Critical Traffic Analysis on the Tor Network




Tor, traffic analysis, hidden services, deanonymization


Tor is a widely-used anonymity network with more than two million daily users. A prominent feature of Tor is the hidden service architecture. Hidden services are a popular method for communicating anonymously or sharing web contents anonymously. For security reasons, in Tor all data packets to be send over the network are structured completely identical. They are encrypted using the TLS protocol and its size is fixed to exactly 512 bytes. In this work we describe a method to deanonymize any hidden service on Tor based on traffic analysis. This method allows an attacker with modest resources to deanonymize any hidden services in less than 12.5 days. This poses a threat to anonymity online.


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Author Biographies

Florian Platzer, Fraunhofer SIT, Germany

Florian Platzer is a research assistant at the Fraunhofer Institute for Secure Information Technology. He is part of the PANDA project at Fraunhofer SIT. The PANDA project is an interdisciplinary project researching the darknet. Within this project he is responsible for the computer science part. Florian studied IT security at the Technical University of Darmstadt, Germany. He wrote his master thesis about deanonymization of Tor hidden services.

Marcel Schäfer, Fraunhofer USA CMA, USA

Marcel Schäfer serves as Senior Research Scientist for the Fraunhofer USA Center for Experimental Engineering CESE in Maryland since 2019. From 2009 to 2018 he was with Fraunhofer Institute for Secure Information Technologies SIT in Germany. With a Master’s degree in mathematics from the University of Wuppertal, Germany and a PhD in computer science from the Technical University of Darmstadt, Germany, he consults and teaches for topics on dark web, privacy networks and anonymous communication, and also serves as a subject matter expert for privacy, e.g. GDPR and data anonymization. As PI, Co-PI and researcher Dr. Schäfer has lead and worked in various projects that discover new challenges and opportunities broadly spread over the fields of cybersecurity and software engineering in both the public and private sector.

Martin Steinebach, Fraunhofer SIT, Germany

Martin Steinebach is the manager of the Media Security and IT Forensics division at Fraunhofer SIT. From 2003 to 2007 he was the manager of the Media Security in IT division at Fraunhofer IPSI. He studied computer science at the Technical University of Darmstadt and finished his diploma thesis on copyright protection for digital audio in 1999. In 2003 he received his PhD at the Technical University of Darmstadt for this work on digital audio watermarking. In 2016 he became honorary professor at the TU Darmstadt. He gives lectures on Multimedia Security as well as Civil Security. He is Principle Investigator at ATHENE and represents IT Forensics and AI security. Before he was Principle Investigator at CASED with the topics Multimedia Security and IT Forensics. In 2012 his work on robust image hashing for detection of child pornography reached the second rank “Deutscher ITSicherheitspreis”, an award funded by Host Görtz.


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