Noah's Ark: Efficient Threshold-FHE Using Noise Flooding
Morten Dahl, Daniel Demmler, Sarah El Kazdadi, Arthur Meyre, Jean-Baptiste Orfila, Dragos Rotaru, Nigel P. Smart, Samuel Tap, Michael Walter
Abstract
We outline a secure and efficient methodology to do threshold distributed decryption for LWE based Fully Homomorphic Encryption schemes. Due to the smaller parameters used in some FHE schemes, such as Torus-FHE (TFHE), the standard technique of "noise flooding'' seems not to apply. We show that noise flooding can also be used with schemes with such small parameters, by utilizing a switch to a scheme with slightly higher parameters and then utilizing the efficient bootstrapping operations which TFHE offers. Our protocol is proved secure via a simulation argument, making its integration in bigger protocols easier to manage.