1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
|
/*
* 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 "private_join_and_compute/crypto/ec_commutative_cipher.h"
#include <utility>
#include "private_join_and_compute/crypto/elgamal.h"
#include "private_join_and_compute/util/status.inc"
namespace private_join_and_compute {
ECCommutativeCipher::ECCommutativeCipher(std::unique_ptr<Context> context,
ECGroup group, BigNum private_key,
HashType hash_type)
: context_(std::move(context)),
group_(std::move(group)),
private_key_(std::move(private_key)),
private_key_inverse_(private_key_.ModInverse(group_.GetOrder())),
hash_type_(hash_type) {}
bool ECCommutativeCipher::ValidateHashType(HashType hash_type) {
return (hash_type == SHA256 || hash_type == SHA512);
}
StatusOr<std::unique_ptr<ECCommutativeCipher>>
ECCommutativeCipher::CreateWithNewKey(int curve_id, HashType hash_type) {
std::unique_ptr<Context> context(new Context);
ASSIGN_OR_RETURN(ECGroup group, ECGroup::Create(curve_id, context.get()));
if (!ECCommutativeCipher::ValidateHashType(hash_type)) {
return InvalidArgumentError("Invalid hash type.");
}
BigNum private_key = group.GeneratePrivateKey();
return std::unique_ptr<ECCommutativeCipher>(new ECCommutativeCipher(
std::move(context), std::move(group), std::move(private_key), hash_type));
}
StatusOr<std::unique_ptr<ECCommutativeCipher>>
ECCommutativeCipher::CreateFromKey(int curve_id, absl::string_view key_bytes,
HashType hash_type) {
std::unique_ptr<Context> context(new Context);
ASSIGN_OR_RETURN(ECGroup group, ECGroup::Create(curve_id, context.get()));
if (!ECCommutativeCipher::ValidateHashType(hash_type)) {
return InvalidArgumentError("Invalid hash type.");
}
BigNum private_key = context->CreateBigNum(key_bytes);
auto status = group.CheckPrivateKey(private_key);
if (!status.ok()) {
return status;
}
return std::unique_ptr<ECCommutativeCipher>(new ECCommutativeCipher(
std::move(context), std::move(group), std::move(private_key), hash_type));
}
StatusOr<std::string> ECCommutativeCipher::Encrypt(
absl::string_view plaintext) {
ASSIGN_OR_RETURN(ECPoint hashed_point, HashToTheCurveInternal(plaintext));
ASSIGN_OR_RETURN(ECPoint encrypted_point, Encrypt(hashed_point));
return encrypted_point.ToBytesCompressed();
}
StatusOr<std::string> ECCommutativeCipher::ReEncrypt(
absl::string_view ciphertext) {
ASSIGN_OR_RETURN(ECPoint point, group_.CreateECPoint(ciphertext));
ASSIGN_OR_RETURN(ECPoint reencrypted_point, Encrypt(point));
return reencrypted_point.ToBytesCompressed();
}
StatusOr<ECPoint> ECCommutativeCipher::Encrypt(const ECPoint& point) {
return point.Mul(private_key_);
}
StatusOr<std::pair<std::string, std::string>>
ECCommutativeCipher::ReEncryptElGamalCiphertext(
const std::pair<std::string, std::string>& elgamal_ciphertext) {
ASSIGN_OR_RETURN(ECPoint u, group_.CreateECPoint(elgamal_ciphertext.first));
ASSIGN_OR_RETURN(ECPoint e, group_.CreateECPoint(elgamal_ciphertext.second));
elgamal::Ciphertext decoded_ciphertext = {std::move(u), std::move(e)};
ASSIGN_OR_RETURN(elgamal::Ciphertext reencrypted_ciphertext,
elgamal::Exp(decoded_ciphertext, private_key_));
ASSIGN_OR_RETURN(std::string serialized_u,
reencrypted_ciphertext.u.ToBytesCompressed());
ASSIGN_OR_RETURN(std::string serialized_e,
reencrypted_ciphertext.e.ToBytesCompressed());
return std::make_pair(std::move(serialized_u), std::move(serialized_e));
}
StatusOr<std::string> ECCommutativeCipher::Decrypt(
absl::string_view ciphertext) {
ASSIGN_OR_RETURN(ECPoint point, group_.CreateECPoint(ciphertext));
ASSIGN_OR_RETURN(ECPoint decrypted_point, point.Mul(private_key_inverse_));
return decrypted_point.ToBytesCompressed();
}
::private_join_and_compute::StatusOr<ECPoint>
ECCommutativeCipher::HashToTheCurveInternal(absl::string_view plaintext) {
StatusOr<ECPoint> status_or_point;
if (hash_type_ == SHA512) {
status_or_point = group_.GetPointByHashingToCurveSha512(plaintext);
} else if (hash_type_ == SHA256) {
status_or_point = group_.GetPointByHashingToCurveSha256(plaintext);
} else {
return InvalidArgumentError("Invalid hash type.");
}
return status_or_point;
}
::private_join_and_compute::StatusOr<std::string>
ECCommutativeCipher::HashToTheCurve(absl::string_view plaintext) {
ASSIGN_OR_RETURN(ECPoint point, HashToTheCurveInternal(plaintext));
return point.ToBytesCompressed();
}
std::string ECCommutativeCipher::GetPrivateKeyBytes() const {
return private_key_.ToBytes();
}
} // namespace private_join_and_compute
|
