DistDecrypt.cpp

#include "DistDecrypt.h"
#include "FHE/P2Data.h"

template<class FD>
DistDecrypt<FD>::DistDecrypt(const Player& P, const FHE_SK& share,
    const FHE_PK& pk, const FD& FTD) :
    P(P), share(share), pk(pk), mf(FTD), f(FTD)
{
  vv.resize(pk.get_params().phi_m());
  vv1.resize(pk.get_params().phi_m());
  // extra limb for operations
  bigint limit = pk.get_params().Q() << 64;
  vv.allocate_slots(limit);
  vv1.allocate_slots(limit);
  mf.allocate_slots(pk.p() << 64);
}

template<class FD>
Plaintext_<FD>& DistDecrypt<FD>::run(const Ciphertext& ctx, bool NewCiphertext)
{
  const FHE_Params& params=ctx.get_params();

  share.dist_decrypt_1(vv, ctx,P.my_num(),P.num_players());

  if (not NewCiphertext)
    intermediate_step();

  // Now pack into an octetStream for broadcasting
  vector<octetStream> os(P.num_players());

  if ((int)vv.size() != params.phi_m())
    throw length_error("wrong length of ring element");
  for (int i=0; i<params.phi_m(); i++)
    { (os[P.my_num()]).store(vv[i]); }

  // Broadcast and Receive the values
  P.Broadcast_Receive(os);

  // Reconstruct the value mod p0 from all shares
  vv1.resize(params.phi_m());
  for (int i=0; i<P.num_players(); i++)
    { if (i!=P.my_num())
        { for (int j=0; j<params.phi_m(); j++)
	    { os[i].get(vv1[j]); }
	  share.dist_decrypt_2(vv,vv1);
        }
    }

  // Now get the final message
  bigint mod=params.p0();
  mf.set_poly_mod(vv,mod);
  return mf;
}


template class DistDecrypt<FFT_Data>;
template class DistDecrypt<P2Data>;