This book constitutes the refereed proceedings of the 4th European Workshop on Security and Privacy in Ad hoc and Sensor Networks, ESAS 2007, held in Cambridge, UK, in July 2007. The 17 revised full papers presented were carefully reviewed and selected from 87 submissions. The papers present original research on all aspects of security and privacy in wireless ad hoc and sensor networks and addressing current topics of network security, cryptography, and wireless networking communities. The papers are organized in topical sections on device pairing, key management, location verification and location privacy, secure routing and forwarding, physical security, as well as detection of compromise, and revocation. You hold in your hands the proceedings of ESAS 2007, the Fourth European Workshop on Security and Privacy in Ad hoc and Sensor Networks. The wo- nd rd shop took place in Cambridge, UK, on the 2 and 3 of July 2007. The workshop was European in name and location but it was de?nitely transatlantic in scope. We had a program chair from Europe and one from the USA, and membership of our program committee was almost evenly split - tween those two regions. When looking at participation, the workshop was even more global than that: the submitted papers came from 25 countries in 6 con- nents. We received 87 submissions. After quick-rejecting 5 papers deemed to be out of scope, the remaining 82 papers were each reviewed by at least three PC members. The two program chairs, who did not submit any works, had sole authoritytodecidewhichpaperstoacceptandreject,basedonlyonthedirective that quality had to be the primary criterion, in order to form a proceedings volume of high international relevance. The number of papers to be accepted was not set in advance: it was selected a posteriori so as to include only solid, innovative and insightful papers. The resulting acceptance rate of about 20%, very strict for a workshop, is a testimonial of how selective we chose to be in accepting only high quality papers. Device Pairing The Candidate Key Protocol for Generating Secret Shared Keys from Similar Sensor Data Streams 1(15) Rene Mayrhofer The Martini Synch: Joint Fuzzy Hashing Via Error Correction 16(15) Darko Kirovski Michael Sinclair David Wilson Private Handshakes 31(12) Jaap-Henk Hoepman Security Associations in Personal Networks: A Comparative Analysis 43(15) Jani Suomalainen Jukka Valkonen N. Asokan Key Management Key Establishment in Heterogeneous Self-organized Networks 58(15) Gelareh Taban Rei Safavi-Naini Enabling Full-Size Public-Key Algorithms on 8-bit Sensor Nodes 73(14) Leif Uhsadel Axel Poschmann Christof Paar Key Distribution in Mobile Ad Hoc Networks Based on Message Relaying 87(14) Johann van der Merwe Dawoud Dawoud Stephen McDonald Location Verification and Location Privacy Distance Bounding in Noisy Environments 101(15) Dave Singelee Bart Preneel Multiple Target Localisation in Sensor Networks with Location Privacy 116(13) Matthew Roughan Jon Arnold On the Effectiveness of Changing Pseudonyms to Provide Location Privacy in VANETs 129(13) Levente Buttyan Tamas Holczer Istvan Vajda Secure Routing and Forwarding ``End-by-Hop'' Data Integrity 142(14) Stephen Farrell Christian D. Jensen Authenticating DSR Using a Novel Multisignature Scheme Based on Cubic LFSR Sequences 156(16) Saikat Chakrabarti Santosh Chandrasekhar Mukesh Singhal Kenneth L. Calvert Physical Security Security for Mobile Low Power Nodes in a Personal Area Network by Means of Trusted Platform Modules 172(15) Ulrich Grossmann Enrik Berkhan Luciana C. Jatoba Joerg Ottenbacher Wilhelm Stork Klaus D. Mueller-Glaser Algsics --- Combining Physics and Cryptography to Enhance Security and Privacy in RFID Systems 187(16) Neil Bird Claudine Conrado Jorge Guajardo Stefan Maubach Geert-Jan Schrijen Boris Skoric Anton M.H. Tombeur Peter Thueringer Pim Tuyls Detection of Compromise, and Revocation Detecting Node Compromise in Hybrid Wireless Sensor Networks Using Attestation Techniques 203(15) Christoph Krau? Frederic Stumpf Claudia Eckert Direct Anonymous Attestation (DAA): Ensuring Privacy with Corrupt Administrators 218(14) Ben Smyth Mark Ryan Liqun Chen Now Strategies for Revocation in Ad-Hoc Networks 232(15) Tyler Moore Jolyon Clulow Shishir Nagaraja Ross Anderson Author Index 247