forked from openfheorg/openfhe-development
-
Notifications
You must be signed in to change notification settings - Fork 0
/
scheme-switching.cpp
1589 lines (1297 loc) · 65 KB
/
scheme-switching.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
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
//==================================================================================
// BSD 2-Clause License
//
// Copyright (c) 2014-2022, NJIT, Duality Technologies Inc. and other contributors
//
// All rights reserved.
//
// Author TPOC: [email protected]
//
// 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.
//==================================================================================
/*
Examples for scheme switching between CKKS and FHEW and back, with intermediate computations
*/
#include "openfhe.h"
#include "binfhecontext.h"
using namespace lbcrypto;
void SwitchCKKSToFHEW();
void SwitchFHEWtoCKKS();
void FloorViaSchemeSwitching();
void ComparisonViaSchemeSwitching();
void FuncViaSchemeSwitching();
void PolyViaSchemeSwitching();
void ArgminViaSchemeSwitching();
void ArgminViaSchemeSwitchingAlt();
void ArgminViaSchemeSwitchingUnit();
void ArgminViaSchemeSwitchingAltUnit();
std::vector<int32_t> RotateInt(const std::vector<int32_t>&, int32_t);
int main() {
SwitchCKKSToFHEW();
SwitchFHEWtoCKKS();
FloorViaSchemeSwitching();
// FuncViaSchemeSwitching();
// PolyViaSchemeSwitching();
ComparisonViaSchemeSwitching();
ArgminViaSchemeSwitching();
ArgminViaSchemeSwitchingAlt();
// ArgminViaSchemeSwitchingUnit();
// ArgminViaSchemeSwitchingAltUnit();
return 0;
}
void SwitchCKKSToFHEW() {
/*
Example of switching a packed ciphertext from CKKS to multiple FHEW ciphertexts.
*/
std::cout << "\n-----SwitchCKKSToFHEW-----\n" << std::endl;
// Step 1: Setup CryptoContext for CKKS
// Specify main parameters
uint32_t multDepth = 3;
uint32_t firstModSize = 60;
uint32_t scaleModSize = 50;
uint32_t ringDim = 4096;
SecurityLevel sl = HEStd_NotSet;
BINFHE_PARAMSET slBin = TOY;
uint32_t logQ_ccLWE = 25;
// uint32_t slots = ringDim / 2; // Uncomment for fully-packed
uint32_t slots = 16; // sparsely-packed
uint32_t batchSize = slots;
CCParams<CryptoContextCKKSRNS> parameters;
parameters.SetMultiplicativeDepth(multDepth);
parameters.SetFirstModSize(firstModSize);
parameters.SetScalingModSize(scaleModSize);
parameters.SetScalingTechnique(FIXEDMANUAL);
parameters.SetSecurityLevel(sl);
parameters.SetRingDim(ringDim);
parameters.SetBatchSize(batchSize);
CryptoContext<DCRTPoly> cc = GenCryptoContext(parameters);
// Enable the features that you wish to use
cc->Enable(PKE);
cc->Enable(KEYSWITCH);
cc->Enable(LEVELEDSHE);
cc->Enable(SCHEMESWITCH);
std::cout << "CKKS scheme is using ring dimension " << cc->GetRingDimension();
std::cout << ", number of slots " << slots << ", and suports a multiplicative depth of " << multDepth << std::endl
<< std::endl;
// Generate encryption keys
auto keys = cc->KeyGen();
// Step 2: Prepare the FHEW cryptocontext and keys for FHEW and scheme switching
auto FHEWparams = cc->EvalCKKStoFHEWSetup(sl, slBin, false, logQ_ccLWE, false, slots);
auto ccLWE = FHEWparams.first;
auto privateKeyFHEW = FHEWparams.second;
cc->EvalCKKStoFHEWKeyGen(keys, privateKeyFHEW);
std::cout << "FHEW scheme is using lattice parameter " << ccLWE.GetParams()->GetLWEParams()->Getn();
std::cout << ", logQ " << logQ_ccLWE;
std::cout << ", and modulus q " << ccLWE.GetParams()->GetLWEParams()->Getq() << std::endl << std::endl;
// Compute the scaling factor to decrypt correctly in FHEW; the LWE mod switch is performed on the ciphertext at the last level
const auto cryptoParams = std::dynamic_pointer_cast<CryptoParametersCKKSRNS>(cc->GetCryptoParameters());
ILDCRTParams<DCRTPoly::Integer> elementParams = *(cryptoParams->GetElementParams());
auto paramsQ = elementParams.GetParams();
auto modulus_CKKS_from = paramsQ[0]->GetModulus();
auto pLWE1 = ccLWE.GetMaxPlaintextSpace().ConvertToInt(); // Small precision
auto modulus_LWE = 1 << logQ_ccLWE;
auto beta = ccLWE.GetBeta().ConvertToInt();
auto pLWE2 = modulus_LWE / (2 * beta); // Large precision
double scFactor = cryptoParams->GetScalingFactorReal(0);
if (cryptoParams->GetScalingTechnique() == FLEXIBLEAUTOEXT)
scFactor = cryptoParams->GetScalingFactorReal(1);
double scale1 = modulus_CKKS_from.ConvertToInt() / (scFactor * pLWE1);
double scale2 = modulus_CKKS_from.ConvertToInt() / (scFactor * pLWE2);
// Perform the precomputation for switching
cc->EvalCKKStoFHEWPrecompute(scale1);
// Step 3: Encoding and encryption of inputs
// Inputs
std::vector<double> x1 = {0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0};
std::vector<double> x2 = {0.0, 271.0, 30000.0, static_cast<double>(pLWE2) - 2};
uint32_t encodedLength1 = x1.size();
uint32_t encodedLength2 = x2.size();
// Encoding as plaintexts
Plaintext ptxt1 = cc->MakeCKKSPackedPlaintext(x1, 1, 0, nullptr);
Plaintext ptxt2 = cc->MakeCKKSPackedPlaintext(x2, 1, 0, nullptr);
// Encrypt the encoded vectors
auto c1 = cc->Encrypt(keys.publicKey, ptxt1);
auto c2 = cc->Encrypt(keys.publicKey, ptxt2);
// Step 4: Scheme switching from CKKS to FHEW
// A: First scheme switching case
// Transform the ciphertext from CKKS to FHEW
auto cTemp = cc->EvalCKKStoFHEW(c1, encodedLength1);
std::cout << "\n---Decrypting switched ciphertext with small precision (plaintext modulus " << NativeInteger(pLWE1)
<< ")---\n"
<< std::endl;
std::vector<int32_t> x1Int(encodedLength1);
std::transform(x1.begin(), x1.end(), x1Int.begin(), [&](const double& elem) {
return static_cast<int32_t>(static_cast<int32_t>(std::round(elem)) % pLWE1);
});
ptxt1->SetLength(encodedLength1);
std::cout << "Input x1: " << ptxt1->GetRealPackedValue() << "; which rounds to: " << x1Int << std::endl;
std::cout << "FHEW decryption: ";
LWEPlaintext result;
for (uint32_t i = 0; i < cTemp.size(); ++i) {
ccLWE.Decrypt(privateKeyFHEW, cTemp[i], &result, pLWE1);
std::cout << result << " ";
}
std::cout << "\n" << std::endl;
// B: Second scheme switching case
// Perform the precomputation for switching
cc->EvalCKKStoFHEWPrecompute(scale2);
// Transform the ciphertext from CKKS to FHEW (only for the number of inputs given)
auto cTemp2 = cc->EvalCKKStoFHEW(c2, encodedLength2);
std::cout << "\n---Decrypting switched ciphertext with large precision (plaintext modulus " << NativeInteger(pLWE2)
<< ")---\n"
<< std::endl;
ptxt2->SetLength(encodedLength2);
std::cout << "Input x2: " << ptxt2->GetRealPackedValue() << std::endl;
std::cout << "FHEW decryption: ";
for (uint32_t i = 0; i < cTemp2.size(); ++i) {
ccLWE.Decrypt(privateKeyFHEW, cTemp2[i], &result, pLWE2);
std::cout << result << " ";
}
std::cout << "\n" << std::endl;
// C: Decompose the FHEW ciphertexts in smaller digits
std::cout << "Decomposed values for digit size of " << NativeInteger(pLWE1) << ": " << std::endl;
// Generate the bootstrapping keys (refresh and switching keys)
ccLWE.BTKeyGen(privateKeyFHEW);
for (uint32_t j = 0; j < cTemp2.size(); j++) {
// Decompose the large ciphertext into small ciphertexts that fit in q
auto decomp = ccLWE.EvalDecomp(cTemp2[j]);
// Decryption
auto p = ccLWE.GetMaxPlaintextSpace().ConvertToInt();
LWECiphertext ct;
for (size_t i = 0; i < decomp.size(); i++) {
ct = decomp[i];
LWEPlaintext resultDecomp;
if (i == decomp.size() - 1) {
p = pLWE2 /
pow(pLWE1, std::floor(std::log(pLWE2) /
std::log(pLWE1))); // The last digit should be up to P / p^floor(log_p(P))
}
ccLWE.Decrypt(privateKeyFHEW, ct, &resultDecomp, p);
std::cout << "(" << resultDecomp << " * " << NativeInteger(pLWE1) << "^" << i << ")";
if (i != decomp.size() - 1) {
std::cout << " + ";
}
}
std::cout << std::endl;
}
}
void SwitchFHEWtoCKKS() {
std::cout << "\n-----SwitchFHEWtoCKKS-----\n" << std::endl;
std::cout << "Output precision is only wrt the operations in CKKS after switching back.\n" << std::endl;
// Step 1: Setup CryptoContext for CKKS to be switched into
// A. Specify main parameters
ScalingTechnique scTech = FIXEDAUTO;
uint32_t multDepth =
3 + 9 + 1; // for r = 3 in FHEWtoCKKS, Chebyshev max depth allowed is 9, 1 more level for postscaling
if (scTech == FLEXIBLEAUTOEXT)
multDepth += 1;
uint32_t scaleModSize = 50;
uint32_t ringDim = 8192;
SecurityLevel sl = HEStd_NotSet; // If this is not HEStd_NotSet, ensure ringDim is compatible
uint32_t logQ_ccLWE = 28;
// uint32_t slots = ringDim/2; // Uncomment for fully-packed
uint32_t slots = 16; // sparsely-packed
uint32_t batchSize = slots;
CCParams<CryptoContextCKKSRNS> parameters;
parameters.SetMultiplicativeDepth(multDepth);
parameters.SetScalingModSize(scaleModSize);
parameters.SetScalingTechnique(scTech);
parameters.SetSecurityLevel(sl);
parameters.SetRingDim(ringDim);
parameters.SetBatchSize(batchSize);
CryptoContext<DCRTPoly> cc = GenCryptoContext(parameters);
// Enable the features that you wish to use
cc->Enable(PKE);
cc->Enable(KEYSWITCH);
cc->Enable(LEVELEDSHE);
cc->Enable(ADVANCEDSHE);
cc->Enable(SCHEMESWITCH);
std::cout << "CKKS scheme is using ring dimension " << cc->GetRingDimension();
std::cout << ", number of slots " << slots << ", and suports a multiplicative depth of " << multDepth << std::endl
<< std::endl;
// Generate encryption keys.
auto keys = cc->KeyGen();
// Step 2: Prepare the FHEW cryptocontext and keys for FHEW and scheme switching
auto ccLWE = BinFHEContext();
ccLWE.BinFHEContext::GenerateBinFHEContext(TOY, false, logQ_ccLWE, 0, GINX, false);
// LWE private key
LWEPrivateKey lwesk;
lwesk = ccLWE.KeyGen();
std::cout << "FHEW scheme is using lattice parameter " << ccLWE.GetParams()->GetLWEParams()->Getn();
std::cout << ", logQ " << logQ_ccLWE;
std::cout << ", and modulus q " << ccLWE.GetParams()->GetLWEParams()->Getq() << std::endl << std::endl;
// Step 3. Precompute the necessary keys and information for switching from FHEW to CKKS
cc->EvalFHEWtoCKKSSetup(ccLWE, slots, logQ_ccLWE);
cc->EvalFHEWtoCKKSKeyGen(keys, lwesk);
// Step 4: Encoding and encryption of inputs
// For correct CKKS decryption, the messages have to be much smaller than the FHEW plaintext modulus!
auto pLWE1 = ccLWE.GetMaxPlaintextSpace().ConvertToInt(); // Small precision
uint32_t pLWE2 = 256; // Medium precision
auto modulus_LWE = 1 << logQ_ccLWE;
auto beta = ccLWE.GetBeta().ConvertToInt();
auto pLWE3 = modulus_LWE / (2 * beta); // Large precision
// Inputs
std::vector<int> x1 = {1, 1, 0, 0, 1, 1, 0, 0, 1, 1, 0, 0, 1, 1, 0, 0};
std::vector<int> x2 = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15};
if (x1.size() < slots) {
std::vector<int> zeros(slots - x1.size(), 0);
x1.insert(x1.end(), zeros.begin(), zeros.end());
x2.insert(x2.end(), zeros.begin(), zeros.end());
}
// Encrypt
std::vector<LWECiphertext> ctxtsLWE1(slots);
for (uint32_t i = 0; i < slots; i++) {
ctxtsLWE1[i] =
ccLWE.Encrypt(lwesk, x1[i]); // encrypted under small plantext modulus p = 4 and ciphertext modulus
}
std::vector<LWECiphertext> ctxtsLWE2(slots);
for (uint32_t i = 0; i < slots; i++) {
ctxtsLWE2[i] =
ccLWE.Encrypt(lwesk, x1[i], FRESH,
pLWE1); // encrypted under larger plaintext modulus p = 16 but small ciphertext modulus
}
std::vector<LWECiphertext> ctxtsLWE3(slots);
for (uint32_t i = 0; i < slots; i++) {
ctxtsLWE3[i] =
ccLWE.Encrypt(lwesk, x2[i], FRESH, pLWE2,
modulus_LWE); // encrypted under larger plaintext modulus and large ciphertext modulus
}
std::vector<LWECiphertext> ctxtsLWE4(slots);
for (uint32_t i = 0; i < slots; i++) {
ctxtsLWE4[i] =
ccLWE.Encrypt(lwesk, x2[i], FRESH, pLWE3,
modulus_LWE); // encrypted under large plaintext modulus and large ciphertext modulus
}
// Step 5. Perform the scheme switching
auto cTemp = cc->EvalFHEWtoCKKS(ctxtsLWE1, slots, slots);
std::cout << "\n---Input x1: " << x1 << " encrypted under p = " << 4 << " and Q = " << ctxtsLWE1[0]->GetModulus()
<< "---" << std::endl;
// Step 6. Decrypt
Plaintext plaintextDec;
cc->Decrypt(keys.secretKey, cTemp, &plaintextDec);
plaintextDec->SetLength(slots);
std::cout << "Switched CKKS decryption 1: " << plaintextDec << std::endl;
// Step 5'. Perform the scheme switching
cTemp = cc->EvalFHEWtoCKKS(ctxtsLWE2, slots, slots, pLWE1, 0, pLWE1);
std::cout << "\n---Input x1: " << x1 << " encrypted under p = " << NativeInteger(pLWE1)
<< " and Q = " << ctxtsLWE2[0]->GetModulus() << "---" << std::endl;
// Step 6'. Decrypt
cc->Decrypt(keys.secretKey, cTemp, &plaintextDec);
plaintextDec->SetLength(slots);
std::cout << "Switched CKKS decryption 2: " << plaintextDec << std::endl;
// Step 5''. Perform the scheme switching
cTemp = cc->EvalFHEWtoCKKS(ctxtsLWE3, slots, slots, pLWE2, 0, pLWE2);
std::cout << "\n---Input x2: " << x2 << " encrypted under p = " << pLWE2
<< " and Q = " << ctxtsLWE3[0]->GetModulus() << "---" << std::endl;
// Step 6''. Decrypt
cc->Decrypt(keys.secretKey, cTemp, &plaintextDec);
plaintextDec->SetLength(slots);
std::cout << "Switched CKKS decryption 3: " << plaintextDec << std::endl;
// Step 5'''. Perform the scheme switching
std::setprecision(logQ_ccLWE + 10);
auto cTemp2 = cc->EvalFHEWtoCKKS(ctxtsLWE4, slots, slots, pLWE3, 0, pLWE3);
std::cout << "\n---Input x2: " << x2 << " encrypted under p = " << NativeInteger(pLWE3)
<< " and Q = " << ctxtsLWE4[0]->GetModulus() << "---" << std::endl;
// Step 6'''. Decrypt
Plaintext plaintextDec2;
cc->Decrypt(keys.secretKey, cTemp2, &plaintextDec2);
plaintextDec2->SetLength(slots);
std::cout << "Switched CKKS decryption 4: " << plaintextDec2 << std::endl;
}
void FloorViaSchemeSwitching() {
std::cout << "\n-----FloorViaSchemeSwitching-----\n" << std::endl;
std::cout << "Output precision is only wrt the operations in CKKS after switching back.\n" << std::endl;
// Step 1: Setup CryptoContext for CKKS
ScalingTechnique scTech = FIXEDAUTO;
uint32_t multDepth =
3 + 9 + 1; // for r = 3 in FHEWtoCKKS, Chebyshev max depth allowed is 9, 1 more level for postscaling
if (scTech == FLEXIBLEAUTOEXT)
multDepth += 1;
uint32_t scaleModSize = 50;
uint32_t ringDim = 8192;
SecurityLevel sl = HEStd_NotSet;
BINFHE_PARAMSET slBin = TOY;
uint32_t logQ_ccLWE = 23;
uint32_t slots = 16; // sparsely-packed
uint32_t batchSize = slots;
CCParams<CryptoContextCKKSRNS> parameters;
parameters.SetMultiplicativeDepth(multDepth);
parameters.SetScalingModSize(scaleModSize);
parameters.SetScalingTechnique(scTech);
parameters.SetSecurityLevel(sl);
parameters.SetRingDim(ringDim);
parameters.SetBatchSize(batchSize);
CryptoContext<DCRTPoly> cc = GenCryptoContext(parameters);
// Enable the features that you wish to use
cc->Enable(PKE);
cc->Enable(KEYSWITCH);
cc->Enable(LEVELEDSHE);
cc->Enable(ADVANCEDSHE);
cc->Enable(SCHEMESWITCH);
std::cout << "CKKS scheme is using ring dimension " << cc->GetRingDimension();
std::cout << ", number of slots " << slots << ", and suports a multiplicative depth of " << multDepth << std::endl
<< std::endl;
// Generate encryption keys.
auto keys = cc->KeyGen();
// Step 2: Prepare the FHEW cryptocontext and keys for FHEW and scheme switching
bool arbFunc = false;
auto FHEWparams = cc->EvalSchemeSwitchingSetup(sl, slBin, arbFunc, logQ_ccLWE, false, slots);
auto ccLWE = FHEWparams.first;
auto privateKeyFHEW = FHEWparams.second;
cc->EvalSchemeSwitchingKeyGen(keys, privateKeyFHEW);
// Generate bootstrapping key for EvalFloor
ccLWE.BTKeyGen(privateKeyFHEW);
std::cout << "FHEW scheme is using lattice parameter " << ccLWE.GetParams()->GetLWEParams()->Getn();
std::cout << ", logQ " << logQ_ccLWE;
std::cout << ", and modulus q " << ccLWE.GetParams()->GetLWEParams()->Getq() << std::endl << std::endl;
// Set the scaling factor to be able to decrypt; the LWE mod switch is performed on the ciphertext at the last level
const auto cryptoParams = std::dynamic_pointer_cast<CryptoParametersCKKSRNS>(cc->GetCryptoParameters());
ILDCRTParams<DCRTPoly::Integer> elementParams = *(cryptoParams->GetElementParams());
auto paramsQ = elementParams.GetParams();
auto modulus_CKKS_from = paramsQ[0]->GetModulus();
auto modulus_LWE = 1 << logQ_ccLWE;
auto beta = ccLWE.GetBeta().ConvertToInt();
auto pLWE = modulus_LWE / (2 * beta); // Large precision
double scFactor = cryptoParams->GetScalingFactorReal(0);
if (cryptoParams->GetScalingTechnique() == FLEXIBLEAUTOEXT)
scFactor = cryptoParams->GetScalingFactorReal(1);
double scaleCF = modulus_CKKS_from.ConvertToInt() / (scFactor * pLWE);
cc->EvalCKKStoFHEWPrecompute(scaleCF);
// Step 3: Encoding and encryption of inputs
// Inputs
std::vector<double> x1 = {0.0, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, 11.0, 12.0, 13.0, 14.0, 15.0};
// Encoding as plaintexts
Plaintext ptxt1 = cc->MakeCKKSPackedPlaintext(x1, 1, 0, nullptr);
// Encrypt the encoded vectors
auto c1 = cc->Encrypt(keys.publicKey, ptxt1);
// Step 4: Scheme switching from CKKS to FHEW
auto cTemp = cc->EvalCKKStoFHEW(c1);
// Step 5: Evaluate the floor function
uint32_t bits = 2;
std::vector<LWECiphertext> cFloor(cTemp.size());
for (uint32_t i = 0; i < cTemp.size(); i++) {
cFloor[i] = ccLWE.EvalFloor(cTemp[i], bits);
}
std::cout << "Input x1: " << ptxt1->GetRealPackedValue() << std::endl;
std::cout << "Expected result for EvalFloor with " << bits << " bits: ";
for (uint32_t i = 0; i < slots; ++i) {
std::cout << (static_cast<int>(ptxt1->GetRealPackedValue()[i]) >> bits) << " ";
}
LWEPlaintext pFloor;
std::cout << "\nFHEW decryption p = " << NativeInteger(pLWE)
<< "/(1 << bits) = " << NativeInteger(pLWE) / (1 << bits) << ": ";
for (uint32_t i = 0; i < cFloor.size(); ++i) {
ccLWE.Decrypt(privateKeyFHEW, cFloor[i], &pFloor, pLWE / (1 << bits));
std::cout << pFloor << " ";
}
std::cout << "\n" << std::endl;
// Step 6: Scheme switching from FHEW to CKKS
auto cTemp2 = cc->EvalFHEWtoCKKS(cFloor, slots, slots, pLWE / (1 << bits), 0, pLWE / (1 << bits));
Plaintext plaintextDec2;
cc->Decrypt(keys.secretKey, cTemp2, &plaintextDec2);
plaintextDec2->SetLength(slots);
std::cout << "Switched floor decryption modulus_LWE mod " << NativeInteger(pLWE) / (1 << bits) << ": "
<< plaintextDec2 << std::endl;
}
void FuncViaSchemeSwitching() {
std::cout << "\n-----FuncViaSchemeSwitching-----\n" << std::endl;
std::cout << "Output precision is only wrt the operations in CKKS after switching back.\n" << std::endl;
// Step 1: Setup CryptoContext for CKKS
uint32_t multDepth = 9 + 3 + 2; // 1 for CKKS to FHEW, 14 for FHEW to CKKS
uint32_t scaleModSize = 50;
uint32_t ringDim = 2048;
SecurityLevel sl = HEStd_NotSet;
BINFHE_PARAMSET slBin = TOY;
uint32_t logQ_ccLWE = 25;
bool arbFunc = true;
uint32_t slots = 8; // sparsely-packed
uint32_t batchSize = slots;
CCParams<CryptoContextCKKSRNS> parameters;
parameters.SetMultiplicativeDepth(multDepth);
parameters.SetScalingModSize(scaleModSize);
parameters.SetScalingTechnique(FIXEDMANUAL);
parameters.SetSecurityLevel(sl);
parameters.SetRingDim(ringDim);
parameters.SetBatchSize(batchSize);
CryptoContext<DCRTPoly> cc = GenCryptoContext(parameters);
// Enable the features that you wish to use
cc->Enable(PKE);
cc->Enable(KEYSWITCH);
cc->Enable(LEVELEDSHE);
cc->Enable(ADVANCEDSHE);
cc->Enable(SCHEMESWITCH);
std::cout << "CKKS scheme is using ring dimension " << cc->GetRingDimension();
std::cout << ", and number of slots " << slots << std::endl << std::endl;
// Generate encryption keys.
auto keys = cc->KeyGen();
// Step 2: Prepare the FHEW cryptocontext and keys for FHEW and scheme switching
auto FHEWparams = cc->EvalSchemeSwitchingSetup(sl, slBin, arbFunc, logQ_ccLWE, false, slots);
auto ccLWE = FHEWparams.first;
auto privateKeyFHEW = FHEWparams.second;
cc->EvalSchemeSwitchingKeyGen(keys, privateKeyFHEW);
// Generate the bootstrapping keys for EvalFunc in FHEW
ccLWE.BTKeyGen(privateKeyFHEW);
std::cout << "FHEW scheme is using lattice parameter " << ccLWE.GetParams()->GetLWEParams()->Getn();
std::cout << ", logQ " << logQ_ccLWE;
std::cout << ", and modulus q " << ccLWE.GetParams()->GetLWEParams()->Getq() << std::endl << std::endl;
// Set the scaling factor to be able to decrypt; the LWE mod switch is performed on the ciphertext at the last level
const auto cryptoParams = std::dynamic_pointer_cast<CryptoParametersCKKSRNS>(cc->GetCryptoParameters());
ILDCRTParams<DCRTPoly::Integer> elementParams = *(cryptoParams->GetElementParams());
auto paramsQ = elementParams.GetParams();
auto modulus_CKKS_from = paramsQ[0]->GetModulus();
auto pLWE =
ccLWE.GetMaxPlaintextSpace().ConvertToInt(); // Small precision because GenerateLUTviaFunction needs p < q
double scFactor = cryptoParams->GetScalingFactorReal(0);
if (cryptoParams->GetScalingTechnique() == FLEXIBLEAUTOEXT)
scFactor = cryptoParams->GetScalingFactorReal(1);
double scaleCF = modulus_CKKS_from.ConvertToInt() / (scFactor * pLWE);
cc->EvalCKKStoFHEWPrecompute(scaleCF);
// Step 3: Initialize the function
// Initialize Function f(x) = x^3 + 2x + 1 % p
auto fp = [](NativeInteger m, NativeInteger p1) -> NativeInteger {
if (m < p1)
return (m * m * m + 2 * m * m + 1) % p1;
else
return ((m - p1 / 2) * (m - p1 / 2) * (m - p1 / 2) + 2 * (m - p1 / 2) * (m - p1 / 2) + 1) % p1;
};
// Generate LUT from function f(x)
auto lut = ccLWE.GenerateLUTviaFunction(fp, pLWE);
// Step 4: Encoding and encryption of inputs
// Inputs
std::vector<double> x1 = {0.0, 0.3, 2.0, 4.0, 5.0, 6.0, 7.0, 8.0};
// Encoding as plaintexts
Plaintext ptxt1 = cc->MakeCKKSPackedPlaintext(x1, 1, 0, nullptr);
// Encrypt the encoded vectors
auto c1 = cc->Encrypt(keys.publicKey, ptxt1);
// Step 5: Scheme switching from CKKS to FHEW
auto cTemp = cc->EvalCKKStoFHEW(c1);
std::cout << "Input x1: " << ptxt1->GetRealPackedValue() << std::endl;
std::cout << "FHEW decryption: ";
LWEPlaintext result;
for (uint32_t i = 0; i < cTemp.size(); ++i) {
ccLWE.Decrypt(privateKeyFHEW, cTemp[i], &result, pLWE);
std::cout << result << " ";
}
// Step 6: Evaluate the function
std::vector<LWECiphertext> cFunc(cTemp.size());
for (uint32_t i = 0; i < cTemp.size(); i++) {
cFunc[i] = ccLWE.EvalFunc(cTemp[i], lut);
}
std::cout << "\nExpected result x^3 + 2*x + 1 mod p: ";
for (uint32_t i = 0; i < slots; ++i) {
std::cout << fp(static_cast<int>(x1[i]) % pLWE, pLWE) << " ";
}
LWEPlaintext pFunc;
std::cout << "\nFHEW decryption mod " << NativeInteger(pLWE) << ": ";
for (uint32_t i = 0; i < cFunc.size(); ++i) {
ccLWE.Decrypt(privateKeyFHEW, cFunc[i], &pFunc, pLWE);
std::cout << pFunc << " ";
}
std::cout << "\n" << std::endl;
// Step 7: Scheme switching from FHEW to CKKS
auto cTemp2 = cc->EvalFHEWtoCKKS(cFunc, slots, slots, pLWE, 0, pLWE);
Plaintext plaintextDec2;
cc->Decrypt(keys.secretKey, cTemp2, &plaintextDec2);
plaintextDec2->SetLength(slots);
std::cout << "\nSwitched decryption modulus_LWE mod " << NativeInteger(pLWE)
<< " works only for messages << p: " << plaintextDec2 << std::endl;
// Transform through arcsine
cTemp2 = cc->EvalFHEWtoCKKS(cFunc, slots, slots, 4, 0, 2);
cc->Decrypt(keys.secretKey, cTemp2, &plaintextDec2);
plaintextDec2->SetLength(slots);
std::cout << "Arcsin(switched result) * p/2pi gives the correct result if messages are < p/4: ";
for (uint32_t i = 0; i < slots; i++) {
double x = std::max(std::min(plaintextDec2->GetRealPackedValue()[i], 1.0), -1.0);
std::cout << std::asin(x) * pLWE / (2 * Pi) << " ";
}
std::cout << "\n";
}
void ComparisonViaSchemeSwitching() {
std::cout << "\n-----ComparisonViaSchemeSwitching-----\n" << std::endl;
std::cout << "Output precision is only wrt the operations in CKKS after switching back.\n" << std::endl;
// Step 1: Setup CryptoContext for CKKS
ScalingTechnique scTech = FIXEDAUTO;
uint32_t multDepth = 17;
if (scTech == FLEXIBLEAUTOEXT)
multDepth += 1;
uint32_t scaleModSize = 50;
uint32_t firstModSize = 60;
uint32_t ringDim = 8192;
SecurityLevel sl = HEStd_NotSet;
BINFHE_PARAMSET slBin = TOY;
uint32_t logQ_ccLWE = 25;
uint32_t slots = 16; // sparsely-packed
uint32_t batchSize = slots;
CCParams<CryptoContextCKKSRNS> parameters;
parameters.SetMultiplicativeDepth(multDepth);
parameters.SetScalingModSize(scaleModSize);
parameters.SetFirstModSize(firstModSize);
parameters.SetScalingTechnique(scTech);
parameters.SetSecurityLevel(sl);
parameters.SetRingDim(ringDim);
parameters.SetBatchSize(batchSize);
parameters.SetSecretKeyDist(UNIFORM_TERNARY);
parameters.SetKeySwitchTechnique(HYBRID);
parameters.SetNumLargeDigits(3);
CryptoContext<DCRTPoly> cc = GenCryptoContext(parameters);
// Enable the features that you wish to use
cc->Enable(PKE);
cc->Enable(KEYSWITCH);
cc->Enable(LEVELEDSHE);
cc->Enable(ADVANCEDSHE);
cc->Enable(SCHEMESWITCH);
std::cout << "CKKS scheme is using ring dimension " << cc->GetRingDimension();
std::cout << ", number of slots " << slots << ", and suports a multiplicative depth of " << multDepth << std::endl
<< std::endl;
// Generate encryption keys.
auto keys = cc->KeyGen();
// Step 2: Prepare the FHEW cryptocontext and keys for FHEW and scheme switching
auto FHEWparams = cc->EvalSchemeSwitchingSetup(sl, slBin, false, logQ_ccLWE, false, slots);
auto ccLWE = FHEWparams.first;
auto privateKeyFHEW = FHEWparams.second;
ccLWE.BTKeyGen(privateKeyFHEW);
cc->EvalSchemeSwitchingKeyGen(keys, privateKeyFHEW);
std::cout << "FHEW scheme is using lattice parameter " << ccLWE.GetParams()->GetLWEParams()->Getn();
std::cout << ", logQ " << logQ_ccLWE;
std::cout << ", and modulus q " << ccLWE.GetParams()->GetLWEParams()->Getq() << std::endl << std::endl;
// Set the scaling factor to be able to decrypt; the LWE mod switch is performed on the ciphertext at the last level
auto pLWE1 = ccLWE.GetMaxPlaintextSpace().ConvertToInt(); // Small precision
auto modulus_LWE = 1 << logQ_ccLWE;
auto beta = ccLWE.GetBeta().ConvertToInt();
auto pLWE2 = modulus_LWE / (2 * beta); // Large precision
double scaleSignFHEW = 1.0;
const auto cryptoParams = std::dynamic_pointer_cast<CryptoParametersCKKSRNS>(cc->GetCryptoParameters());
uint32_t init_level = 0;
if (cryptoParams->GetScalingTechnique() == FLEXIBLEAUTOEXT)
init_level = 1;
cc->EvalCompareSwitchPrecompute(pLWE2, init_level, scaleSignFHEW);
// Step 3: Encoding and encryption of inputs
// Inputs
std::vector<double> x1 = {0.0, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, 11.0, 12.0, 13.0, 14.0, 15.0};
std::vector<double> x2(slots, 5.25);
// Encoding as plaintexts
Plaintext ptxt1 = cc->MakeCKKSPackedPlaintext(x1, 1, 0, nullptr, slots);
Plaintext ptxt2 = cc->MakeCKKSPackedPlaintext(x2, 1, 0, nullptr, slots);
// Encrypt the encoded vectors
auto c1 = cc->Encrypt(keys.publicKey, ptxt1);
auto c2 = cc->Encrypt(keys.publicKey, ptxt2);
// Compute the difference to compare to zero
auto cDiff = cc->EvalSub(c1, c2);
// Step 4: CKKS to FHEW switching and sign evaluation to test correctness
Plaintext pDiff;
cc->Decrypt(keys.secretKey, cDiff, &pDiff);
pDiff->SetLength(slots);
std::cout << "Difference of inputs: ";
for (uint32_t i = 0; i < slots; ++i) {
std::cout << pDiff->GetRealPackedValue()[i] << " ";
}
const double eps = 0.0001;
std::cout << "\nExpected sign result from CKKS: ";
for (uint32_t i = 0; i < slots; ++i) {
std::cout << int(std::round(pDiff->GetRealPackedValue()[i] / eps) * eps < 0) << " ";
}
std::cout << "\n";
auto LWECiphertexts = cc->EvalCKKStoFHEW(cDiff, slots);
LWEPlaintext plainLWE;
std::cout << "\nFHEW decryption with plaintext modulus " << NativeInteger(pLWE2) << ": ";
for (uint32_t i = 0; i < LWECiphertexts.size(); ++i) {
ccLWE.Decrypt(privateKeyFHEW, LWECiphertexts[i], &plainLWE, pLWE2);
std::cout << plainLWE << " ";
}
std::cout << "\nExpected sign result in FHEW with plaintext modulus " << NativeInteger(pLWE2) << " and scale "
<< scaleSignFHEW << ": ";
for (uint32_t i = 0; i < slots; ++i) {
std::cout << (static_cast<int>(std::round(pDiff->GetRealPackedValue()[i] * scaleSignFHEW)) % pLWE2 -
pLWE2 / 2.0 >=
0)
<< " ";
}
std::cout << "\n";
std::cout << "Obtained sign result in FHEW with plaintext modulus " << NativeInteger(pLWE2) << " and scale "
<< scaleSignFHEW << ": ";
std::vector<LWECiphertext> LWESign(LWECiphertexts.size());
for (uint32_t i = 0; i < LWECiphertexts.size(); ++i) {
LWESign[i] = ccLWE.EvalSign(LWECiphertexts[i]);
ccLWE.Decrypt(privateKeyFHEW, LWESign[i], &plainLWE, 2);
std::cout << plainLWE << " ";
}
std::cout << "\n";
// Step 5: Direct comparison via CKKS->FHEW->CKKS
auto cResult = cc->EvalCompareSchemeSwitching(c1, c2, slots, slots);
Plaintext plaintextDec3;
cc->Decrypt(keys.secretKey, cResult, &plaintextDec3);
plaintextDec3->SetLength(slots);
std::cout << "Decrypted switched result: " << plaintextDec3 << std::endl;
// Step 2': Recompute the scaled matrix using a larger scaling
scaleSignFHEW = 8.0;
cc->EvalCompareSwitchPrecompute(pLWE2, init_level, scaleSignFHEW);
// Step 4': CKKS to FHEW switching and sign evaluation to test correctness
LWECiphertexts = cc->EvalCKKStoFHEW(cDiff, slots);
std::cout << "\nFHEW decryption with plaintext modulus " << NativeInteger(pLWE2) << " and scale " << scaleSignFHEW
<< ": ";
for (uint32_t i = 0; i < LWECiphertexts.size(); ++i) {
ccLWE.Decrypt(privateKeyFHEW, LWECiphertexts[i], &plainLWE, pLWE2);
std::cout << plainLWE << " ";
}
std::cout << "\nExpected sign result in FHEW with plaintext modulus " << NativeInteger(pLWE2) << " and scale "
<< scaleSignFHEW << ": ";
for (uint32_t i = 0; i < slots; ++i) {
std::cout << (static_cast<int>(std::round(pDiff->GetRealPackedValue()[i] * scaleSignFHEW)) % pLWE2 -
pLWE2 / 2.0 >=
0)
<< " ";
}
std::cout << "\n";
std::cout << "Obtained sign result in FHEW with plaintext modulus " << NativeInteger(pLWE2) << " and scale "
<< scaleSignFHEW << ": ";
for (uint32_t i = 0; i < LWECiphertexts.size(); ++i) {
LWESign[i] = ccLWE.EvalSign(LWECiphertexts[i]);
ccLWE.Decrypt(privateKeyFHEW, LWESign[i], &plainLWE, 2);
std::cout << plainLWE << " ";
}
std::cout << "\n";
// Step 5': Direct comparison via CKKS->FHEW->CKKS
cResult = cc->EvalCompareSchemeSwitching(c1, c2, slots, slots);
cc->Decrypt(keys.secretKey, cResult, &plaintextDec3);
plaintextDec3->SetLength(slots);
std::cout << "Decrypted switched result: " << plaintextDec3 << std::endl;
// Step 2'': Recompute the scaled matrix using other parameters
std::cout
<< "\nFor very small LWE plaintext modulus and initial fractional inputs, the sign does not always behave properly close to the boundaries at 0 and p/2."
<< std::endl;
scaleSignFHEW = 1.0;
cc->EvalCompareSwitchPrecompute(pLWE1, init_level, scaleSignFHEW);
// Step 4'': CKKS to FHEW switching and sign evaluation to test correctness
LWECiphertexts = cc->EvalCKKStoFHEW(cDiff, slots);
std::cout << "\nFHEW decryption with plaintext modulus " << NativeInteger(pLWE1) << ": ";
for (uint32_t i = 0; i < LWECiphertexts.size(); ++i) {
ccLWE.Decrypt(privateKeyFHEW, LWECiphertexts[i], &plainLWE, pLWE1);
std::cout << plainLWE << " ";
}
std::cout << "\nExpected sign result in FHEW with plaintext modulus " << NativeInteger(pLWE1) << " and scale "
<< scaleSignFHEW << ": ";
for (uint32_t i = 0; i < slots; ++i) {
std::cout << (static_cast<int>(std::round(pDiff->GetRealPackedValue()[i] * scaleSignFHEW)) % pLWE1 -
pLWE1 / 2.0 >=
0)
<< " ";
}
std::cout << "\n";
std::cout << "Obtained sign result in FHEW with plaintext modulus " << NativeInteger(pLWE1) << " and scale "
<< scaleSignFHEW << ": ";
for (uint32_t i = 0; i < LWECiphertexts.size(); ++i) {
LWESign[i] = ccLWE.EvalSign(LWECiphertexts[i]);
ccLWE.Decrypt(privateKeyFHEW, LWESign[i], &plainLWE, 2);
std::cout << plainLWE << " ";
}
std::cout << "\n";
// Step 5'': Direct comparison via CKKS->FHEW->CKKS
cResult = cc->EvalCompareSchemeSwitching(c1, c2, slots, slots, 0, scaleSignFHEW);
cc->Decrypt(keys.secretKey, cResult, &plaintextDec3);
plaintextDec3->SetLength(slots);
std::cout << "Decrypted switched result: " << plaintextDec3 << std::endl;
}
void ArgminViaSchemeSwitching() {
std::cout << "\n-----ArgminViaSchemeSwitching-----\n" << std::endl;
std::cout << "Output precision is only wrt the operations in CKKS after switching back\n" << std::endl;
// Step 1: Setup CryptoContext for CKKS
uint32_t scaleModSize = 50;
uint32_t firstModSize = 60;
uint32_t ringDim = 8192;
SecurityLevel sl = HEStd_NotSet;
BINFHE_PARAMSET slBin = TOY;
uint32_t logQ_ccLWE = 25;
bool arbFunc = false;
bool oneHot = true; // Change to false if the output should not be one-hot encoded
uint32_t slots = 16; // sparsely-packed
uint32_t batchSize = slots;
uint32_t numValues = 16;
ScalingTechnique scTech = FIXEDMANUAL;
uint32_t multDepth =
9 + 3 + 1 + static_cast<int>(std::log2(numValues)); // 13 for FHEW to CKKS, log2(numValues) for argmin
if (scTech == FLEXIBLEAUTOEXT)
multDepth += 1;
CCParams<CryptoContextCKKSRNS> parameters;
parameters.SetMultiplicativeDepth(multDepth);
parameters.SetScalingModSize(scaleModSize);
parameters.SetFirstModSize(firstModSize);
parameters.SetScalingTechnique(scTech);
parameters.SetSecurityLevel(sl);
parameters.SetRingDim(ringDim);
parameters.SetBatchSize(batchSize);
CryptoContext<DCRTPoly> cc = GenCryptoContext(parameters);
// Enable the features that you wish to use
cc->Enable(PKE);
cc->Enable(KEYSWITCH);
cc->Enable(LEVELEDSHE);
cc->Enable(ADVANCEDSHE);
cc->Enable(SCHEMESWITCH);
std::cout << "CKKS scheme is using ring dimension " << cc->GetRingDimension();
std::cout << ", and number of slots " << slots << ", and supports a depth of " << multDepth << std::endl
<< std::endl;
// Generate encryption keys
auto keys = cc->KeyGen();
// Step 2: Prepare the FHEW cryptocontext and keys for FHEW and scheme switching
auto FHEWparams = cc->EvalSchemeSwitchingSetup(sl, slBin, arbFunc, logQ_ccLWE, false, slots);
auto ccLWE = FHEWparams.first;
auto privateKeyFHEW = FHEWparams.second;
cc->EvalSchemeSwitchingKeyGen(keys, privateKeyFHEW, numValues, oneHot);
std::cout << "FHEW scheme is using lattice parameter " << ccLWE.GetParams()->GetLWEParams()->Getn();
std::cout << ", logQ " << logQ_ccLWE;
std::cout << ", and modulus q " << ccLWE.GetParams()->GetLWEParams()->Getq() << std::endl << std::endl;
// Scale the inputs to ensure their difference is correctly represented after switching to FHEW
double scaleSign = 512.0;
auto modulus_LWE = 1 << logQ_ccLWE;
auto beta = ccLWE.GetBeta().ConvertToInt();
auto pLWE = modulus_LWE / (2 * beta); // Large precision
uint32_t init_level = 0;
const auto cryptoParams = std::dynamic_pointer_cast<CryptoParametersCKKSRNS>(cc->GetCryptoParameters());
if (cryptoParams->GetScalingTechnique() == FLEXIBLEAUTOEXT)
init_level = 1;
// This formulation is for clarity
cc->EvalCompareSwitchPrecompute(pLWE, init_level, scaleSign);
// But we can also include the scaleSign in pLWE (here we use the fact both pLWE and scaleSign are powers of two)
// cc->EvalCompareSwitchPrecompute(pLWE / scaleSign, init_level, 1);
// Step 3: Encoding and encryption of inputs
// Inputs
std::vector<double> x1 = {-1.125, -1.12, 5.0, 6.0, -1.0, 2.0, 8.0, -1.0,
9.0, 10.0, 11.0, 12.0, 13.0, 14.0, 15.25, 15.30};
std::cout << "Expected minimum value " << *(std::min_element(x1.begin(), x1.begin() + numValues)) << " at location "
<< std::min_element(x1.begin(), x1.begin() + numValues) - x1.begin() << std::endl;
std::cout << "Expected maximum value " << *(std::max_element(x1.begin(), x1.begin() + numValues)) << " at location "
<< std::max_element(x1.begin(), x1.begin() + numValues) - x1.begin() << std::endl
<< std::endl;
// Encoding as plaintexts
Plaintext ptxt1 = cc->MakeCKKSPackedPlaintext(x1); // Only if we we set batchsize
// Plaintext ptxt1 = cc->MakeCKKSPackedPlaintext(x1, 1, 0, nullptr, slots); // If batchsize is not set
// Encrypt the encoded vectors
auto c1 = cc->Encrypt(keys.publicKey, ptxt1);
// Step 4: Argmin evaluation
auto result = cc->EvalMinSchemeSwitching(c1, keys.publicKey, numValues, slots, oneHot);
Plaintext ptxtMin;
cc->Decrypt(keys.secretKey, result[0], &ptxtMin);
ptxtMin->SetLength(1);
std::cout << "Minimum value: " << ptxtMin << std::endl;
cc->Decrypt(keys.secretKey, result[1], &ptxtMin);
if (oneHot) {
ptxtMin->SetLength(numValues);
std::cout << "Argmin indicator vector: " << ptxtMin << std::endl;
}
else {
ptxtMin->SetLength(1);
std::cout << "Argmin: " << ptxtMin << std::endl;
}
result = cc->EvalMaxSchemeSwitching(c1, keys.publicKey, numValues, slots, oneHot);
Plaintext ptxtMax;
cc->Decrypt(keys.secretKey, result[0], &ptxtMax);
ptxtMax->SetLength(1);
std::cout << "Maximum value: " << ptxtMax << std::endl;
cc->Decrypt(keys.secretKey, result[1], &ptxtMax);
if (oneHot) {
ptxtMax->SetLength(numValues);
std::cout << "Argmax indicator vector: " << ptxtMax << std::endl;
}
else {
ptxtMax->SetLength(1);
std::cout << "Argmax: " << ptxtMax << std::endl;
}
}