As explained in the introduction, some types (Serverkey, Ciphertext) are meant to be shared with the server that does the computations.
The easiest way to send these data to a server is to use the serialization and deserialization features. TFHE-rs uses the serde framework, so serde's Serialize and Deserialize are implemented.
To be able to serialize our data, a data format needs to be picked. Here, bincode is a good choice, mainly because it is binary format.
# Cargo.toml
# ...
bincode = "1.3.3"
use bincode;
use std::io::Cursor;
use tfhe::integer::{gen_keys_radix, ServerKey, RadixCiphertextBig};
use tfhe::shortint::parameters::PARAM_MESSAGE_2_CARRY_2;
fn main() -> Result<(), Box<dyn std::error::Error>> {
// We generate a set of client/server keys, using the default parameters:
let num_block = 4;
let (client_key, server_key) = gen_keys_radix(&PARAM_MESSAGE_2_CARRY_2, num_block);
let msg1 = 201;
let msg2 = 12;
// message_modulus^vec_length
let modulus = client_key.parameters().message_modulus.0.pow(num_block as u32) as u64;
let ct_1 = client_key.encrypt(msg1);
let ct_2 = client_key.encrypt(msg2);
let mut serialized_data = Vec::new();
bincode::serialize_into(&mut serialized_data, &server_key)?;
bincode::serialize_into(&mut serialized_data, &ct_1)?;
bincode::serialize_into(&mut serialized_data, &ct_2)?;
// Simulate sending serialized data to a server and getting
// back the serialized result
let serialized_result = server_function(&serialized_data)?;
let result: RadixCiphertextBig = bincode::deserialize(&serialized_result)?;
let output: u64 = client_key.decrypt(&result);
assert_eq!(output, (msg1 + msg2) % modulus);
fn server_function(serialized_data: &[u8]) -> Result<Vec<u8>, Box<dyn std::error::Error>> {
let mut serialized_data = Cursor::new(serialized_data);
let server_key: ServerKey = bincode::deserialize_from(&mut serialized_data)?;
let ct_1: RadixCiphertextBig = bincode::deserialize_from(&mut serialized_data)?;
let ct_2: RadixCiphertextBig = bincode::deserialize_from(&mut serialized_data)?;
let result = server_key.unchecked_add(&ct_1, &ct_2);
let serialized_result = bincode::serialize(&result)?;