#include #ifdef BN_MP_EXPT_D_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. * * The library is free for all purposes without any express * guarantee it works. * * Tom St Denis, tomstdenis@gmail.com, http://math.libtomcrypt.com */ /* calculate c = a**b using a square-multiply algorithm */ int mp_expt_d (mp_int * a, mp_digit b, mp_int * c) { int res, x; mp_int g; if ((res = mp_init_copy (&g, a)) != MP_OKAY) { return res; } /* set initial result */ mp_set (c, 1); for (x = 0; x < (int) DIGIT_BIT; x++) { /* square */ if ((res = mp_sqr (c, c)) != MP_OKAY) { mp_clear (&g); return res; } /* if the bit is set multiply */ if ((b & (mp_digit) (((mp_digit)1) << (DIGIT_BIT - 1))) != 0) { if ((res = mp_mul (c, &g, c)) != MP_OKAY) { mp_clear (&g); return res; } } /* shift to next bit */ b <<= 1; } mp_clear (&g); return MP_OKAY; } #endif /* $Source: /cvsroot/tcl/libtommath/bn_mp_expt_d.c,v $ */ /* $Revision: 1.1.1.3 $ */ /* $Date: 2006/12/01 00:08:11 $ */