HElib 1.0 Implementing Homomorphic Encryption

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FHEContext.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 */
16 #ifndef _FHEcontext_H_
17 #define _FHEcontext_H_
18
22 #include <NTL/xdouble.h>
23 #include "PAlgebra.h"
24 #include "CModulus.h"
25 #include "IndexSet.h"
26
39 long FindM(long k, long L, long c, long p, long d, long s, long chosen_m, bool verbose=false);
40
45 class FHEcontext {
46 vector<Cmodulus> moduli; // Cmodulus objects for the different primes
47 // This is private since the implementation assumes that the list of
48 // primes only grows and no prime is ever modified or removed.
49
50 public:
51 // FHEContext is meant for convenience, not encapsulation: Most data
52 // members are public and can be initialized by the application program.
53
55 PAlgebra zMStar;
56
58 PAlgebraMod alMod;
59
61 xdouble stdev;
62
72 IndexSet ctxtPrimes;
73
78 IndexSet specialPrimes;
79
96 vector<IndexSet> digits; // digits of ctxt/columns of key-switching matrix
97
98 // Constructors must ensure that alMod points to zMStar
99
100 // constructor
101 FHEcontext(unsigned m, unsigned p, unsigned r): zMStar(m, p), alMod(zMStar, r)
102 { stdev=3.2; }
103
104 bool operator==(const FHEcontext& other) const;
105 bool operator!=(const FHEcontext& other) const { return !(*this==other); }
106
108 long ithPrime(unsigned i) const
109 { return (i<moduli.size())? moduli[i].getQ() :0; }
110
112 const Cmodulus& ithModulus(unsigned i) const { return moduli[i]; }
113
115 long numPrimes() const { return moduli.size(); }
116
118 bool isZeroDivisor(const ZZ& num) const {
119 for (unsigned i=0; i<moduli.size(); i++)
120 if (divide(num,moduli[i].getQ())) return true;
121 return false;
122 }
123
125 bool inChain(long p) const {
126 for (unsigned i=0; i<moduli.size(); i++)
127 if (p==moduli[i].getQ()) return true;
128 return false;
129 }
130
133 void productOfPrimes(ZZ& p, const IndexSet& s) const;
134 ZZ productOfPrimes(const IndexSet& s) const {
135 ZZ p;
136 productOfPrimes(p,s);
137 return p;
138 }
140
141 // FIXME: run-time error when ithPrime(i) returns 0
143 double logOfPrime(unsigned i) const { return log(ithPrime(i)); }
144
146 double logOfProduct(const IndexSet& s) const {
147 if (s.last() >= numPrimes())
148 Error("FHEContext::logOfProduct: IndexSet has too many rows");
149
150 double ans = 0.0;
151 for (long i = s.first(); i <= s.last(); i = s.next(i))
152 ans += logOfPrime(i);
153 return ans;
154 }
155
157 void AddPrime(long p, bool special);
158
159
161
194
195 friend void writeContextBase(ostream& str, const FHEcontext& context);
196
198 friend ostream& operator<< (ostream &str, const FHEcontext& context);
199
201 friend void readContextBase(istream& str, unsigned& m, unsigned& p, unsigned& r);
202
204 friend istream& operator>> (istream &str, FHEcontext& context);
206 };
207
209 void writeContextBase(ostream& s, const FHEcontext& context);
211 void readContextBase(istream& s, unsigned& m, unsigned& p, unsigned& r);
212
213 // VJS: compiler seems to need these declarations out here...wtf...
214
216
217
220 double AddPrimesBySize(FHEcontext& context, double totalSize,
221 bool special=false);
222
225 double AddPrimesByNumber(FHEcontext& context, long nPrimes,
226 long startAt=1,
227 bool special=false);
228
230 void buildModChain(FHEcontext &context, long nLvls, long c=3);
232 extern FHEcontext* activeContext; // Points to the "current" context
233 #endif // ifndef _FHEcontext_H_