Abstracts of Invited Talks -- Security and Cooperation in Wireless Networks -- Grey-Box Cryptography: Physical Unclonable Functions -- Regular Papers -- Low-Cost Elliptic Curve Cryptography for Wireless Sensor Networks -- Re-visited: Denial of Service Resilient Access Control for Wireless Sensor Networks -- Tiny 3-TLS: A Trust Delegation Protocol for Wireless Sensor Networks -- Impact of Pseudonym Changes on Geographic Routing in VANETs -- Identification in Infrastructureless Networks -- Two's Company, Three Is a Crowd: A Group-Admission Protocol for WSNs -- So Near and Yet So Far: Distance-Bounding Attacks in Wireless Networks -- Dynamics of Learning Algorithms for the On-Demand Secure Byzantine Routing Protocol -- On the Wiretap Channel Induced by Noisy Tags -- On Optimality of Key Pre-distribution Schemes for Distributed Sensor Networks -- Cryptographic Protocol to Establish Trusted History of Interactions -- Ad Hoc Security Associations for Groups -- Verifiable Agreement: Limits of Non-repudiation in Mobile Peer-to-Peer Ad Hoc Networks -- Using Radio Device Fingerprinting for the Detection of Impersonation and Sybil Attacks in Wireless Networks.

Theseproceedingscontainthepapersofthe3rdEuropeanWorkshoponSecurity and Privacy in Ad Hoc and Sensor Networks (ESAS 2006), which was held in Hamburg, Germany, September 20-21, 2006, in conjunction with the 11th European Symposium on Research in Computer Security (ESORICS 2006). This year, a total of 44 full papers were submitted to ESAS. Each subm- ted paper was reviewed by at least three expert referees. After a short period of discussion and deliberation, the Program Committee selected 14 papers for presentation and subsequent publication in the workshop proceedings. This c- responds to an acceptance rate of 32% - a respectable rate by any measure. In addition to the presented papers, this year's workshop also featured two keynote speeches and seven project presentations. In the ?rst keynote, Jean-Pierre Hubaux (EPFL) gave an overview of "Security and Cooperation in WirelessNetworks".ThesecondkeynotewasgivenbyPimTuyls(Philips)onthe interesting topic of "Grey-Box Cryptography: Physical Unclonable Functions". The project presentations covered the following European Projects: S3MS, SeVeCom, BIONETS, CASCADAS, MOBIUS, EYES and UbiSecSens. Unf- tunately, the extended abstracts of these presentations could not be included in the proceedings. As the Chairs of ESAS 2006, we are very happy with the outcome of the workshop that clearly demonstrates the continued importance, popularity, and timeliness of the topic: Security and Privacy in Ad Hoc and Sensor Networks.