HE is all you need: Compressing FHE Ciphertexts using Additive HE. (arXiv:2303.09043v1 [cs.CR])

Fully Homomorphic Encryption (FHE) permits the evaluation of an arbitrary
function on encrypted data. However, FHE ciphertexts, particularly those based
on lattice assumptions such as LWE/RLWE are very large compared to the
underlying plaintext. Large ciphertexts are hard to communicate over the
network and this is an obstacle to the adoption of FHE, particularly for
clients with limited bandwidth. In this work, we propose the first technique to
compress ciphertexts sent from the server to the client using an additive
encryption scheme with smaller ciphertexts. Using the additive scheme, the
client sends auxiliary information to the server which is used to compress the
ciphertext. Our evaluation shows up to 95% percent and 97% compression for LWE
and RLWE ciphertexts, respectively.