Files
MP-SPDZ/FHE/Ring_Element.cpp
2022-05-27 14:20:31 +02:00

590 lines
14 KiB
C++

#include "FHE/Ring_Element.h"
#include "Tools/Exceptions.h"
#include "FHE/FFT.h"
#include "Math/modp.hpp"
void reduce_step(vector<modp>& aa,int i,const FFT_Data& FFTD)
{ modp temp=aa[i];
for (int j=0; j<FFTD.phi_m(); j++)
{
if (FFTD.Phi()[j] > 0)
for (int k = 0; k < FFTD.Phi()[j]; k++)
Sub(aa[i-FFTD.phi_m()+j],aa[i-FFTD.phi_m()+j],temp,FFTD.get_prD());
else
for (int k = 0; k < abs(FFTD.Phi()[j]); k++)
Add(aa[i-FFTD.phi_m()+j],aa[i-FFTD.phi_m()+j],temp,FFTD.get_prD());
}
}
void reduce(vector<modp>& aa, int top, int bottom, const FFT_Data& FFTD)
{
for (int i = top - 1; i >= bottom; i--)
reduce_step(aa, i, FFTD);
}
Ring_Element::Ring_Element(const FFT_Data& fftd,RepType r)
{
FFTD=&fftd;
rep=r;
assign_zero();
}
void Ring_Element::prepare(const Ring_Element& other)
{
assert(this != &other);
FFTD = other.FFTD;
rep = other.rep;
prepare_push();
}
void Ring_Element::prepare_push()
{
element.clear();
element.reserve(FFTD->phi_m());
}
void Ring_Element::allocate()
{
assert(FFTD);
element.resize(FFTD->phi_m());
}
void Ring_Element::assign_zero()
{
element.clear();
}
void Ring_Element::assign_one()
{
allocate();
modp fill;
if (rep==polynomial) { assignZero(fill,(*FFTD).get_prD()); }
else { assignOne(fill,(*FFTD).get_prD()); }
for (int i=1; i<(*FFTD).phi_m(); i++)
{ element[i]=fill; }
assignOne(element[0],(*FFTD).get_prD());
}
void Ring_Element::negate()
{
if (element.empty())
return;
for (int i=0; i<(*FFTD).phi_m(); i++)
{ Negate(element[i],element[i],(*FFTD).get_prD()); }
}
void add(Ring_Element& ans,const Ring_Element& a,const Ring_Element& b)
{
if (a.FFTD!=b.FFTD) { throw pr_mismatch(); }
if (a.element.empty())
{
ans = b;
return;
}
else if (b.element.empty())
{
ans = a;
return;
}
if (a.rep!=b.rep) { throw rep_mismatch(); }
if (&ans == &a)
{
ans += b;
return;
}
else if (&ans == &b)
{
ans += a;
return;
}
ans.prepare(a);
for (int i=0; i<(*ans.FFTD).phi_m(); i++)
ans.element.push_back(a.element[i].add(b.element[i], a.FFTD->get_prD()));
}
void sub(Ring_Element& ans,const Ring_Element& a,const Ring_Element& b)
{
if (a.rep!=b.rep) { throw rep_mismatch(); }
if (a.FFTD!=b.FFTD) { throw pr_mismatch(); }
if (a.element.empty())
{
ans = b;
ans.negate();
return;
}
else if (b.element.empty())
{
ans = a;
return;
}
if (&ans == &a)
{
ans -= b;
return;
}
ans.prepare(a);
for (int i=0; i<(*ans.FFTD).phi_m(); i++)
ans.element.push_back(a.element[i].sub(b.element[i], a.FFTD->get_prD()));
}
void mul(Ring_Element& ans,const Ring_Element& a,const Ring_Element& b)
{
if (a.rep!=b.rep) { throw rep_mismatch(); }
if (a.FFTD!=b.FFTD) { throw pr_mismatch(); }
if (a.element.empty() or b.element.empty())
{
ans = Ring_Element(*a.FFTD, a.rep);
return;
}
if (a.rep==evaluation)
{ // In evaluation representation, so we can just multiply componentwise
if (&ans == &a)
{
ans *= b;
return;
}
else if (&ans == &b)
{
ans *= a;
return;
}
ans.prepare(a);
for (int i=0; i<(*ans.FFTD).phi_m(); i++)
ans.element.push_back(a.element[i].mul(b.element[i], a.FFTD->get_prD()));
}
else if ((*a.FFTD).get_twop()!=0)
{ // This is the case where m is not a power of two
// Here we have to do a poly mult followed by a reduction
// We could be clever (e.g. use Karatsuba etc), but instead
// we do the school book method followed by term re-writing
// School book mult
vector<modp> aa(2*(*a.FFTD).phi_m());
for (int i=0; i<2*(*a.FFTD).phi_m(); i++)
{ assignZero(aa[i],(*a.FFTD).get_prD()); }
modp temp;
for (int i=0; i<(*a.FFTD).phi_m(); i++)
{ for (int j=0; j<(*a.FFTD).phi_m(); j++)
{ Mul(temp,a.element[i],b.element[j],(*a.FFTD).get_prD());
int k=i+j;
Add(aa[k],aa[k],temp,(*a.FFTD).get_prD());
}
}
// Now apply reduction, assumes Ring.poly is monic
reduce(aa, 2*(*a.FFTD).phi_m(), (*a.FFTD).phi_m(), *a.FFTD);
// Now stick into answer
ans.partial_assign(a);
for (int i=0; i<(*ans.FFTD).phi_m(); i++)
{ ans.element[i]=aa[i]; }
}
else if ((*a.FFTD).get_twop()==0)
{ // m a power of two case
ans.partial_assign(a);
Ring_Element aa(*ans.FFTD,ans.rep);
modp temp;
for (int i=0; i<(*ans.FFTD).phi_m(); i++)
{ for (int j=0; j<(*ans.FFTD).phi_m(); j++)
{ Mul(temp,a.element[i],b.element[j],(*a.FFTD).get_prD());
int k=i+j;
if (k>=(*ans.FFTD).phi_m())
{ k-=(*ans.FFTD).phi_m();
Negate(temp,temp,(*a.FFTD).get_prD());
}
Add(aa.element[k],aa.element[k],temp,(*a.FFTD).get_prD());
}
}
ans=aa;
}
else
{ throw not_implemented(); }
}
void mul(Ring_Element& ans,const Ring_Element& a,const modp& b)
{
if (&ans == &a)
{
ans *= b;
return;
}
ans.prepare(a);
if (a.element.empty())
return;
for (int i=0; i<(*ans.FFTD).phi_m(); i++)
ans.element.push_back(a.element[i].mul(b, a.FFTD->get_prD()));
}
Ring_Element& Ring_Element::operator +=(const Ring_Element& other)
{
assert(element.size() == other.element.size());
assert(FFTD == other.FFTD);
assert(rep == other.rep);
for (size_t i = 0; i < element.size(); i++)
element[i] = element[i].add(other.element[i], FFTD->get_prD());
return *this;
}
Ring_Element& Ring_Element::operator -=(const Ring_Element& other)
{
assert(element.size() == other.element.size());
assert(FFTD == other.FFTD);
assert(rep == other.rep);
for (size_t i = 0; i < element.size(); i++)
element[i] = element[i].sub(other.element[i], FFTD->get_prD());
return *this;
}
Ring_Element& Ring_Element::operator *=(const Ring_Element& other)
{
assert(element.size() == other.element.size());
assert(FFTD == other.FFTD);
assert(rep == other.rep);
assert(rep == evaluation);
for (size_t i = 0; i < element.size(); i++)
element[i] = element[i].mul(other.element[i], FFTD->get_prD());
return *this;
}
Ring_Element& Ring_Element::operator *=(const modp& other)
{
for (size_t i = 0; i < element.size(); i++)
element[i] = element[i].mul(other, FFTD->get_prD());
return *this;
}
Ring_Element Ring_Element::mul_by_X_i(int j) const
{
Ring_Element ans;
ans.prepare(*this);
if (element.empty())
return ans;
auto& a = *this;
if (ans.rep == evaluation)
{
modp xj, xj2;
Power(xj, (*ans.FFTD).get_root(0), j, (*a.FFTD).get_prD());
Sqr(xj2, xj, (*a.FFTD).get_prD());
ans.prepare_push();
modp tmp;
for (int i= 0; i < (*ans.FFTD).phi_m(); i++)
{
Mul(tmp, a.element[i], xj, (*a.FFTD).get_prD());
ans.element.push_back(tmp);
Mul(xj, xj, xj2, (*a.FFTD).get_prD());
}
}
else
{
Ring_Element aa(*ans.FFTD, ans.rep);
aa.allocate();
for (int i= 0; i < (*ans.FFTD).phi_m(); i++)
{
int k= j + i, s= 1;
while (k >= (*ans.FFTD).phi_m())
{
k-= (*ans.FFTD).phi_m();
s= -s;
}
if (s == 1)
{
aa.element[k]= a.element[i];
}
else
{
Negate(aa.element[k], a.element[i], (*a.FFTD).get_prD());
}
}
ans= aa;
}
return ans;
}
void Ring_Element::randomize(PRNG& G,bool Diag)
{
allocate();
if (Diag==false)
{ for (int i=0; i<(*FFTD).phi_m(); i++)
{ element[i].randomize(G,(*FFTD).get_prD()); }
}
else
{ element[0].randomize(G,(*FFTD).get_prD());
if (rep==polynomial)
{ for (int i=1; i<(*FFTD).phi_m(); i++)
{ assignZero(element[i],(*FFTD).get_prD()); }
}
else
{ for (int i=1; i<(*FFTD).phi_m(); i++)
{ element[i]=element[0]; }
}
}
}
void Ring_Element::change_rep(RepType r)
{
if (element.empty())
{
rep = r;
return;
}
if (rep==r) { return; }
if (r==evaluation)
{ rep=evaluation;
if ((*FFTD).get_twop()==0)
{ // m a power of two variant
FFT_Iter2(element,(*FFTD).phi_m(),(*FFTD).get_roots(),(*FFTD).get_prD());
}
else
{ // Non m power of two variant and FFT enabled
FFT_non_power_of_two(element, element, *FFTD);
}
}
else
{ rep=polynomial;
if ((*FFTD).get_twop()==0)
{ // m a power of two variant
modp root2;
Sqr(root2,(*FFTD).get_root(1),(*FFTD).get_prD());
FFT_Iter(element, (*FFTD).phi_m(),root2,(*FFTD).get_prD());
modp w;
w = (*FFTD).get_iphi();
for (int i=0; i<(*FFTD).phi_m(); i++)
{ Mul(element[i], element[i], w, (*FFTD).get_prD());
Mul(w, w, (*FFTD).get_root(1),(*FFTD).get_prD());
}
}
else
{ // Non power of 2 m variant and FFT enabled
vector<modp> fft((*FFTD).m());
for (int i=0; i<(*FFTD).m(); i++)
{ assignZero(fft[i],(*FFTD).get_prD()); }
for (int i=0; i<(*FFTD).phi_m(); i++)
{ fft[(*FFTD).p(i)]=element[i]; }
BFFT(fft,fft,*FFTD,false);
// Need to reduce fft mod Phi_m
reduce(fft, (*FFTD).m(), (*FFTD).phi_m(), *FFTD);
for (int i=0; i<(*FFTD).phi_m(); i++)
{ element[i]=fft[i]; }
}
}
}
bool Ring_Element::equals(const Ring_Element& a) const
{
if (rep!=a.rep) { throw rep_mismatch(); }
if (*FFTD!=*a.FFTD) { throw pr_mismatch(); }
if (is_zero() or a.is_zero())
return is_zero() and a.is_zero();
for (int i=0; i<(*FFTD).phi_m(); i++)
{ if (!areEqual(element[i],a.element[i],(*FFTD).get_prD())) { return false; } }
return true;
}
bool Ring_Element::is_zero() const
{
if (element.empty())
return true;
for (auto& x : element)
if (not ::isZero(x, FFTD->get_prD()))
return false;
return true;
}
ConversionIterator Ring_Element::get_iterator() const
{
if (rep != polynomial)
throw runtime_error("simple iterator only available in polynomial represention");
assert(not element.empty());
return {element, (*FFTD).get_prD()};
}
RingReadIterator Ring_Element::get_copy_iterator() const
{
return *this;
}
RingWriteIterator Ring_Element::get_write_iterator()
{
return *this;
}
vector<bigint> Ring_Element::to_vec_bigint() const
{
vector<bigint> v;
to_vec_bigint(v);
return v;
}
void Ring_Element::to_vec_bigint(vector<bigint>& v) const
{
v.resize(FFTD->phi_m());
if (element.empty())
return;
if (rep==polynomial)
{ for (int i=0; i<(*FFTD).phi_m(); i++)
{ to_bigint(v[i],element[i],(*FFTD).get_prD()); }
}
else
{ Ring_Element a=*this;
a.change_rep(polynomial);
for (int i=0; i<(*FFTD).phi_m(); i++)
{ to_bigint(v[i],a.element[i],(*FFTD).get_prD()); }
}
}
modp Ring_Element::get_constant() const
{
if (element.empty())
return {};
else
return element[0];
}
void store(octetStream& o,const vector<modp>& v,const Zp_Data& ZpD)
{
ZpD.pack(o);
o.store((int)v.size());
for (unsigned int i=0; i<v.size(); i++)
{ v[i].pack(o,ZpD); }
}
void get(octetStream& o,vector<modp>& v,const Zp_Data& ZpD)
{
Zp_Data check_Zpd;
check_Zpd.unpack(o);
if (check_Zpd != ZpD)
throw runtime_error(
"mismatch: " + to_string(check_Zpd.pr_bit_length) + "/"
+ to_string(ZpD.pr_bit_length));
unsigned int length;
o.get(length);
v.clear();
v.reserve(length);
modp tmp;
for (unsigned int i=0; i<length; i++)
{
tmp.unpack(o,ZpD);
v.push_back(tmp);
}
}
void Ring_Element::pack(octetStream& o) const
{
check_size();
o.store(unsigned(rep));
store(o,element,(*FFTD).get_prD());
}
void Ring_Element::unpack(octetStream& o)
{
unsigned int a;
o.get(a);
rep=(RepType) a;
check_rep();
get(o,element,(*FFTD).get_prD());
check_size();
}
void Ring_Element::check_rep()
{
if (rep != evaluation and rep != polynomial)
throw runtime_error("invalid representation");
}
void Ring_Element::check_size() const
{
if (not element.empty() and (int)element.size() != FFTD->phi_m())
throw runtime_error("invalid element size");
}
void Ring_Element::output(ostream& s) const
{
s.write((char*)&rep, sizeof(rep));
auto size = element.size();
s.write((char*)&size, sizeof(size));
for (auto& x : element)
x.output(s, FFTD->get_prD(), false);
}
void Ring_Element::input(istream& s)
{
s.read((char*)&rep, sizeof(rep));
check_rep();
auto size = element.size();
s.read((char*)&size, sizeof(size));
element.resize(size);
for (auto& x : element)
x.input(s, FFTD->get_prD(), false);
}
void Ring_Element::check(const FFT_Data& FFTD) const
{
if (&FFTD != this->FFTD)
throw params_mismatch();
if (is_zero())
throw runtime_error("element is zero");
}
size_t Ring_Element::report_size(ReportType type) const
{
if (type == CAPACITY)
return sizeof(modp) * element.capacity();
else
return sizeof(mp_limb_t) * (*FFTD).get_prD().get_t() * element.size();
}
template void Ring_Element::from(const Generator<bigint>& generator);
template void Ring_Element::from(const Generator<int>& generator);