1 /*****************************************************************************
2 * dvd_css.c: Functions for DVD authentification and unscrambling
3 *****************************************************************************
4 * Copyright (C) 1999-2001 VideoLAN
5 * $Id: dvd_css.c,v 1.24 2001/04/11 04:31:59 sam Exp $
7 * Author: Stéphane Borel <stef@via.ecp.fr>
10 * - css-auth by Derek Fawcus <derek@spider.com>
11 * - DVD CSS ioctls example program by Andrew T. Veliath <andrewtv@usa.net>
12 * - The Divide and conquer attack by Frank A. Stevenson <frank@funcom.com>
13 * - DeCSSPlus by Ethan Hawke
15 * see http://www.lemuria.org/DeCSS/ by Tom Vogt for more information.
17 * This program is free software; you can redistribute it and/or modify
18 * it under the terms of the GNU General Public License as published by
19 * the Free Software Foundation; either version 2 of the License, or
20 * (at your option) any later version.
22 * This program is distributed in the hope that it will be useful,
23 * but WITHOUT ANY WARRANTY; without even the implied warranty of
24 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
25 * GNU General Public License for more details.
27 * You should have received a copy of the GNU General Public License
28 * along with this program; if not, write to the Free Software
29 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111, USA.
30 *****************************************************************************/
32 /*****************************************************************************
34 *****************************************************************************/
48 #include "dvd_csstables.h"
50 #include "dvd_ioctl.h"
53 #include "input_dvd.h"
55 /*****************************************************************************
57 *****************************************************************************/
59 static int CSSGetASF ( int i_fd );
60 static void CSSCryptKey ( int i_key_type, int i_varient,
61 u8 const * pi_challenge, u8* pi_key );
62 static int CSSCracker ( int i_start, unsigned char * p_crypted,
63 unsigned char * p_decrypted,
64 dvd_key_t * p_sector_key, dvd_key_t * p_key );
67 /*****************************************************************************
68 * CSSTest : check if the disc is encrypted or not
69 *****************************************************************************/
70 int CSSTest( int i_fd )
72 int i_ret, i_copyright;
74 i_ret = ioctl_ReadCopyright( i_fd, 0 /* i_layer */, &i_copyright );
78 /* Since it's the first ioctl we try to issue, we add a notice */
79 intf_ErrMsg( "css error: ioctl_ReadCopyright failed, "
80 "make sure DVD ioctls were compiled in" );
88 /*****************************************************************************
89 * CSSInit : CSS Structure initialisation and DVD authentication.
90 *****************************************************************************
91 * It simulates the mutual authentication between logical unit and host.
92 * Since we don't need the disc key to find the title key, we just run the
93 * basic unavoidable commands to authenticate device and disc.
94 *****************************************************************************/
95 int CSSInit( int i_fd, css_t * p_css )
98 /* structures defined in cdrom.h or dvdio.h */
99 char p_buffer[2048 + 4 + 1];
104 /* Test authentication success */
105 switch( CSSGetASF( i_fd ) )
111 intf_WarnMsg( 3, "css info: already authenticated" );
115 intf_WarnMsg( 3, "css info: need to authenticate" );
118 /* Init sequence, request AGID */
119 for( i = 1; i < 4 ; ++i )
121 intf_WarnMsg( 3, "css info: requesting AGID %d", i );
123 i_ret = ioctl_LUSendAgid( i_fd, &i_agid );
127 /* No error during ioctl: we know the device is authenticated */
131 intf_ErrMsg( "css error: ioctl_LUSendAgid failed, invalidating" );
134 ioctl_InvalidateAgid( i_fd, &i_agid );
137 /* Unable to authenticate without AGID */
140 intf_ErrMsg( "css error: ioctl_LUSendAgid failed, fatal" );
144 for( i = 0 ; i < 10; ++i )
146 p_css->disc.pi_challenge[i] = i;
149 /* Get challenge from host */
150 for( i = 0 ; i < 10 ; ++i )
152 p_buffer[9-i] = p_css->disc.pi_challenge[i];
155 /* Send challenge to LU */
156 if( ioctl_HostSendChallenge( i_fd, &i_agid, p_buffer ) < 0 )
158 intf_ErrMsg( "css error: ioctl_HostSendChallenge failed" );
162 /* Get key1 from LU */
163 if( ioctl_LUSendKey1( i_fd, &i_agid, p_buffer ) < 0)
165 intf_ErrMsg( "css error: ioctl_LUSendKey1 failed" );
169 /* Send key1 to host */
170 for( i = 0 ; i < KEY_SIZE ; i++ )
172 p_css->disc.pi_key1[i] = p_buffer[4-i];
175 for( i = 0 ; i < 32 ; ++i )
177 CSSCryptKey( 0, i, p_css->disc.pi_challenge,
178 p_css->disc.pi_key_check );
180 if( memcmp( p_css->disc.pi_key_check,
181 p_css->disc.pi_key1, KEY_SIZE ) == 0 )
183 intf_WarnMsg( 3, "css info: drive authentic, using variant %d", i);
184 p_css->disc.i_varient = i;
191 intf_ErrMsg( "css error: drive would not authenticate" );
195 /* Get challenge from LU */
196 if( ioctl_LUSendChallenge( i_fd, &i_agid, p_buffer ) < 0 )
198 intf_ErrMsg( "css error: ioctl_LUSendKeyChallenge failed" );
202 /* Send challenge to host */
203 for( i = 0 ; i < 10 ; ++i )
205 p_css->disc.pi_challenge[i] = p_buffer[9-i];
208 CSSCryptKey( 1, p_css->disc.i_varient, p_css->disc.pi_challenge,
209 p_css->disc.pi_key2 );
211 /* Get key2 from host */
212 for( i = 0 ; i < KEY_SIZE ; ++i )
214 p_buffer[4-i] = p_css->disc.pi_key2[i];
217 /* Send key2 to LU */
218 if( ioctl_HostSendKey2( i_fd, &i_agid, p_buffer ) < 0 )
220 intf_ErrMsg( "css error: ioctl_HostSendKey2 failed" );
224 intf_WarnMsg( 3, "css info: authentication established" );
226 memcpy( p_css->disc.pi_challenge, p_css->disc.pi_key1, KEY_SIZE );
227 memcpy( p_css->disc.pi_challenge+KEY_SIZE, p_css->disc.pi_key2, KEY_SIZE );
229 CSSCryptKey( 2, p_css->disc.i_varient, p_css->disc.pi_challenge,
230 p_css->disc.pi_key_check );
232 intf_WarnMsg( 1, "css info: received session key" );
239 /* Test authentication success */
240 switch( CSSGetASF( i_fd ) )
246 intf_WarnMsg( 3, "css info: already authenticated" );
250 intf_WarnMsg( 3, "css info: need to get disc key" );
253 /* Get encrypted disc key */
254 if( ioctl_ReadKey( i_fd, &i_agid, p_buffer ) < 0 )
256 intf_ErrMsg( "css error: ioctl_ReadKey failed" );
260 /* Unencrypt disc key using bus key */
261 for( i = 0 ; i < 2048 ; i++ )
263 p_buffer[ i ] ^= p_css->disc.pi_key_check[ 4 - (i % KEY_SIZE) ];
265 memcpy( p_css->disc.pi_key_check, p_buffer, 2048 );
267 /* Test authentication success */
268 switch( CSSGetASF( i_fd ) )
274 intf_WarnMsg( 3, "css info: successfully authenticated" );
278 intf_ErrMsg( "css error: no way to authenticate" );
283 intf_ErrMsg( "css error: CSS decryption is disabled in this module" );
285 #endif /* HAVE_CSS */
290 /*****************************************************************************
291 * CSSGetKey : get title key.
292 *****************************************************************************
293 * The DVD should have been opened and authenticated before.
294 *****************************************************************************/
295 int CSSGetKey( int i_fd, css_t * p_css )
299 * Title key cracking method from Ethan Hawke,
300 * with Frank A. Stevenson algorithm.
301 * Does not use any player key table and ioctls.
305 title_key_t p_title_key[10];
307 boolean_t b_encrypted;
308 boolean_t b_stop_scanning;
313 int i_registered_keys;
314 int i_total_keys_found;
318 memset( p_title_key, 0, 10 );
319 memset( &pi_key, 0, 10 );
322 i_registered_keys = 0 ;
323 i_total_keys_found = 0 ;
326 /* Position of the title on the disc */
327 i_title = p_css->i_title;
328 i_pos = p_css->i_title_pos;
330 //fprintf( stderr, "CSS %d start pos: %lld\n", i_title, i_pos );
333 i_pos = lseek( i_fd, i_pos, SEEK_SET );
334 i_bytes_read = read( i_fd, pi_buf, 0x800 );
336 /* PES_scrambling_control */
337 if( pi_buf[0x14] & 0x30 )
343 for( i = 2 ; i < 0x30 ; i++ )
345 for( j = i ; ( j < 0x80 ) &&
346 ( pi_buf[0x7F - (j%i)] == pi_buf[0x7F-j] ) ; j++ );
348 if( ( j > i_best_plen ) && ( j > i ) )
356 if( ( i_best_plen > 20 ) && ( i_best_plen / i_best_p >= 2) )
358 i = CSSCracker( 0, &pi_buf[0x80],
359 &pi_buf[0x80 - ( i_best_plen / i_best_p) *i_best_p],
360 (dvd_key_t*)&pi_buf[0x54],
365 for( j=0 ; j<i_registered_keys ; j++ )
367 if( memcmp( &(p_title_key[j].pi_key),
368 &pi_key, sizeof(dvd_key_t) ) == 0 )
370 p_title_key[j].i_occ++;
371 i_total_keys_found++;
378 memcpy( &(p_title_key[i_registered_keys].pi_key),
379 &pi_key, sizeof(dvd_key_t) );
380 p_title_key[i_registered_keys++].i_occ = 1;
381 i_total_keys_found++;
383 i = CSSCracker( i, &pi_buf[0x80],
384 &pi_buf[0x80 - ( i_best_plen / i_best_p) *i_best_p],
385 (dvd_key_t*)&pi_buf[0x54], &pi_key);
388 /* Stop search if we find one occurence of the key
389 * I have never found a DVD for which it is not enough
390 * but we should take care of that */
391 if( i_registered_keys == 1 && p_title_key[0].i_occ >= 1 )
398 i_pos += i_bytes_read;
399 } while( i_bytes_read == 0x800 && !b_stop_scanning);
404 "css info: found enough occurencies of the same key." );
409 intf_WarnMsg( 3, "css warning: this file was _NOT_ encrypted!" );
413 if( b_encrypted && i_registered_keys == 0 )
415 intf_ErrMsg( "css error: unable to determine keys from file" );
419 for( i = 0 ; i < i_registered_keys - 1 ; i++ )
421 for( j = i + 1 ; j < i_registered_keys ; j++ )
423 if( p_title_key[j].i_occ > p_title_key[i].i_occ )
425 memcpy( &pi_key, &(p_title_key[j].pi_key), sizeof(dvd_key_t) );
426 k = p_title_key[j].i_occ;
428 memcpy( &(p_title_key[j].pi_key),
429 &(p_title_key[i].pi_key), sizeof(dvd_key_t) );
430 p_title_key[j].i_occ = p_title_key[i].i_occ;
432 memcpy( &(p_title_key[i].pi_key),&pi_key, sizeof(dvd_key_t) );
433 p_title_key[i].i_occ = k;
439 intf_WarnMsg( 1, "css info: key(s) & key probability" );
440 intf_WarnMsg( 1, "----------------------------------" );
442 for( i=0 ; i<i_registered_keys ; i++ )
445 intf_WarnMsg( 1, "%d) %02X %02X %02X %02X %02X - %3.2f%%", i,
446 p_title_key[i].pi_key[0], p_title_key[i].pi_key[1],
447 p_title_key[i].pi_key[2], p_title_key[i].pi_key[3],
448 p_title_key[i].pi_key[4],
449 p_title_key[i].i_occ * 100.0 / i_total_keys_found );
451 if( p_title_key[i_highest].i_occ * 100.0 / i_total_keys_found
452 <= p_title_key[i].i_occ*100.0 / i_total_keys_found )
459 /* The "find the key with the highest probability" code
460 * is untested, as I haven't been able to find a VOB that
461 * produces multiple keys (RT)
463 intf_WarnMsg( 3, "css info: title %d, key %02X %02X %02X %02X %02X",
464 i_title, p_title_key[i_highest].pi_key[0],
465 p_title_key[i_highest].pi_key[1],
466 p_title_key[i_highest].pi_key[2],
467 p_title_key[i_highest].pi_key[3],
468 p_title_key[i_highest].pi_key[4] );
470 memcpy( p_css->pi_title_key,
471 p_title_key[i_highest].pi_key, KEY_SIZE );
473 intf_WarnMsg( 2, "css info: vts key initialized" );
477 intf_ErrMsg( "css error: css decryption unavailable" );
480 #endif /* HAVE_CSS */
483 /*****************************************************************************
484 * CSSDescrambleSector
485 *****************************************************************************
486 * sec : sector to descramble
487 * key : title key for this sector
488 *****************************************************************************/
489 int CSSDescrambleSector( dvd_key_t pi_key, u8* pi_sec )
492 unsigned int i_t1, i_t2, i_t3, i_t4, i_t5, i_t6;
493 u8* pi_end = pi_sec + 0x800;
495 /* PES_scrambling_control */
496 if( pi_sec[0x14] & 0x30)
498 i_t1 = ((pi_key)[0] ^ pi_sec[0x54]) | 0x100;
499 i_t2 = (pi_key)[1] ^ pi_sec[0x55];
500 i_t3 = (((pi_key)[2]) | ((pi_key)[3] << 8) |
501 ((pi_key)[4] << 16)) ^ ((pi_sec[0x56]) |
502 (pi_sec[0x57] << 8) | (pi_sec[0x58] << 16));
504 i_t3 = i_t3 * 2 + 8 - i_t4;
508 while( pi_sec != pi_end )
510 i_t4 = pi_css_tab2[i_t2] ^ pi_css_tab3[i_t1];
512 i_t1 = ( ( i_t1 & 1 ) << 8 ) ^ i_t4;
513 i_t4 = pi_css_tab5[i_t4];
514 i_t6 = ((((((( i_t3 >> 3 ) ^ i_t3 ) >> 1 ) ^
515 i_t3 ) >> 8 ) ^ i_t3 ) >> 5) & 0xff;
516 i_t3 = (i_t3 << 8 ) | i_t6;
517 i_t6 = pi_css_tab4[i_t6];
519 *pi_sec = pi_css_tab1[*pi_sec] ^( i_t5 & 0xff );
530 #endif /* HAVE_CSS */
535 /* Following functions are local */
537 /*****************************************************************************
538 * CSSGetASF : Get Authentification success flag
539 *****************************************************************************
542 * 0 if the device needs to be authenticated,
544 *****************************************************************************/
545 static int CSSGetASF( int i_fd )
550 for( i_agid = 0 ; i_agid < 4 ; i_agid++ )
552 if( ioctl_LUSendASF( i_fd, &i_agid, &i_asf ) == 0 )
554 intf_WarnMsg( 3, "css info: GetASF %sauthenticated",
561 /* The ioctl process has failed */
562 intf_ErrMsg( "css error: GetASF fatal error" );
566 /*****************************************************************************
567 * CSSCryptKey : shuffles bits and unencrypt keys.
568 *****************************************************************************
569 * Used during authentication and disc key negociation in CSSInit.
570 * i_key_type : 0->key1, 1->key2, 2->buskey.
571 * i_varient : between 0 and 31.
572 *****************************************************************************/
573 static void CSSCryptKey( int i_key_type, int i_varient,
574 u8 const * pi_challenge, u8* pi_key )
576 /* Permutation table for challenge */
577 u8 ppi_perm_challenge[3][10] =
578 { { 1, 3, 0, 7, 5, 2, 9, 6, 4, 8 },
579 { 6, 1, 9, 3, 8, 5, 7, 4, 0, 2 },
580 { 4, 0, 3, 5, 7, 2, 8, 6, 1, 9 } };
582 /* Permutation table for varient table for key2 and buskey */
583 u8 ppi_perm_varient[2][32] =
584 { { 0x0a, 0x08, 0x0e, 0x0c, 0x0b, 0x09, 0x0f, 0x0d,
585 0x1a, 0x18, 0x1e, 0x1c, 0x1b, 0x19, 0x1f, 0x1d,
586 0x02, 0x00, 0x06, 0x04, 0x03, 0x01, 0x07, 0x05,
587 0x12, 0x10, 0x16, 0x14, 0x13, 0x11, 0x17, 0x15 },
588 { 0x12, 0x1a, 0x16, 0x1e, 0x02, 0x0a, 0x06, 0x0e,
589 0x10, 0x18, 0x14, 0x1c, 0x00, 0x08, 0x04, 0x0c,
590 0x13, 0x1b, 0x17, 0x1f, 0x03, 0x0b, 0x07, 0x0f,
591 0x11, 0x19, 0x15, 0x1d, 0x01, 0x09, 0x05, 0x0d } };
594 { 0xB7, 0x74, 0x85, 0xD0, 0xCC, 0xDB, 0xCA, 0x73,
595 0x03, 0xFE, 0x31, 0x03, 0x52, 0xE0, 0xB7, 0x42,
596 0x63, 0x16, 0xF2, 0x2A, 0x79, 0x52, 0xFF, 0x1B,
597 0x7A, 0x11, 0xCA, 0x1A, 0x9B, 0x40, 0xAD, 0x01 };
599 /* The "secret" key */
600 u8 pi_secret[5] = { 0x55, 0xD6, 0xC4, 0xC5, 0x28 };
606 u8 i_lfsr0_o; /* 1 bit used */
607 u8 i_lfsr1_o; /* 1 bit used */
620 for (i = 9; i >= 0; --i)
621 pi_scratch[i] = pi_challenge[ppi_perm_challenge[i_key_type][i]];
623 i_css_varient = ( i_key_type == 0 ) ? i_varient :
624 ppi_perm_varient[i_key_type-1][i_varient];
627 * This encryption engine implements one of 32 variations
628 * one the same theme depending upon the choice in the
629 * varient parameter (0 - 31).
631 * The algorithm itself manipulates a 40 bit input into
633 * The parameter 'input' is 80 bits. It consists of
634 * the 40 bit input value that is to be encrypted followed
635 * by a 40 bit seed value for the pseudo random number
639 /* Feed the secret into the input values such that
640 * we alter the seed to the LFSR's used above, then
641 * generate the bits to play with.
643 for( i = 5 ; --i >= 0 ; )
645 pi_tmp1[i] = pi_scratch[5 + i] ^ pi_secret[i] ^ pi_crypt_tab2[i];
649 * We use two LFSR's (seeded from some of the input data bytes) to
650 * generate two streams of pseudo-random bits. These two bit streams
651 * are then combined by simply adding with carry to generate a final
652 * sequence of pseudo-random bits which is stored in the buffer that
653 * 'output' points to the end of - len is the size of this buffer.
655 * The first LFSR is of degree 25, and has a polynomial of:
656 * x^13 + x^5 + x^4 + x^1 + 1
658 * The second LSFR is of degree 17, and has a (primitive) polynomial of:
661 * I don't know if these polynomials are primitive modulo 2, and thus
662 * represent maximal-period LFSR's.
665 * Note that we take the output of each LFSR from the new shifted in
666 * bit, not the old shifted out bit. Thus for ease of use the LFSR's
667 * are implemented in bit reversed order.
671 /* In order to ensure that the LFSR works we need to ensure that the
672 * initial values are non-zero. Thus when we initialise them from
673 * the seed, we ensure that a bit is set.
675 i_lfsr0 = ( pi_tmp1[0] << 17 ) | ( pi_tmp1[1] << 9 ) |
676 (( pi_tmp1[2] & ~7 ) << 1 ) | 8 | ( pi_tmp1[2] & 7 );
677 i_lfsr1 = ( pi_tmp1[3] << 9 ) | 0x100 | pi_tmp1[4];
679 i_index = sizeof(pi_bits);
684 for( i_bit = 0, i_val = 0 ; i_bit < 8 ; ++i_bit )
687 i_lfsr0_o = ( ( i_lfsr0 >> 24 ) ^ ( i_lfsr0 >> 21 ) ^
688 ( i_lfsr0 >> 20 ) ^ ( i_lfsr0 >> 12 ) ) & 1;
689 i_lfsr0 = ( i_lfsr0 << 1 ) | i_lfsr0_o;
691 i_lfsr1_o = ( ( i_lfsr1 >> 16 ) ^ ( i_lfsr1 >> 2 ) ) & 1;
692 i_lfsr1 = ( i_lfsr1 << 1 ) | i_lfsr1_o;
694 i_combined = !i_lfsr1_o + i_carry + !i_lfsr0_o;
696 i_carry = ( i_combined >> 1 ) & 1;
697 i_val |= ( i_combined & 1 ) << i_bit;
700 pi_bits[--i_index] = i_val;
701 } while( i_index > 0 );
703 /* This term is used throughout the following to
704 * select one of 32 different variations on the
707 i_cse = pi_varients[i_css_varient] ^ pi_crypt_tab2[i_css_varient];
709 /* Now the actual blocks doing the encryption. Each
710 * of these works on 40 bits at a time and are quite
714 for( i = 5, i_term = 0 ; --i >= 0 ; i_term = pi_scratch[i] )
716 i_index = pi_bits[25 + i] ^ pi_scratch[i];
717 i_index = pi_crypt_tab1[i_index] ^ ~pi_crypt_tab2[i_index] ^ i_cse;
719 pi_tmp1[i] = pi_crypt_tab2[i_index] ^ pi_crypt_tab3[i_index] ^ i_term;
721 pi_tmp1[4] ^= pi_tmp1[0];
723 for( i = 5, i_term = 0 ; --i >= 0 ; i_term = pi_tmp1[i] )
725 i_index = pi_bits[20 + i] ^ pi_tmp1[i];
726 i_index = pi_crypt_tab1[i_index] ^ ~pi_crypt_tab2[i_index] ^ i_cse;
728 pi_tmp2[i] = pi_crypt_tab2[i_index] ^ pi_crypt_tab3[i_index] ^ i_term;
730 pi_tmp2[4] ^= pi_tmp2[0];
732 for( i = 5, i_term = 0 ; --i >= 0 ; i_term = pi_tmp2[i] )
734 i_index = pi_bits[15 + i] ^ pi_tmp2[i];
735 i_index = pi_crypt_tab1[i_index] ^ ~pi_crypt_tab2[i_index] ^ i_cse;
736 i_index = pi_crypt_tab2[i_index] ^ pi_crypt_tab3[i_index] ^ i_term;
738 pi_tmp1[i] = pi_crypt_tab0[i_index] ^ pi_crypt_tab2[i_index];
740 pi_tmp1[4] ^= pi_tmp1[0];
742 for( i = 5, i_term = 0 ; --i >= 0 ; i_term = pi_tmp1[i] )
744 i_index = pi_bits[10 + i] ^ pi_tmp1[i];
745 i_index = pi_crypt_tab1[i_index] ^ ~pi_crypt_tab2[i_index] ^ i_cse;
747 i_index = pi_crypt_tab2[i_index] ^ pi_crypt_tab3[i_index] ^ i_term;
749 pi_tmp2[i] = pi_crypt_tab0[i_index] ^ pi_crypt_tab2[i_index];
751 pi_tmp2[4] ^= pi_tmp2[0];
753 for( i = 5, i_term = 0 ; --i >= 0 ; i_term = pi_tmp2[i] )
755 i_index = pi_bits[5 + i] ^ pi_tmp2[i];
756 i_index = pi_crypt_tab1[i_index] ^ ~pi_crypt_tab2[i_index] ^ i_cse;
758 pi_tmp1[i] = pi_crypt_tab2[i_index] ^ pi_crypt_tab3[i_index] ^ i_term;
760 pi_tmp1[4] ^= pi_tmp1[0];
762 for(i = 5, i_term = 0 ; --i >= 0 ; i_term = pi_tmp1[i] )
764 i_index = pi_bits[i] ^ pi_tmp1[i];
765 i_index = pi_crypt_tab1[i_index] ^ ~pi_crypt_tab2[i_index] ^ i_cse;
767 pi_key[i] = pi_crypt_tab2[i_index] ^ pi_crypt_tab3[i_index] ^ i_term;
773 /*****************************************************************************
774 * CSSCracker : title key decryption by cracking
775 *****************************************************************************
776 * This function is called by CSSGetKeys to find a key
777 *****************************************************************************/
778 static int CSSCracker( int i_start,
779 unsigned char * p_crypted,
780 unsigned char * p_decrypted,
781 dvd_key_t * p_sector_key,
784 unsigned char pi_buffer[10];
785 unsigned int i_t1, i_t2, i_t3, i_t4, i_t5, i_t6;
787 unsigned int i_candidate;
792 for( i = 0 ; i < 10 ; i++ )
794 pi_buffer[i] = pi_css_tab1[p_crypted[i]] ^ p_decrypted[i];
797 for( i_try = i_start ; i_try < 0x10000 ; i_try++ )
799 i_t1 = i_try >> 8 | 0x100;
801 i_t3 = 0; /* not needed */
804 /* iterate cipher 4 times to reconstruct LFSR2 */
805 for( i = 0 ; i < 4 ; i++ )
807 /* advance LFSR1 normaly */
808 i_t4 = pi_css_tab2[i_t2] ^ pi_css_tab3[i_t1];
810 i_t1 = ( ( i_t1 & 1 ) << 8 ) ^ i_t4;
811 i_t4 = pi_css_tab5[i_t4];
812 /* deduce i_t6 & i_t5 */
816 i_t6 = ( i_t6 + 0xff ) & 0x0ff;
824 i_t6 = pi_css_tab4[ i_t6 ];
825 /* feed / advance i_t3 / i_t5 */
826 i_t3 = ( i_t3 << 8 ) | i_t6;
832 /* iterate 6 more times to validate candidate key */
833 for( ; i < 10 ; i++ )
835 i_t4 = pi_css_tab2[i_t2] ^ pi_css_tab3[i_t1];
837 i_t1 = ( ( i_t1 & 1 ) << 8 ) ^ i_t4;
838 i_t4 = pi_css_tab5[i_t4];
839 i_t6 = ((((((( i_t3 >> 3 ) ^ i_t3 ) >> 1 ) ^
840 i_t3 ) >> 8 ) ^ i_t3 ) >> 5 ) & 0xff;
841 i_t3 = ( i_t3 << 8 ) | i_t6;
842 i_t6 = pi_css_tab4[i_t6];
844 if( ( i_t5 & 0xff ) != pi_buffer[i] )
854 /* Do 4 backwards steps of iterating t3 to deduce initial state */
856 for( i = 0 ; i < 4 ; i++ )
859 i_t3 = ( i_t3 >> 8 );
860 /* easy to code, and fast enough bruteforce
861 * search for byte shifted in */
862 for( j = 0 ; j < 256 ; j++ )
864 i_t3 = ( i_t3 & 0x1ffff) | ( j << 17 );
865 i_t6 = ((((((( i_t3 >> 3 ) ^ i_t3 ) >> 1 ) ^
866 i_t3 ) >> 8 ) ^ i_t3 ) >> 5 ) & 0xff;
874 i_t4 = ( i_t3 >> 1 ) - 4;
875 for( i_t5 = 0 ; i_t5 < 8; i_t5++ )
877 if( ( ( i_t4 + i_t5 ) * 2 + 8 - ( (i_t4 + i_t5 ) & 7 ) )
880 (*p_key)[0] = i_try>>8;
881 (*p_key)[1] = i_try & 0xFF;
882 (*p_key)[2] = ( ( i_t4 + i_t5 ) >> 0) & 0xFF;
883 (*p_key)[3] = ( ( i_t4 + i_t5 ) >> 8) & 0xFF;
884 (*p_key)[4] = ( ( i_t4 + i_t5 ) >> 16) & 0xFF;
893 (*p_key)[0] ^= (*p_sector_key)[0];
894 (*p_key)[1] ^= (*p_sector_key)[1];
895 (*p_key)[2] ^= (*p_sector_key)[2];
896 (*p_key)[3] ^= (*p_sector_key)[3];
897 (*p_key)[4] ^= (*p_sector_key)[4];
903 #endif /* HAVE_CSS */