Evaluating convolutions using encrypted data

Abstract

A client device encodes one or more input datasets of real numbers into a plaintext polynomial with integral coefficients that do not include an imaginary component and generates an input ciphertext by encrypting the plaintext polynomial according to a Fully Homomorphic Encryption (FHE) scheme. The input ciphertext includes at least encrypted coefficients of an input polynomial. A server receives the input ciphertext and performs a convolution on the input ciphertext using a kernel by at least in part separately multiplying the input polynomial by one or more kernel polynomials to result in one or more corresponding convolved polynomials. The one or more kernel polynomials include kernel coefficients encoded using kernel values for the kernel. At least a plurality of coefficients is used from each of the one or more convolved polynomials to derive an output ciphertext representing an output of the convolution on the input ciphertext using the kernel.