view libtommath/bn_mp_toradix_n.c @ 1659:d32bcb5c557d

Add Ed25519 support (#91) * Add support for Ed25519 as a public key type Ed25519 is a elliptic curve signature scheme that offers better security than ECDSA and DSA and good performance. It may be used for both user and host keys. OpenSSH key import and fuzzer are not supported yet. Initially inspired by Peter Szabo. * Add curve25519 and ed25519 fuzzers * Add import and export of Ed25519 keys
author Vladislav Grishenko <themiron@users.noreply.github.com>
date Wed, 11 Mar 2020 21:09:45 +0500
parents f52919ffd3b1
children
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#include "tommath_private.h"
#ifdef BN_MP_TORADIX_N_C
/* LibTomMath, multiple-precision integer library -- Tom St Denis
 *
 * LibTomMath is a library that provides multiple-precision
 * integer arithmetic as well as number theoretic functionality.
 *
 * The library was designed directly after the MPI library by
 * Michael Fromberger but has been written from scratch with
 * additional optimizations in place.
 *
 * SPDX-License-Identifier: Unlicense
 */

/* stores a bignum as a ASCII string in a given radix (2..64)
 *
 * Stores upto maxlen-1 chars and always a NULL byte
 */
int mp_toradix_n(const mp_int *a, char *str, int radix, int maxlen)
{
   int     res, digs;
   mp_int  t;
   mp_digit d;
   char   *_s = str;

   /* check range of the maxlen, radix */
   if ((maxlen < 2) || (radix < 2) || (radix > 64)) {
      return MP_VAL;
   }

   /* quick out if its zero */
   if (mp_iszero(a) == MP_YES) {
      *str++ = '0';
      *str = '\0';
      return MP_OKAY;
   }

   if ((res = mp_init_copy(&t, a)) != MP_OKAY) {
      return res;
   }

   /* if it is negative output a - */
   if (t.sign == MP_NEG) {
      /* we have to reverse our digits later... but not the - sign!! */
      ++_s;

      /* store the flag and mark the number as positive */
      *str++ = '-';
      t.sign = MP_ZPOS;

      /* subtract a char */
      --maxlen;
   }

   digs = 0;
   while (mp_iszero(&t) == MP_NO) {
      if (--maxlen < 1) {
         /* no more room */
         break;
      }
      if ((res = mp_div_d(&t, (mp_digit)radix, &t, &d)) != MP_OKAY) {
         mp_clear(&t);
         return res;
      }
      *str++ = mp_s_rmap[d];
      ++digs;
   }

   /* reverse the digits of the string.  In this case _s points
    * to the first digit [exluding the sign] of the number
    */
   bn_reverse((unsigned char *)_s, digs);

   /* append a NULL so the string is properly terminated */
   *str = '\0';

   mp_clear(&t);
   return MP_OKAY;
}

#endif

/* ref:         HEAD -> master, tag: v1.1.0 */
/* git commit:  08549ad6bc8b0cede0b357a9c341c5c6473a9c55 */
/* commit time: 2019-01-28 20:32:32 +0100 */