HElib 1.0 Implementing Homomorphic Encryption

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DoubleCRT.h
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1 /* Copyright (C) 2012,2013 IBM Corp.
2 * This program is free software; you can redistribute it and/or modify
3 * it under the terms of the GNU General Public License as published by
4 * the Free Software Foundation; either version 2 of the License, or
5 * (at your option) any later version.
6 *
7 * This program is distributed in the hope that it will be useful,
8 * but WITHOUT ANY WARRANTY; without even the implied warranty of
9 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
10 * See the GNU General Public License for more details.
11 *
12 * You should have received a copy of the GNU General Public License along
13 * with this program; if not, write to the Free Software Foundation, Inc.,
14 * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
15 */
21 #if 0 // change to #if 1 to get an alternative implementation
22
23 #define DoubleCRT AltCRT
24 #include "AltCRT.h"
25 #else
26 #ifndef _DoubleCRT_H_
27 #define _DoubleCRT_H_
28
29 #include <vector>
30 #include <NTL/ZZX.h>
31 #include <NTL/vec_vec_long.h>
32 #include "NumbTh.h"
33 #include "IndexMap.h"
34 #include "FHEContext.h"
35 NTL_CLIENT
36
37 class SingleCRT;
38
45 class DoubleCRTHelper : public IndexMapInit<vec_long> {
46 private:
47 long val;
48
49 public:
50 DoubleCRTHelper(const FHEcontext& context) {
51 val = context.zMStar.getPhiM();
52 }
53
55 virtual void init(vec_long& v) {
56 v.FixLength(val);
57 }
58
60 virtual IndexMapInit<vec_long> * clone() const {
61 return new DoubleCRTHelper(*this);
62 }
63 private:
64 DoubleCRTHelper(); // disable default constructor
65 };
66
67
88 class DoubleCRT {
89 const FHEcontext& context; // the context
90 IndexMap<vec_long> map; // the data itself: if the i'th prime is in use then
91 // map[i] is the vector of evaluations wrt this prime
92
95 void verify();
96
97 // Generic operators.
98 // The behavior when *this and other use different primes depends on the flag
99 // matchIndexSets. When it is set to true then the effective modulus is
100 // determined by the union of the two index sets; otherwise, the index set
101 // of *this.
102
103 class AddFun {
104 public:
105 long apply(long a, long b, long n) { return AddMod(a, b, n); }
106 };
107
108 class SubFun {
109 public:
110 long apply(long a, long b, long n) { return SubMod(a, b, n); }
111 };
112
113 class MulFun {
114 public:
115 long apply(long a, long b, long n) { return MulMod(a, b, n); }
116 };
117
118
119 template<class Fun>
120 DoubleCRT& Op(const DoubleCRT &other, Fun fun,
121 bool matchIndexSets=true);
122
123 template<class Fun>
124 DoubleCRT& Op(const ZZ &num, Fun fun);
125
126 template<class Fun>
127 DoubleCRT& Op(const ZZX &poly, Fun fun);
128
129 static bool dryRun; // do not actually perform any of the operations
130
131 public:
132
133 // Constructors and assignment operators
134
135 // representing an integer polynomial as DoubleCRT. If the set of primes
136 // to use is not specified, the resulting object uses all the primes in
137 // the context. If the coefficients of poly are larger than the product of
138 // the used primes, they are effectively reduced modulo that product
139
140 // copy constructor: default
141
146 DoubleCRT(const ZZX&poly, const FHEcontext& _context, const IndexSet& indexSet);
147 DoubleCRT(const ZZX&poly, const FHEcontext& _context);
148
150 // (run-time error if active context is NULL)
151 // declared "explicit" to avoid implicit type conversion
152 explicit DoubleCRT(const ZZX&poly);
153
154 // Without specifying a ZZX, we get the zero polynomial
155 explicit DoubleCRT(const FHEcontext &_context);
156 // declare "explicit" to avoid implicit type conversion
157
159 DoubleCRT(const FHEcontext &_context, const IndexSet& indexSet);
160
161 // Assignment operator, the following two lines are equivalent:
162 // DoubleCRT dCRT(poly, context, indexSet);
163 // or
164 // DoubleCRT dCRT(context, indexSet); dCRT = poly;
165
166 DoubleCRT& operator=(const DoubleCRT& other);
167
168 // Copy only the primes in s \intersect other.getIndexSet()
169 // void partialCopy(const DoubleCRT& other, const IndexSet& s);
170
171 DoubleCRT& operator=(const SingleCRT& other);
172 DoubleCRT& operator=(const ZZX& poly);
173 DoubleCRT& operator=(const ZZ& num);
174 DoubleCRT& operator=(const long num) { *this = to_ZZ(num); return *this; }
175
182 void toPoly(ZZX& p, const IndexSet& s, bool positive=false) const;
183 void toPoly(ZZX& p, bool positive=false) const;
184
185 // The variant toPolyMod has another argument, which is a modulus Q, and it
186 // computes toPoly() mod Q. This is offerred as a separate function in the
187 // hope that one day we will figure out a more efficient method of computing
188 // this. Right now it is not implemented
189 //
190 // void toPolyMod(ZZX& p, const ZZ &Q, const IndexSet& s) const;
191
192
193 bool operator==(const DoubleCRT& other) const {
194 assert(&context == &other.context);
195 return map == other.map;
196 }
197
198 bool operator!=(const DoubleCRT& other) const {
199 return !(*this==other);
200 }
201
202 // @brief Set to zero
203 DoubleCRT& SetZero() {
204 *this = ZZ::zero();
205 return *this;
206 }
207
208 // @brief Set to one
209 DoubleCRT& SetOne() {
210 *this = 1;
211 return *this;
212 }
213
216 void breakIntoDigits(vector<DoubleCRT>& dgts, long n) const;
217
220 void addPrimes(const IndexSet& s1);
221
224 double addPrimesAndScale(const IndexSet& s1);
225
227 void removePrimes(const IndexSet& s1) {
228 map.remove(s1);
229 }
230
231
237
238
239 // Addition, negation, subtraction
240 DoubleCRT& Negate(const DoubleCRT& other);
241 DoubleCRT& Negate() { return Negate(*this); }
242
243 DoubleCRT& operator+=(const DoubleCRT &other) {
244 return Op(other, AddFun());
245 }
246
247 DoubleCRT& operator+=(const ZZX &poly) {
248 return Op(poly, AddFun());
249 }
250
251 DoubleCRT& operator+=(const ZZ &num) {
252 return Op(num, AddFun());
253 }
254
255 DoubleCRT& operator+=(long num) {
256 return Op(to_ZZ(num), AddFun());
257 }
258
259 DoubleCRT& operator-=(const DoubleCRT &other) {
260 return Op(other,SubFun());
261 }
262
263 DoubleCRT& operator-=(const ZZX &poly) {
264 return Op(poly,SubFun());
265 }
266
267 DoubleCRT& operator-=(const ZZ &num) {
268 return Op(num, SubFun());
269 }
270
271 DoubleCRT& operator-=(long num) {
272 return Op(to_ZZ(num), SubFun());
273 }
274
275 // These are the prefix versions, ++dcrt and --dcrt.
276 DoubleCRT& operator++() { return (*this += 1); };
277 DoubleCRT& operator--() { return (*this -= 1); };
278
279 // These are the postfix versions -- return type is void,
280 // so it is offered just for style...
281 void operator++(int) { *this += 1; };
282 void operator--(int) { *this -= 1; };
283
284
285 // Multiplication
286 DoubleCRT& operator*=(const DoubleCRT &other) {
287 return Op(other,MulFun());
288 }
289
290 DoubleCRT& operator*=(const ZZX &poly) {
291 return Op(poly,MulFun());
292 }
293
294 DoubleCRT& operator*=(const ZZ &num) {
295 return Op(num,MulFun());
296 }
297
298 DoubleCRT& operator*=(long num) {
299 return Op(to_ZZ(num),MulFun());
300 }
301
302
303 // Procedural equivalents, supporting also the matchIndexSets flag
304 void Add(const DoubleCRT &other, bool matchIndexSets=true) {
305 Op(other, AddFun(), matchIndexSets);
306 }
307
308 void Sub(const DoubleCRT &other, bool matchIndexSets=true) {
309 Op(other, SubFun(), matchIndexSets);
310 }
311
312 void Mul(const DoubleCRT &other, bool matchIndexSets=true) {
313 Op(other, MulFun(), matchIndexSets);
314 }
315
316 // Division by constant
317 DoubleCRT& operator/=(const ZZ &num);
318 DoubleCRT& operator/=(long num) { return (*this /= to_ZZ(num)); }
319
321 void Exp(long k);
322
323 // Apply the automorphism F(X) --> F(X^k) (with gcd(k,m)=1)
324 void automorph(long k);
325 DoubleCRT& operator>>=(long k) { automorph(k); return *this; }
327
328 // Utilities
329
330 const FHEcontext& getContext() const { return context; }
331 const IndexMap<vec_long>& getMap() const { return map; }
332 const IndexSet& getIndexSet() const { return map.getIndexSet(); }
333
334 // Choose random DoubleCRT's, either at random or with small/Gaussian
335 // coefficients.
336
338 void randomize(const ZZ* seed=NULL);
339
341 void sampleSmall() {
342 ZZX poly;
343 ::sampleSmall(poly,context.zMStar.getPhiM()); // degree-(phi(m)-1) polynomial
344 *this = poly; // convert to DoubleCRT
345 }
346
348 void sampleHWt(long Hwt) {
349 ZZX poly;
350 ::sampleHWt(poly,Hwt,context.zMStar.getPhiM());
351 *this = poly; // convert to DoubleCRT
352 }
353
355 void sampleGaussian(double stdev=0.0) {
356 if (stdev==0.0) stdev=to_double(context.stdev);
357 ZZX poly;
358 ::sampleGaussian(poly, context.zMStar.getPhiM(), stdev);
359 *this = poly; // convert to DoubleCRT
360 }
361
362
364 // Restricted to the given index set, if specified
365 void toSingleCRT(SingleCRT& scrt, const IndexSet& s) const;
366 void toSingleCRT(SingleCRT& scrt) const;
367
368 // used to implement modulus switching
369 void scaleDownToSet(const IndexSet& s, long ptxtSpace);
370
371 // I/O: ONLY the matrix is outputted/recovered, not the moduli chain!! An
372 // error is raised on input if this is not consistent with the current chain
373
374 friend ostream& operator<< (ostream &s, const DoubleCRT &d);
375 friend istream& operator>> (istream &s, DoubleCRT &d);
376
381 static bool setDryRun(bool toWhat=true) { dryRun=toWhat; return dryRun; }
382 };
383
384
385
386
387 inline void conv(DoubleCRT &d, const ZZX &p) { d=p; }
388
389 inline DoubleCRT to_DoubleCRT(const ZZX& p) {
390 return DoubleCRT(p);
391 }
392
393 inline void conv(ZZX &p, const DoubleCRT &d) { d.toPoly(p); }
394
395 inline ZZX to_ZZX(const DoubleCRT &d) { ZZX p; d.toPoly(p); return p; }
396
397 inline void conv(DoubleCRT& d, const SingleCRT& s) { d=s; }
398
399
400 #endif // #ifndef _DoubleCRT_H_
401
402 #endif // DoubleCRT or AltCRT