core/lib/libtomcrypt/src/pk/ecc/ecc_export.c

// SPDX-License-Identifier: BSD-2-Clause
/* 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.
 */

#include "tomcrypt_private.h"

/**
  @file ecc_export.c
  ECC Crypto, Tom St Denis
*/

#ifdef LTC_MECC

/**
  Export an ECC key as a binary packet
  @param out     [out] Destination for the key
  @param outlen  [in/out] Max size and resulting size of the exported key
  @param type    The type of key you want to export (PK_PRIVATE or PK_PUBLIC)
  @param key     The key to export
  @return CRYPT_OK if successful
*/
int ecc_export(unsigned char *out, unsigned long *outlen, int type, const ecc_key *key)
{
   int           err;
   unsigned char flags[1];
   unsigned long key_size;

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

   /* type valid? */
   if (key->type != PK_PRIVATE && type == PK_PRIVATE) {
      return CRYPT_PK_TYPE_MISMATCH;
   }

   /* we store the NIST byte size */
   key_size = key->dp.size;

   if (type == PK_PRIVATE) {
       flags[0] = 1;
       err = der_encode_sequence_multi(out, outlen,
                                 LTC_ASN1_BIT_STRING,      1UL, flags,
                                 LTC_ASN1_SHORT_INTEGER,   1UL, &key_size,
                                 LTC_ASN1_INTEGER,         1UL, key->pubkey.x,
                                 LTC_ASN1_INTEGER,         1UL, key->pubkey.y,
                                 LTC_ASN1_INTEGER,         1UL, key->k,
                                 LTC_ASN1_EOL,             0UL, NULL);
   } else {
       flags[0] = 0;
       err = der_encode_sequence_multi(out, outlen,
                                 LTC_ASN1_BIT_STRING,      1UL, flags,
                                 LTC_ASN1_SHORT_INTEGER,   1UL, &key_size,
                                 LTC_ASN1_INTEGER,         1UL, key->pubkey.x,
                                 LTC_ASN1_INTEGER,         1UL, key->pubkey.y,
                                 LTC_ASN1_EOL,             0UL, NULL);
   }

   return err;
}

#endif
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