Mercurial > dropbear
view bn_mp_reduce_is_2k.c @ 145:a96ff234ff19 libtommath
propagate of fc94c38452d9fd684a8e1eb9e3a73120aac0d38f and 3e4de4cbef3d9035a7b2f0c25e9f86e297f9f6d1 from branch 'au.asn.ucc.matt.ltm-orig' to 'au.asn.ucc.matt.ltm-db'
author | Matt Johnston <matt@ucc.asn.au> |
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date | Sun, 19 Dec 2004 15:57:19 +0000 |
parents | d29b64170cf0 |
children | d8254fc979e9 |
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#include <tommath.h> #ifdef BN_MP_REDUCE_IS_2K_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, [email protected], http://math.libtomcrypt.org */ /* determines if mp_reduce_2k can be used */ int mp_reduce_is_2k(mp_int *a) { int ix, iy, iw; mp_digit iz; if (a->used == 0) { return 0; } else if (a->used == 1) { return 1; } else if (a->used > 1) { iy = mp_count_bits(a); iz = 1; iw = 1; /* Test every bit from the second digit up, must be 1 */ for (ix = DIGIT_BIT; ix < iy; ix++) { if ((a->dp[iw] & iz) == 0) { return 0; } iz <<= 1; if (iz > (mp_digit)MP_MASK) { ++iw; iz = 1; } } } return 1; } #endif