forked from openfheorg/openfhe-development
-
Notifications
You must be signed in to change notification settings - Fork 0
/
advanced-ckks-bootstrapping.cpp
195 lines (166 loc) · 8.83 KB
/
advanced-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
190
191
192
193
194
195
//==================================================================================
// 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 CKKS bootstrapping with sparse packing
*/
#define PROFILE
#include "openfhe.h"
using namespace lbcrypto;
void BootstrapExample(uint32_t numSlots);
int main(int argc, char* argv[]) {
// We run the example with 8 slots and ring dimension 4096 to illustrate how to run bootstrapping with a sparse plaintext.
// Using a sparse plaintext and specifying the smaller number of slots gives a performance improvement (typically up to 3x).
BootstrapExample(8);
}
void BootstrapExample(uint32_t numSlots) {
// Step 1: Set CryptoContext
CCParams<CryptoContextCKKSRNS> parameters;
// A. Specify main parameters
/* A1) Secret key distribution
* The secret key distribution for CKKS should either be SPARSE_TERNARY or UNIFORM_TERNARY.
* The SPARSE_TERNARY distribution was used in the original CKKS paper,
* but in this example, we use UNIFORM_TERNARY because this is included in the homomorphic
* encryption standard.
*/
SecretKeyDist secretKeyDist = UNIFORM_TERNARY;
parameters.SetSecretKeyDist(secretKeyDist);
/* A2) Desired security level based on FHE standards.
* In this example, we use the "NotSet" option, so the example can run more quickly with
* a smaller ring dimension. Note that this should be used only in
* non-production environments, or by experts who understand the security
* implications of their choices. In production-like environments, we recommend using
* HEStd_128_classic, HEStd_192_classic, or HEStd_256_classic for 128-bit, 192-bit,
* or 256-bit security, respectively. If you choose one of these as your security level,
* you do not need to set the ring dimension.
*/
parameters.SetSecurityLevel(HEStd_NotSet);
parameters.SetRingDim(1 << 12);
/* A3) Key switching parameters.
* By default, we use HYBRID key switching with a digit size of 3.
* Choosing a larger digit size can reduce complexity, but the size of keys will increase.
* Note that you can leave these lines of code out completely, since these are the default values.
*/
parameters.SetNumLargeDigits(3);
parameters.SetKeySwitchTechnique(HYBRID);
/* A4) Scaling parameters.
* By default, we set the modulus sizes and rescaling technique to the following values
* to obtain a good precision and performance tradeoff. We recommend keeping the parameters
* below unless you are an FHE expert.
*/
#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);
/* A4) Bootstrapping parameters.
* We set a budget for the number of levels we can consume in bootstrapping for encoding and decoding, respectively.
* Using larger numbers of levels reduces the complexity and number of rotation keys,
* but increases the depth required for bootstrapping.
* We must choose values smaller than ceil(log2(slots)). A level budget of {4, 4} is good for higher ring
* dimensions (65536 and higher).
*/
std::vector<uint32_t> levelBudget = {3, 3};
/* We give the user the option of configuring values for an optimization algorithm in bootstrapping.
* Here, we specify the giant step for the baby-step-giant-step algorithm in linear transforms
* for encoding and decoding, respectively. Either choose this to be a power of 2
* or an exact divisor of the number of slots. Setting it to have the default value of {0, 0} allows OpenFHE to choose
* the values automatically.
*/
std::vector<uint32_t> bsgsDim = {0, 0};
/* A5) Multiplicative depth.
* The goal of bootstrapping is to increase the number of available levels we have, or in other words,
* to dynamically increase the multiplicative depth. However, the bootstrapping procedure itself
* needs to consume a few levels to run. We compute the number of bootstrapping levels required
* using GetBootstrapDepth, and add it to levelsAvailableAfterBootstrap to set our initial multiplicative
* depth.
*/
uint32_t levelsAvailableAfterBootstrap = 10;
usint depth = levelsAvailableAfterBootstrap + FHECKKSRNS::GetBootstrapDepth(levelBudget, secretKeyDist);
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
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);
std::cout << "Initial number of levels remaining: " << depth - ciph->GetLevel() << std::endl;
// Step 5: Perform the bootstrapping operation. The goal is to increase the number of levels remaining
// for HE computation.
auto ciphertextAfter = cryptoContext->EvalBootstrap(ciph);
std::cout << "Number of levels remaining after bootstrapping: " << depth - ciphertextAfter->GetLevel() << std::endl
<< std::endl;
// Step 7: Decryption and output
Plaintext result;
cryptoContext->Decrypt(keyPair.secretKey, ciphertextAfter, &result);
result->SetLength(numSlots);
std::cout << "Output after bootstrapping \n\t" << result << std::endl;
}