• Home
  • Line#
  • Scopes#
  • Navigate#
  • Raw
  • Download
1 /* crypto/bn/bn_recp.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 
BN_RECP_CTX_init(BN_RECP_CTX * recp)63 void BN_RECP_CTX_init(BN_RECP_CTX *recp)
64 	{
65 	BN_init(&(recp->N));
66 	BN_init(&(recp->Nr));
67 	recp->num_bits=0;
68 	recp->flags=0;
69 	}
70 
BN_RECP_CTX_new(void)71 BN_RECP_CTX *BN_RECP_CTX_new(void)
72 	{
73 	BN_RECP_CTX *ret;
74 
75 	if ((ret=(BN_RECP_CTX *)OPENSSL_malloc(sizeof(BN_RECP_CTX))) == NULL)
76 		return(NULL);
77 
78 	BN_RECP_CTX_init(ret);
79 	ret->flags=BN_FLG_MALLOCED;
80 	return(ret);
81 	}
82 
BN_RECP_CTX_free(BN_RECP_CTX * recp)83 void BN_RECP_CTX_free(BN_RECP_CTX *recp)
84 	{
85 	if(recp == NULL)
86 	    return;
87 
88 	BN_free(&(recp->N));
89 	BN_free(&(recp->Nr));
90 	if (recp->flags & BN_FLG_MALLOCED)
91 		OPENSSL_free(recp);
92 	}
93 
BN_RECP_CTX_set(BN_RECP_CTX * recp,const BIGNUM * d,BN_CTX * ctx)94 int BN_RECP_CTX_set(BN_RECP_CTX *recp, const BIGNUM *d, BN_CTX *ctx)
95 	{
96 	if (!BN_copy(&(recp->N),d)) return 0;
97 	BN_zero(&(recp->Nr));
98 	recp->num_bits=BN_num_bits(d);
99 	recp->shift=0;
100 	return(1);
101 	}
102 
BN_mod_mul_reciprocal(BIGNUM * r,const BIGNUM * x,const BIGNUM * y,BN_RECP_CTX * recp,BN_CTX * ctx)103 int BN_mod_mul_reciprocal(BIGNUM *r, const BIGNUM *x, const BIGNUM *y,
104 	BN_RECP_CTX *recp, BN_CTX *ctx)
105 	{
106 	int ret=0;
107 	BIGNUM *a;
108 	const BIGNUM *ca;
109 
110 	BN_CTX_start(ctx);
111 	if ((a = BN_CTX_get(ctx)) == NULL) goto err;
112 	if (y != NULL)
113 		{
114 		if (x == y)
115 			{ if (!BN_sqr(a,x,ctx)) goto err; }
116 		else
117 			{ if (!BN_mul(a,x,y,ctx)) goto err; }
118 		ca = a;
119 		}
120 	else
121 		ca=x; /* Just do the mod */
122 
123 	ret = BN_div_recp(NULL,r,ca,recp,ctx);
124 err:
125 	BN_CTX_end(ctx);
126 	bn_check_top(r);
127 	return(ret);
128 	}
129 
BN_div_recp(BIGNUM * dv,BIGNUM * rem,const BIGNUM * m,BN_RECP_CTX * recp,BN_CTX * ctx)130 int BN_div_recp(BIGNUM *dv, BIGNUM *rem, const BIGNUM *m,
131 	BN_RECP_CTX *recp, BN_CTX *ctx)
132 	{
133 	int i,j,ret=0;
134 	BIGNUM *a,*b,*d,*r;
135 
136 	BN_CTX_start(ctx);
137 	a=BN_CTX_get(ctx);
138 	b=BN_CTX_get(ctx);
139 	if (dv != NULL)
140 		d=dv;
141 	else
142 		d=BN_CTX_get(ctx);
143 	if (rem != NULL)
144 		r=rem;
145 	else
146 		r=BN_CTX_get(ctx);
147 	if (a == NULL || b == NULL || d == NULL || r == NULL) goto err;
148 
149 	if (BN_ucmp(m,&(recp->N)) < 0)
150 		{
151 		BN_zero(d);
152 		if (!BN_copy(r,m)) return 0;
153 		BN_CTX_end(ctx);
154 		return(1);
155 		}
156 
157 	/* We want the remainder
158 	 * Given input of ABCDEF / ab
159 	 * we need multiply ABCDEF by 3 digests of the reciprocal of ab
160 	 *
161 	 */
162 
163 	/* i := max(BN_num_bits(m), 2*BN_num_bits(N)) */
164 	i=BN_num_bits(m);
165 	j=recp->num_bits<<1;
166 	if (j>i) i=j;
167 
168 	/* Nr := round(2^i / N) */
169 	if (i != recp->shift)
170 		recp->shift=BN_reciprocal(&(recp->Nr),&(recp->N),
171 			i,ctx); /* BN_reciprocal returns i, or -1 for an error */
172 	if (recp->shift == -1) goto err;
173 
174 	/* d := |round(round(m / 2^BN_num_bits(N)) * recp->Nr / 2^(i - BN_num_bits(N)))|
175 	 *    = |round(round(m / 2^BN_num_bits(N)) * round(2^i / N) / 2^(i - BN_num_bits(N)))|
176 	 *   <= |(m / 2^BN_num_bits(N)) * (2^i / N) * (2^BN_num_bits(N) / 2^i)|
177 	 *    = |m/N|
178 	 */
179 	if (!BN_rshift(a,m,recp->num_bits)) goto err;
180 	if (!BN_mul(b,a,&(recp->Nr),ctx)) goto err;
181 	if (!BN_rshift(d,b,i-recp->num_bits)) goto err;
182 	d->neg=0;
183 
184 	if (!BN_mul(b,&(recp->N),d,ctx)) goto err;
185 	if (!BN_usub(r,m,b)) goto err;
186 	r->neg=0;
187 
188 #if 1
189 	j=0;
190 	while (BN_ucmp(r,&(recp->N)) >= 0)
191 		{
192 		if (j++ > 2)
193 			{
194 			BNerr(BN_F_BN_DIV_RECP,BN_R_BAD_RECIPROCAL);
195 			goto err;
196 			}
197 		if (!BN_usub(r,r,&(recp->N))) goto err;
198 		if (!BN_add_word(d,1)) goto err;
199 		}
200 #endif
201 
202 	r->neg=BN_is_zero(r)?0:m->neg;
203 	d->neg=m->neg^recp->N.neg;
204 	ret=1;
205 err:
206 	BN_CTX_end(ctx);
207 	bn_check_top(dv);
208 	bn_check_top(rem);
209 	return(ret);
210 	}
211 
212 /* len is the expected size of the result
213  * We actually calculate with an extra word of precision, so
214  * we can do faster division if the remainder is not required.
215  */
216 /* r := 2^len / m */
BN_reciprocal(BIGNUM * r,const BIGNUM * m,int len,BN_CTX * ctx)217 int BN_reciprocal(BIGNUM *r, const BIGNUM *m, int len, BN_CTX *ctx)
218 	{
219 	int ret= -1;
220 	BIGNUM *t;
221 
222 	BN_CTX_start(ctx);
223 	if((t = BN_CTX_get(ctx)) == NULL) goto err;
224 
225 	if (!BN_set_bit(t,len)) goto err;
226 
227 	if (!BN_div(r,NULL,t,m,ctx)) goto err;
228 
229 	ret=len;
230 err:
231 	bn_check_top(r);
232 	BN_CTX_end(ctx);
233 	return(ret);
234 	}
235