tfhe 1.6.1

TFHE-rs is a fully homomorphic encryption (FHE) library that implements Zama's variant of TFHE.
Documentation 
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use crate::shortint::keycache::{KEY_CACHE, KEY_CACHE_KSK};
use crate::shortint::parameters::test_params::*;
use crate::shortint::parameters::ShortintKeySwitchingParameters;

#[test]
fn gen_multi_keys_test_fresh_ci_run_filter() {
    let keys = KEY_CACHE_KSK.get_from_param((
        TEST_PARAM_MESSAGE_1_CARRY_1_KS_PBS_GAUSSIAN_2M128,
        TEST_PARAM_MESSAGE_2_CARRY_2_KS_PBS_GAUSSIAN_2M128,
        TEST_PARAM_KEYSWITCH_1_1_KS_PBS_TO_2_2_KS_PBS_GAUSSIAN_2M128,
    ));
    let ck1 = keys.client_key_1();
    let (ck2, sk2) = (keys.client_key_2(), keys.server_key_2());
    let ksk = keys.key_switching_key();

    assert_eq!(ksk.key_switching_key_material.cast_rshift, 2);

    // Message 0 Carry 0
    let cipher = ck1.encrypt(0);
    let output_of_cast = ksk.cast(&cipher);
    let clear = ck2.decrypt(&output_of_cast);
    assert_eq!(clear, 0);
    let ct_carry = sk2.carry_extract(&output_of_cast);
    let carry = ck2.decrypt(&ct_carry);
    assert_eq!(carry, 0);

    // Message 1 Carry 0
    let cipher = ck1.encrypt(1);
    let output_of_cast = ksk.cast(&cipher);
    let clear = ck2.decrypt(&output_of_cast);
    assert_eq!(clear, 1);
    let ct_carry = sk2.carry_extract(&output_of_cast);
    let carry = ck2.decrypt(&ct_carry);
    assert_eq!(carry, 0);

    // Message 0 Carry 1
    let cipher = ck1.unchecked_encrypt(2);
    let output_of_cast = ksk.cast(&cipher);
    let clear = ck2.decrypt(&output_of_cast);
    assert_eq!(clear, 2);
    let ct_carry = sk2.carry_extract(&output_of_cast);
    let carry = ck2.decrypt(&ct_carry);
    assert_eq!(carry, 0);

    // Message 1 Carry 1
    let cipher = ck1.unchecked_encrypt(3);
    let output_of_cast = ksk.cast(&cipher);
    let clear = ck2.decrypt(&output_of_cast);
    assert_eq!(clear, 3);
    let ct_carry = sk2.carry_extract(&output_of_cast);
    let carry = ck2.decrypt(&ct_carry);
    assert_eq!(carry, 0);
}

#[test]
fn gen_multi_keys_test_fresh_2_ci_run_filter() {
    let keys2 = KEY_CACHE.get_from_param(TEST_PARAM_MESSAGE_3_CARRY_3_KS_PBS_GAUSSIAN_2M128);
    let (ck2, sk2) = (keys2.client_key(), keys2.server_key());

    let ksk_params = ShortintKeySwitchingParameters::new(
        ck2.parameters().ks_base_log(),
        ck2.parameters().ks_level(),
        ck2.parameters().encryption_key_choice(),
    );

    let keys = KEY_CACHE_KSK.get_from_param((
        TEST_PARAM_MESSAGE_1_CARRY_1_KS_PBS_GAUSSIAN_2M128,
        TEST_PARAM_MESSAGE_3_CARRY_3_KS_PBS_GAUSSIAN_2M128,
        ksk_params,
    ));
    let ck1 = keys.client_key_1();
    let ksk = keys.key_switching_key();

    assert_eq!(ksk.key_switching_key_material.cast_rshift, 4);

    // Message 0 Carry 0
    let cipher = ck1.encrypt(0);
    let output_of_cast = ksk.cast(&cipher);
    let clear = ck2.decrypt(&output_of_cast);
    let ct_carry = sk2.carry_extract(&output_of_cast);
    let carry = ck2.decrypt(&ct_carry);
    assert_eq!(clear, 0);
    assert_eq!(carry, 0);

    // Message 1 Carry 0
    let cipher = ck1.encrypt(1);
    let output_of_cast = ksk.cast(&cipher);
    let clear = ck2.decrypt(&output_of_cast);
    let ct_carry = sk2.carry_extract(&output_of_cast);
    let carry = ck2.decrypt(&ct_carry);
    assert_eq!(clear, 1);
    assert_eq!(carry, 0);

    // Message 0 Carry 1
    let cipher = ck1.unchecked_encrypt(2);
    let output_of_cast = ksk.cast(&cipher);
    let clear = ck2.decrypt(&output_of_cast);
    let ct_carry = sk2.carry_extract(&output_of_cast);
    let carry = ck2.decrypt(&ct_carry);
    assert_eq!(clear, 2);
    assert_eq!(carry, 0);

    // Message 1 Carry 1
    let cipher = ck1.unchecked_encrypt(3);
    let output_of_cast = ksk.cast(&cipher);
    let clear = ck2.decrypt(&output_of_cast);
    let ct_carry = sk2.carry_extract(&output_of_cast);
    let carry = ck2.decrypt(&ct_carry);
    assert_eq!(clear, 3);
    assert_eq!(carry, 0);
}

#[test]
fn gen_multi_keys_test_add_with_overflow_ci_run_filter() {
    let keys = KEY_CACHE_KSK.get_from_param((
        TEST_PARAM_MESSAGE_1_CARRY_1_KS_PBS_GAUSSIAN_2M128,
        TEST_PARAM_MESSAGE_2_CARRY_2_KS_PBS_GAUSSIAN_2M128,
        TEST_PARAM_KEYSWITCH_1_1_KS_PBS_TO_2_2_KS_PBS_GAUSSIAN_2M128,
    ));
    let (ck1, sk1) = (keys.client_key_1(), keys.server_key_1());
    let (ck2, sk2) = (keys.client_key_2(), keys.server_key_2());
    let ksk = keys.key_switching_key();

    // voluntary overflow
    let c1 = ck1.encrypt(1);
    let c2 = ck1.encrypt(1);

    let c3 = sk1.unchecked_scalar_mul(&c1, 2);
    let c4 = sk1.unchecked_add(&c3, &c2);

    // The optimized atomic pattern requires a ciphertext with NoiseLevel::NOMINAL, i.e. a
    // ciphertext fresh out of a bootstrap
    let id_lut = sk1.generate_lookup_table(|x| x);
    let c5 = sk1.apply_lookup_table(&c4, &id_lut);

    let output_of_cast = ksk.cast(&c5);
    let clear = ck2.decrypt(&output_of_cast);
    assert_eq!(clear, 3);
    let ct_carry = sk2.carry_extract(&output_of_cast);
    let carry = ck2.decrypt(&ct_carry);
    assert_eq!(carry, 0);
}

#[test]
fn gen_multi_keys_test_no_shift_ci_run_filter() {
    let keys2 = KEY_CACHE.get_from_param(TEST_PARAM_MESSAGE_1_CARRY_1_KS_PBS_GAUSSIAN_2M128);
    let ck2 = keys2.client_key();

    let ksk_params = ShortintKeySwitchingParameters::new(
        ck2.parameters().ks_base_log(),
        ck2.parameters().ks_level(),
        ck2.parameters().encryption_key_choice(),
    );

    let keys = KEY_CACHE_KSK.get_from_param((
        TEST_PARAM_MESSAGE_1_CARRY_1_KS_PBS_GAUSSIAN_2M128,
        TEST_PARAM_MESSAGE_1_CARRY_1_KS_PBS_GAUSSIAN_2M128,
        ksk_params,
    ));
    let ksk = keys.key_switching_key();

    assert_eq!(ksk.key_switching_key_material.cast_rshift, 0);
}

#[test]
fn gen_multi_keys_test_truncate_ci_run_filter() {
    let keys2 = KEY_CACHE.get_from_param(TEST_PARAM_MESSAGE_1_CARRY_1_KS_PBS_GAUSSIAN_2M128);
    let (ck2, sk2) = (keys2.client_key(), keys2.server_key());

    let ksk_params = ShortintKeySwitchingParameters::new(
        ck2.parameters().ks_base_log(),
        ck2.parameters().ks_level(),
        ck2.parameters().encryption_key_choice(),
    );

    let keys = KEY_CACHE_KSK.get_from_param((
        TEST_PARAM_MESSAGE_2_CARRY_2_KS_PBS_GAUSSIAN_2M128,
        TEST_PARAM_MESSAGE_1_CARRY_1_KS_PBS_GAUSSIAN_2M128,
        ksk_params,
    ));
    let (ck1, sk1) = (keys.client_key_1(), keys.server_key_1());
    let ksk = keys.key_switching_key();

    assert_eq!(ksk.key_switching_key_material.cast_rshift, -2);

    // Message 0 Carry 0
    let cipher = ck1.unchecked_encrypt(0);
    let output_of_cast = ksk.cast(&cipher);
    assert_eq!(output_of_cast.degree.get(), 3);
    let clear = ck2.decrypt(&output_of_cast);
    assert_eq!(clear, 0);
    let ct_carry = sk2.carry_extract(&output_of_cast);
    let carry = ck2.decrypt(&ct_carry);
    assert_eq!(carry, 0);

    // Message 1 Carry 0
    let cipher = ck1.unchecked_encrypt(1);
    let output_of_cast = ksk.cast(&cipher);
    assert_eq!(output_of_cast.degree.get(), 3);
    let clear = ck2.decrypt(&output_of_cast);
    assert_eq!(clear, 1);
    let ct_carry = sk2.carry_extract(&output_of_cast);
    let carry = ck2.decrypt(&ct_carry);
    assert_eq!(carry, 0);

    // Message 0 Carry 1
    let cipher = ck1.unchecked_encrypt(2);
    let output_of_cast = ksk.cast(&cipher);
    assert_eq!(output_of_cast.degree.get(), 3);
    let clear = ck2.decrypt(&output_of_cast);
    assert_eq!(clear, 0);
    let ct_carry = sk2.carry_extract(&output_of_cast);
    let carry = ck2.decrypt(&ct_carry);
    assert_eq!(carry, 1);

    // Message 1 Carry 1
    let cipher = ck1.unchecked_encrypt(3);
    let output_of_cast = ksk.cast(&cipher);
    assert_eq!(output_of_cast.degree.get(), 3);
    let clear = ck2.decrypt(&output_of_cast);
    assert_eq!(clear, 1);
    let ct_carry = sk2.carry_extract(&output_of_cast);
    let carry = ck2.decrypt(&ct_carry);
    assert_eq!(carry, 1);

    // Actual truncation
    let cipher = ck1.unchecked_encrypt(12);
    let clear = ck1.decrypt(&cipher);
    let ct_carry = sk1.carry_extract(&cipher);
    let carry = ck1.decrypt(&ct_carry);
    assert_eq!((clear, carry), (0, 3));

    let output_of_cast = ksk.cast(&cipher);
    assert_eq!(output_of_cast.degree.get(), 3);
    let clear = ck2.decrypt(&output_of_cast);
    assert_eq!(clear, 0);
    let ct_carry = sk2.carry_extract(&output_of_cast);
    let carry = ck2.decrypt(&ct_carry);
    assert_eq!(carry, 0);
}