diff options
Diffstat (limited to 'comm/third_party/libgcrypt/mpi/mpi-mpow.c')
| -rw-r--r-- | comm/third_party/libgcrypt/mpi/mpi-mpow.c | 223 |
1 files changed, 223 insertions, 0 deletions
diff --git a/comm/third_party/libgcrypt/mpi/mpi-mpow.c b/comm/third_party/libgcrypt/mpi/mpi-mpow.c new file mode 100644 index 0000000000..43bd641fb5 --- /dev/null +++ b/comm/third_party/libgcrypt/mpi/mpi-mpow.c @@ -0,0 +1,223 @@ +/* mpi-mpow.c - MPI functions + * Copyright (C) 1998, 1999, 2001, 2002, 2003 Free Software Foundation, Inc. + * + * This file is part of Libgcrypt. + * + * Libgcrypt is free software; you can redistribute it and/or modify + * it under the terms of the GNU Lesser General Public License as + * published by the Free Software Foundation; either version 2.1 of + * the License, or (at your option) any later version. + * + * Libgcrypt is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with this program; if not, write to the Free Software + * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA + */ + +#include <config.h> +#include <stdio.h> +#include <stdlib.h> + +#include "mpi-internal.h" +#include "longlong.h" +#include "g10lib.h" + + +/* Barrett is slower than the classical way. It can be tweaked by + * using partial multiplications + */ +/*#define USE_BARRETT*/ + + + +#ifdef USE_BARRETT +static void barrett_mulm( gcry_mpi_t w, gcry_mpi_t u, gcry_mpi_t v, gcry_mpi_t m, gcry_mpi_t y, int k, gcry_mpi_t r1, gcry_mpi_t r2 ); +static gcry_mpi_t init_barrett( gcry_mpi_t m, int *k, gcry_mpi_t *r1, gcry_mpi_t *r2 ); +static int calc_barrett( gcry_mpi_t r, gcry_mpi_t x, gcry_mpi_t m, gcry_mpi_t y, int k, gcry_mpi_t r1, gcry_mpi_t r2 ); +#else +#define barrett_mulm( w, u, v, m, y, k, r1, r2 ) _gcry_mpi_mulm( (w), (u), (v), (m) ) +#endif + + +static int +build_index( gcry_mpi_t *exparray, int k, int i, int t ) +{ + int j, bitno; + int idx = 0; + + bitno = t-i; + for(j=k-1; j >= 0; j-- ) { + idx <<= 1; + if( mpi_test_bit( exparray[j], bitno ) ) + idx |= 1; + } + /*log_debug("t=%d i=%d idx=%d\n", t, i, idx );*/ + return idx; +} + +/**************** + * RES = (BASE[0] ^ EXP[0]) * (BASE[1] ^ EXP[1]) * ... * mod M + */ +void +_gcry_mpi_mulpowm( gcry_mpi_t res, gcry_mpi_t *basearray, gcry_mpi_t *exparray, gcry_mpi_t m) +{ + int k; /* number of elements */ + int t; /* bit size of largest exponent */ + int i, j, idx; + gcry_mpi_t *G; /* table with precomputed values of size 2^k */ + gcry_mpi_t tmp; +#ifdef USE_BARRETT + gcry_mpi_t barrett_y, barrett_r1, barrett_r2; + int barrett_k; +#endif + + for(k=0; basearray[k]; k++ ) + ; + gcry_assert(k); + for(t=0, i=0; (tmp=exparray[i]); i++ ) { + /*log_mpidump("exp: ", tmp );*/ + j = mpi_get_nbits(tmp); + if( j > t ) + t = j; + } + /*log_mpidump("mod: ", m );*/ + gcry_assert (i==k); + gcry_assert (t); + gcry_assert (k < 10); + + G = xcalloc( (1<<k) , sizeof *G ); +#ifdef USE_BARRETT + barrett_y = init_barrett( m, &barrett_k, &barrett_r1, &barrett_r2 ); +#endif + /* and calculate */ + tmp = mpi_alloc( mpi_get_nlimbs(m)+1 ); + mpi_set_ui( res, 1 ); + for(i = 1; i <= t; i++ ) { + barrett_mulm(tmp, res, res, m, barrett_y, barrett_k, + barrett_r1, barrett_r2 ); + idx = build_index( exparray, k, i, t ); + gcry_assert (idx >= 0 && idx < (1<<k)); + if( !G[idx] ) { + if( !idx ) + G[0] = mpi_alloc_set_ui( 1 ); + else { + for(j=0; j < k; j++ ) { + if( (idx & (1<<j) ) ) { + if( !G[idx] ) + G[idx] = mpi_copy( basearray[j] ); + else + barrett_mulm( G[idx], G[idx], basearray[j], + m, barrett_y, barrett_k, barrett_r1, barrett_r2 ); + } + } + if( !G[idx] ) + G[idx] = mpi_alloc(0); + } + } + barrett_mulm(res, tmp, G[idx], m, barrett_y, barrett_k, barrett_r1, barrett_r2 ); + } + + /* cleanup */ + mpi_free(tmp); +#ifdef USE_BARRETT + mpi_free(barrett_y); + mpi_free(barrett_r1); + mpi_free(barrett_r2); +#endif + for(i=0; i < (1<<k); i++ ) + mpi_free(G[i]); + xfree(G); +} + + + +#ifdef USE_BARRETT +static void +barrett_mulm( gcry_mpi_t w, gcry_mpi_t u, gcry_mpi_t v, gcry_mpi_t m, gcry_mpi_t y, int k, gcry_mpi_t r1, gcry_mpi_t r2 ) +{ + mpi_mul(w, u, v); + if( calc_barrett( w, w, m, y, k, r1, r2 ) ) + mpi_fdiv_r( w, w, m ); +} + +/**************** + * Barrett precalculation: y = floor(b^(2k) / m) + */ +static gcry_mpi_t +init_barrett( gcry_mpi_t m, int *k, gcry_mpi_t *r1, gcry_mpi_t *r2 ) +{ + gcry_mpi_t tmp; + + mpi_normalize( m ); + *k = mpi_get_nlimbs( m ); + tmp = mpi_alloc( *k + 1 ); + mpi_set_ui( tmp, 1 ); + mpi_lshift_limbs( tmp, 2 * *k ); + mpi_fdiv_q( tmp, tmp, m ); + *r1 = mpi_alloc( 2* *k + 1 ); + *r2 = mpi_alloc( 2* *k + 1 ); + return tmp; +} + +/**************** + * Barrett reduction: We assume that these conditions are met: + * Given x =(x_2k-1 ...x_0)_b + * m =(m_k-1 ....m_0)_b with m_k-1 != 0 + * Output r = x mod m + * Before using this function init_barret must be used to calucalte y and k. + * Returns: false = no error + * true = can't perform barret reduction + */ +static int +calc_barrett( gcry_mpi_t r, gcry_mpi_t x, gcry_mpi_t m, gcry_mpi_t y, int k, gcry_mpi_t r1, gcry_mpi_t r2 ) +{ + int xx = k > 3 ? k-3:0; + + mpi_normalize( x ); + if( mpi_get_nlimbs(x) > 2*k ) + return 1; /* can't do it */ + + /* 1. q1 = floor( x / b^k-1) + * q2 = q1 * y + * q3 = floor( q2 / b^k+1 ) + * Actually, we don't need qx, we can work direct on r2 + */ + mpi_set( r2, x ); + mpi_rshift_limbs( r2, k-1 ); + mpi_mul( r2, r2, y ); + mpi_rshift_limbs( r2, k+1 ); + + /* 2. r1 = x mod b^k+1 + * r2 = q3 * m mod b^k+1 + * r = r1 - r2 + * 3. if r < 0 then r = r + b^k+1 + */ + mpi_set( r1, x ); + if( r1->nlimbs > k+1 ) /* quick modulo operation */ + r1->nlimbs = k+1; + mpi_mul( r2, r2, m ); + if( r2->nlimbs > k+1 ) /* quick modulo operation */ + r2->nlimbs = k+1; + mpi_sub( r, r1, r2 ); + + if( mpi_has_sign (r) ) { + gcry_mpi_t tmp; + + tmp = mpi_alloc( k + 2 ); + mpi_set_ui( tmp, 1 ); + mpi_lshift_limbs( tmp, k+1 ); + mpi_add( r, r, tmp ); + mpi_free(tmp); + } + + /* 4. while r >= m do r = r - m */ + while( mpi_cmp( r, m ) >= 0 ) + mpi_sub( r, r, m ); + + return 0; +} +#endif /* USE_BARRETT */ |