sealy 0.2.0

Rust bindings for Microsoft's SEAL Fully Homomorphic Encryption (FHE) library
Documentation 
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mod test_common;
use sealy::{DegreeType, Evaluator};

#[test]
fn overflow_does_not_bleed_into_other_lanes() {
	test_common::run_bfv_test(
		17,
		DegreeType::D8192,
		|decryptor, encoder, encryptor, eval, _| {
			let mut data = Vec::with_capacity(8192);

			for i in 0..8192 {
				if i == 1 {
					data.push(10_000);
				} else {
					data.push(100);
				}
			}

			let p = encoder.encode_i64(&data).unwrap();

			let c = encryptor.encrypt(&p).unwrap();

			let c_2 = eval.multiply(&c, &c).unwrap();

			let p_2 = decryptor.decrypt(&c_2).unwrap();
			let out = encoder.decode_i64(&p_2).unwrap();

			for (i, lane) in out.into_iter().enumerate() {
				if i == 1 {
					// This lane overflowed...
					assert_eq!(lane, -8808);
				} else {
					assert_eq!(lane, 10_000);
				}
			}
		},
	)
}

#[test]
fn multiply_ciphertext_increases_terms() {
	test_common::run_bfv_test(17, DegreeType::D8192, |_, encoder, encryptor, eval, _| {
		let mut data = Vec::with_capacity(8192);

		for i in 0..8192 {
			if i == 1 {
				data.push(10_000);
			} else {
				data.push(100);
			}
		}

		let p = encoder.encode_i64(&data).unwrap();
		let c = encryptor.encrypt(&p).unwrap();

		assert_eq!(c.num_polynomials(), 2);

		let c_2 = eval.multiply(&c, &c).unwrap();

		assert_eq!(c_2.num_polynomials(), 3);
	})
}

#[test]
fn multiply_plaintext_does_not_increase_polynomials() {
	test_common::run_bfv_test(17, DegreeType::D8192, |_, encoder, encryptor, eval, _| {
		let mut data = Vec::with_capacity(8192);

		for i in 0..8192 {
			if i == 1 {
				data.push(10_000);
			} else {
				data.push(100);
			}
		}

		let p = encoder.encode_i64(&data).unwrap();
		let c = encryptor.encrypt(&p).unwrap();

		assert_eq!(c.num_polynomials(), 2);

		let c_2 = eval.multiply_plain(&c, &p).unwrap();

		assert_eq!(c_2.num_polynomials(), 2);
	})
}

#[test]
fn lanes_have_same_modulus() {
	test_common::run_bfv_test(
		17,
		DegreeType::D8192,
		|decryptor, encoder, encryptor, eval, _| {
			let mut data = Vec::with_capacity(8192);

			for _i in 0..8192 {
				data.push(100);
			}

			let p = encoder.encode_i64(&data).unwrap();
			let c = encryptor.encrypt(&p).unwrap();

			// 10_000 ^ 2 should produce the same value in every lane if the modulus
			// is the same in every lane.
			let c_2 = eval.multiply(&c, &c).unwrap();

			let p_2 = decryptor.decrypt(&c_2).unwrap();
			let out = encoder.decode_i64(&p_2).unwrap();

			for lane in out {
				assert_eq!(lane, 10_000);
			}
		},
	)
}

#[test]
fn lane_modulus_is_not_power_of_2() {
	test_common::run_bfv_test(
		17,
		DegreeType::D8192,
		|decryptor, encoder, encryptor, eval, _| {
			// Modulus should be 114_689
			let mut data = Vec::with_capacity(8192);
			let mut data_2 = Vec::with_capacity(8192);

			for _i in 0..8192 {
				data.push(114_688);
				data_2.push(1);
			}

			let p = encoder.encode_u64(&data).unwrap();
			let p_2 = encoder.encode_u64(&data_2).unwrap();
			let c = encryptor.encrypt(&p).unwrap();

			// 10_000 ^ 2 should produce the same value in every lane if the modulus
			// is the same in every lane.
			let c_2 = eval.add_plain(&c, &p_2).unwrap();

			let p_2 = decryptor.decrypt(&c_2).unwrap();
			let out = encoder.decode_u64(&p_2).unwrap();

			for lane in out {
				assert_eq!(lane, 0);
			}
		},
	)
}

#[test]
fn relinearization_consumes_no_noise_budget() {
	use sealy::*;

	let degree = DegreeType::D8192;
	let lane_bits = 18;

	let params = BFVEncryptionParametersBuilder::new()
		.set_poly_modulus_degree(degree)
		.set_coefficient_modulus(
			CoefficientModulusFactory::bfv(degree, SecurityLevel::TC128).unwrap(),
		)
		.set_plain_modulus(PlainModulusFactory::batching(degree, lane_bits).unwrap())
		.build()
		.unwrap();

	let ctx = Context::new(&params, false, SecurityLevel::TC128).unwrap();
	let gen = KeyGenerator::new(&ctx).unwrap();

	let encoder = BFVEncoder::new(&ctx).unwrap();

	let public_key = gen.create_public_key();
	let private_key = gen.secret_key();
	let relin_key = gen.create_relinearization_keys().unwrap();

	let encryptor = Encryptor::with_public_and_secret_key(&ctx, &public_key, &private_key).unwrap();
	let decryptor = Decryptor::new(&ctx, &private_key).unwrap();
	let eval = BFVEvaluator::new(&ctx).unwrap();

	// Modulus should be 114_689
	let mut data = Vec::with_capacity(8192);
	let mut data_2 = Vec::with_capacity(8192);

	for _i in 0..8192 {
		data.push(114_688);
		data_2.push(1);
	}

	let p = encoder.encode_u64(&data).unwrap();
	let c_1 = encryptor.encrypt(&p).unwrap();
	let c_2 = encryptor.encrypt(&p).unwrap();

	// 10_000 ^ 2 should produce the same value in every lane if the modulus
	// is the same in every lane.
	let c_2 = eval.multiply(&c_1, &c_2).unwrap();

	let noise_pre = decryptor.invariant_noise_budget(&c_2).unwrap();

	let c_3 = eval.relinearize(&c_2, &relin_key).unwrap();

	let noise_post = decryptor.invariant_noise_budget(&c_3).unwrap();

	println!("{}", noise_pre);
	println!("{}", noise_post);

	assert_eq!(noise_post, noise_pre);
}

#[test]
fn addition_noise_less_equal_operands() {
	use sealy::*;

	let degree = DegreeType::D8192;
	let lane_bits = 18;

	let params = BFVEncryptionParametersBuilder::new()
		.set_poly_modulus_degree(degree)
		.set_coefficient_modulus(
			CoefficientModulusFactory::bfv(degree, SecurityLevel::TC128).unwrap(),
		)
		.set_plain_modulus(PlainModulusFactory::batching(degree, lane_bits).unwrap())
		.build()
		.unwrap();

	let ctx = Context::new(&params, false, SecurityLevel::TC128).unwrap();
	let gen = KeyGenerator::new(&ctx).unwrap();

	let encoder = BFVEncoder::new(&ctx).unwrap();

	let public_key = gen.create_public_key();
	let private_key = gen.secret_key();

	let encryptor = Encryptor::with_public_and_secret_key(&ctx, &public_key, &private_key).unwrap();
	let decryptor = Decryptor::new(&ctx, &private_key).unwrap();
	let eval = BFVEvaluator::new(&ctx).unwrap();

	// Modulus should be 114_689
	let mut data = Vec::with_capacity(8192);
	let mut data_2 = Vec::with_capacity(8192);

	for _i in 0..8192 {
		data.push(114_688);
		data_2.push(1);
	}

	let p = encoder.encode_u64(&data).unwrap();
	let c_1 = encryptor.encrypt(&p).unwrap();
	let c_2 = encryptor.encrypt(&p).unwrap();

	let noise_a = decryptor.invariant_noise(&c_1).unwrap();
	let noise_b = decryptor.invariant_noise(&c_2).unwrap();

	// 10_000 ^ 2 should produce the same value in every lane if the modulus
	// is the same in every lane.
	let c_2 = eval.add(&c_1, &c_2).unwrap();

	let noise_c = decryptor.invariant_noise(&c_2).unwrap();

	assert!(noise_a + noise_b >= noise_c);
}