BigPoly exponentiate_poly_polymod_coeffmod(const BigPoly &operand, const BigUInt &exponent, const BigPoly &poly_modulus, const BigUInt &coeff_modulus, const MemoryPoolHandle &pool) { BigPoly result(poly_modulus.coeff_count(), coeff_modulus.significant_bit_count()); exponentiate_poly_polymod_coeffmod(operand, exponent, poly_modulus, coeff_modulus, result, pool); return result; }
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()); } }