Mercurial > dropbear
diff bn_mp_rand.c @ 1:22d5cf7d4b1a libtommath
Renaming branch
author | Matt Johnston <matt@ucc.asn.au> |
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date | Mon, 31 May 2004 18:23:46 +0000 |
parents | |
children | d29b64170cf0 |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/bn_mp_rand.c Mon May 31 18:23:46 2004 +0000 @@ -0,0 +1,49 @@ +/* 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. + * + * The library is free for all purposes without any express + * guarantee it works. + * + * Tom St Denis, [email protected], http://math.libtomcrypt.org + */ +#include <tommath.h> + +/* makes a pseudo-random int of a given size */ +int +mp_rand (mp_int * a, int digits) +{ + int res; + mp_digit d; + + mp_zero (a); + if (digits <= 0) { + return MP_OKAY; + } + + /* first place a random non-zero digit */ + do { + d = ((mp_digit) abs (rand ())); + } while (d == 0); + + if ((res = mp_add_d (a, d, a)) != MP_OKAY) { + return res; + } + + while (digits-- > 0) { + if ((res = mp_lshd (a, 1)) != MP_OKAY) { + return res; + } + + if ((res = mp_add_d (a, ((mp_digit) abs (rand ())), a)) != MP_OKAY) { + return res; + } + } + + return MP_OKAY; +}