernej autentizácie využívajúcich symetrickú kryptografiu, funkciu HMAC a hashovaciu funkciu postupne v nástrojoch AVISPA, ProVerif a Scyther. Na záver je porovnanie výsledkov.This diploma thesis deals with cryptography. It describes its basic allocation and problems of number theory that needs to be addressed. It also deals with methods used to review the formal security of cryptographic protocols from a mathematical point of view. It analyse the tools used to automatic and semi-automatic evaluation of the safety of cryptographic protocols. It describes the process of working with these tools and finally test the security of protocols Kerberos, EKE and Unilateral authentication using symmetric cryptography, HMAC function and hash function. These tests are in tools AVISPA, ProVerif and Scyther. At the end is comparison of results.

Specifying authentication using signal events in CSP

The formal analysis of cryptographic protocols has developed into a comprehensive body of knowledge, building on a wide variety of formalisms and treating a diverse range of security properties, foremost of which is authentication. The formal specification of authentication has long been a subject of examination. In this paper, we discuss the use of correspondence to formally specify authentication and focus on Schneider's use of signal events in the process algebra Communicating Sequential Processes (CSP) to specify authentication. The purpose of this effort is to strengthen this formalism further. We develop a formal structure for these events and use them to specify a general authentication property. We then develop specifications for recentness and injectivity as sub-properties, and use them to refine authentication further. Finally, we use signal events to specify a range of authentication definitions and protocol examples to clarify their use and make explicit related theoretical issues. our work is motivated by the desire to effectively analyse and express security properties in formal terms, so as to make them precise and clear. (C) 2008 Elsevier Ltd. All rights reserved

Finite Model Finding for Parameterized Verification

In this paper we investigate to which extent a very simple and natural "reachability as deducibility" approach, originated in the research in formal methods in security, is applicable to the automated verification of large classes of infinite state and parameterized systems. The approach is based on modeling the reachability between (parameterized) states as deducibility between suitable encodings of states by formulas of first-order predicate logic. The verification of a safety property is reduced to a pure logical problem of finding a countermodel for a first-order formula. The later task is delegated then to the generic automated finite model building procedures. In this paper we first establish the relative completeness of the finite countermodel finding method (FCM) for a class of parameterized linear arrays of finite automata. The method is shown to be at least as powerful as known methods based on monotonic abstraction and symbolic backward reachability. Further, we extend the relative completeness of the approach and show that it can solve all safety verification problems which can be solved by the traditional regular model checking.Comment: 17 pages, slightly different version of the paper is submitted to TACAS 201

09311 Abstracts Collection -- Classical and Quantum Information Assurance Foundations and Practice

From 26 July 2009 to 31 July 2009, the Dagstuhl Seminar 09311 ``Classical and Quantum Information Assurance Foundations and Practice\u27\u27 was held in Schloss Dagstuhl~--~Leibniz Center for Informatics. The workshop was intended to explore the latest developments and discuss the open issues in the theory and practice of classical and quantum information assurance. A further goal of the workshop was to bring together practitioners from both the classical and the quantum information assurance communities. To date, with a few exceptions, these two communities seem to have existed largely separately and in a state of mutual ignorance. It is clear however that there is great potential for synergy and cross-fertilization between and this we sought to stimulate and facilitate

Unification modulo a 2-sorted Equational theory for Cipher-Decipher Block Chaining

We investigate unification problems related to the Cipher Block Chaining (CBC) mode of encryption. We first model chaining in terms of a simple, convergent, rewrite system over a signature with two disjoint sorts: list and element. By interpreting a particular symbol of this signature suitably, the rewrite system can model several practical situations of interest. An inference procedure is presented for deciding the unification problem modulo this rewrite system. The procedure is modular in the following sense: any given problem is handled by a system of `list-inferences', and the set of equations thus derived between the element-terms of the problem is then handed over to any (`black-box') procedure which is complete for solving these element-equations. An example of application of this unification procedure is given, as attack detection on a Needham-Schroeder like protocol, employing the CBC encryption mode based on the associative-commutative (AC) operator XOR. The 2-sorted convergent rewrite system is then extended into one that fully captures a block chaining encryption-decryption mode at an abstract level, using no AC-symbols; and unification modulo this extended system is also shown to be decidable.Comment: 26 page

Finite Models vs Tree Automata in Safety Verification

In this paper we deal with verification of safety properties of term-rewriting systems. The verification problem is translated to a purely logical problem of finding a finite countermodel for a first-order formula, which is further resolved by a generic finite model finding procedure. A finite countermodel produced during successful verification provides with a concise description of the system invariant sufficient to demonstrate a specific safety property. We show the relative completeness of this approach with respect to the tree automata completion technique. On a set of examples taken from the literature we demonstrate the efficiency of finite model finding approach as well as its explanatory power