A Trace Logic for Local Security Properties

We propose a new simple \emph{trace} logic that can be used to specify \emph{local security properties}, i.e. security properties that refer to a single participant of the protocol specification. Our technique allows a protocol designer to provide a formal specification of the desired security properties, and integrate it naturally into the design process of cryptographic protocols. Furthermore, the logic can be used for formal verification. We illustrate the utility of our technique by exposing new attacks on the well studied protocol TMN.Comment: New versio

Attacking Group Multicast Key Management Protocol using CORAL

This paper describes the modelling of a two multicast group key management protocols in a first-order inductive model, and the discovery of previously unknown attacks on them by the automated inductive counterexample finder CORAL. These kinds of protocols had not been analysed in a scenario with an active intruder before. CORAL proved to be a suitable tool for a job because, unlike most automated tools for discovering attacks, it deals directly with an open-ended model where the number of agents and the roles they play are unbounded. Additionally, CORAL’s model allows us to reason explicitly about lists of terms in a message, which proved to be essential for modelling the second protocol. In the course of the case studies, we also discuss other issues surrounding multicast protocol analysis, including identifying the goals of the protocol with respect to the intended trust model, modelling of the control conditions, which are considerably more complex than for standard two and three party protocols, and effective searching of the state space generated by the model, which has a much larger branching rate than for standard protocols

DGKD: Distributed Group Key Distribution with Authentication Capability

Group key management (GKM} is the most important issue in secure group communication (SCC). The existing GKM protocols fall into three typical classes: centralized group key distribution (CGKD), decentralized group key management (DGKM), and distributed/contributory group key agreement (CGKA). Serious problems remains in these protocols, as they require existence of central trusted entities (such as group controller or subgroup controllers), relaying of messages (by subgroup controllers), or strict member synchronization (JOT multiple round stepwise key agreement), thus suffering from the single point of failure and attack, performance bottleneck, or mis-operations in the situation of transmission delay or network failure. In this paper, we propose a new class of GKM protocols: distributed group key distribution (DGKD). The new DGKD protocol solves the above problems and surpasses the existing GKM protocols ZR terms of simplicity, efficiency, scalability, and robustness

DGKD: Distributed Group Key Distribution with Authentication Capability

Group key management (GKM} is the most important issue in secure group communication (SCC). The existing GKM protocols fall into three typical classes: centralized group key distribution (CGKD), decentralized group key management (DGKM), and distributed/contributory group key agreement (CGKA). Serious problems remains in these protocols, as they require existence of central trusted entities (such as group controller or subgroup controllers), relaying of messages (by subgroup controllers), or strict member synchronization (JOT multiple round stepwise key agreement), thus suffering from the single point of failure and attack, performance bottleneck, or mis-operations in the situation of transmission delay or network failure. In this paper, we propose a new class of GKM protocols: distributed group key distribution (DGKD). The new DGKD protocol solves the above problems and surpasses the existing GKM protocols ZR terms of simplicity, efficiency, scalability, and robustness

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

Formalizing GDOI group key management requirements in NPATRL

Although there is a substantial amount of work on formal requirements for two and three-party key distribution protocols, very little has been done on requirements for group protocols. However, since the latter have security requirements that can differ in important but subtle ways, we believe that a rigorous expression of these requirements can be useful in determining whether a given protocol can satisfy an application’s needs. In this paper we make a first step in providing a formal understanding of security requirements for group key distribution by using the NPATRL language, a temporal requirement specification language for use with the NRL Protocol Analyzer. We specify the requirements for GDOI, a protocol being proposed as an IETF standard, which we are formally specifying and verifying in cooperation with the MSec working group. 1

Secure group key agreement

As a result of the increased popularity of group-oriented applications and protocols, group communication occurs in many different settings: from network multicasting to application layer tele- and video-conferencing. Regardless of the application environment, security services are necessary to provide communication privacy and integrity. This thesis considers the problem of key management in a special class of groups, namely dynamic peer groups. Key management, especially in a group setting, is the corner stone for all other security services. Dynamic peer groups require not only initial key agreement but also auxiliary key agreement operations such as member addition, member exclusion and group fusion. We discuss all group key agreement operations and present a concrete protocol suite, CLIQUES, which offers all of these operations. By providing the first formal model for group key establishment and investigating carefully the underlying cryptographic assumptions as well as their relations, we formally prove the security of a subset of the protocols based on the security of the Decisional Diffie-Hellman assumption; achieving as a side-effect the first provably secure group key agreement protocolMit der Verbreitung offener Netze, insbesondere des Internets, fand auch die Gruppenkommunikation eine rasante Verbreitung. Eine Vielzahl heutiger Protokolle sind gruppen-orientiert: angefangen bei Multicast-Diensten in der Netzwerkschicht bis hin zu Videokonferenzsystemen auf der Anwendungsschicht. Alle diese Dienste haben Sicherheitsanforderungen wie Vertraulichkeit und Integrität zu erfüllen, die den Einsatz kryptographischer Techniken und die Verfügbarkeit gemeinsamer kryptographischen Schlüssel oft unumgänglich machen. In der folgenden Doktorarbeit betrachte ich dieses grundlegendste Problem der Gruppenkommunikation, nämlich das Schlüsselmanagement, für dynamische Gruppen, die sogenannten "Dynamic Peer-Groups';. Die Dynamik dieser Gruppen erfordert nicht nur initialen Schlüsselaustausch innerhalb einer Gruppe sondern auch sichere und effiziente Verfahren für die Aufnahme neuer und den Ausschluß alter Gruppenmitglieder. Ich diskutiere alle dafür notwendigen Dienste und präsentiere CLIQUES, eine Familie von Protokollen, die diese Dienste implementiert. Ich gebe erstmalig eine formale Definition fü sicheres Gruppen-Schlüsselmanagement und beweise die Sicherheit der genannten Protokolle basierend auf einer kryptographischen Standardannahme, der "Decisional Diffie-Hellman'; Annahme. Diese Sicherheitsbetrachtung wird durch eine detaillierte Untersuchung dieser Annahme und ihrer Relation zu verwandten Annahmen abgeschlossen

Secure group key agreement

As a result of the increased popularity of group-oriented applications and protocols, group communication occurs in many different settings: from network multicasting to application layer tele- and video-conferencing. Regardless of the application environment, security services are necessary to provide communication privacy and integrity. This thesis considers the problem of key management in a special class of groups, namely dynamic peer groups. Key management, especially in a group setting, is the corner stone for all other security services. Dynamic peer groups require not only initial key agreement but also auxiliary key agreement operations such as member addition, member exclusion and group fusion. We discuss all group key agreement operations and present a concrete protocol suite, CLIQUES, which offers all of these operations. By providing the first formal model for group key establishment and investigating carefully the underlying cryptographic assumptions as well as their relations, we formally prove the security of a subset of the protocols based on the security of the Decisional Diffie-Hellman assumption; achieving as a side-effect the first provably secure group key agreement protocolMit der Verbreitung offener Netze, insbesondere des Internets, fand auch die Gruppenkommunikation eine rasante Verbreitung. Eine Vielzahl heutiger Protokolle sind gruppen-orientiert: angefangen bei Multicast-Diensten in der Netzwerkschicht bis hin zu Videokonferenzsystemen auf der Anwendungsschicht. Alle diese Dienste haben Sicherheitsanforderungen wie Vertraulichkeit und Integrität zu erfüllen, die den Einsatz kryptographischer Techniken und die Verfügbarkeit gemeinsamer kryptographischen Schlüssel oft unumgänglich machen. In der folgenden Doktorarbeit betrachte ich dieses grundlegendste Problem der Gruppenkommunikation, nämlich das Schlüsselmanagement, für dynamische Gruppen, die sogenannten "Dynamic Peer-Groups\u27;. Die Dynamik dieser Gruppen erfordert nicht nur initialen Schlüsselaustausch innerhalb einer Gruppe sondern auch sichere und effiziente Verfahren für die Aufnahme neuer und den Ausschluß alter Gruppenmitglieder. Ich diskutiere alle dafür notwendigen Dienste und präsentiere CLIQUES, eine Familie von Protokollen, die diese Dienste implementiert. Ich gebe erstmalig eine formale Definition fü sicheres Gruppen-Schlüsselmanagement und beweise die Sicherheit der genannten Protokolle basierend auf einer kryptographischen Standardannahme, der "Decisional Diffie-Hellman\u27; Annahme. Diese Sicherheitsbetrachtung wird durch eine detaillierte Untersuchung dieser Annahme und ihrer Relation zu verwandten Annahmen abgeschlossen