#include <stdio.h>
#include <string.h>
#include "crypto_hash_sha512.h"
#include "crypto_kem.h"
#include "params.h"
#include "rq.h"
#include "hide.h"

#if crypto_kem_CIPHERTEXTBYTES != rq_encoderounded_len + 32 + 128
#error "crypto_kem_CIPHERTEXTBYTES must match rq_encoderounded_len + 32 + 128"
#endif

void hide(unsigned char *cstr,unsigned char *k,const unsigned char *pk,const unsigned char *r)
{
  modq G[p];
  modq A[p];
  unsigned char k12[64];
  unsigned char k34[64];
  small b[p];
  modq B[p];
  modq C[p];
  int i;

  rq_fromseed(G,pk);
  rq_decoderounded(A,pk + 32);

  crypto_hash_sha512(k12,r,32);
  small_seeded_weightw(b,k12);
  crypto_hash_sha512(k34,k12 + 32,32);

  rq_mult(B,G,b);
  rq_round3(B,B);

  rq_mult(C,A,b);
  for (i = 0;i < 256;++i) {
    modq x = C[i];
    x = modq_sum(x,2295 * (1 & (r[i / 8] >> (i & 7))));
    x = ((x + 2156) * 114 + 16384) >> 15;
    C[i] = x; /* between 0 and 15 */
  }

  memcpy(cstr,k34,32); cstr += 32;
  memcpy(k,k34 + 32,32);

  rq_encoderounded(cstr,B); cstr += rq_encoderounded_len;

  for (i = 0;i < 128;++i)
    *cstr++ = C[2*i] + (C[2*i + 1] << 4);
}