void KeyGenerator::generate()
{
// Handle test-mode case.
if (mode_ == TEST_MODE)
{
public_key_.set_zero();
public_key_[0] = 1;
secret_key_.set_zero();
secret_key_[0] = 1;
for (int i = 0; i < evaluation_keys_.count(); ++i)
{
evaluation_keys_[i].set_zero();
evaluation_keys_[i][0] = 1;
}
return;
}
// Extract encryption parameters.
int coeff_count = poly_modulus_.coeff_count();
int coeff_bit_count = poly_modulus_.coeff_bit_count();
int coeff_uint64_count = divide_round_up(coeff_bit_count, bits_per_uint64);
// Loop until find a valid secret key.
uint64_t *secret_key = secret_key_.pointer();
set_zero_poly(coeff_count, coeff_uint64_count, secret_key);
Pointer secret_key_inv(allocate_poly(coeff_count, coeff_uint64_count, pool_));
while (true)
{
// Create noise with random [-1, 1] coefficients.
set_poly_coeffs_zero_one_negone(secret_key);
// Calculate secret_key * plaintext_modulus + 1.
multiply_poly_scalar_coeffmod(secret_key, coeff_count, plain_modulus_.pointer(), mod_, secret_key, pool_);
uint64_t *constant_coeff = get_poly_coeff(secret_key, 0, coeff_uint64_count);
increment_uint_mod(constant_coeff, coeff_modulus_.pointer(), coeff_uint64_count, constant_coeff);
// Attempt to invert secret_key.
if (try_invert_poly_coeffmod(secret_key, poly_modulus_.pointer(), coeff_count, mod_, secret_key_inv.get(), pool_))
{
// Secret_key is invertible, so is valid
break;
}
}
// Calculate plaintext_modulus * noise * secret_key_inv.
Pointer noise(allocate_poly(coeff_count, coeff_uint64_count, pool_));
set_poly_coeffs_zero_one_negone(noise.get());
uint64_t *public_key = public_key_.pointer();
multiply_poly_poly_polymod_coeffmod(noise.get(), secret_key_inv.get(), polymod_, mod_, noise.get(), pool_);
multiply_poly_scalar_coeffmod(noise.get(), coeff_count, plain_modulus_.pointer(), mod_, public_key, pool_);
// Create evaluation keys.
Pointer evaluation_factor(allocate_uint(coeff_uint64_count, pool_));
set_uint(1, coeff_uint64_count, evaluation_factor.get());
for (int i = 0; i < evaluation_keys_.count(); ++i)
{
// Multiply secret_key by evaluation_factor (mod coeff modulus).
uint64_t *evaluation_key = evaluation_keys_[i].pointer();
multiply_poly_scalar_coeffmod(secret_key, coeff_count, evaluation_factor.get(), mod_, evaluation_key, pool_);
// Multiply public_key*normal noise and add into evaluation_key.
set_poly_coeffs_normal(noise.get());
multiply_poly_poly_polymod_coeffmod(noise.get(), public_key, polymod_, mod_, noise.get(), pool_);
add_poly_poly_coeffmod(noise.get(), evaluation_key, coeff_count, coeff_modulus_.pointer(), coeff_uint64_count, evaluation_key);
// Add-in more normal noise to evaluation_key.
set_poly_coeffs_normal(noise.get());
add_poly_poly_coeffmod(noise.get(), evaluation_key, coeff_count, coeff_modulus_.pointer(), coeff_uint64_count, evaluation_key);
// Left shift evaluation factor.
left_shift_uint(evaluation_factor.get(), decomposition_bit_count_, coeff_uint64_count, evaluation_factor.get());
}
}
void KeyGenerator::generate(const BigPoly &secret_key, uint64_t power)
{
// Validate arguments.
if (secret_key.is_zero())
{
throw invalid_argument("secret_key cannot be zero");
}
if (power == 0)
{
throw invalid_argument("power cannot be zero");
}
// Handle test-mode case.
if (mode_ == TEST_MODE)
{
public_key_.set_zero();
public_key_[0] = 1;
secret_key_.set_zero();
secret_key_[0] = 1;
for (int i = 0; i < evaluation_keys_.count(); ++i)
{
evaluation_keys_[i].set_zero();
evaluation_keys_[i][0] = 1;
}
return;
}
// Extract encryption parameters.
int coeff_count = poly_modulus_.coeff_count();
int coeff_bit_count = poly_modulus_.coeff_bit_count();
int coeff_uint64_count = divide_round_up(coeff_bit_count, bits_per_uint64);
// Verify secret key looks valid.
secret_key_ = secret_key;
if (secret_key_.coeff_count() != coeff_count || secret_key_.coeff_bit_count() != coeff_bit_count)
{
throw invalid_argument("secret_key is not valid for encryption parameters");
}
#ifdef _DEBUG
if (secret_key_.significant_coeff_count() == coeff_count || !are_poly_coefficients_less_than(secret_key_, coeff_modulus_))
{
throw invalid_argument("secret_key is not valid for encryption parameters");
}
#endif
// Raise level of secret key.
if (power > 1)
{
exponentiate_poly_polymod_coeffmod(secret_key_.pointer(), &power, 1, polymod_, mod_, secret_key_.pointer(), pool_);
}
// Attempt to invert secret_key.
Pointer secret_key_inv(allocate_poly(coeff_count, coeff_uint64_count, pool_));
if (!try_invert_poly_coeffmod(secret_key_.pointer(), poly_modulus_.pointer(), coeff_count, mod_, secret_key_inv.get(), pool_))
{
// Secret_key is not invertible, so not valid.
throw invalid_argument("secret_key is not valid for encryption parameters");
}
// Calculate plaintext_modulus * noise * secret_key_inv.
Pointer noise(allocate_poly(coeff_count, coeff_uint64_count, pool_));
set_poly_coeffs_zero_one_negone(noise.get());
uint64_t *public_key = public_key_.pointer();
multiply_poly_poly_polymod_coeffmod(noise.get(), secret_key_inv.get(), polymod_, mod_, noise.get(), pool_);
multiply_poly_scalar_coeffmod(noise.get(), coeff_count, plain_modulus_.pointer(), mod_, public_key, pool_);
// Create evaluation keys.
Pointer evaluation_factor(allocate_uint(coeff_uint64_count, pool_));
set_uint(1, coeff_uint64_count, evaluation_factor.get());
for (int i = 0; i < evaluation_keys_.count(); ++i)
{
// Multiply secret_key by evaluation_factor (mod coeff modulus).
uint64_t *evaluation_key = evaluation_keys_[i].pointer();
multiply_poly_scalar_coeffmod(secret_key_.pointer(), coeff_count, evaluation_factor.get(), mod_, evaluation_key, pool_);
// Multiply public_key*normal noise and add into evaluation_key.
set_poly_coeffs_normal(noise.get());
multiply_poly_poly_polymod_coeffmod(noise.get(), public_key, polymod_, mod_, noise.get(), pool_);
add_poly_poly_coeffmod(noise.get(), evaluation_key, coeff_count, coeff_modulus_.pointer(), coeff_uint64_count, evaluation_key);
// Add-in more normal noise to evaluation_key.
set_poly_coeffs_normal(noise.get());
add_poly_poly_coeffmod(noise.get(), evaluation_key, coeff_count, coeff_modulus_.pointer(), coeff_uint64_count, evaluation_key);
// Left shift evaluation factor.
left_shift_uint(evaluation_factor.get(), decomposition_bit_count_, coeff_uint64_count, evaluation_factor.get());
}
}
KeyGenerator::KeyGenerator(const EncryptionParameters &parms) :
poly_modulus_(parms.poly_modulus()), coeff_modulus_(parms.coeff_modulus()), plain_modulus_(parms.plain_modulus()),
noise_standard_deviation_(parms.noise_standard_deviation()), noise_max_deviation_(parms.noise_max_deviation()),
decomposition_bit_count_(parms.decomposition_bit_count()), mode_(parms.mode()),
random_generator_(parms.random_generator() != nullptr ? parms.random_generator()->create() : UniformRandomGeneratorFactory::default_factory()->create())
{
// Verify required parameters are non-zero and non-nullptr.
if (poly_modulus_.is_zero())
{
throw invalid_argument("poly_modulus cannot be zero");
}
if (coeff_modulus_.is_zero())
{
throw invalid_argument("coeff_modulus cannot be zero");
}
if (plain_modulus_.is_zero())
{
throw invalid_argument("plain_modulus cannot be zero");
}
if (noise_standard_deviation_ < 0)
{
throw invalid_argument("noise_standard_deviation must be non-negative");
}
if (noise_max_deviation_ < 0)
{
throw invalid_argument("noise_max_deviation must be non-negative");
}
if (decomposition_bit_count_ <= 0)
{
throw invalid_argument("decomposition_bit_count must be positive");
}
// Verify parameters.
if (plain_modulus_ >= coeff_modulus_)
{
throw invalid_argument("plain_modulus must be smaller than coeff_modulus");
}
if (!are_poly_coefficients_less_than(poly_modulus_, coeff_modulus_))
{
throw invalid_argument("poly_modulus cannot have coefficients larger than coeff_modulus");
}
// Resize encryption parameters to consistent size.
int coeff_count = poly_modulus_.significant_coeff_count();
int coeff_bit_count = coeff_modulus_.significant_bit_count();
int coeff_uint64_count = divide_round_up(coeff_bit_count, bits_per_uint64);
if (poly_modulus_.coeff_count() != coeff_count || poly_modulus_.coeff_bit_count() != coeff_bit_count)
{
poly_modulus_.resize(coeff_count, coeff_bit_count);
}
if (coeff_modulus_.bit_count() != coeff_bit_count)
{
coeff_modulus_.resize(coeff_bit_count);
}
if (plain_modulus_.bit_count() != coeff_bit_count)
{
plain_modulus_.resize(coeff_bit_count);
}
if (decomposition_bit_count_ > coeff_bit_count)
{
decomposition_bit_count_ = coeff_bit_count;
}
// Calculate -1 (mod coeff_modulus).
coeff_modulus_minus_one_.resize(coeff_bit_count);
decrement_uint(coeff_modulus_.pointer(), coeff_uint64_count, coeff_modulus_minus_one_.pointer());
// Initialize public and secret key.
public_key_.resize(coeff_count, coeff_bit_count);
secret_key_.resize(coeff_count, coeff_bit_count);
// Initialize evaluation keys.
int evaluation_key_count = 0;
Pointer evaluation_factor(allocate_uint(coeff_uint64_count, pool_));
set_uint(1, coeff_uint64_count, evaluation_factor.get());
while (!is_zero_uint(evaluation_factor.get(), coeff_uint64_count) && is_less_than_uint_uint(evaluation_factor.get(), coeff_modulus_.pointer(), coeff_uint64_count))
{
left_shift_uint(evaluation_factor.get(), decomposition_bit_count_, coeff_uint64_count, evaluation_factor.get());
evaluation_key_count++;
}
evaluation_keys_.resize(evaluation_key_count);
for (int i = 0; i < evaluation_key_count; ++i)
{
evaluation_keys_[i].resize(coeff_count, coeff_bit_count);
}
// Initialize moduli.
polymod_ = PolyModulus(poly_modulus_.pointer(), coeff_count, coeff_uint64_count);
mod_ = Modulus(coeff_modulus_.pointer(), coeff_uint64_count, pool_);
}
Evaluator::Evaluator(const EncryptionParameters &parms, const EvaluationKeys &evaluation_keys) :
poly_modulus_(parms.poly_modulus()), coeff_modulus_(parms.coeff_modulus()), plain_modulus_(parms.plain_modulus()),
decomposition_bit_count_(parms.decomposition_bit_count()), evaluation_keys_(evaluation_keys), mode_(parms.mode())
{
// Verify required parameters are non-zero and non-nullptr.
if (poly_modulus_.is_zero())
{
throw invalid_argument("poly_modulus cannot be zero");
}
if (coeff_modulus_.is_zero())
{
throw invalid_argument("coeff_modulus cannot be zero");
}
if (plain_modulus_.is_zero())
{
throw invalid_argument("plain_modulus cannot be zero");
}
if (decomposition_bit_count_ <= 0)
{
throw invalid_argument("decomposition_bit_count must be positive");
}
if (evaluation_keys_.count() == 0)
{
throw invalid_argument("evaluation_keys cannot be empty");
}
// Verify parameters.
if (plain_modulus_ >= coeff_modulus_)
{
throw invalid_argument("plain_modulus must be smaller than coeff_modulus");
}
if (!are_poly_coefficients_less_than(poly_modulus_, coeff_modulus_))
{
throw invalid_argument("poly_modulus cannot have coefficients larger than coeff_modulus");
}
// Resize encryption parameters to consistent size.
int coeff_count = poly_modulus_.significant_coeff_count();
int coeff_bit_count = coeff_modulus_.significant_bit_count();
int coeff_uint64_count = divide_round_up(coeff_bit_count, bits_per_uint64);
if (poly_modulus_.coeff_count() != coeff_count || poly_modulus_.coeff_bit_count() != coeff_bit_count)
{
poly_modulus_.resize(coeff_count, coeff_bit_count);
}
if (coeff_modulus_.bit_count() != coeff_bit_count)
{
coeff_modulus_.resize(coeff_bit_count);
}
if (plain_modulus_.bit_count() != coeff_bit_count)
{
plain_modulus_.resize(coeff_bit_count);
}
if (decomposition_bit_count_ > coeff_bit_count)
{
decomposition_bit_count_ = coeff_bit_count;
}
// Determine correct number of evaluation keys.
int evaluation_key_count = 0;
Pointer evaluation_factor(allocate_uint(coeff_uint64_count, pool_));
set_uint(1, coeff_uint64_count, evaluation_factor.get());
while (!is_zero_uint(evaluation_factor.get(), coeff_uint64_count) && is_less_than_uint_uint(evaluation_factor.get(), coeff_modulus_.pointer(), coeff_uint64_count))
{
left_shift_uint(evaluation_factor.get(), decomposition_bit_count_, coeff_uint64_count, evaluation_factor.get());
evaluation_key_count++;
}
// Verify evaluation keys.
if (evaluation_keys_.count() != evaluation_key_count)
{
throw invalid_argument("evaluation_keys is not valid for encryption parameters");
}
for (int i = 0; i < evaluation_keys_.count(); ++i)
{
BigPoly &evaluation_key = evaluation_keys_[i];
if (evaluation_key.coeff_count() != coeff_count || evaluation_key.coeff_bit_count() != coeff_bit_count ||
evaluation_key.significant_coeff_count() == coeff_count || !are_poly_coefficients_less_than(evaluation_key, coeff_modulus_))
{
throw invalid_argument("evaluation_keys is not valid for encryption parameters");
}
}
// Calculate coeff_modulus / plain_modulus.
coeff_div_plain_modulus_.resize(coeff_bit_count);
Pointer temp(allocate_uint(coeff_uint64_count, pool_));
divide_uint_uint(coeff_modulus_.pointer(), plain_modulus_.pointer(), coeff_uint64_count, coeff_div_plain_modulus_.pointer(), temp.get(), pool_);
// Calculate (plain_modulus + 1) / 2.
plain_upper_half_threshold_.resize(coeff_bit_count);
half_round_up_uint(plain_modulus_.pointer(), coeff_uint64_count, plain_upper_half_threshold_.pointer());
// Calculate coeff_modulus - plain_modulus.
plain_upper_half_increment_.resize(coeff_bit_count);
sub_uint_uint(coeff_modulus_.pointer(), plain_modulus_.pointer(), coeff_uint64_count, plain_upper_half_increment_.pointer());
// Calculate (plain_modulus + 1) / 2 * coeff_div_plain_modulus.
upper_half_threshold_.resize(coeff_bit_count);
multiply_truncate_uint_uint(plain_upper_half_threshold_.pointer(), coeff_div_plain_modulus_.pointer(), coeff_uint64_count, upper_half_threshold_.pointer());
// Calculate upper_half_increment.
upper_half_increment_.resize(coeff_bit_count);
multiply_truncate_uint_uint(plain_modulus_.pointer(), coeff_div_plain_modulus_.pointer(), coeff_uint64_count, upper_half_increment_.pointer());
sub_uint_uint(coeff_modulus_.pointer(), upper_half_increment_.pointer(), coeff_uint64_count, upper_half_increment_.pointer());
// Widen coeff modulus.
int product_coeff_bit_count = coeff_bit_count + coeff_bit_count + get_significant_bit_count(static_cast<uint64_t>(coeff_count));
int plain_modulus_bit_count = plain_modulus_.significant_bit_count();
int wide_bit_count = product_coeff_bit_count + plain_modulus_bit_count;
int wide_uint64_count = divide_round_up(wide_bit_count, bits_per_uint64);
wide_coeff_modulus_.resize(wide_bit_count);
wide_coeff_modulus_ = coeff_modulus_;
// Calculate wide_coeff_modulus_ / 2.
wide_coeff_modulus_div_two_.resize(wide_bit_count);
right_shift_uint(wide_coeff_modulus_.pointer(), 1, wide_uint64_count, wide_coeff_modulus_div_two_.pointer());
// Initialize moduli.
polymod_ = PolyModulus(poly_modulus_.pointer(), coeff_count, coeff_uint64_count);
if (mode_ == TEST_MODE)
{
mod_ = Modulus(plain_modulus_.pointer(), coeff_uint64_count, pool_);
}
else
{
mod_ = Modulus(coeff_modulus_.pointer(), coeff_uint64_count, pool_);
}
}