/* LibTomCrypt, modular cryptographic library -- Tom St Denis
 *
 * LibTomCrypt is a library that provides various cryptographic
 * algorithms in a highly modular and flexible manner.
 *
 * The library is free for all purposes without any express
 * guarantee it works.
 *
 */

/* Implements ECC over Z/pZ for curve y^2 = x^3 + a*x + b
 *
 */

#include "tomcrypt.h"

#ifdef LTC_MECC

int ecc_export_point(unsigned char *out, unsigned long *outlen, void *x, void *y, unsigned long size, int compressed)
{
  int err;
  unsigned char buf[ECC_BUF_SIZE];
  unsigned long xsize, ysize;

  if (size > sizeof(buf)) return CRYPT_BUFFER_OVERFLOW;
  if ((xsize = mp_unsigned_bin_size(x)) > size) return CRYPT_BUFFER_OVERFLOW;
  if ((ysize = mp_unsigned_bin_size(y)) > size) return CRYPT_BUFFER_OVERFLOW;

  if(compressed) {
   if (*outlen < (1 + size)) {
       *outlen = 1 + size;
       return CRYPT_BUFFER_OVERFLOW;
    }
    /* store first byte */
    out[0] = mp_isodd(y) ? 0x03 : 0x02;
    /* pad and store x */
    zeromem(buf, sizeof(buf));
    if ((err = mp_to_unsigned_bin(x, buf + (size - xsize))) != CRYPT_OK) return err;
    XMEMCPY(out+1, buf, size);
    /* adjust outlen */
    *outlen = 1 + size;
  }
  else {
    if (*outlen < (1 + 2*size)) {
      *outlen = 1 + 2*size;
      return CRYPT_BUFFER_OVERFLOW;
    }
    /* store byte 0x04 */
    out[0] = 0x04;
    /* pad and store x */
    zeromem(buf, sizeof(buf));
    if ((err = mp_to_unsigned_bin(x, buf + (size - xsize))) != CRYPT_OK) return err;
    XMEMCPY(out+1, buf, size);
    /* pad and store y */
    zeromem(buf, sizeof(buf));
    if ((err = mp_to_unsigned_bin(y, buf + (size - ysize))) != CRYPT_OK) return err;
    XMEMCPY(out+1+size, buf, size);
    /* adjust outlen */
    *outlen = 1 + 2*size;
  }
  return CRYPT_OK;
}

/** Export raw public or private key (public keys = ANS X9.63 compressed or uncompressed; private keys = raw bytes)
  @param out    [out] destination of export
  @param outlen [in/out]  Length of destination and final output size
  @param type   PK_PRIVATE, PK_PUBLIC or PK_PUBLIC_COMPRESSED
  @param key    Key to export
  Return        CRYPT_OK on success
*/

int ecc_export_raw(unsigned char *out, unsigned long *outlen, int type, ecc_key *key)
{
  unsigned long size, ksize;
  int err;

  LTC_ARGCHK(key    != NULL);
  LTC_ARGCHK(out    != NULL);
  LTC_ARGCHK(outlen != NULL);

  if (ltc_ecc_is_valid_idx(key->idx) == 0) {
     return CRYPT_INVALID_ARG;
  }
  size = key->dp->size;

  if (type == PK_PUBLIC_COMPRESSED) {
    if ((err = ecc_export_point(out, outlen, key->pubkey.x, key->pubkey.y, size, 1)) != CRYPT_OK) return err;
  }
  else if (type == PK_PUBLIC) {
    if ((err = ecc_export_point(out, outlen, key->pubkey.x, key->pubkey.y, size, 0)) != CRYPT_OK) return err;
  }
  else if (type == PK_PRIVATE) {
    if (key->type != PK_PRIVATE)                                                return CRYPT_PK_TYPE_MISMATCH;
    *outlen = size;
    if (size > *outlen)                                                         return CRYPT_BUFFER_OVERFLOW;
    if ((ksize = mp_unsigned_bin_size(key->k)) > size)                          return CRYPT_BUFFER_OVERFLOW;
    /* pad and store k */
    if ((err = mp_to_unsigned_bin(key->k, out + (size - ksize))) != CRYPT_OK)   return err;
    zeromem(out, size - ksize);
  }
  else {
    return CRYPT_INVALID_ARG;
  }

  return CRYPT_OK;
}

#endif
