05 Fakultät Informatik, Elektrotechnik und Informationstechnik
Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/6
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Item Open Access Formal security analysis of the OpenID FAPI 2.0 Security Profile with FAPI 2.0 Message Signing, FAPI-CIBA, Dynamic Client Registration and Management : technical report(2023) Hosseyni, Pedram; Küsters, Ralf; Würtele, TimBuilding on our recent formal security analysis of the FAPI 2.0 Security Profile, we here extend the analysis effort to FAPI 2.0 Message Signing, combined with Dynamic Client Registration, Dynamic Client Management, and FAPI-CIBA. Overall, we model an ecosystem which uses all these profiles and extensions in parallel. Like the previous work on the FAPI 2.0 Security Profile, this analysis is based on the Web Infrastructure Model, a Dolev-Yao style model of the web infrastructure - in fact, it is the most comprehensive and detailed model of the web infrastructure to date. We identify several attacks, propose fixes and prove the fixed protocols secure with respect to authorization, authentication, session integrity for both authorization and authentication, and non-repudiation for the messages covered by FAPI 2.0 Message Signing. The attacks and proposed fixes have been reported to the responsible FAPI Working Group at the OpenID Foundation, and fixes have since been incorporated into the specifications.Item Open Access The Grant Negotiation and Authorization Protocol : attacking, fixing, and verifying an emerging standard(2023) Helmschmidt, Florian; Hosseyni, Pedram; Küsters, Ralf; Pruiksma, Klaas; Waldmann, Clara; Würtele, TimThe Grant Negotiation and Authorization Protocol (GNAP) is an emerging authorization and authentication protocol which aims to consolidate and unify several use-cases of OAuth 2.0 and many of its common extensions while providing a higher degree of security. OAuth 2.0 is an essential cornerstone of the security of authorization and authentication for the Web, IoT, and beyond, and is used, among others, by many global players, like Google, Facebook, and Microsoft. Historical limitations of OAuth 2.0 and its extensions have led prominent members of the OAuth community to create GNAP, a newly designed protocol for authorization and authentication. Given GNAP's advantages over OAuth 2.0 and its support within the OAuth community, GNAP is expected to become at least as important as OAuth 2.0. In this work, we present the first formal security analysis of GNAP. We build a detailed formal model of GNAP, based on the Web Infrastructure Model (WIM) of Fett, Küsters, and Schmitz, and provide formal statements of the key security properties of GNAP, namely authorization, authentication, and session integrity. We discovered several attacks on GNAP in the process of trying to prove these properties. We present these attacks, as well as changes to the protocol that prevent them. These modifications have been incorporated into the GNAP specification after discussion with the GNAP working group. We give the first formal security guarantees for GNAP, by proving that GNAP, with our modifications applied, satisfies the mentioned security properties. GNAP was still an early draft when we began our analysis, but is now on track to be adopted as an IETF standard. Hence, our analysis is just in time to help ensure the security of this important emerging standard.Item Open Access Entwurf und Analyse eines sicheren und effizienten Bulletin Board auf Basis von Blockchains(2018) Würtele, TimIn vielen durch die Wähler und unabhängige Beobachter verifizierbaren eVoting-Systemen wird ein sogenanntes Bulletin Board benötigt. Ein Bulletin Board ist eine Art öffentliches schwarzes Brett, auf dem jeder Nachrichten veröffentlichen und von dem jeder die veröffentlichten Nachrichten lesen kann. Ein solches Bulletin Board sollte mindestens die Eigenschaft haben, dass Nachrichten, die einmal veröffentlicht wurden, nicht wieder entfernt oder verändert werden können. Bisher wurden Bulletin Boards - wenn die Implementierung überhaupt berücksichtigt wurde - in der Regel entweder als zentraler Server, dem vertraut werden muss, oder als verteiltes System implementiert. Mit den seit 2008 bekannten Blockchains gibt es eine Technologie, die ein ähnliches Versprechen gibt: Dass nur Daten angehängt, bestehende aber nicht verändert werden können. In dieser Arbeit werden zunächst Blockchains und Bulletin Boards zusammen mit ihren wesentlichen Eigenschaften diskutiert und anschließend wird untersucht, wie sich ein Bulletin Board auf Basis bzw. mithilfe einer Blockchain implementieren lässt.Item Open Access Layered symbolic security analysis in DY*(2023) Bhargavan, Karthikeyan; Bichhawat, Abhishek; Hosseyni, Pedram; Küsters, Ralf; Pruiksma, Klaas; Schmitz, Guido; Waldmann, Clara; Würtele, TimWhile cryptographic protocols are often analyzed in isolation, they are typically deployed within a stack of protocols, where each layer relies on the security guarantees provided by the protocol layer below it, and in turn provides its own security functionality to the layer above. Formally analyzing the whole stack in one go is infeasible even for semi-automated verification tools, and impossible for pen-and-paper proofs. The DY* protocol verification framework offers a modular and scalable technique that can reason about large protocols, specified as a set of F* modules. However, it does not support the compositional verification of layered protocols since it treats the global security invariants monolithically. In this paper, we extend DY* with a new methodology that allows analysts to modularly analyze each layer in a way that compose to provide security for a protocol stack. Importantly, our technique allows a layer to be replaced by another implementation, without affecting the proofs of other layers. We demonstrate this methodology on two case studies. We also present a verified library of generic authenticated and confidential communication patterns that can be used in future protocol analyses and is of independent interest.