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/*
* Copyright 2019 Google Inc.
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* https://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "crypto/commutative_elgamal.h"
#include <memory>
#define GLOG_NO_ABBREVIATED_SEVERITIES
#include "absl/strings/string_view.h"
#include "crypto/big_num.h"
#include "crypto/ec_group.h"
#include "crypto/ec_point.h"
#include "crypto/elgamal.h"
#include "glog/logging.h"
#include "util/status.inc"
namespace private_join_and_compute {
CommutativeElGamal::CommutativeElGamal(
std::unique_ptr<Context> ctx, ECGroup group,
std::unique_ptr<elgamal::PublicKey> elgamal_public_key,
std::unique_ptr<elgamal::PrivateKey> elgamal_private_key)
: context_(std::move(ctx)),
group_(std::move(group)),
encrypter_(new ElGamalEncrypter(&group_, std::move(elgamal_public_key))),
decrypter_(new ElGamalDecrypter(std::move(elgamal_private_key))) {}
CommutativeElGamal::CommutativeElGamal(
std::unique_ptr<Context> ctx, ECGroup group,
std::unique_ptr<elgamal::PublicKey> elgamal_public_key)
: context_(std::move(ctx)),
group_(std::move(group)),
encrypter_(new ElGamalEncrypter(&group_, std::move(elgamal_public_key))),
decrypter_(nullptr) {}
StatusOr<std::unique_ptr<CommutativeElGamal>>
CommutativeElGamal::CreateWithNewKeyPair(int curve_id) {
std::unique_ptr<Context> context(new Context);
ASSIGN_OR_RETURN(ECGroup group, ECGroup::Create(curve_id, context.get()));
ASSIGN_OR_RETURN(auto key_pair, elgamal::GenerateKeyPair(group));
std::unique_ptr<CommutativeElGamal> result(new CommutativeElGamal(
std::move(context), std::move(group), std::move(key_pair.first),
std::move(key_pair.second)));
return {std::move(result)};
}
StatusOr<std::unique_ptr<CommutativeElGamal>>
CommutativeElGamal::CreateFromPublicKey(
int curve_id, const std::pair<std::string, std::string>& public_key_bytes) {
std::unique_ptr<Context> context(new Context);
ASSIGN_OR_RETURN(ECGroup group, ECGroup::Create(curve_id, context.get()));
ASSIGN_OR_RETURN(ECPoint g, group.CreateECPoint(public_key_bytes.first));
ASSIGN_OR_RETURN(ECPoint y, group.CreateECPoint(public_key_bytes.second));
std::unique_ptr<elgamal::PublicKey> public_key(
new elgamal::PublicKey({std::move(g), std::move(y)}));
std::unique_ptr<CommutativeElGamal> result(new CommutativeElGamal(
std::move(context), std::move(group), std::move(public_key)));
return {std::move(result)};
}
StatusOr<std::unique_ptr<CommutativeElGamal>>
CommutativeElGamal::CreateFromPublicAndPrivateKeys(
int curve_id, const std::pair<std::string, std::string>& public_key_bytes,
absl::string_view private_key_bytes) {
std::unique_ptr<Context> context(new Context);
ASSIGN_OR_RETURN(ECGroup group, ECGroup::Create(curve_id, context.get()));
ASSIGN_OR_RETURN(ECPoint g, group.CreateECPoint(public_key_bytes.first));
ASSIGN_OR_RETURN(ECPoint y, group.CreateECPoint(public_key_bytes.second));
BigNum x = context->CreateBigNum(private_key_bytes);
ASSIGN_OR_RETURN(ECPoint expected_y, g.Mul(x));
if (y != expected_y) {
return InvalidArgumentError(
"CommutativeElGamal::CreateFromPublicAndPrivateKeys : Public key is "
"not consistent with private key");
}
std::unique_ptr<elgamal::PublicKey> public_key(
new elgamal::PublicKey({std::move(g), std::move(y)}));
std::unique_ptr<elgamal::PrivateKey> private_key(
new elgamal::PrivateKey({std::move(x)}));
std::unique_ptr<CommutativeElGamal> result(
new CommutativeElGamal(std::move(context), std::move(group),
std::move(public_key), std::move(private_key)));
return {std::move(result)};
}
StatusOr<std::pair<std::string, std::string>> CommutativeElGamal::Encrypt(
absl::string_view plaintext) const {
ASSIGN_OR_RETURN(ECPoint plaintext_point, group_.CreateECPoint(plaintext));
ASSIGN_OR_RETURN(elgamal::Ciphertext ciphertext,
encrypter_->Encrypt(plaintext_point));
ASSIGN_OR_RETURN(std::string u_string, ciphertext.u.ToBytesCompressed());
ASSIGN_OR_RETURN(std::string e_string, ciphertext.e.ToBytesCompressed());
return {std::make_pair(std::move(u_string), std::move(e_string))};
}
StatusOr<std::pair<std::string, std::string>>
CommutativeElGamal::EncryptIdentityElement() const {
ASSIGN_OR_RETURN(ECPoint plaintext_point, group_.GetPointAtInfinity());
ASSIGN_OR_RETURN(elgamal::Ciphertext ciphertext,
encrypter_->Encrypt(plaintext_point));
ASSIGN_OR_RETURN(std::string u_string, ciphertext.u.ToBytesCompressed());
ASSIGN_OR_RETURN(std::string e_string, ciphertext.e.ToBytesCompressed());
return {std::make_pair(std::move(u_string), std::move(e_string))};
}
StatusOr<std::string> CommutativeElGamal::Decrypt(
const std::pair<std::string, std::string>& ciphertext) const {
if (nullptr == decrypter_) {
return InvalidArgumentError(
"CommutativeElGamal::Decrypt: cannot decrypt without the private key.");
}
ASSIGN_OR_RETURN(ECPoint u_point, group_.CreateECPoint(ciphertext.first));
ASSIGN_OR_RETURN(ECPoint e_point, group_.CreateECPoint(ciphertext.second));
elgamal::Ciphertext decoded_ciphertext(
{std::move(u_point), std::move(e_point)});
ASSIGN_OR_RETURN(ECPoint plaintext_point,
decrypter_->Decrypt(decoded_ciphertext));
ASSIGN_OR_RETURN(std::string plaintext, plaintext_point.ToBytesCompressed());
return {std::move(plaintext)};
}
StatusOr<std::pair<std::string, std::string>>
CommutativeElGamal::GetPublicKeyBytes() const {
const elgamal::PublicKey* public_key = encrypter_->getPublicKey();
ASSIGN_OR_RETURN(std::string g_string, public_key->g.ToBytesCompressed());
ASSIGN_OR_RETURN(std::string y_string, public_key->y.ToBytesCompressed());
return {std::make_pair(std::move(g_string), std::move(y_string))};
}
StatusOr<std::string> CommutativeElGamal::GetPrivateKeyBytes() const {
if (nullptr == decrypter_) {
return InvalidArgumentError(
"CommutativeElGamal::GetPrivateKeyBytes: private key is not known.");
}
return {decrypter_->getPrivateKey()->x.ToBytes()};
}
} // namespace private_join_and_compute
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