1 /*****************************************************************************
2 * dvd_css.c: Functions for DVD authentification and unscrambling
3 *****************************************************************************
4 * Copyright (C) 1999-2001 VideoLAN
5 * $Id: dvd_css.c,v 1.19 2001/04/02 23:30:41 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 ( css_t *p_css );
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 = dvd_ReadCopyright( i_fd, 0 /* i_layer */, &i_copyright );
84 /*****************************************************************************
85 * CSSInit : CSS Structure initialisation and DVD authentication.
86 *****************************************************************************
87 * It simulates the mutual authentication between logical unit and host.
88 * Since we don't need the disc key to find the title key, we just run the
89 * basic unavoidable commands to authenticate device and disc.
90 *****************************************************************************/
91 int CSSInit( css_t * p_css )
94 /* structures defined in cdrom.h or dvdio.h */
95 char p_buffer[2048 + 4 + 1];
101 /* Test authentication success */
102 switch( CSSGetASF( p_css ) )
111 intf_WarnMsg( 3, "css info: authenticating" );
114 /* Init sequence, request AGID */
115 for( i = 1; i < 4 ; ++i )
117 intf_WarnMsg( 3, "css info: requesting AGID %d", i );
119 i_ret = dvd_LUSendAgid( p_css );
123 /* No error during ioctl: we know the device is authenticated */
127 intf_ErrMsg( "css error: AGID N/A, invalidating" );
130 dvd_InvalidateAgid( p_css );
133 /* Unable to authenticate without AGID */
136 intf_ErrMsg( "css error: could not get AGID" );
140 for( i = 0 ; i < 10; ++i )
142 p_css->disc.pi_challenge[i] = i;
145 /* Get challenge from host */
146 for( i = 0 ; i < 10 ; ++i )
148 p_buffer[9-i] = p_css->disc.pi_challenge[i];
151 /* Send challenge to LU */
152 if( dvd_HostSendChallenge( p_css, p_buffer ) < 0 )
154 intf_ErrMsg( "css error: failed sending challenge to LU" );
158 /* Get key1 from LU */
159 if( dvd_LUSendKey1( p_css, p_buffer ) < 0)
161 intf_ErrMsg( "css error: failed getting key1 from LU" );
165 /* Send key1 to host */
166 for( i = 0 ; i < KEY_SIZE ; i++ )
168 p_css->disc.pi_key1[i] = p_buffer[4-i];
171 for( i = 0 ; i < 32 ; ++i )
173 CSSCryptKey( 0, i, p_css->disc.pi_challenge,
174 p_css->disc.pi_key_check );
176 if( memcmp( p_css->disc.pi_key_check,
177 p_css->disc.pi_key1, KEY_SIZE ) == 0 )
179 intf_WarnMsg( 3, "css info: drive authentic, using variant %d", i);
180 p_css->disc.i_varient = i;
187 intf_ErrMsg( "css error: drive would not authenticate" );
191 /* Get challenge from LU */
192 if( dvd_LUSendChallenge( p_css, p_buffer ) < 0 )
194 intf_ErrMsg( "css error: failed getting challenge from LU" );
198 /* Send challenge to host */
199 for( i = 0 ; i < 10 ; ++i )
201 p_css->disc.pi_challenge[i] = p_buffer[9-i];
204 CSSCryptKey( 1, p_css->disc.i_varient, p_css->disc.pi_challenge,
205 p_css->disc.pi_key2 );
207 /* Get key2 from host */
208 for( i = 0 ; i < KEY_SIZE ; ++i )
210 p_buffer[4-i] = p_css->disc.pi_key2[i];
213 /* Send key2 to LU */
214 if( dvd_HostSendKey2( p_css, p_buffer ) < 0 )
216 intf_ErrMsg( "css error: failed sending key2 to LU" );
220 intf_WarnMsg( 3, "css info: authentication established" );
222 memcpy( p_css->disc.pi_challenge, p_css->disc.pi_key1, KEY_SIZE );
223 memcpy( p_css->disc.pi_challenge+KEY_SIZE, p_css->disc.pi_key2, KEY_SIZE );
224 CSSCryptKey( 2, p_css->disc.i_varient, p_css->disc.pi_challenge,
225 p_css->disc.pi_key_check );
227 intf_WarnMsg( 1, "css info: received Session Key" );
229 if( p_css->i_agid < 0 )
234 /* Test authentication success */
235 switch( CSSGetASF( p_css ) )
244 intf_WarnMsg( 3, "css info: getting disc key" );
247 /* Get encrypted disc key */
248 if( dvd_ReadKey( p_css, p_buffer ) < 0 )
250 intf_ErrMsg( "css error: could not read Disc Key" );
254 /* Unencrypt disc key using bus key */
255 for( i = 0 ; i < 2048 ; i++ )
257 p_buffer[ i ] ^= p_css->disc.pi_key_check[ 4 - (i % KEY_SIZE) ];
259 memcpy( p_css->disc.pi_key_check, p_buffer, 2048 );
261 /* Test authentication success */
262 switch( CSSGetASF( p_css ) )
275 intf_ErrMsg( "css error: CSS decryption is disabled in this module" );
279 #endif /* HAVE_CSS */
282 /*****************************************************************************
283 * CSSEnd : frees css structure
284 *****************************************************************************/
285 void CSSEnd( css_t * p_css )
291 #endif /* HAVE_CSS */
294 /*****************************************************************************
295 * CSSGetKey : get title key.
296 *****************************************************************************
297 * The DVD should have been opened and authenticated before.
298 *****************************************************************************/
299 int CSSGetKey( css_t * p_css )
303 * Title key cracking method from Ethan Hawke,
304 * with Frank A. Stevenson algorithm.
305 * Does not use any player key table and ioctls.
309 title_key_t p_title_key[10];
311 boolean_t b_encrypted;
312 boolean_t b_stop_scanning;
317 int i_registered_keys;
318 int i_total_keys_found;
322 memset( p_title_key, 0, 10 );
323 memset( &pi_key, 0, 10 );
326 i_registered_keys = 0 ;
327 i_total_keys_found = 0 ;
330 /* Position of the title on the disc */
331 i_title = p_css->i_title;
332 i_pos = p_css->i_title_pos;
334 //fprintf( stderr, "CSS %d start pos: %lld\n", i_title, i_pos );
337 i_pos = lseek( p_css->i_fd, i_pos, SEEK_SET );
338 i_bytes_read = read( p_css->i_fd, pi_buf, 0x800 );
340 /* PES_scrambling_control */
341 if( pi_buf[0x14] & 0x30 )
347 for( i = 2 ; i < 0x30 ; i++ )
349 for( j = i ; ( j < 0x80 ) &&
350 ( pi_buf[0x7F - (j%i)] == pi_buf[0x7F-j] ) ; j++ );
352 if( ( j > i_best_plen ) && ( j > i ) )
360 if( ( i_best_plen > 20 ) && ( i_best_plen / i_best_p >= 2) )
362 i = CSSCracker( 0, &pi_buf[0x80],
363 &pi_buf[0x80 - ( i_best_plen / i_best_p) *i_best_p],
364 (dvd_key_t*)&pi_buf[0x54],
369 for( j=0 ; j<i_registered_keys ; j++ )
371 if( memcmp( &(p_title_key[j].pi_key),
372 &pi_key, sizeof(dvd_key_t) ) == 0 )
374 p_title_key[j].i_occ++;
375 i_total_keys_found++;
382 memcpy( &(p_title_key[i_registered_keys].pi_key),
383 &pi_key, sizeof(dvd_key_t) );
384 p_title_key[i_registered_keys++].i_occ = 1;
385 i_total_keys_found++;
387 i = CSSCracker( i, &pi_buf[0x80],
388 &pi_buf[0x80 - ( i_best_plen / i_best_p) *i_best_p],
389 (dvd_key_t*)&pi_buf[0x54], &pi_key);
392 /* Stop search if we find one occurence of the key
393 * I have never found a DVD for which it is not enough
394 * but we should take care of that */
395 if( i_registered_keys == 1 && p_title_key[0].i_occ >= 1 )
402 i_pos += i_bytes_read;
403 } while( i_bytes_read == 0x800 && !b_stop_scanning);
408 "css info: found enough occurencies of the same key." );
413 intf_WarnMsg( 3, "css warning: this file was _NOT_ encrypted!" );
417 if( b_encrypted && i_registered_keys == 0 )
419 intf_ErrMsg( "css error: unable to determine keys from file" );
423 for( i = 0 ; i < i_registered_keys - 1 ; i++ )
425 for( j = i + 1 ; j < i_registered_keys ; j++ )
427 if( p_title_key[j].i_occ > p_title_key[i].i_occ )
429 memcpy( &pi_key, &(p_title_key[j].pi_key), sizeof(dvd_key_t) );
430 k = p_title_key[j].i_occ;
432 memcpy( &(p_title_key[j].pi_key),
433 &(p_title_key[i].pi_key), sizeof(dvd_key_t) );
434 p_title_key[j].i_occ = p_title_key[i].i_occ;
436 memcpy( &(p_title_key[i].pi_key),&pi_key, sizeof(dvd_key_t) );
437 p_title_key[i].i_occ = k;
443 intf_WarnMsg( 1, "css info: key(s) & key probability" );
444 intf_WarnMsg( 1, "----------------------------------" );
446 for( i=0 ; i<i_registered_keys ; i++ )
449 intf_WarnMsg( 1, "%d) %02X %02X %02X %02X %02X - %3.2f%%", i,
450 p_title_key[i].pi_key[0], p_title_key[i].pi_key[1],
451 p_title_key[i].pi_key[2], p_title_key[i].pi_key[3],
452 p_title_key[i].pi_key[4],
453 p_title_key[i].i_occ * 100.0 / i_total_keys_found );
455 if( p_title_key[i_highest].i_occ * 100.0 / i_total_keys_found
456 <= p_title_key[i].i_occ*100.0 / i_total_keys_found )
463 /* The "find the key with the highest probability" code
464 * is untested, as I haven't been able to find a VOB that
465 * produces multiple keys (RT)
467 intf_WarnMsg( 3, "css info: title %d, key %02X %02X %02X %02X %02X",
468 i_title, p_title_key[i_highest].pi_key[0],
469 p_title_key[i_highest].pi_key[1],
470 p_title_key[i_highest].pi_key[2],
471 p_title_key[i_highest].pi_key[3],
472 p_title_key[i_highest].pi_key[4] );
474 memcpy( p_css->pi_title_key,
475 p_title_key[i_highest].pi_key, KEY_SIZE );
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 );
527 #endif /* HAVE_CSS */
532 * Following functions are local
535 /*****************************************************************************
536 * CSSGetASF : Get Authentification success flag
537 *****************************************************************************
540 * 0 if the device needs to be authenticated,
542 *****************************************************************************/
543 static int CSSGetASF( css_t *p_css )
545 int i_oldagid = p_css->i_agid, i_asf = 0;
547 for( p_css->i_agid = 0 ; p_css->i_agid < 4 ; p_css->i_agid++ )
549 if( dvd_LUSendASF( p_css, &i_asf ) == 0 )
551 intf_WarnMsg( 3, "css info: %sauthenticated", i_asf ? "":"not " );
553 p_css->i_agid = i_oldagid;
558 /* The ioctl process has failed */
559 intf_ErrMsg( "css error: GetASF fatal error" );
561 p_css->i_agid = i_oldagid;
565 /*****************************************************************************
566 * CSSCryptKey : shuffles bits and unencrypt keys.
567 *****************************************************************************
568 * Used during authentication and disc key negociation in CSSInit.
569 * i_key_type : 0->key1, 1->key2, 2->buskey.
570 * i_varient : between 0 and 31.
571 *****************************************************************************/
572 static void CSSCryptKey( int i_key_type, int i_varient,
573 u8 const * pi_challenge, u8* pi_key )
575 /* Permutation table for challenge */
576 u8 ppi_perm_challenge[3][10] =
577 { { 1, 3, 0, 7, 5, 2, 9, 6, 4, 8 },
578 { 6, 1, 9, 3, 8, 5, 7, 4, 0, 2 },
579 { 4, 0, 3, 5, 7, 2, 8, 6, 1, 9 } };
581 /* Permutation table for varient table for key2 and buskey */
582 u8 ppi_perm_varient[2][32] =
583 { { 0x0a, 0x08, 0x0e, 0x0c, 0x0b, 0x09, 0x0f, 0x0d,
584 0x1a, 0x18, 0x1e, 0x1c, 0x1b, 0x19, 0x1f, 0x1d,
585 0x02, 0x00, 0x06, 0x04, 0x03, 0x01, 0x07, 0x05,
586 0x12, 0x10, 0x16, 0x14, 0x13, 0x11, 0x17, 0x15 },
587 { 0x12, 0x1a, 0x16, 0x1e, 0x02, 0x0a, 0x06, 0x0e,
588 0x10, 0x18, 0x14, 0x1c, 0x00, 0x08, 0x04, 0x0c,
589 0x13, 0x1b, 0x17, 0x1f, 0x03, 0x0b, 0x07, 0x0f,
590 0x11, 0x19, 0x15, 0x1d, 0x01, 0x09, 0x05, 0x0d } };
593 { 0xB7, 0x74, 0x85, 0xD0, 0xCC, 0xDB, 0xCA, 0x73,
594 0x03, 0xFE, 0x31, 0x03, 0x52, 0xE0, 0xB7, 0x42,
595 0x63, 0x16, 0xF2, 0x2A, 0x79, 0x52, 0xFF, 0x1B,
596 0x7A, 0x11, 0xCA, 0x1A, 0x9B, 0x40, 0xAD, 0x01 };
598 /* The "secret" key */
599 u8 pi_secret[5] = { 0x55, 0xD6, 0xC4, 0xC5, 0x28 };
605 u8 i_lfsr0_o; /* 1 bit used */
606 u8 i_lfsr1_o; /* 1 bit used */
619 for (i = 9; i >= 0; --i)
620 pi_scratch[i] = pi_challenge[ppi_perm_challenge[i_key_type][i]];
622 i_css_varient = ( i_key_type == 0 ) ? i_varient :
623 ppi_perm_varient[i_key_type-1][i_varient];
626 * This encryption engine implements one of 32 variations
627 * one the same theme depending upon the choice in the
628 * varient parameter (0 - 31).
630 * The algorithm itself manipulates a 40 bit input into
632 * The parameter 'input' is 80 bits. It consists of
633 * the 40 bit input value that is to be encrypted followed
634 * by a 40 bit seed value for the pseudo random number
638 /* Feed the secret into the input values such that
639 * we alter the seed to the LFSR's used above, then
640 * generate the bits to play with.
642 for( i = 5 ; --i >= 0 ; )
644 pi_tmp1[i] = pi_scratch[5 + i] ^ pi_secret[i] ^ pi_crypt_tab2[i];
648 * We use two LFSR's (seeded from some of the input data bytes) to
649 * generate two streams of pseudo-random bits. These two bit streams
650 * are then combined by simply adding with carry to generate a final
651 * sequence of pseudo-random bits which is stored in the buffer that
652 * 'output' points to the end of - len is the size of this buffer.
654 * The first LFSR is of degree 25, and has a polynomial of:
655 * x^13 + x^5 + x^4 + x^1 + 1
657 * The second LSFR is of degree 17, and has a (primitive) polynomial of:
660 * I don't know if these polynomials are primitive modulo 2, and thus
661 * represent maximal-period LFSR's.
664 * Note that we take the output of each LFSR from the new shifted in
665 * bit, not the old shifted out bit. Thus for ease of use the LFSR's
666 * are implemented in bit reversed order.
670 /* In order to ensure that the LFSR works we need to ensure that the
671 * initial values are non-zero. Thus when we initialise them from
672 * the seed, we ensure that a bit is set.
674 i_lfsr0 = ( pi_tmp1[0] << 17 ) | ( pi_tmp1[1] << 9 ) |
675 (( pi_tmp1[2] & ~7 ) << 1 ) | 8 | ( pi_tmp1[2] & 7 );
676 i_lfsr1 = ( pi_tmp1[3] << 9 ) | 0x100 | pi_tmp1[4];
678 i_index = sizeof(pi_bits);
683 for( i_bit = 0, i_val = 0 ; i_bit < 8 ; ++i_bit )
686 i_lfsr0_o = ( ( i_lfsr0 >> 24 ) ^ ( i_lfsr0 >> 21 ) ^
687 ( i_lfsr0 >> 20 ) ^ ( i_lfsr0 >> 12 ) ) & 1;
688 i_lfsr0 = ( i_lfsr0 << 1 ) | i_lfsr0_o;
690 i_lfsr1_o = ( ( i_lfsr1 >> 16 ) ^ ( i_lfsr1 >> 2 ) ) & 1;
691 i_lfsr1 = ( i_lfsr1 << 1 ) | i_lfsr1_o;
693 i_combined = !i_lfsr1_o + i_carry + !i_lfsr0_o;
695 i_carry = ( i_combined >> 1 ) & 1;
696 i_val |= ( i_combined & 1 ) << i_bit;
699 pi_bits[--i_index] = i_val;
700 } while( i_index > 0 );
702 /* This term is used throughout the following to
703 * select one of 32 different variations on the
706 i_cse = pi_varients[i_css_varient] ^ pi_crypt_tab2[i_css_varient];
708 /* Now the actual blocks doing the encryption. Each
709 * of these works on 40 bits at a time and are quite
713 for( i = 5, i_term = 0 ; --i >= 0 ; i_term = pi_scratch[i] )
715 i_index = pi_bits[25 + i] ^ pi_scratch[i];
716 i_index = pi_crypt_tab1[i_index] ^ ~pi_crypt_tab2[i_index] ^ i_cse;
718 pi_tmp1[i] = pi_crypt_tab2[i_index] ^ pi_crypt_tab3[i_index] ^ i_term;
720 pi_tmp1[4] ^= pi_tmp1[0];
722 for( i = 5, i_term = 0 ; --i >= 0 ; i_term = pi_tmp1[i] )
724 i_index = pi_bits[20 + i] ^ pi_tmp1[i];
725 i_index = pi_crypt_tab1[i_index] ^ ~pi_crypt_tab2[i_index] ^ i_cse;
727 pi_tmp2[i] = pi_crypt_tab2[i_index] ^ pi_crypt_tab3[i_index] ^ i_term;
729 pi_tmp2[4] ^= pi_tmp2[0];
731 for( i = 5, i_term = 0 ; --i >= 0 ; i_term = pi_tmp2[i] )
733 i_index = pi_bits[15 + i] ^ pi_tmp2[i];
734 i_index = pi_crypt_tab1[i_index] ^ ~pi_crypt_tab2[i_index] ^ i_cse;
735 i_index = pi_crypt_tab2[i_index] ^ pi_crypt_tab3[i_index] ^ i_term;
737 pi_tmp1[i] = pi_crypt_tab0[i_index] ^ pi_crypt_tab2[i_index];
739 pi_tmp1[4] ^= pi_tmp1[0];
741 for( i = 5, i_term = 0 ; --i >= 0 ; i_term = pi_tmp1[i] )
743 i_index = pi_bits[10 + i] ^ pi_tmp1[i];
744 i_index = pi_crypt_tab1[i_index] ^ ~pi_crypt_tab2[i_index] ^ i_cse;
746 i_index = pi_crypt_tab2[i_index] ^ pi_crypt_tab3[i_index] ^ i_term;
748 pi_tmp2[i] = pi_crypt_tab0[i_index] ^ pi_crypt_tab2[i_index];
750 pi_tmp2[4] ^= pi_tmp2[0];
752 for( i = 5, i_term = 0 ; --i >= 0 ; i_term = pi_tmp2[i] )
754 i_index = pi_bits[5 + i] ^ pi_tmp2[i];
755 i_index = pi_crypt_tab1[i_index] ^ ~pi_crypt_tab2[i_index] ^ i_cse;
757 pi_tmp1[i] = pi_crypt_tab2[i_index] ^ pi_crypt_tab3[i_index] ^ i_term;
759 pi_tmp1[4] ^= pi_tmp1[0];
761 for(i = 5, i_term = 0 ; --i >= 0 ; i_term = pi_tmp1[i] )
763 i_index = pi_bits[i] ^ pi_tmp1[i];
764 i_index = pi_crypt_tab1[i_index] ^ ~pi_crypt_tab2[i_index] ^ i_cse;
766 pi_key[i] = pi_crypt_tab2[i_index] ^ pi_crypt_tab3[i_index] ^ i_term;
772 /*****************************************************************************
773 * CSSCracker : title key decryption by cracking
774 *****************************************************************************
775 * This function is called by CSSGetKeys to find a key
776 *****************************************************************************/
777 static int CSSCracker( int i_start,
778 unsigned char * p_crypted,
779 unsigned char * p_decrypted,
780 dvd_key_t * p_sector_key,
783 unsigned char pi_buffer[10];
784 unsigned int i_t1, i_t2, i_t3, i_t4, i_t5, i_t6;
786 unsigned int i_candidate;
791 for( i = 0 ; i < 10 ; i++ )
793 pi_buffer[i] = pi_css_tab1[p_crypted[i]] ^ p_decrypted[i];
796 for( i_try = i_start ; i_try < 0x10000 ; i_try++ )
798 i_t1 = i_try >> 8 | 0x100;
800 i_t3 = 0; /* not needed */
803 /* iterate cipher 4 times to reconstruct LFSR2 */
804 for( i = 0 ; i < 4 ; i++ )
806 /* advance LFSR1 normaly */
807 i_t4 = pi_css_tab2[i_t2] ^ pi_css_tab3[i_t1];
809 i_t1 = ( ( i_t1 & 1 ) << 8 ) ^ i_t4;
810 i_t4 = pi_css_tab5[i_t4];
811 /* deduce i_t6 & i_t5 */
815 i_t6 = ( i_t6 + 0xff ) & 0x0ff;
823 i_t6 = pi_css_tab4[ i_t6 ];
824 /* feed / advance i_t3 / i_t5 */
825 i_t3 = ( i_t3 << 8 ) | i_t6;
831 /* iterate 6 more times to validate candidate key */
832 for( ; i < 10 ; i++ )
834 i_t4 = pi_css_tab2[i_t2] ^ pi_css_tab3[i_t1];
836 i_t1 = ( ( i_t1 & 1 ) << 8 ) ^ i_t4;
837 i_t4 = pi_css_tab5[i_t4];
838 i_t6 = ((((((( i_t3 >> 3 ) ^ i_t3 ) >> 1 ) ^
839 i_t3 ) >> 8 ) ^ i_t3 ) >> 5 ) & 0xff;
840 i_t3 = ( i_t3 << 8 ) | i_t6;
841 i_t6 = pi_css_tab4[i_t6];
843 if( ( i_t5 & 0xff ) != pi_buffer[i] )
853 /* Do 4 backwards steps of iterating t3 to deduce initial state */
855 for( i = 0 ; i < 4 ; i++ )
858 i_t3 = ( i_t3 >> 8 );
859 /* easy to code, and fast enough bruteforce
860 * search for byte shifted in */
861 for( j = 0 ; j < 256 ; j++ )
863 i_t3 = ( i_t3 & 0x1ffff) | ( j << 17 );
864 i_t6 = ((((((( i_t3 >> 3 ) ^ i_t3 ) >> 1 ) ^
865 i_t3 ) >> 8 ) ^ i_t3 ) >> 5 ) & 0xff;
873 i_t4 = ( i_t3 >> 1 ) - 4;
874 for( i_t5 = 0 ; i_t5 < 8; i_t5++ )
876 if( ( ( i_t4 + i_t5 ) * 2 + 8 - ( (i_t4 + i_t5 ) & 7 ) )
879 (*p_key)[0] = i_try>>8;
880 (*p_key)[1] = i_try & 0xFF;
881 (*p_key)[2] = ( ( i_t4 + i_t5 ) >> 0) & 0xFF;
882 (*p_key)[3] = ( ( i_t4 + i_t5 ) >> 8) & 0xFF;
883 (*p_key)[4] = ( ( i_t4 + i_t5 ) >> 16) & 0xFF;
892 (*p_key)[0] ^= (*p_sector_key)[0];
893 (*p_key)[1] ^= (*p_sector_key)[1];
894 (*p_key)[2] ^= (*p_sector_key)[2];
895 (*p_key)[3] ^= (*p_sector_key)[3];
896 (*p_key)[4] ^= (*p_sector_key)[4];
901 #endif /* HAVE_CSS */