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Collective blog of the Computational Privacy Group at Imperial College London

When the signal is in the noise: Exploiting Aircloak's Diffix anonymization mechanism

Information about us is being constantly collected, through our phones and the services we use online. This data is hugely valuable but also highly personal, and often sensitive. This raises a crucial question: can we use this data without disclosing people’s private information? We studied Diffix, a system developed and commercialized by Aircloak to anonymise data by adding noise to SQL queries sent by analysts. In a manuscript we just published on arXiv, we show that Diffix is vulnerable to a noise-exploitation attack. In short, our attack uses the noise added by Diffix to infer people’s private information with high accuracy. We share Diffix’s creators opinion that it is time to take a fresh look at building practical anonymization systems. However, as we increasingly rely on security mechanisms to protect privacy, we need to learn from the security community: secure systems have to be fully open and part of a larger layered security approach. Privacy is hard, it is time to admit that we won’t find a silver bullet and start engineering systems.

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