1 /* mpi-mul.c  -  MPI functions
2  * Copyright (C) 1994, 1996, 1998, 2001, 2002,
3  *               2003 Free Software Foundation, Inc.
4  *
5  * This file is part of Libgcrypt.
6  *
7  * Note: This code is heavily based on the GNU MP Library.
8  *	 Actually it's the same code with only minor changes in the
9  *	 way the data is stored; this is to support the abstraction
10  *	 of an optional secure memory allocation which may be used
11  *	 to avoid revealing of sensitive data due to paging etc.
12  */
13 
14 #include "mpi-internal.h"
15 
mpi_mul(MPI w,MPI u,MPI v)16 void mpi_mul(MPI w, MPI u, MPI v)
17 {
18 	mpi_size_t usize, vsize, wsize;
19 	mpi_ptr_t up, vp, wp;
20 	mpi_limb_t cy;
21 	int usign, vsign, sign_product;
22 	int assign_wp = 0;
23 	mpi_ptr_t tmp_limb = NULL;
24 
25 	if (u->nlimbs < v->nlimbs) {
26 		/* Swap U and V. */
27 		usize = v->nlimbs;
28 		usign = v->sign;
29 		up    = v->d;
30 		vsize = u->nlimbs;
31 		vsign = u->sign;
32 		vp    = u->d;
33 	} else {
34 		usize = u->nlimbs;
35 		usign = u->sign;
36 		up    = u->d;
37 		vsize = v->nlimbs;
38 		vsign = v->sign;
39 		vp    = v->d;
40 	}
41 	sign_product = usign ^ vsign;
42 	wp = w->d;
43 
44 	/* Ensure W has space enough to store the result.  */
45 	wsize = usize + vsize;
46 	if (w->alloced < wsize) {
47 		if (wp == up || wp == vp) {
48 			wp = mpi_alloc_limb_space(wsize);
49 			assign_wp = 1;
50 		} else {
51 			mpi_resize(w, wsize);
52 			wp = w->d;
53 		}
54 	} else { /* Make U and V not overlap with W.	*/
55 		if (wp == up) {
56 			/* W and U are identical.  Allocate temporary space for U. */
57 			up = tmp_limb = mpi_alloc_limb_space(usize);
58 			/* Is V identical too?  Keep it identical with U.  */
59 			if (wp == vp)
60 				vp = up;
61 			/* Copy to the temporary space.  */
62 			MPN_COPY(up, wp, usize);
63 		} else if (wp == vp) {
64 			/* W and V are identical.  Allocate temporary space for V. */
65 			vp = tmp_limb = mpi_alloc_limb_space(vsize);
66 			/* Copy to the temporary space.  */
67 			MPN_COPY(vp, wp, vsize);
68 		}
69 	}
70 
71 	if (!vsize)
72 		wsize = 0;
73 	else {
74 		mpihelp_mul(wp, up, usize, vp, vsize, &cy);
75 		wsize -= cy ? 0:1;
76 	}
77 
78 	if (assign_wp)
79 		mpi_assign_limb_space(w, wp, wsize);
80 	w->nlimbs = wsize;
81 	w->sign = sign_product;
82 	if (tmp_limb)
83 		mpi_free_limb_space(tmp_limb);
84 }
85 EXPORT_SYMBOL_GPL(mpi_mul);
86 
mpi_mulm(MPI w,MPI u,MPI v,MPI m)87 void mpi_mulm(MPI w, MPI u, MPI v, MPI m)
88 {
89 	mpi_mul(w, u, v);
90 	mpi_tdiv_r(w, w, m);
91 }
92 EXPORT_SYMBOL_GPL(mpi_mulm);
93