1 /* crypto/bn/bn_word.c */
2 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
3 * All rights reserved.
4 *
5 * This package is an SSL implementation written
6 * by Eric Young (eay@cryptsoft.com).
7 * The implementation was written so as to conform with Netscapes SSL.
8 *
9 * This library is free for commercial and non-commercial use as long as
10 * the following conditions are aheared to. The following conditions
11 * apply to all code found in this distribution, be it the RC4, RSA,
12 * lhash, DES, etc., code; not just the SSL code. The SSL documentation
13 * included with this distribution is covered by the same copyright terms
14 * except that the holder is Tim Hudson (tjh@cryptsoft.com).
15 *
16 * Copyright remains Eric Young's, and as such any Copyright notices in
17 * the code are not to be removed.
18 * If this package is used in a product, Eric Young should be given attribution
19 * as the author of the parts of the library used.
20 * This can be in the form of a textual message at program startup or
21 * in documentation (online or textual) provided with the package.
22 *
23 * Redistribution and use in source and binary forms, with or without
24 * modification, are permitted provided that the following conditions
25 * are met:
26 * 1. Redistributions of source code must retain the copyright
27 * notice, this list of conditions and the following disclaimer.
28 * 2. Redistributions in binary form must reproduce the above copyright
29 * notice, this list of conditions and the following disclaimer in the
30 * documentation and/or other materials provided with the distribution.
31 * 3. All advertising materials mentioning features or use of this software
32 * must display the following acknowledgement:
33 * "This product includes cryptographic software written by
34 * Eric Young (eay@cryptsoft.com)"
35 * The word 'cryptographic' can be left out if the rouines from the library
36 * being used are not cryptographic related :-).
37 * 4. If you include any Windows specific code (or a derivative thereof) from
38 * the apps directory (application code) you must include an acknowledgement:
39 * "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
40 *
41 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
42 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
43 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
44 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
45 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
46 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
47 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
48 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
49 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
50 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
51 * SUCH DAMAGE.
52 *
53 * The licence and distribution terms for any publically available version or
54 * derivative of this code cannot be changed. i.e. this code cannot simply be
55 * copied and put under another distribution licence
56 * [including the GNU Public Licence.]
57 */
58
59 #include <stdio.h>
60 #include "cryptlib.h"
61 #include "bn_lcl.h"
62
63 BN_ULONG BN_mod_word(const BIGNUM *a, BN_ULONG w)
64 {
65 #ifndef BN_LLONG
66 BN_ULONG ret=0;
67 #else
68 BN_ULLONG ret=0;
69 #endif
70 int i;
71
72 if (w == 0)
73 return (BN_ULONG)-1;
74
75 bn_check_top(a);
76 w&=BN_MASK2;
77 for (i=a->top-1; i>=0; i--)
78 {
79 #ifndef BN_LLONG
80 ret=((ret<<BN_BITS4)|((a->d[i]>>BN_BITS4)&BN_MASK2l))%w;
81 ret=((ret<<BN_BITS4)|(a->d[i]&BN_MASK2l))%w;
82 #else
83 ret=(BN_ULLONG)(((ret<<(BN_ULLONG)BN_BITS2)|a->d[i])%
84 (BN_ULLONG)w);
85 #endif
86 }
87 return((BN_ULONG)ret);
88 }
89
90 BN_ULONG BN_div_word(BIGNUM *a, BN_ULONG w)
91 {
92 BN_ULONG ret = 0;
93 int i, j;
94
95 bn_check_top(a);
96 w &= BN_MASK2;
97
98 if (!w)
99 /* actually this an error (division by zero) */
100 return (BN_ULONG)-1;
101 if (a->top == 0)
102 return 0;
103
104 /* normalize input (so bn_div_words doesn't complain) */
105 j = BN_BITS2 - BN_num_bits_word(w);
106 w <<= j;
107 if (!BN_lshift(a, a, j))
108 return (BN_ULONG)-1;
109
110 for (i=a->top-1; i>=0; i--)
111 {
112 BN_ULONG l,d;
113
114 l=a->d[i];
115 d=bn_div_words(ret,l,w);
116 ret=(l-((d*w)&BN_MASK2))&BN_MASK2;
117 a->d[i]=d;
118 }
119 if ((a->top > 0) && (a->d[a->top-1] == 0))
120 a->top--;
121 ret >>= j;
122 bn_check_top(a);
123 return(ret);
124 }
125
126 int BN_add_word(BIGNUM *a, BN_ULONG w)
127 {
128 BN_ULONG l;
129 int i;
130
131 bn_check_top(a);
132 w &= BN_MASK2;
133
134 /* degenerate case: w is zero */
135 if (!w) return 1;
136 /* degenerate case: a is zero */
137 if(BN_is_zero(a)) return BN_set_word(a, w);
138 /* handle 'a' when negative */
139 if (a->neg)
140 {
141 a->neg=0;
142 i=BN_sub_word(a,w);
143 if (!BN_is_zero(a))
144 a->neg=!(a->neg);
145 return(i);
146 }
147 for (i=0;w!=0 && i<a->top;i++)
148 {
149 a->d[i] = l = (a->d[i]+w)&BN_MASK2;
150 w = (w>l)?1:0;
151 }
152 if (w && i==a->top)
153 {
154 if (bn_wexpand(a,a->top+1) == NULL) return 0;
155 a->top++;
156 a->d[i]=w;
157 }
158 bn_check_top(a);
159 return(1);
160 }
161
162 int BN_sub_word(BIGNUM *a, BN_ULONG w)
163 {
164 int i;
165
166 bn_check_top(a);
167 w &= BN_MASK2;
168
169 /* degenerate case: w is zero */
170 if (!w) return 1;
171 /* degenerate case: a is zero */
172 if(BN_is_zero(a))
173 {
174 i = BN_set_word(a,w);
175 if (i != 0)
176 BN_set_negative(a, 1);
177 return i;
178 }
179 /* handle 'a' when negative */
180 if (a->neg)
181 {
182 a->neg=0;
183 i=BN_add_word(a,w);
184 a->neg=1;
185 return(i);
186 }
187
188 if ((a->top == 1) && (a->d[0] < w))
189 {
190 a->d[0]=w-a->d[0];
191 a->neg=1;
192 return(1);
193 }
194 i=0;
195 for (;;)
196 {
197 if (a->d[i] >= w)
198 {
199 a->d[i]-=w;
200 break;
201 }
202 else
203 {
204 a->d[i]=(a->d[i]-w)&BN_MASK2;
205 i++;
206 w=1;
207 }
208 }
209 if ((a->d[i] == 0) && (i == (a->top-1)))
210 a->top--;
211 bn_check_top(a);
212 return(1);
213 }
214
215 int BN_mul_word(BIGNUM *a, BN_ULONG w)
216 {
217 BN_ULONG ll;
218
219 bn_check_top(a);
220 w&=BN_MASK2;
221 if (a->top)
222 {
223 if (w == 0)
224 BN_zero(a);
225 else
226 {
227 ll=bn_mul_words(a->d,a->d,a->top,w);
228 if (ll)
229 {
230 if (bn_wexpand(a,a->top+1) == NULL) return(0);
231 a->d[a->top++]=ll;
232 }
233 }
234 }
235 bn_check_top(a);
236 return(1);
237 }