Symposium “Privacy in the era of censorship and bitcoin”.

October 5, 2017

Before the defence of our PhD students Anna Krasnova and Wouter Lueks on October 9, we are organising a small but interesting  Symposium on “Privacy in the era of censorship and bitcoin”.

Date and time: October 9, 2017, 9:30 – 12:30

Location: Faculty Club Huize Heyendael, Nijmegen



9:30 – 10:15: Ian Goldberg, University of Waterloo, Canada, "Perfect Imitation and Secure Asymmetry for Decoy Routing Systems with Slitheen"

10:15 – 10:45: coffe break

10:45 – 11: 30: Gildas Avooine, INSA, Rennes, France, “An introduction to relay attacks and countermeasures”

11:30 – 12:15: Bart Preneel, imec-COSIC KU Leuven, “A Perspective on Cryptocurrencies”



1) "Perfect Imitation and Secure Asymmetry for Decoy Routing Systems with Slitheen"

Censorship circumvention is often characterized as an arms race between a nation-state censor and the developers of censorship-resistance systems. Decoy routing offers a solution to censorship resistance that has the potential to tilt this arms race in the favour of the censorship resistor. Decoy routing uses real connections to unblocked, overt sites to deliver censored content to users. However, the widespread deployment of decoy routers has yet to reach fruition.  Obstacles to deployment such as the heavy requirements on routers that deploy decoy router relay stations, asymmetric traffic routes, and possible effects on the quality of service for existing costumers that pass through deployed decoy routers have deterred potential participants from deploying existing systems.

Although more deployable decoy routing systems have been proposed, these solutions suffer from security vulnerabilities that put their users at risk of discovery. In this talk, we propose techniques for supporting route asymmetry in previously symmetric decoy routing systems and a more secure alternative to existing lightweight systems that provides additional defenses against routing around decoys (RAD) attacks.

 2) “An introduction to relay attacks and countermeasures”

A relay attack is a fraud where an attacker impersonates a genuine communicating party by relaying the messages he exchanges with another party during a protocol execution. Relay attacks are one of the most effective and feared attacks against contactless systems.

Due to their physical nature, relay attacks are not captured by conventional security models. To detect such attacks, it is necessary to look beyond the content of the exchanged messages and incorporate the physical context of the interaction into the model.

Distance-bounding protocols are promising solutions to prevent relay attacks. They measure the round-trip time of short messages exchanged between the parties to estimate an upper-bound on the distance between them. How to design secure and practical distance-bounding protocols is an open research challenge, though.

During the presentation, we will introduce the concept of relay attack and explain how it can be easily performed with off-the-shelf devices.

We will then describe real-life scenarios. We will finally sketch possible countermeasures.

3) “A Perspective on Cryptocurrencies”

This talk explores the technological innovations created by cryptocurrencies such as Bitcoin. We discuss the principles of distributed currencies and discuss their strengths and weaknesses. We also explain how the blockchain mechanism interacts with the other features to create a complex ecosystem. We also touch on the issues of stability and incentive compatibility and we discuss which properties of blockchains are relevant for the key use cases.