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195 lines
4.5 KiB
C
195 lines
4.5 KiB
C
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/* mpi-mul.c - MPI functions
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* Copyright (C) 1994, 1996 Free Software Foundation, Inc.
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* Copyright (C) 1998, 2001 Free Software Foundation, Inc.
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*
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* This file is part of GnuPG.
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*
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* GnuPG is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* GnuPG is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
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*
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* Note: This code is heavily based on the GNU MP Library.
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* Actually it's the same code with only minor changes in the
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* way the data is stored; this is to support the abstraction
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* of an optional secure memory allocation which may be used
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* to avoid revealing of sensitive data due to paging etc.
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* The GNU MP Library itself is published under the LGPL;
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* however I decided to publish this code under the plain GPL.
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*/
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#include "mpi-internal.h"
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int mpi_mul_ui(MPI prod, MPI mult, unsigned long small_mult)
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{
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mpi_size_t size, prod_size;
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mpi_ptr_t prod_ptr;
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mpi_limb_t cy;
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int sign;
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size = mult->nlimbs;
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sign = mult->sign;
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if (!size || !small_mult) {
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prod->nlimbs = 0;
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prod->sign = 0;
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return 0;
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}
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prod_size = size + 1;
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if (prod->alloced < prod_size)
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if (mpi_resize(prod, prod_size) < 0)
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return -ENOMEM;
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prod_ptr = prod->d;
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cy = mpihelp_mul_1(prod_ptr, mult->d, size, (mpi_limb_t) small_mult);
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if (cy)
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prod_ptr[size++] = cy;
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prod->nlimbs = size;
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prod->sign = sign;
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return 0;
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}
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int mpi_mul_2exp(MPI w, MPI u, unsigned long cnt)
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{
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mpi_size_t usize, wsize, limb_cnt;
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mpi_ptr_t wp;
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mpi_limb_t wlimb;
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int usign, wsign;
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usize = u->nlimbs;
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usign = u->sign;
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if (!usize) {
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w->nlimbs = 0;
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w->sign = 0;
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return 0;
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}
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limb_cnt = cnt / BITS_PER_MPI_LIMB;
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wsize = usize + limb_cnt + 1;
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if (w->alloced < wsize)
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if (mpi_resize(w, wsize) < 0)
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return -ENOMEM;
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wp = w->d;
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wsize = usize + limb_cnt;
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wsign = usign;
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cnt %= BITS_PER_MPI_LIMB;
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if (cnt) {
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wlimb = mpihelp_lshift(wp + limb_cnt, u->d, usize, cnt);
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if (wlimb) {
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wp[wsize] = wlimb;
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wsize++;
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}
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} else {
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MPN_COPY_DECR(wp + limb_cnt, u->d, usize);
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}
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/* Zero all whole limbs at low end. Do it here and not before calling
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* mpn_lshift, not to lose for U == W. */
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MPN_ZERO(wp, limb_cnt);
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w->nlimbs = wsize;
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w->sign = wsign;
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return 0;
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}
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int mpi_mul(MPI w, MPI u, MPI v)
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{
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int rc = -ENOMEM;
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mpi_size_t usize, vsize, wsize;
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mpi_ptr_t up, vp, wp;
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mpi_limb_t cy;
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int usign, vsign, sign_product;
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int assign_wp = 0;
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mpi_ptr_t tmp_limb = NULL;
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if (u->nlimbs < v->nlimbs) { /* Swap U and V. */
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usize = v->nlimbs;
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usign = v->sign;
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up = v->d;
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vsize = u->nlimbs;
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vsign = u->sign;
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vp = u->d;
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} else {
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usize = u->nlimbs;
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usign = u->sign;
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up = u->d;
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vsize = v->nlimbs;
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vsign = v->sign;
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vp = v->d;
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}
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sign_product = usign ^ vsign;
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wp = w->d;
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/* Ensure W has space enough to store the result. */
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wsize = usize + vsize;
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if (w->alloced < (size_t) wsize) {
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if (wp == up || wp == vp) {
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wp = mpi_alloc_limb_space(wsize);
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if (!wp)
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goto nomem;
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assign_wp = 1;
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} else {
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if (mpi_resize(w, wsize) < 0)
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goto nomem;
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wp = w->d;
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}
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} else { /* Make U and V not overlap with W. */
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if (wp == up) {
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/* W and U are identical. Allocate temporary space for U. */
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up = tmp_limb = mpi_alloc_limb_space(usize);
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if (!up)
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goto nomem;
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/* Is V identical too? Keep it identical with U. */
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if (wp == vp)
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vp = up;
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/* Copy to the temporary space. */
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MPN_COPY(up, wp, usize);
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} else if (wp == vp) {
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/* W and V are identical. Allocate temporary space for V. */
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vp = tmp_limb = mpi_alloc_limb_space(vsize);
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if (!vp)
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goto nomem;
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/* Copy to the temporary space. */
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MPN_COPY(vp, wp, vsize);
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}
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}
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if (!vsize)
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wsize = 0;
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else {
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if (mpihelp_mul(wp, up, usize, vp, vsize, &cy) < 0)
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goto nomem;
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wsize -= cy ? 0 : 1;
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}
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if (assign_wp)
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mpi_assign_limb_space(w, wp, wsize);
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w->nlimbs = wsize;
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w->sign = sign_product;
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rc = 0;
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nomem:
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if (tmp_limb)
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mpi_free_limb_space(tmp_limb);
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return rc;
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}
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int mpi_mulm(MPI w, MPI u, MPI v, MPI m)
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{
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if (mpi_mul(w, u, v) < 0)
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return -ENOMEM;
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return mpi_fdiv_r(w, w, m);
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}
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