Analysing Unlinkability and Anonymity Using the Applied Pi Calculus

Abstract

Abstract-An attacker that can identify messages as coming from the same source, can use this information to build up a picture of targets' behaviour, and so, threaten their privacy. In response to this danger, unlinkable protocols aim to make it impossible for a third party to identify two runs of a protocol as coming from the same device. We present a framework for analysing unlinkability and anonymity in the applied pi calculus. We show that unlinkability and anonymity are complementary properties; one does not imply the other. Using our framework we show that the French RFID e-passport preserves anonymity but it is linkable therefore anyone carrying a French e-passport can be physically traced.

From Security Protocols to Pushdown Automata

“…Trace equivalence can be used to formalise many interesting security properties, in particular privacy-type properties, such as those studied for instance in [1,6]. We first introduce a notion of intruder's knowledge well-suited to cryptographic primitives for which the success of decrypting or checking a signature is visible.…”

“…However, privacy properties such as vote secrecy, anonymity, or untraceability cannot be expressed as such. They are instead defined as indistinguishability properties in [1,6]. For example, Alice's identity remains private if an attacker cannot distinguish a session where Alice is talking from a session where Bob is talking.…”

DEEPSEC: Deciding Equivalence Properties in Security Protocols Theory and Practice

“…A typical example is real-or-random secrecy: after interacting with a protocol, an adversary is unable to distinguish the real secret used in the protocol from a random value. Privacy-type properties can also be expressed as such: anonymity may be modeled as the adversary's inability to distinguish two instances of a protocol executed by different agents; vote privacy [DKR09] has been expressed as indistinguishability of the situations where the votes of two agents have been swapped or not; unlinkability [ACRR10] is seen as indistinguishability of two sessions, either both executed by the same agent A, or by two different agents A and B.…”

Formal Analysis of Privacy for Anonymous Location Based Services

“…In this paper, we bring the privacy analysis of location-based services into the world of formal methods, leveraging previous work on privacy for vehicular mix-zones [10], electronic voting [11,15], and RFID tags [3,8]. In particular, we concentrate on VPriv [7], a proposed scheme for building location-based services using zero-knowledge techniques, designed to ensure that the paths of drivers are not revealed to the service providers, while nonetheless preventing drivers from reporting fake paths.…”