view libtommath/bn_mp_radix_size.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 1051e4eea25a
line wrap: on
line source

#include "tommath_private.h"
#ifdef BN_MP_RADIX_SIZE_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
 */

/* returns size of ASCII reprensentation */
int mp_radix_size(const mp_int *a, int radix, int *size)
{
   int     res, digs;
   mp_int  t;
   mp_digit d;

   *size = 0;

   /* make sure the radix is in range */
   if ((radix < 2) || (radix > 64)) {
      return MP_VAL;
   }

   if (mp_iszero(a) == MP_YES) {
      *size = 2;
      return MP_OKAY;
   }

   /* special case for binary */
   if (radix == 2) {
      *size = mp_count_bits(a) + ((a->sign == MP_NEG) ? 1 : 0) + 1;
      return MP_OKAY;
   }

   /* digs is the digit count */
   digs = 0;

   /* if it's negative add one for the sign */
   if (a->sign == MP_NEG) {
      ++digs;
   }

   /* init a copy of the input */
   if ((res = mp_init_copy(&t, a)) != MP_OKAY) {
      return res;
   }

   /* force temp to positive */
   t.sign = MP_ZPOS;

   /* fetch out all of the digits */
   while (mp_iszero(&t) == MP_NO) {
      if ((res = mp_div_d(&t, (mp_digit)radix, &t, &d)) != MP_OKAY) {
         mp_clear(&t);
         return res;
      }
      ++digs;
   }
   mp_clear(&t);

   /* return digs + 1, the 1 is for the NULL byte that would be required. */
   *size = digs + 1;
   return MP_OKAY;
}

#endif

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