It is quite interesting that this year’s NDSS, has a special session on “Traffic Protection”. It contains two papers, one about attack (or stepping stone detection) and one on defense (or traffic analysis resistance).

The first paper from Anmir Houmansadr, Negar Kiyavash and Nikita Borisov proposes an active watermarking scheme for network flows, based on spread spectrum techniques, called RAINBOW.It seems like solid work, particularly when it comes to detectability. The authors use a statistical test to determine the covertness of the scheme, that might actually not be optimal for detection. I foresee that covertness would be the property to look at in order to break the scheme or improve on it. The full reference is:

The second paper (presented as a write) is about Traffic Morphing, i.e. how to make encrypted traffic meta-data look like traffic of another class. Unlike anonymity solutions the aim is not to make all traffic look the same, but instead to fool a classifier. This is an interesting approach, but may open up an arms a race between traffic analysis resistance solutions, and those who build better and better classifiers. The full reference is:

(No pdf is yet available for the second work.)

I am currently at NDSS 2009, to present our recent work with Prateek Mittal on SybilInfer [pdf], an inference engine to detect sybil attacks in social networks. Interestingly Carrie Gates is also presenting (right now) a traffic analysis paper on detecting coordinated scans. It would be greatly improved if cast in an inference framework but the techniques and assumptions are still quite interesting.

Coordinated Scan Detection

Carrie Gates, CA Labs
Coordinated attacks distribute the tasks involved in an attack amongst multiple sources. We present a detection algorithm that is based on an adversary model of desired information gain and employs heuristics similar to those for solving the set covering problem. A detector is developed and tested against coordinated horizontal and strobe scanning activity. Experimental results demonstrate an acceptably low false positive rate, and we discuss the conditions required to maximize the detection rate.

Strangely I cannot find a copy of it on-line…

Lords recommend PETs

6 February 2009

The house of Lords Constitution Committeehas just published a report on Surveillance: Citizens and the State as well as the evidence they heard. As part of their recommendations they push Privacy enhancing Technologies to be part of the procurement process of government projects. In particular they say:

485. We recommend that the Government review their procurement processes so as to incorporate design solutions that include privacy-enhancing technologies in new or planned data gathering and processing systems. (paragraph 349)

They also push, albeit in an indirect way, for privacy enhanced identification schemes and ID cards, citing the example of Austria. This is basically a recommendation to implement selective disclosure credential technologies:

478. We recommend that the Government’s development of identification systems should give priority to citizen-oriented considerations. (paragraph 268)

Which refers to:

268. The Information Commissioner’s Office (ICO) drew attention to the use in Austria of a system of identification numbers that allows access to information in different databases “without the need for a single widely known personal identification number that may be misused.” (p 5) The Royal Academy of Engineering (RAE) explained that it is possible for individuals to fulfil their legitimate need or desire to maintain multiple roles or identities in transactions with state or other organisations and to avoid the possibility of those organisations needlessly correlating them. The technology involved in identification can be developed to suit an individual’s preference to keep domestic status and work life separate, where the protection of identity is necessary to avoid abusive relationships or stalking, or where witnesses and children need protection.118 We recommend that the Government’s development of identification systems should give priority to citizen-oriented considerations.

This is all good news! It is indeed at the procurement phase that such requirements for PETs should be specified and entrenched in the delivery contracts. Negotiating PETs for complex surveillance technologies will also make the cost of recording data just-in-case visible.