| [25] | 1 | #include <tommath.h> |
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| 2 | #ifdef BN_MP_MUL_C |
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| 3 | /* LibTomMath, multiple-precision integer library -- Tom St Denis |
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| 4 | * |
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| 5 | * LibTomMath is a library that provides multiple-precision |
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| 6 | * integer arithmetic as well as number theoretic functionality. |
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| 7 | * |
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| 8 | * The library was designed directly after the MPI library by |
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| 9 | * Michael Fromberger but has been written from scratch with |
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| 10 | * additional optimizations in place. |
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| 11 | * |
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| 12 | * The library is free for all purposes without any express |
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| 13 | * guarantee it works. |
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| 14 | * |
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| 15 | * Tom St Denis, tomstdenis@gmail.com, http://math.libtomcrypt.com |
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| 16 | */ |
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| 17 | |
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| 18 | /* high level multiplication (handles sign) */ |
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| 19 | int mp_mul (mp_int * a, mp_int * b, mp_int * c) |
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| 20 | { |
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| 21 | int res, neg; |
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| 22 | neg = (a->sign == b->sign) ? MP_ZPOS : MP_NEG; |
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| 23 | |
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| 24 | /* use Toom-Cook? */ |
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| 25 | #ifdef BN_MP_TOOM_MUL_C |
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| 26 | if (MIN (a->used, b->used) >= TOOM_MUL_CUTOFF) { |
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| 27 | res = mp_toom_mul(a, b, c); |
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| 28 | } else |
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| 29 | #endif |
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| 30 | #ifdef BN_MP_KARATSUBA_MUL_C |
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| 31 | /* use Karatsuba? */ |
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| 32 | if (MIN (a->used, b->used) >= KARATSUBA_MUL_CUTOFF) { |
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| 33 | res = mp_karatsuba_mul (a, b, c); |
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| 34 | } else |
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| 35 | #endif |
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| 36 | { |
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| 37 | /* can we use the fast multiplier? |
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| 38 | * |
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| 39 | * The fast multiplier can be used if the output will |
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| 40 | * have less than MP_WARRAY digits and the number of |
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| 41 | * digits won't affect carry propagation |
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| 42 | */ |
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| 43 | int digs = a->used + b->used + 1; |
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| 44 | |
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| 45 | #ifdef BN_FAST_S_MP_MUL_DIGS_C |
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| 46 | if ((digs < MP_WARRAY) && |
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| 47 | MIN(a->used, b->used) <= |
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| 48 | (1 << ((CHAR_BIT * sizeof (mp_word)) - (2 * DIGIT_BIT)))) { |
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| 49 | res = fast_s_mp_mul_digs (a, b, c, digs); |
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| 50 | } else |
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| 51 | #endif |
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| 52 | #ifdef BN_S_MP_MUL_DIGS_C |
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| 53 | res = s_mp_mul (a, b, c); /* uses s_mp_mul_digs */ |
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| 54 | #else |
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| 55 | res = MP_VAL; |
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| 56 | #endif |
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| 57 | |
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| 58 | } |
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| 59 | c->sign = (c->used > 0) ? neg : MP_ZPOS; |
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| 60 | return res; |
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| 61 | } |
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| 62 | #endif |
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| 63 | |
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| 64 | /* $Source: /cvsroot/tcl/libtommath/bn_mp_mul.c,v $ */ |
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| 65 | /* $Revision: 1.1.1.3 $ */ |
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| 66 | /* $Date: 2006/12/01 00:08:11 $ */ |
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