Analysing the Woo-Lam Protocol Using CSP and Rank Functions

Designing security protocols is a challenging and deceptive exercise. Even small protocols providing straightforward security goals, such as authentication, have been hard to design correctly, leading to the presence of many subtle attacks. Over the years various formal approaches have emerged to analyse security protocols making use of different formalisms. Schneider has developed a formal approach to modelling security protocols using the process algebra CSP (Communicating Sequential Processes). He introduces the notion of rank functions to analyse the protocols. We demonstrate an application of this approach to the Woo-Lam protocol. We describe the protocol in detail along with an established attack on its goals. We then describe Schneider’s rank function theorem and use it to analyse the protocol

Analysis of Selected Security Protocols

Předmětem této diplomové práce je studium dostupných bezpečnostních protokolů a nástrojů sloužících k jejich verifikaci. První část práce se krátce věnuje popisu pojmů souvisejících s oblastí bezpečnostních protokolů a verifikačních logik. Druhá část již přímo uvádí jednotlivé protokoly spolu s nalezenými útoky a chybami v návrhu. V další kapitole jsou detailněji popsány nejdůležitější nástroje pro automatickou analýzu bezpečnostních protokolů. Hlavní část práce se zabývá verifikací vybraných bezpečnostních protokolů ve zvoleném nástroji Scyther. Na závěr jsou uvedeny příklady víceprotokolových útoků spolu s přehledovou tabulkou.The subject of this thesis is to study available security protocols and tools for their verification. The first part is devoted to briefly describe the concepts related to the area of security protocols and verification logics. The second part directly lists various protocols, along with attacks and errors found in design. Next chapter describes the most important tools for automatic analysis of security protocols in more detail. The main part deals with verification of security protocols selected in the chosen tool called Scyther. In conclusion, examples of multiprotocol attacks along with a summary table are displayed.

Synthesising end-to-end security schemes through endorsement intermediaries

Composing secure interaction protocols dynamically for e-commerce continue to pose a number of challenges, such as lack of standard notations for expressing requirements and the difficulty involved in enforcing them. Furthermore, interaction with unknown entities may require finding common trusted intermediaries. Securing messages sent through such intermediaries require schemes that provide end-to-end security guarantees. In the past, e-commerce protocols such as SET were created to provide such end-to-end guarantees. However, such complex hand crafted protocols proved difficult to model check. This thesis addresses the end-to-end problems in an open dynamic setting where trust relationships evolve, and requirements of interacting entities change over time. Before interaction protocols can be synthesised, a number of research questions must be addressed. Firstly, to meet end-to-end security requirements, the security level along the message path must be made to reflect the requirements. Secondly, the type of endorsement intermediaries must reflect the message category. Thirdly, intermediaries must be made liable for their endorsements. This thesis proposes a number of solutions to address the research problems. End-to-end security requirements were arrived by aggregating security requirements of all interacting parties. These requirements were enforced by interleaving and composing basic schemes derived from challenge-response mechanisms. The institutional trust promoting mechanism devised allowed all vital data to be endorsed by authorised category specific intermediaries. Intermediaries were made accountable for their endorsements by being required to discharge or transfer proof obligations placed on them. The techniques devised for aggregating and enforcing security requirements allow dynamic creation of end-to-end security schemes. The novel interleaving technique devised allows creation of provably secure multiparty schemes for any number of recipients. The structured technique combining compositional approach with appropriate invariants and preconditions makes model checking of synthesised schemes unnecessary. The proposed framework combining endorsement trust with schemes making intermediaries accountable provides a way to alleviate distrust between previously unknown e-commerce entities