ecdh works against OpenSSH
author Matt Johnston Mon, 08 Apr 2013 23:12:20 +0800 5ff8218bcee9 60fc6476e044
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```#include <tommath.h>
/* 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
*
* The library is free for all purposes without any express
* guarantee it works.
*
* Tom St Denis, [email protected], http://math.libtomcrypt.com
*/

/* returns size of ASCII reprensentation */
{
int     res, digs;
mp_int  t;
mp_digit d;

*size = 0;

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

/* make sure the radix is in range */
return MP_VAL;
}

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