NTL_CLIENT
#include "FHE.h"
#include "timing.h"
#include "EncryptedArray.h"
#include <cstdio>
// Map all non-zero slots to 1, leaving zero slots as zero.
// Assumes that r=1, and that all the slot contain elements from GF(p^d).
//
// We compute x^{p^d-1} = x^{(1+p+...+p^{d-1})*(p-1)} by setting y=x^{p-1}
// and then outputting y * y^p * ... * y^{p^{d-1}}, with exponentiation to
// powers of p done via Frobenius.
// FIXME: the computation of the "norm" y * y^p * ... * y^{p^{d-1}}
// can be done using O(log d) automorphisms, rather than O(d).
void mapTo01(const EncryptedArray& ea, Ctxt& ctxt)
{
long p = ctxt.getPtxtSpace();
if (p != ea.getPAlgebra().getP()) // ptxt space is p^r for r>1
throw helib::LogicError("mapTo01 not implemented for r>1");
if (p>2)
ctxt.power(p-1); // set y = x^{p-1}
long d = ea.getDegree();
if (d>1) { // compute the product of the d automorphisms
std::vector<Ctxt> v(d, ctxt);
for (long i=1; i<d; i++)
v[i].frobeniusAutomorph(i);
totalProduct(ctxt, v);
}
}
// Apply a permutation network to a ciphertext
void PermNetwork::applyToCtxt(Ctxt& c, const EncryptedArray& ea) const
{
const PAlgebra& al = ea.getPAlgebra();
// Apply the layers, one at a time
for (long i=0; i<layers.length(); i++) {
const PermNetLayer& lyr = layers[i];
if (lyr.isID) continue; // this layer is the identity permutation
// This layer is shifted via powers of g^e mod m
long g2e = PowerMod(al.ZmStarGen(lyr.genIdx), lyr.e, al.getM());
Vec<long> unused = lyr.shifts; // copy to a new vector
vector<long> mask(lyr.shifts.length()); // buffer to hold masks
Ctxt sum(c.getPubKey(), c.getPtxtSpace()); // an empty ciphertext
long shamt = 0;
bool frst = true;
while (true) {
pair<long,bool> ret=makeMask(mask, unused, shamt); // compute mask
if (ret.second) { // non-empty mask
Ctxt tmp = c;
ZZX maskPoly;
ea.encode(maskPoly, mask); // encode mask as polynomial
tmp.multByConstant(maskPoly); // multiply by mask
if (shamt!=0) // rotate if the shift amount is nonzero
tmp.smartAutomorph(PowerMod(g2e, shamt, al.getM()));
if (frst) {
sum = tmp;
frst = false;
}
else
sum += tmp;
}
if (ret.first >= 0)
shamt = unused[ret.first]; // next shift amount to use
else break; // unused is all-zero, done with this layer
}
c = sum; // update the cipehrtext c before the next layer
}
}
