92 строки
2.1 KiB
C
92 строки
2.1 KiB
C
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/* mpi-mul.c - MPI functions
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* Copyright (C) 1994, 1996, 1998, 2001, 2002,
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* 2003 Free Software Foundation, Inc.
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*
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* This file is part of Libgcrypt.
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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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*/
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#include "mpi-internal.h"
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void mpi_mul(MPI w, MPI u, MPI v)
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{
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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) {
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/* 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 < wsize) {
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if (wp == up || wp == vp) {
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wp = mpi_alloc_limb_space(wsize);
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assign_wp = 1;
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} else {
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mpi_resize(w, wsize);
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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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/* 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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/* 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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mpihelp_mul(wp, up, usize, vp, vsize, &cy);
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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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if (tmp_limb)
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mpi_free_limb_space(tmp_limb);
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}
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void mpi_mulm(MPI w, MPI u, MPI v, MPI m)
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{
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mpi_mul(w, u, v);
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mpi_tdiv_r(w, w, m);
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}
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EXPORT_SYMBOL_GPL(mpi_mulm);
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