1 /* crypto/ec/ec2_mult.c */
2 /* ====================================================================
3 * Copyright 2002 Sun Microsystems, Inc. ALL RIGHTS RESERVED.
5 * The Elliptic Curve Public-Key Crypto Library (ECC Code) included
6 * herein is developed by SUN MICROSYSTEMS, INC., and is contributed
7 * to the OpenSSL project.
9 * The ECC Code is licensed pursuant to the OpenSSL open source
10 * license provided below.
12 * The software is originally written by Sheueling Chang Shantz and
13 * Douglas Stebila of Sun Microsystems Laboratories.
16 /* ====================================================================
17 * Copyright (c) 1998-2002 The OpenSSL Project. All rights reserved.
19 * Redistribution and use in source and binary forms, with or without
20 * modification, are permitted provided that the following conditions
23 * 1. Redistributions of source code must retain the above copyright
24 * notice, this list of conditions and the following disclaimer.
26 * 2. Redistributions in binary form must reproduce the above copyright
27 * notice, this list of conditions and the following disclaimer in
28 * the documentation and/or other materials provided with the
31 * 3. All advertising materials mentioning features or use of this
32 * software must display the following acknowledgment:
33 * "This product includes software developed by the OpenSSL Project
34 * for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
36 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
37 * endorse or promote products derived from this software without
38 * prior written permission. For written permission, please contact
39 * openssl-core@openssl.org.
41 * 5. Products derived from this software may not be called "OpenSSL"
42 * nor may "OpenSSL" appear in their names without prior written
43 * permission of the OpenSSL Project.
45 * 6. Redistributions of any form whatsoever must retain the following
47 * "This product includes software developed by the OpenSSL Project
48 * for use in the OpenSSL Toolkit (http://www.openssl.org/)"
50 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
51 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
52 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
53 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR
54 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
55 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
56 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
57 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
58 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
59 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
60 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
61 * OF THE POSSIBILITY OF SUCH DAMAGE.
62 * ====================================================================
64 * This product includes cryptographic software written by Eric Young
65 * (eay@cryptsoft.com). This product includes software written by Tim
66 * Hudson (tjh@cryptsoft.com).
70 #include <openssl/err.h>
75 /* Compute the x-coordinate x/z for the point 2*(x/z) in Montgomery projective
77 * Uses algorithm Mdouble in appendix of
78 * Lopez, J. and Dahab, R. "Fast multiplication on elliptic curves over
79 * GF(2^m) without precomputation".
80 * modified to not require precomputation of c=b^{2^{m-1}}.
82 static int Mdouble(const EC_GROUP *group, BIGNUM *x, BIGNUM *z, BN_CTX *ctx)
87 /* Since Mdouble is static we can guarantee that ctx != NULL. */
90 if (t1 == NULL) goto err;
92 if (!group->meth->field_sqr(group, x, x, ctx)) goto err;
93 if (!group->meth->field_sqr(group, t1, z, ctx)) goto err;
94 if (!group->meth->field_mul(group, z, x, t1, ctx)) goto err;
95 if (!group->meth->field_sqr(group, x, x, ctx)) goto err;
96 if (!group->meth->field_sqr(group, t1, t1, ctx)) goto err;
97 if (!group->meth->field_mul(group, t1, &group->b, t1, ctx)) goto err;
98 if (!BN_GF2m_add(x, x, t1)) goto err;
107 /* Compute the x-coordinate x1/z1 for the point (x1/z1)+(x2/x2) in Montgomery
108 * projective coordinates.
109 * Uses algorithm Madd in appendix of
110 * Lopex, J. and Dahab, R. "Fast multiplication on elliptic curves over
111 * GF(2^m) without precomputation".
113 static int Madd(const EC_GROUP *group, const BIGNUM *x, BIGNUM *x1, BIGNUM *z1,
114 const BIGNUM *x2, const BIGNUM *z2, BN_CTX *ctx)
119 /* Since Madd is static we can guarantee that ctx != NULL. */
121 t1 = BN_CTX_get(ctx);
122 t2 = BN_CTX_get(ctx);
123 if (t2 == NULL) goto err;
125 if (!BN_copy(t1, x)) goto err;
126 if (!group->meth->field_mul(group, x1, x1, z2, ctx)) goto err;
127 if (!group->meth->field_mul(group, z1, z1, x2, ctx)) goto err;
128 if (!group->meth->field_mul(group, t2, x1, z1, ctx)) goto err;
129 if (!BN_GF2m_add(z1, z1, x1)) goto err;
130 if (!group->meth->field_sqr(group, z1, z1, ctx)) goto err;
131 if (!group->meth->field_mul(group, x1, z1, t1, ctx)) goto err;
132 if (!BN_GF2m_add(x1, x1, t2)) goto err;
141 /* Compute the affine coordinates x2, y2=z2 for the point (x1/z1) and (x2/x2) in
142 * Montgomery projective coordinates.
143 * Uses algorithm Mxy in appendix of
144 * Lopex, J. and Dahab, R. "Fast multiplication on elliptic curves over
145 * GF(2^m) without precomputation".
148 * 1 if return value should be the point at infinity
151 static int Mxy(const EC_GROUP *group, const BIGNUM *x, const BIGNUM *y, BIGNUM *x1,
152 BIGNUM *z1, BIGNUM *x2, BIGNUM *z2, BN_CTX *ctx)
154 BIGNUM *t3, *t4, *t5;
159 if (!BN_zero(x2)) return 0;
160 if (!BN_zero(z2)) return 0;
166 if (!BN_copy(x2, x)) return 0;
167 if (!BN_GF2m_add(z2, x, y)) return 0;
171 /* Since Mxy is static we can guarantee that ctx != NULL. */
173 t3 = BN_CTX_get(ctx);
174 t4 = BN_CTX_get(ctx);
175 t5 = BN_CTX_get(ctx);
176 if (t5 == NULL) goto err;
178 if (!BN_one(t5)) goto err;
180 if (!group->meth->field_mul(group, t3, z1, z2, ctx)) goto err;
182 if (!group->meth->field_mul(group, z1, z1, x, ctx)) goto err;
183 if (!BN_GF2m_add(z1, z1, x1)) goto err;
184 if (!group->meth->field_mul(group, z2, z2, x, ctx)) goto err;
185 if (!group->meth->field_mul(group, x1, z2, x1, ctx)) goto err;
186 if (!BN_GF2m_add(z2, z2, x2)) goto err;
188 if (!group->meth->field_mul(group, z2, z2, z1, ctx)) goto err;
189 if (!group->meth->field_sqr(group, t4, x, ctx)) goto err;
190 if (!BN_GF2m_add(t4, t4, y)) goto err;
191 if (!group->meth->field_mul(group, t4, t4, t3, ctx)) goto err;
192 if (!BN_GF2m_add(t4, t4, z2)) goto err;
194 if (!group->meth->field_mul(group, t3, t3, x, ctx)) goto err;
195 if (!group->meth->field_div(group, t3, t5, t3, ctx)) goto err;
196 if (!group->meth->field_mul(group, t4, t3, t4, ctx)) goto err;
197 if (!group->meth->field_mul(group, x2, x1, t3, ctx)) goto err;
198 if (!BN_GF2m_add(z2, x2, x)) goto err;
200 if (!group->meth->field_mul(group, z2, z2, t4, ctx)) goto err;
201 if (!BN_GF2m_add(z2, z2, y)) goto err;
210 /* Computes scalar*point and stores the result in r.
211 * point can not equal r.
212 * Uses algorithm 2P of
213 * Lopex, J. and Dahab, R. "Fast multiplication on elliptic curves over
214 * GF(2^m) without precomputation".
216 static int point_multiply(const EC_GROUP *group, EC_POINT *r, const BIGNUM *scalar,
217 const EC_POINT *point, BN_CTX *ctx)
219 BIGNUM *x1, *x2, *z1, *z2;
225 ECerr(EC_F_EC_POINT_MUL, EC_R_INVALID_ARGUMENT);
229 /* if result should be point at infinity */
230 if ((scalar == NULL) || BN_is_zero(scalar) || (point == NULL) ||
231 EC_POINT_is_at_infinity(group, point))
233 return EC_POINT_set_to_infinity(group, r);
236 /* only support affine coordinates */
237 if (!point->Z_is_one) return 0;
239 /* Since point_multiply is static we can guarantee that ctx != NULL. */
241 x1 = BN_CTX_get(ctx);
242 z1 = BN_CTX_get(ctx);
243 if (z1 == NULL) goto err;
248 if (!BN_GF2m_mod_arr(x1, &point->X, group->poly)) goto err; /* x1 = x */
249 if (!BN_one(z1)) goto err; /* z1 = 1 */
250 if (!group->meth->field_sqr(group, z2, x1, ctx)) goto err; /* z2 = x1^2 = x^2 */
251 if (!group->meth->field_sqr(group, x2, z2, ctx)) goto err;
252 if (!BN_GF2m_add(x2, x2, &group->b)) goto err; /* x2 = x^4 + b */
254 /* find top most bit and go one past it */
255 i = scalar->top - 1; j = BN_BITS2 - 1;
257 while (!(scalar->d[i] & mask)) { mask >>= 1; j--; }
259 /* if top most bit was at word break, go to next word */
262 i--; j = BN_BITS2 - 1;
270 if (scalar->d[i] & mask)
272 if (!Madd(group, &point->X, x1, z1, x2, z2, ctx)) goto err;
273 if (!Mdouble(group, x2, z2, ctx)) goto err;
277 if (!Madd(group, &point->X, x2, z2, x1, z1, ctx)) goto err;
278 if (!Mdouble(group, x1, z1, ctx)) goto err;
286 /* convert out of "projective" coordinates */
287 i = Mxy(group, &point->X, &point->Y, x1, z1, x2, z2, ctx);
288 if (i == 0) goto err;
291 if (!EC_POINT_set_to_infinity(group, r)) goto err;
295 if (!BN_one(&r->Z)) goto err;
299 /* GF(2^m) field elements should always have BIGNUM::neg = 0 */
312 * scalar*group->generator + scalars[0]*points[0] + ... + scalars[num-1]*points[num-1]
313 * gracefully ignoring NULL scalar values.
315 int ec_GF2m_mont_mul(const EC_GROUP *group, EC_POINT *r, const BIGNUM *scalar,
316 size_t num, const EC_POINT *points[], const BIGNUM *scalars[], BN_CTX *ctx)
318 BN_CTX *new_ctx = NULL;
324 ctx = new_ctx = BN_CTX_new();
329 /* This implementation is more efficient than the wNAF implementation for 2
330 * or fewer points. Use the ec_wNAF_mul implementation for 3 or more points.
332 if ((scalar && (num > 1)) || (num > 2))
334 ret = ec_wNAF_mul(group, r, scalar, num, points, scalars, ctx);
338 if ((p = EC_POINT_new(group)) == NULL) goto err;
340 if (!EC_POINT_set_to_infinity(group, r)) goto err;
344 if (!point_multiply(group, p, scalar, group->generator, ctx)) goto err;
345 if (scalar->neg) if (!group->meth->invert(group, p, ctx)) goto err;
346 if (!group->meth->add(group, r, r, p, ctx)) goto err;
349 for (i = 0; i < num; i++)
351 if (!point_multiply(group, p, scalars[i], points[i], ctx)) goto err;
352 if (scalars[i]->neg) if (!group->meth->invert(group, p, ctx)) goto err;
353 if (!group->meth->add(group, r, r, p, ctx)) goto err;
359 if (p) EC_POINT_free(p);
361 BN_CTX_free(new_ctx);
366 /* Precomputation for point multiplication. */
367 int ec_GF2m_mont_precompute_mult(EC_GROUP *group, BN_CTX *ctx)
369 /* There is no precomputation to do for Montgomery scalar multiplication but
370 * since this implementation falls back to the wNAF multiplication for more than
371 * two points, call the wNAF implementation's precompute.
373 return ec_wNAF_precompute_mult(group, ctx);