Plug-and-play sanitization for TFHE

Fully Homomorphic Encryption allows evaluating an arbitrary function over encrypted data while preserving the privacy of the messages. This property has found numerous applications especially in the case where one would like to process data stored in the cloud in a private way. In this talk, we will focus on the privacy of the algorithm processed by the cloud. Fully Homomorphic Encryption sanitation guarantees that, all the information about how a ciphertext has been obtained is destroyed, except the associated message. In particular, it is impossible to say which computation has been processed in order to obtain a given ciphertext, even knowing the secret key. We will see how to build a sanitization algorithm from the TFHE bootstrapping (Asiacrypt 2016) and how it compares to the previous soak-and-spin strategy from Ducas and Stehlé (Eurocrypt 2016).

This is joint work with Florian Bourse.