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The following topics are dealt with: authorization; multilayer protocols and key conjuring; protocols and cryptographic foundations; secure implementation; information flow; privacy; vulnerability analysis and information-theoretic security; security protocol analysis.
We present a declarative authorization language that strikes a careful balance between syntactic and semantic simplicity, policy expressiveness, and execution efficiency. The syntax is close to natural language, and the semantics consists of just three deduction rules. The language can express many common policy idioms using constraints, controlled delegation, recursive predicates, and negated queries...
We address the programmatic realization of the access control model of security in distributed systems. Our aim is to bridge the gap between abstract/declarative policies and their concrete/operational implementations. We present a programming formalism (which extends the asynchronous pi-calculus with explicit principals) and a specification logic (which extends Datalog with primitives from authorization...
We consider the problem of statically verifying the conformance of the code of a system to an explicit authorization policy. In a distributed setting, some part of the system may be compromised, that is, some nodes of the system and their security credentials may be under the control of an attacker. To help predict and bound the impact of such partial compromise, we advocate logic-based policies that...
The transmission of voice communications as datagram packets over IP networks, commonly known as voice-over-IP (VoIP) telephony, is rapidly gaining wide acceptance. With private phone conversations being conducted on insecure public networks, security of VoIP communications is increasingly important. We present a structured security analysis of the VoIP protocol stack, which consists of signaling...
There has been excellent progress on languages for rigorously describing key exchange protocols and techniques for proving that the network security tunnels they establish preserve confidentiality and integrity. New problems arise in describing and analyzing establishment protocols and tunnels when they are used as building blocks to achieve high-level security goals for network administrative domains...
Key conjuring is the process by which an attacker obtains an unknown, encrypted key by repeatedly calling a cryptographic API function with random values in place of keys. We propose a formalism for detecting computationally feasible key conjuring operations, incorporated into a Dolev-Yao style model of the security API. We show that security in the presence of key conjuring operations is decidable...
We present a new mechanized prover for showing correspondence assertions for cryptographic protocols in the computational model. Correspondence assertions are useful in particular for establishing authentication. Our technique produces proofs by sequences of games, as standard in cryptography. These proofs are valid for a number of sessions polynomial in the security parameter, in the presence of...
Key-dependent message security, short KDM security, was introduced by Black, Rogaway and Shrimpton to address the case where key cycles occur among encryptions, e.g., a key is encrypted with itself. It was mainly motivated by key cycles in Dolev-Yao models, i.e., symbolic abstractions of cryptography by term algebras, and a corresponding soundness result was later shown by Adao et al. However, both...
Task-PIOA is a modeling framework for distributed systems with both probabilistic and nondeterministic behaviors. It is suitable for cryptographic applications because its task-based scheduling mechanism is less powerful than the traditional perfect-information scheduler. Moreover, one can speak of two types of complexity restrictions: time bounds on description of task-PIOAs and time bounds on length...
We study simulation relations for probabilistic automata that require transitions to be matched up to negligible sets provided that computation lengths are polynomially bounded. These relations are meant to provide rigorous grounds to parts of correctness proofs for cryptographic protocols that are usually carried out by semi-formal arguments. We illustrate our ideas by recasting a correctness proof...
Work on electronic voting systems to date has largely focused around first-past-the-post voting. However, the governments of many countries, and many non-governmental organisations, use a single transferable vote system, in which the voter needs to indicate not just a single preferred candidate but a preference ranking of (some or all of) the candidates on offer. This paper investigates the possibility...
Distributed applications can be structured as parties that exchange messages according to some pre-arranged communication patterns. These sessions (or contracts, or protocols) simplify distributed programming: when coding a role for a given session, each party just has to follow the intended message flow, under the assumption that the other parties are also compliant. In an adversarial setting, remote...
Li and Zdancewic have recently proposed an approach to provide information-flow security via a library rather than producing a new language from the scratch. They have shown how to implement such a library in Haskell by using arrow combinators. However, their approach only works with computations that have no side-effects. In fact, they leave as an open question how their library, and the mechanisms...
Although static systems for information flow security are well-studied, few works address run-time information flow monitoring. Run-time information flow control offers distinct advantages in precision and in the ability to support dynamically defined policies. To this end, we here develop a new run-time information flow system based on the runtime tracking of indirect dependencies between program...
Noninterference is typically used as a baseline security policy to formalize confidentiality of secret information manipulated by a program. In contrast to static checking of noninterference, this paper considers dynamic, automaton-based, monitoring of information flow for a single execution of a concurrent program. The monitoring mechanism is based on a combination of dynamic and static analyses...
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