forked from openfheorg/openfhe-development
-
Notifications
You must be signed in to change notification settings - Fork 0
/
iterative-ckks-bootstrapping.cpp
189 lines (156 loc) · 8.18 KB
/
iterative-ckks-bootstrapping.cpp
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
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
//==================================================================================
// BSD 2-Clause License
//
// Copyright (c) 2014-2022, NJIT, Duality Technologies Inc. and other contributors
//
// All rights reserved.
//
// Author TPOC: contact@openfhe.org
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
// 1. Redistributions of source code must retain the above copyright notice, this
// list of conditions and the following disclaimer.
//
// 2. Redistributions in binary form must reproduce the above copyright notice,
// this list of conditions and the following disclaimer in the documentation
// and/or other materials provided with the distribution.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
//==================================================================================
/*
Example for multiple iterations of CKKS bootstrapping to improve precision. Note that you need to run a
single iteration of bootstrapping first, to measure the precision. Then, you can input the measured
precision as a parameter to EvalBootstrap with multiple iterations. With 2 iterations, you can achieve
double the precision of a single bootstrapping.
* Source: Bae Y., Cheon J., Cho W., Kim J., and Kim T. META-BTS: Bootstrapping Precision
* Beyond the Limit. Cryptology ePrint Archive, Report
* 2022/1167. (https://eprint.iacr.org/2022/1167.pdf)
*/
#define PROFILE
#include "openfhe.h"
using namespace lbcrypto;
void IterativeBootstrapExample();
int main(int argc, char* argv[]) {
// We run the example with 8 slots and ring dimension 4096.
IterativeBootstrapExample();
}
// CalculateApproximationError() calculates the precision number (or approximation error).
// The higher the precision, the less the error.
double CalculateApproximationError(const std::vector<std::complex<double>>& result,
const std::vector<std::complex<double>>& expectedResult) {
if (result.size() != expectedResult.size())
OPENFHE_THROW(config_error, "Cannot compare vectors with different numbers of elements");
// using the infinity norm
double maxError = 0;
for (size_t i = 0; i < result.size(); ++i) {
double error = std::abs(result[i].real() - expectedResult[i].real());
if (maxError < error)
maxError = error;
}
return std::abs(std::log2(maxError));
}
void IterativeBootstrapExample() {
// Step 1: Set CryptoContext
CCParams<CryptoContextCKKSRNS> parameters;
SecretKeyDist secretKeyDist = UNIFORM_TERNARY;
parameters.SetSecretKeyDist(secretKeyDist);
parameters.SetSecurityLevel(HEStd_NotSet);
parameters.SetRingDim(1 << 12);
#if NATIVEINT == 128 && !defined(__EMSCRIPTEN__)
// Currently, only FIXEDMANUAL and FIXEDAUTO modes are supported for 128-bit CKKS bootstrapping.
ScalingTechnique rescaleTech = FIXEDAUTO;
usint dcrtBits = 78;
usint firstMod = 89;
#else
// All modes are supported for 64-bit CKKS bootstrapping.
ScalingTechnique rescaleTech = FLEXIBLEAUTO;
usint dcrtBits = 59;
usint firstMod = 60;
#endif
parameters.SetScalingModSize(dcrtBits);
parameters.SetScalingTechnique(rescaleTech);
parameters.SetFirstModSize(firstMod);
// Here, we specify the number of iterations to run bootstrapping. Note that we currently only support 1 or 2 iterations.
// Two iterations should give us approximately double the precision of one iteration.
uint32_t numIterations = 2;
std::vector<uint32_t> levelBudget = {3, 3};
std::vector<uint32_t> bsgsDim = {0, 0};
uint32_t levelsAvailableAfterBootstrap = 10;
usint depth =
levelsAvailableAfterBootstrap + FHECKKSRNS::GetBootstrapDepth(levelBudget, secretKeyDist) + (numIterations - 1);
parameters.SetMultiplicativeDepth(depth);
// Generate crypto context.
CryptoContext<DCRTPoly> cryptoContext = GenCryptoContext(parameters);
// Enable features that you wish to use. Note, we must enable FHE to use bootstrapping.
cryptoContext->Enable(PKE);
cryptoContext->Enable(KEYSWITCH);
cryptoContext->Enable(LEVELEDSHE);
cryptoContext->Enable(ADVANCEDSHE);
cryptoContext->Enable(FHE);
usint ringDim = cryptoContext->GetRingDimension();
std::cout << "CKKS scheme is using ring dimension " << ringDim << std::endl << std::endl;
// Step 2: Precomputations for bootstrapping
// We use a sparse packing.
uint32_t numSlots = 8;
cryptoContext->EvalBootstrapSetup(levelBudget, bsgsDim, numSlots);
// Step 3: Key Generation
auto keyPair = cryptoContext->KeyGen();
cryptoContext->EvalMultKeyGen(keyPair.secretKey);
// Generate bootstrapping keys.
cryptoContext->EvalBootstrapKeyGen(keyPair.secretKey, numSlots);
// Step 4: Encoding and encryption of inputs
// Generate random input
std::vector<double> x;
std::random_device rd;
std::mt19937 gen(rd());
std::uniform_real_distribution<> dis(0.0, 1.0);
for (size_t i = 0; i < numSlots; i++) {
x.push_back(dis(gen));
}
// Encoding as plaintexts
// We specify the number of slots as numSlots to achieve a performance improvement.
// We use the other default values of depth 1, levels 0, and no params.
// Alternatively, you can also set batch size as a parameter in the CryptoContext as follows:
// parameters.SetBatchSize(numSlots);
// Here, we assume all ciphertexts in the cryptoContext will have numSlots slots.
// We start with a depleted ciphertext that has used up all of its levels.
Plaintext ptxt = cryptoContext->MakeCKKSPackedPlaintext(x, 1, depth - 1, nullptr, numSlots);
ptxt->SetLength(numSlots);
std::cout << "Input: " << ptxt << std::endl;
// Encrypt the encoded vectors
Ciphertext<DCRTPoly> ciph = cryptoContext->Encrypt(keyPair.publicKey, ptxt);
// Step 5: Measure the precision of a single bootstrapping operation.
auto ciphertextAfter = cryptoContext->EvalBootstrap(ciph);
Plaintext result;
cryptoContext->Decrypt(keyPair.secretKey, ciphertextAfter, &result);
result->SetLength(numSlots);
uint32_t precision =
std::floor(CalculateApproximationError(result->GetCKKSPackedValue(), ptxt->GetCKKSPackedValue()));
std::cout << "Bootstrapping precision after 1 iteration: " << precision << std::endl;
// Set precision equal to empirically measured value after many test runs.
precision = 17;
std::cout << "Precision input to algorithm: " << precision << std::endl;
// Step 6: Run bootstrapping with multiple iterations.
auto ciphertextTwoIterations = cryptoContext->EvalBootstrap(ciph, numIterations, precision);
Plaintext resultTwoIterations;
cryptoContext->Decrypt(keyPair.secretKey, ciphertextTwoIterations, &resultTwoIterations);
result->SetLength(numSlots);
auto actualResult = resultTwoIterations->GetCKKSPackedValue();
std::cout << "Output after two iterations of bootstrapping: " << actualResult << std::endl;
double precisionMultipleIterations = CalculateApproximationError(actualResult, ptxt->GetCKKSPackedValue());
// Output the precision of bootstrapping after two iterations. It should be approximately double the original precision.
std::cout << "Bootstrapping precision after 2 iterations: " << precisionMultipleIterations << std::endl;
std::cout << "Number of levels remaining after 2 bootstrappings: " << depth - ciphertextTwoIterations->GetLevel()
<< std::endl;
}