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annotate bn_mp_reduce_setup.c @ 1:22d5cf7d4b1a libtommath

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author Matt Johnston <matt@ucc.asn.au>
date Mon, 31 May 2004 18:23:46 +0000
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1 /* LibTomMath, multiple-precision integer library -- Tom St Denis
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2 *
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3 * LibTomMath is a library that provides multiple-precision
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4 * integer arithmetic as well as number theoretic functionality.
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5 *
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6 * The library was designed directly after the MPI library by
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7 * Michael Fromberger but has been written from scratch with
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8 * additional optimizations in place.
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9 *
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10 * The library is free for all purposes without any express
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11 * guarantee it works.
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12 *
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13 * Tom St Denis, [email protected], http://math.libtomcrypt.org
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14 */
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15 #include <tommath.h>
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16
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17 /* pre-calculate the value required for Barrett reduction
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18 * For a given modulus "b" it calulates the value required in "a"
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19 */
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20 int
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21 mp_reduce_setup (mp_int * a, mp_int * b)
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22 {
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23 int res;
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24
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25 if ((res = mp_2expt (a, b->used * 2 * DIGIT_BIT)) != MP_OKAY) {
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26 return res;
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27 }
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28 return mp_div (a, b, a, NULL);
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29 }