bn_exp.c revision 59191
142660Smarkm/* crypto/bn/bn_exp.c */ 2146515Sru/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com) 321495Sjmacd * All rights reserved. 4146515Sru * 5116525Sru * This package is an SSL implementation written 621495Sjmacd * by Eric Young (eay@cryptsoft.com). 721495Sjmacd * The implementation was written so as to conform with Netscapes SSL. 821495Sjmacd * 921495Sjmacd * This library is free for commercial and non-commercial use as long as 1021495Sjmacd * the following conditions are aheared to. The following conditions 1121495Sjmacd * apply to all code found in this distribution, be it the RC4, RSA, 1221495Sjmacd * lhash, DES, etc., code; not just the SSL code. The SSL documentation 1321495Sjmacd * included with this distribution is covered by the same copyright terms 1421495Sjmacd * except that the holder is Tim Hudson (tjh@cryptsoft.com). 1521495Sjmacd * 1621495Sjmacd * Copyright remains Eric Young's, and as such any Copyright notices in 1721495Sjmacd * the code are not to be removed. 1821495Sjmacd * If this package is used in a product, Eric Young should be given attribution 1921495Sjmacd * as the author of the parts of the library used. 2021495Sjmacd * This can be in the form of a textual message at program startup or 2121495Sjmacd * in documentation (online or textual) provided with the package. 2221495Sjmacd * 2356160Sru * Redistribution and use in source and binary forms, with or without 2442660Smarkm * modification, are permitted provided that the following conditions 2521495Sjmacd * are met: 2642660Smarkm * 1. Redistributions of source code must retain the copyright 2742660Smarkm * notice, this list of conditions and the following disclaimer. 2842660Smarkm * 2. Redistributions in binary form must reproduce the above copyright 2993139Sru * notice, this list of conditions and the following disclaimer in the 3042660Smarkm * documentation and/or other materials provided with the distribution. 3142660Smarkm * 3. All advertising materials mentioning features or use of this software 3242660Smarkm * must display the following acknowledgement: 3342660Smarkm * "This product includes cryptographic software written by 3442660Smarkm * Eric Young (eay@cryptsoft.com)" 3542660Smarkm * The word 'cryptographic' can be left out if the rouines from the library 3642660Smarkm * being used are not cryptographic related :-). 3742660Smarkm * 4. If you include any Windows specific code (or a derivative thereof) from 3842660Smarkm * the apps directory (application code) you must include an acknowledgement: 3921495Sjmacd * "This product includes software written by Tim Hudson (tjh@cryptsoft.com)" 4093139Sru * 4121495Sjmacd * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND 4221495Sjmacd * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 4342660Smarkm * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 4421495Sjmacd * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 4521495Sjmacd * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 4621495Sjmacd * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 4742660Smarkm * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 4842660Smarkm * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 4942660Smarkm * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 5042660Smarkm * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 5142660Smarkm * SUCH DAMAGE. 5242660Smarkm * 5342660Smarkm * The licence and distribution terms for any publically available version or 5442660Smarkm * derivative of this code cannot be changed. i.e. this code cannot simply be 5542660Smarkm * copied and put under another distribution licence 5642660Smarkm * [including the GNU Public Licence.] 5742660Smarkm */ 5842660Smarkm 5942660Smarkm#include <stdio.h> 6042660Smarkm#include "cryptlib.h" 6142660Smarkm#include "bn_lcl.h" 6242660Smarkm#ifdef ATALLA 6342660Smarkm# include <alloca.h> 6442660Smarkm# include <atasi.h> 6542660Smarkm# include <assert.h> 6642660Smarkm# include <dlfcn.h> 6742660Smarkm#endif 6842660Smarkm 6942660Smarkm#define TABLE_SIZE 16 7042660Smarkm 7142660Smarkm/* slow but works */ 7242660Smarkmint BN_mod_mul(BIGNUM *ret, BIGNUM *a, BIGNUM *b, const BIGNUM *m, BN_CTX *ctx) 7342660Smarkm { 7442660Smarkm BIGNUM *t; 7542660Smarkm int r=0; 7642660Smarkm 7742660Smarkm bn_check_top(a); 7842660Smarkm bn_check_top(b); 7942660Smarkm bn_check_top(m); 8042660Smarkm 8142660Smarkm BN_CTX_start(ctx); 8242660Smarkm if ((t = BN_CTX_get(ctx)) == NULL) goto err; 8342660Smarkm if (a == b) 8442660Smarkm { if (!BN_sqr(t,a,ctx)) goto err; } 8542660Smarkm else 8642660Smarkm { if (!BN_mul(t,a,b,ctx)) goto err; } 8742660Smarkm if (!BN_mod(ret,t,m,ctx)) goto err; 8842660Smarkm r=1; 8942660Smarkmerr: 9042660Smarkm BN_CTX_end(ctx); 9142660Smarkm return(r); 9242660Smarkm } 9342660Smarkm 9421495Sjmacd#if 0 9521495Sjmacd/* this one works - simple but works */ 9642660Smarkmint BN_mod_exp(BIGNUM *r, BIGNUM *a, BIGNUM *p, BIGNUM *m, BN_CTX *ctx) 9742660Smarkm { 9842660Smarkm int i,bits,ret=0; 9942660Smarkm BIGNUM *v,*tmp; 10042660Smarkm 10142660Smarkm BN_CTX_start(ctx); 10242660Smarkm v = BN_CTX_get(ctx); 10321495Sjmacd tmp = BN_CTX_get(ctx); 10421495Sjmacd if (v == NULL || tmp == NULL) goto err; 10521495Sjmacd 10621495Sjmacd if (BN_copy(v,a) == NULL) goto err; 10721495Sjmacd bits=BN_num_bits(p); 10821495Sjmacd 10921495Sjmacd if (BN_is_odd(p)) 11021495Sjmacd { if (BN_copy(r,a) == NULL) goto err; } 11121495Sjmacd else { if (!BN_one(r)) goto err; } 11221495Sjmacd 11321495Sjmacd for (i=1; i<bits; i++) 11421495Sjmacd { 11521495Sjmacd if (!BN_sqr(tmp,v,ctx)) goto err; 11621495Sjmacd if (!BN_mod(v,tmp,m,ctx)) goto err; 11721495Sjmacd if (BN_is_bit_set(p,i)) 11821495Sjmacd { 11921495Sjmacd if (!BN_mul(tmp,r,v,ctx)) goto err; 12056160Sru if (!BN_mod(r,tmp,m,ctx)) goto err; 12156160Sru } 12256160Sru } 12393139Sru ret=1; 12493139Sruerr: 12593139Sru BN_CTX_end(ctx); 12621495Sjmacd return(ret); 12721495Sjmacd } 12821495Sjmacd 129146515Sru#endif 13021495Sjmacd 131146515Sru/* this one works - simple but works */ 132146515Sruint BN_exp(BIGNUM *r, BIGNUM *a, BIGNUM *p, BN_CTX *ctx) 13321495Sjmacd { 134116525Sru int i,bits,ret=0; 135116525Sru BIGNUM *v,*rr; 136116525Sru 137116525Sru BN_CTX_start(ctx); 138116525Sru if ((r == a) || (r == p)) 139116525Sru rr = BN_CTX_get(ctx); 140116525Sru else 141116525Sru rr = r; 142116525Sru if ((v = BN_CTX_get(ctx)) == NULL) goto err; 143116525Sru 144116525Sru if (BN_copy(v,a) == NULL) goto err; 145116525Sru bits=BN_num_bits(p); 146116525Sru 147116525Sru if (BN_is_odd(p)) 148116525Sru { if (BN_copy(rr,a) == NULL) goto err; } 149116525Sru else { if (!BN_one(rr)) goto err; } 15021495Sjmacd 15142660Smarkm for (i=1; i<bits; i++) 15293139Sru { 153146515Sru if (!BN_sqr(v,v,ctx)) goto err; 154146515Sru if (BN_is_bit_set(p,i)) 15593139Sru { 15693139Sru if (!BN_mul(rr,rr,v,ctx)) goto err; 157146515Sru } 158146515Sru } 15942660Smarkm ret=1; 16042660Smarkmerr: 161 if (r != rr) BN_copy(r,rr); 162 BN_CTX_end(ctx); 163 return(ret); 164 } 165 166#ifdef ATALLA 167 168/* 169 * This routine will dynamically check for the existance of an Atalla AXL-200 170 * SSL accelerator module. If one is found, the variable 171 * asi_accelerator_present is set to 1 and the function pointers 172 * ptr_ASI_xxxxxx above will be initialized to corresponding ASI API calls. 173 */ 174typedef int tfnASI_GetPerformanceStatistics(int reset_flag, 175 unsigned int *ret_buf); 176typedef int tfnASI_GetHardwareConfig(long card_num, unsigned int *ret_buf); 177typedef int tfnASI_RSAPrivateKeyOpFn(RSAPrivateKey * rsaKey, 178 unsigned char *output, 179 unsigned char *input, 180 unsigned int modulus_len); 181 182static tfnASI_GetHardwareConfig *ptr_ASI_GetHardwareConfig; 183static tfnASI_RSAPrivateKeyOpFn *ptr_ASI_RSAPrivateKeyOpFn; 184static tfnASI_GetPerformanceStatistics *ptr_ASI_GetPerformanceStatistics; 185static int asi_accelerator_present; 186static int tried_atalla; 187 188void atalla_initialize_accelerator_handle(void) 189 { 190 void *dl_handle; 191 int status; 192 unsigned int config_buf[1024]; 193 static int tested; 194 195 if(tested) 196 return; 197 198 tested=1; 199 200 bzero((void *)config_buf, 1024); 201 202 /* 203 * Check to see if the library is present on the system 204 */ 205 dl_handle = dlopen("atasi.so", RTLD_NOW); 206 if (dl_handle == (void *) NULL) 207 { 208/* printf("atasi.so library is not present on the system\n"); 209 printf("No HW acceleration available\n");*/ 210 return; 211 } 212 213 /* 214 * The library is present. Now we'll check to insure that the 215 * LDM is up and running. First we'll get the address of the 216 * function in the atasi library that we need to see if the 217 * LDM is operating. 218 */ 219 220 ptr_ASI_GetHardwareConfig = 221 (tfnASI_GetHardwareConfig *)dlsym(dl_handle,"ASI_GetHardwareConfig"); 222 223 if (ptr_ASI_GetHardwareConfig) 224 { 225 /* 226 * We found the call, now we'll get our config 227 * status. If we get a non 0 result, the LDM is not 228 * running and we cannot use the Atalla ASI * 229 * library. 230 */ 231 status = (*ptr_ASI_GetHardwareConfig)(0L, config_buf); 232 if (status != 0) 233 { 234 printf("atasi.so library is present but not initialized\n"); 235 printf("No HW acceleration available\n"); 236 return; 237 } 238 } 239 else 240 { 241/* printf("We found the library, but not the function. Very Strange!\n");*/ 242 return ; 243 } 244 245 /* 246 * It looks like we have acceleration capabilities. Load up the 247 * pointers to our ASI API calls. 248 */ 249 ptr_ASI_RSAPrivateKeyOpFn= 250 (tfnASI_RSAPrivateKeyOpFn *)dlsym(dl_handle, "ASI_RSAPrivateKeyOpFn"); 251 if (ptr_ASI_RSAPrivateKeyOpFn == NULL) 252 { 253/* printf("We found the library, but no RSA function. Very Strange!\n");*/ 254 return; 255 } 256 257 ptr_ASI_GetPerformanceStatistics = 258 (tfnASI_GetPerformanceStatistics *)dlsym(dl_handle, "ASI_GetPerformanceStatistics"); 259 if (ptr_ASI_GetPerformanceStatistics == NULL) 260 { 261/* printf("We found the library, but no stat function. Very Strange!\n");*/ 262 return; 263 } 264 265 /* 266 * Indicate that acceleration is available 267 */ 268 asi_accelerator_present = 1; 269 270/* printf("This system has acceleration!\n");*/ 271 272 return; 273 } 274 275/* make sure this only gets called once when bn_mod_exp calls bn_mod_exp_mont */ 276int BN_mod_exp_atalla(BIGNUM *r, BIGNUM *a, const BIGNUM *p, const BIGNUM *m) 277 { 278 unsigned char *abin; 279 unsigned char *pbin; 280 unsigned char *mbin; 281 unsigned char *rbin; 282 int an,pn,mn,ret; 283 RSAPrivateKey keydata; 284 285 atalla_initialize_accelerator_handle(); 286 if(!asi_accelerator_present) 287 return 0; 288 289 290/* We should be able to run without size testing */ 291# define ASIZE 128 292 an=BN_num_bytes(a); 293 pn=BN_num_bytes(p); 294 mn=BN_num_bytes(m); 295 296 if(an <= ASIZE && pn <= ASIZE && mn <= ASIZE) 297 { 298 int size=mn; 299 300 assert(an <= mn); 301 abin=alloca(size); 302 memset(abin,'\0',mn); 303 BN_bn2bin(a,abin+size-an); 304 305 pbin=alloca(pn); 306 BN_bn2bin(p,pbin); 307 308 mbin=alloca(size); 309 memset(mbin,'\0',mn); 310 BN_bn2bin(m,mbin+size-mn); 311 312 rbin=alloca(size); 313 314 memset(&keydata,'\0',sizeof keydata); 315 keydata.privateExponent.data=pbin; 316 keydata.privateExponent.len=pn; 317 keydata.modulus.data=mbin; 318 keydata.modulus.len=size; 319 320 ret=(*ptr_ASI_RSAPrivateKeyOpFn)(&keydata,rbin,abin,keydata.modulus.len); 321/*fprintf(stderr,"!%s\n",BN_bn2hex(a));*/ 322 if(!ret) 323 { 324 BN_bin2bn(rbin,keydata.modulus.len,r); 325/*fprintf(stderr,"?%s\n",BN_bn2hex(r));*/ 326 return 1; 327 } 328 } 329 return 0; 330 } 331#endif /* def ATALLA */ 332 333int BN_mod_exp(BIGNUM *r, BIGNUM *a, const BIGNUM *p, const BIGNUM *m, 334 BN_CTX *ctx) 335 { 336 int ret; 337 338 bn_check_top(a); 339 bn_check_top(p); 340 bn_check_top(m); 341 342#ifdef ATALLA 343 if(BN_mod_exp_atalla(r,a,p,m)) 344 return 1; 345/* If it fails, try the other methods (but don't try atalla again) */ 346 tried_atalla=1; 347#endif 348 349#ifdef MONT_MUL_MOD 350 /* I have finally been able to take out this pre-condition of 351 * the top bit being set. It was caused by an error in BN_div 352 * with negatives. There was also another problem when for a^b%m 353 * a >= m. eay 07-May-97 */ 354/* if ((m->d[m->top-1]&BN_TBIT) && BN_is_odd(m)) */ 355 356 if (BN_is_odd(m)) 357 { ret=BN_mod_exp_mont(r,a,p,m,ctx,NULL); } 358 else 359#endif 360#ifdef RECP_MUL_MOD 361 { ret=BN_mod_exp_recp(r,a,p,m,ctx); } 362#else 363 { ret=BN_mod_exp_simple(r,a,p,m,ctx); } 364#endif 365 366#ifdef ATALLA 367 tried_atalla=0; 368#endif 369 370 return(ret); 371 } 372 373/* #ifdef RECP_MUL_MOD */ 374int BN_mod_exp_recp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p, 375 const BIGNUM *m, BN_CTX *ctx) 376 { 377 int i,j,bits,ret=0,wstart,wend,window,wvalue; 378 int start=1,ts=0; 379 BIGNUM *aa; 380 BIGNUM val[TABLE_SIZE]; 381 BN_RECP_CTX recp; 382 383 bits=BN_num_bits(p); 384 385 if (bits == 0) 386 { 387 BN_one(r); 388 return(1); 389 } 390 391 BN_CTX_start(ctx); 392 if ((aa = BN_CTX_get(ctx)) == NULL) goto err; 393 394 BN_RECP_CTX_init(&recp); 395 if (BN_RECP_CTX_set(&recp,m,ctx) <= 0) goto err; 396 397 BN_init(&(val[0])); 398 ts=1; 399 400 if (!BN_mod(&(val[0]),a,m,ctx)) goto err; /* 1 */ 401 if (!BN_mod_mul_reciprocal(aa,&(val[0]),&(val[0]),&recp,ctx)) 402 goto err; /* 2 */ 403 404 if (bits <= 17) /* This is probably 3 or 0x10001, so just do singles */ 405 window=1; 406 else if (bits >= 256) 407 window=5; /* max size of window */ 408 else if (bits >= 128) 409 window=4; 410 else 411 window=3; 412 413 j=1<<(window-1); 414 for (i=1; i<j; i++) 415 { 416 BN_init(&val[i]); 417 if (!BN_mod_mul_reciprocal(&(val[i]),&(val[i-1]),aa,&recp,ctx)) 418 goto err; 419 } 420 ts=i; 421 422 start=1; /* This is used to avoid multiplication etc 423 * when there is only the value '1' in the 424 * buffer. */ 425 wvalue=0; /* The 'value' of the window */ 426 wstart=bits-1; /* The top bit of the window */ 427 wend=0; /* The bottom bit of the window */ 428 429 if (!BN_one(r)) goto err; 430 431 for (;;) 432 { 433 if (BN_is_bit_set(p,wstart) == 0) 434 { 435 if (!start) 436 if (!BN_mod_mul_reciprocal(r,r,r,&recp,ctx)) 437 goto err; 438 if (wstart == 0) break; 439 wstart--; 440 continue; 441 } 442 /* We now have wstart on a 'set' bit, we now need to work out 443 * how bit a window to do. To do this we need to scan 444 * forward until the last set bit before the end of the 445 * window */ 446 j=wstart; 447 wvalue=1; 448 wend=0; 449 for (i=1; i<window; i++) 450 { 451 if (wstart-i < 0) break; 452 if (BN_is_bit_set(p,wstart-i)) 453 { 454 wvalue<<=(i-wend); 455 wvalue|=1; 456 wend=i; 457 } 458 } 459 460 /* wend is the size of the current window */ 461 j=wend+1; 462 /* add the 'bytes above' */ 463 if (!start) 464 for (i=0; i<j; i++) 465 { 466 if (!BN_mod_mul_reciprocal(r,r,r,&recp,ctx)) 467 goto err; 468 } 469 470 /* wvalue will be an odd number < 2^window */ 471 if (!BN_mod_mul_reciprocal(r,r,&(val[wvalue>>1]),&recp,ctx)) 472 goto err; 473 474 /* move the 'window' down further */ 475 wstart-=wend+1; 476 wvalue=0; 477 start=0; 478 if (wstart < 0) break; 479 } 480 ret=1; 481err: 482 BN_CTX_end(ctx); 483 for (i=0; i<ts; i++) 484 BN_clear_free(&(val[i])); 485 BN_RECP_CTX_free(&recp); 486 return(ret); 487 } 488/* #endif */ 489 490/* #ifdef MONT_MUL_MOD */ 491int BN_mod_exp_mont(BIGNUM *rr, BIGNUM *a, const BIGNUM *p, 492 const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *in_mont) 493 { 494 int i,j,bits,ret=0,wstart,wend,window,wvalue; 495 int start=1,ts=0; 496 BIGNUM *d,*r; 497 BIGNUM *aa; 498 BIGNUM val[TABLE_SIZE]; 499 BN_MONT_CTX *mont=NULL; 500 501 bn_check_top(a); 502 bn_check_top(p); 503 bn_check_top(m); 504 505#ifdef ATALLA 506 if(!tried_atalla && BN_mod_exp_atalla(rr,a,p,m)) 507 return 1; 508/* If it fails, try the other methods */ 509#endif 510 511 if (!(m->d[0] & 1)) 512 { 513 BNerr(BN_F_BN_MOD_EXP_MONT,BN_R_CALLED_WITH_EVEN_MODULUS); 514 return(0); 515 } 516 bits=BN_num_bits(p); 517 if (bits == 0) 518 { 519 BN_one(rr); 520 return(1); 521 } 522 BN_CTX_start(ctx); 523 d = BN_CTX_get(ctx); 524 r = BN_CTX_get(ctx); 525 if (d == NULL || r == NULL) goto err; 526 527 /* If this is not done, things will break in the montgomery 528 * part */ 529 530#if 1 531 if (in_mont != NULL) 532 mont=in_mont; 533 else 534#endif 535 { 536 if ((mont=BN_MONT_CTX_new()) == NULL) goto err; 537 if (!BN_MONT_CTX_set(mont,m,ctx)) goto err; 538 } 539 540 BN_init(&val[0]); 541 ts=1; 542 if (BN_ucmp(a,m) >= 0) 543 { 544 BN_mod(&(val[0]),a,m,ctx); 545 aa= &(val[0]); 546 } 547 else 548 aa=a; 549 if (!BN_to_montgomery(&(val[0]),aa,mont,ctx)) goto err; /* 1 */ 550 if (!BN_mod_mul_montgomery(d,&(val[0]),&(val[0]),mont,ctx)) goto err; /* 2 */ 551 552 if (bits <= 20) /* This is probably 3 or 0x10001, so just do singles */ 553 window=1; 554 else if (bits >= 256) 555 window=5; /* max size of window */ 556 else if (bits >= 128) 557 window=4; 558 else 559 window=3; 560 561 j=1<<(window-1); 562 for (i=1; i<j; i++) 563 { 564 BN_init(&(val[i])); 565 if (!BN_mod_mul_montgomery(&(val[i]),&(val[i-1]),d,mont,ctx)) 566 goto err; 567 } 568 ts=i; 569 570 start=1; /* This is used to avoid multiplication etc 571 * when there is only the value '1' in the 572 * buffer. */ 573 wvalue=0; /* The 'value' of the window */ 574 wstart=bits-1; /* The top bit of the window */ 575 wend=0; /* The bottom bit of the window */ 576 577 if (!BN_to_montgomery(r,BN_value_one(),mont,ctx)) goto err; 578 for (;;) 579 { 580 if (BN_is_bit_set(p,wstart) == 0) 581 { 582 if (!start) 583 { 584 if (!BN_mod_mul_montgomery(r,r,r,mont,ctx)) 585 goto err; 586 } 587 if (wstart == 0) break; 588 wstart--; 589 continue; 590 } 591 /* We now have wstart on a 'set' bit, we now need to work out 592 * how bit a window to do. To do this we need to scan 593 * forward until the last set bit before the end of the 594 * window */ 595 j=wstart; 596 wvalue=1; 597 wend=0; 598 for (i=1; i<window; i++) 599 { 600 if (wstart-i < 0) break; 601 if (BN_is_bit_set(p,wstart-i)) 602 { 603 wvalue<<=(i-wend); 604 wvalue|=1; 605 wend=i; 606 } 607 } 608 609 /* wend is the size of the current window */ 610 j=wend+1; 611 /* add the 'bytes above' */ 612 if (!start) 613 for (i=0; i<j; i++) 614 { 615 if (!BN_mod_mul_montgomery(r,r,r,mont,ctx)) 616 goto err; 617 } 618 619 /* wvalue will be an odd number < 2^window */ 620 if (!BN_mod_mul_montgomery(r,r,&(val[wvalue>>1]),mont,ctx)) 621 goto err; 622 623 /* move the 'window' down further */ 624 wstart-=wend+1; 625 wvalue=0; 626 start=0; 627 if (wstart < 0) break; 628 } 629 BN_from_montgomery(rr,r,mont,ctx); 630 ret=1; 631err: 632 if ((in_mont == NULL) && (mont != NULL)) BN_MONT_CTX_free(mont); 633 BN_CTX_end(ctx); 634 for (i=0; i<ts; i++) 635 BN_clear_free(&(val[i])); 636 return(ret); 637 } 638/* #endif */ 639 640/* The old fallback, simple version :-) */ 641int BN_mod_exp_simple(BIGNUM *r, BIGNUM *a, BIGNUM *p, BIGNUM *m, 642 BN_CTX *ctx) 643 { 644 int i,j,bits,ret=0,wstart,wend,window,wvalue,ts=0; 645 int start=1; 646 BIGNUM *d; 647 BIGNUM val[TABLE_SIZE]; 648 649 bits=BN_num_bits(p); 650 651 if (bits == 0) 652 { 653 BN_one(r); 654 return(1); 655 } 656 657 BN_CTX_start(ctx); 658 if ((d = BN_CTX_get(ctx)) == NULL) goto err; 659 660 BN_init(&(val[0])); 661 ts=1; 662 if (!BN_mod(&(val[0]),a,m,ctx)) goto err; /* 1 */ 663 if (!BN_mod_mul(d,&(val[0]),&(val[0]),m,ctx)) 664 goto err; /* 2 */ 665 666 if (bits <= 17) /* This is probably 3 or 0x10001, so just do singles */ 667 window=1; 668 else if (bits >= 256) 669 window=5; /* max size of window */ 670 else if (bits >= 128) 671 window=4; 672 else 673 window=3; 674 675 j=1<<(window-1); 676 for (i=1; i<j; i++) 677 { 678 BN_init(&(val[i])); 679 if (!BN_mod_mul(&(val[i]),&(val[i-1]),d,m,ctx)) 680 goto err; 681 } 682 ts=i; 683 684 start=1; /* This is used to avoid multiplication etc 685 * when there is only the value '1' in the 686 * buffer. */ 687 wvalue=0; /* The 'value' of the window */ 688 wstart=bits-1; /* The top bit of the window */ 689 wend=0; /* The bottom bit of the window */ 690 691 if (!BN_one(r)) goto err; 692 693 for (;;) 694 { 695 if (BN_is_bit_set(p,wstart) == 0) 696 { 697 if (!start) 698 if (!BN_mod_mul(r,r,r,m,ctx)) 699 goto err; 700 if (wstart == 0) break; 701 wstart--; 702 continue; 703 } 704 /* We now have wstart on a 'set' bit, we now need to work out 705 * how bit a window to do. To do this we need to scan 706 * forward until the last set bit before the end of the 707 * window */ 708 j=wstart; 709 wvalue=1; 710 wend=0; 711 for (i=1; i<window; i++) 712 { 713 if (wstart-i < 0) break; 714 if (BN_is_bit_set(p,wstart-i)) 715 { 716 wvalue<<=(i-wend); 717 wvalue|=1; 718 wend=i; 719 } 720 } 721 722 /* wend is the size of the current window */ 723 j=wend+1; 724 /* add the 'bytes above' */ 725 if (!start) 726 for (i=0; i<j; i++) 727 { 728 if (!BN_mod_mul(r,r,r,m,ctx)) 729 goto err; 730 } 731 732 /* wvalue will be an odd number < 2^window */ 733 if (!BN_mod_mul(r,r,&(val[wvalue>>1]),m,ctx)) 734 goto err; 735 736 /* move the 'window' down further */ 737 wstart-=wend+1; 738 wvalue=0; 739 start=0; 740 if (wstart < 0) break; 741 } 742 ret=1; 743err: 744 BN_CTX_end(ctx); 745 for (i=0; i<ts; i++) 746 BN_clear_free(&(val[i])); 747 return(ret); 748 } 749 750