Homomorphic additions, multiplications, and rotations for vectors of integers via BFV

Overview

This Rust example demonstrates basic homomorphic encryption operations such as addition, multiplication, and rotation on vectors of integers using the BFVrns3 scheme provided by the openfhe library. The example walks through the setup of cryptographic parameters, key generation, encryption of plaintext vectors, performing homomorphic operations, and decrypting the results. The example for this code is located in :code:`examples/simple_integers.rs <https://github.com/fairmath/openfhe-rs/blob/master/examples/simple_integers.rs>`_.

Code breakdown

Importing libraries

We start by importing the necessary libraries and modules:

use openfhe::cxx::{CxxVector};
use openfhe::ffi as ffi;

The code example

The main function contains the entire workflow for setting up the BFV scheme, performing encryption, executing homomorphic operations, and decrypting the results.

Generating Parameters

We define the cryptographic parameters for the BFV scheme, namely plaintext modulus and multiplicative depth.

let mut _cc_params_bfvrns = ffi::GenParamsBFVRNS();
_cc_params_bfvrns.pin_mut().SetPlaintextModulus(65537);
_cc_params_bfvrns.pin_mut().SetMultiplicativeDepth(2);

Creating Crypto Context

We create a crypto context based on the defined parameters and enable necessary features.

let _cc = ffi::DCRTPolyGenCryptoContextByParamsBFVRNS(&_cc_params_bfvrns);
_cc.EnableByFeature(ffi::PKESchemeFeature::PKE);
_cc.EnableByFeature(ffi::PKESchemeFeature::KEYSWITCH);
_cc.EnableByFeature(ffi::PKESchemeFeature::LEVELEDSHE);

Key Generation

We generate the necessary keys for encryption, including evaluation keys for multiplication and rotation.

let _key_pair = _cc.KeyGen();
_cc.EvalMultKeyGen(&_key_pair.GetPrivateKey());

let mut _index_list = CxxVector::<i32>::new();
_index_list.pin_mut().push(1);
_index_list.pin_mut().push(2);
_index_list.pin_mut().push(-1);
_index_list.pin_mut().push(-2);
_cc.EvalRotateKeyGen(&_key_pair.GetPrivateKey(), &_index_list, &ffi::DCRTPolyGenNullPublicKey());

Plaintext Vector Creation

let mut _vector_of_ints_1 = CxxVector::<i64>::new();
_vector_of_ints_1.pin_mut().push(1);
_vector_of_ints_1.pin_mut().push(2);
...
let _plain_text_1 = _cc.MakePackedPlaintext(&_vector_of_ints_1, 1, 0);

Encrypting Plaintext Vectors

We encrypt the plaintext vectors using the generated public key.

let _cipher_text_1 = _cc.EncryptByPublicKey(&_key_pair.GetPublicKey(), &_plain_text_1);

Performing Homomorphic Operations

We perform various homomorphic operations on the encrypted data, including addition, multiplication, and rotations.

let _cipher_text_add_1_2 = _cc.EvalAddByCiphertexts(&_cipher_text_1, &_cipher_text_2);
let _cipher_text_mult_result = _cc.EvalMultByCiphertexts(&_cipher_text_mul_1_2, &_cipher_text_3);
let _cipher_text_rot_1 = _cc.EvalRotate(&_cipher_text_1, 1);

Decrypting and Printing Results

Finally, we decrypt the results of the homomorphic computations and print them.

let mut _plain_text_add_result = ffi::GenNullPlainText();
_cc.DecryptByPrivateKeyAndCiphertext(&_key_pair.GetPrivateKey(), &_cipher_text_add_result, _plain_text_add_result.pin_mut());
println!("Plaintext #1: {}", _plain_text_1.GetString());

Running the example

Ensure the openfhe-rs library is installed and properly configured, see the About OpenFHE-rs section.
Go to the openfhe-rs directory.
Compile and run the simple_integers.rs example:

cargo run --example simple_integers

This should output the results of the homomorphic computations to the console.