Privacy Protection of IoT Based on Fully Homomorphic Encryption

Algorithm 3

Batched bootstrapping implementation of our scheme.

tep 1. The user first post-processes the -secret-key by encrypting as a -ciphertext

with respect to the -secret-key , namely the user has

where

with small coefficients.

tep 2. The server computes homomorphically. Specifically, the server compute the mod-

inner product homomorphically by setting

tep 3. Apply a homomorphic inverse-DFT transformation to convert to CRT-based “packed”

ciphertexts that hold the coefficients of in their plaintext slots.

tep 4. Apply the bit extraction procedure to all these slots in parallel. The result is encryption of

polynomials that have the coefficients of in their plaintext slots.

tep 5. Apply a homomorphic DFT transformation to get back a ciphertext that encrypts the

polynomial itself.