Files
MP-SPDZ/FHE/Ciphertext.cpp
2020-12-11 16:24:28 +11:00

124 lines
2.9 KiB
C++

#include "Ciphertext.h"
#include "PPData.h"
#include "P2Data.h"
#include "Exceptions/Exceptions.h"
#include "Math/modp.hpp"
Ciphertext::Ciphertext(const FHE_PK& pk) : Ciphertext(pk.get_params())
{
}
void Ciphertext::set(const Rq_Element& a0, const Rq_Element& a1,
const FHE_PK& pk)
{
set(a0, a1, pk.a().get(0).get_element(0).get_limb(0));
}
word check_pk_id(word a, word b)
{
if (a == 0)
return b;
else if (b == 0 or a == b)
return a;
else
{
cout << a << " vs " << b << endl;
throw runtime_error("public keys of ciphertext operands don't match");
}
}
void add(Ciphertext& ans,const Ciphertext& c0,const Ciphertext& c1)
{
if (c0.params!=c1.params) { throw params_mismatch(); }
if (ans.params!=c1.params) { throw params_mismatch(); }
ans.pk_id = check_pk_id(c0.pk_id, c1.pk_id);
add(ans.cc0,c0.cc0,c1.cc0);
add(ans.cc1,c0.cc1,c1.cc1);
}
void sub(Ciphertext& ans,const Ciphertext& c0,const Ciphertext& c1)
{
if (c0.params!=c1.params) { throw params_mismatch(); }
if (ans.params!=c1.params) { throw params_mismatch(); }
ans.pk_id = check_pk_id(c0.pk_id, c1.pk_id);
sub(ans.cc0,c0.cc0,c1.cc0);
sub(ans.cc1,c0.cc1,c1.cc1);
}
void mul(Ciphertext& ans,const Ciphertext& c0,const Ciphertext& c1,
const FHE_PK& pk)
{
if (c0.params!=c1.params) { throw params_mismatch(); }
if (ans.params!=c1.params) { throw params_mismatch(); }
// Switch Modulus for c0 and c1 down to level 0
Ciphertext cc0=c0,cc1=c1;
cc0.Scale(pk.p()); cc1.Scale(pk.p());
// Now do the multiply
Rq_Element d0,d1,d2;
mul(d0,cc0.cc0,cc1.cc0);
mul(d1,cc0.cc0,cc1.cc1);
mul(d2,cc0.cc1,cc1.cc0);
add(d1,d1,d2);
mul(d2,cc0.cc1,cc1.cc1);
d2.negate();
// Now do the switch key
d2.raise_level();
Rq_Element t;
d0.mul_by_p1();
mul(t,pk.bs(),d2);
add(d0,d0,t);
d1.mul_by_p1();
mul(t,pk.as(),d2);
add(d1,d1,t);
ans.set(d0, d1, check_pk_id(c0.pk_id, c1.pk_id));
ans.Scale(pk.p());
}
template<class T,class FD,class S>
void mul(Ciphertext& ans,const Plaintext<T,FD,S>& a,const Ciphertext& c)
{
a.to_poly();
int lev=c.cc0.level();
Rq_Element ra((*ans.params).FFTD(),evaluation,evaluation);
if (lev==0) { ra.lower_level(); }
ra.from(a.get_iterator());
ans.mul(c, ra);
}
void Ciphertext::mul(const Ciphertext& c, const Rq_Element& ra)
{
if (params!=c.params) { throw params_mismatch(); }
pk_id = c.pk_id;
::mul(cc0,ra,c.cc0);
::mul(cc1,ra,c.cc1);
}
void Ciphertext::add(octetStream& os)
{
Ciphertext tmp(*params);
tmp.unpack(os);
*this += tmp;
}
template void mul(Ciphertext& ans,const Plaintext<gfp,FFT_Data,bigint>& a,const Ciphertext& c);
template void mul(Ciphertext& ans,const Plaintext<gfp,PPData,bigint>& a,const Ciphertext& c);
template void mul(Ciphertext& ans,const Plaintext<gf2n_short,P2Data,int>& a,const Ciphertext& c);