1 /*****************************************************************************
2 * dvd_css.c: Functions for DVD authentification and unscrambling
3 *****************************************************************************
4 * Copyright (C) 1999-2001 VideoLAN
5 * $Id: dvd_css.c,v 1.21 2001/04/06 09:15:47 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 = ioctl_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 ) )
108 intf_WarnMsg( 3, "css info: already authenticated" );
112 intf_WarnMsg( 3, "css info: need to authenticate" );
115 /* Init sequence, request AGID */
116 for( i = 1; i < 4 ; ++i )
118 intf_WarnMsg( 3, "css info: requesting AGID %d", i );
120 i_ret = ioctl_LUSendAgid( p_css );
124 /* No error during ioctl: we know the device is authenticated */
128 intf_ErrMsg( "css error: AGID N/A, invalidating" );
131 ioctl_InvalidateAgid( p_css );
134 /* Unable to authenticate without AGID */
137 intf_ErrMsg( "css error: could not get AGID" );
141 for( i = 0 ; i < 10; ++i )
143 p_css->disc.pi_challenge[i] = i;
146 /* Get challenge from host */
147 for( i = 0 ; i < 10 ; ++i )
149 p_buffer[9-i] = p_css->disc.pi_challenge[i];
152 /* Send challenge to LU */
153 if( ioctl_HostSendChallenge( p_css, p_buffer ) < 0 )
155 intf_ErrMsg( "css error: failed sending challenge to LU" );
159 /* Get key1 from LU */
160 if( ioctl_LUSendKey1( p_css, p_buffer ) < 0)
162 intf_ErrMsg( "css error: failed getting key1 from LU" );
166 /* Send key1 to host */
167 for( i = 0 ; i < KEY_SIZE ; i++ )
169 p_css->disc.pi_key1[i] = p_buffer[4-i];
172 for( i = 0 ; i < 32 ; ++i )
174 CSSCryptKey( 0, i, p_css->disc.pi_challenge,
175 p_css->disc.pi_key_check );
177 if( memcmp( p_css->disc.pi_key_check,
178 p_css->disc.pi_key1, KEY_SIZE ) == 0 )
180 intf_WarnMsg( 3, "css info: drive authentic, using variant %d", i);
181 p_css->disc.i_varient = i;
188 intf_ErrMsg( "css error: drive would not authenticate" );
192 /* Get challenge from LU */
193 if( ioctl_LUSendChallenge( p_css, p_buffer ) < 0 )
195 intf_ErrMsg( "css error: failed getting challenge from LU" );
199 /* Send challenge to host */
200 for( i = 0 ; i < 10 ; ++i )
202 p_css->disc.pi_challenge[i] = p_buffer[9-i];
205 CSSCryptKey( 1, p_css->disc.i_varient, p_css->disc.pi_challenge,
206 p_css->disc.pi_key2 );
208 /* Get key2 from host */
209 for( i = 0 ; i < KEY_SIZE ; ++i )
211 p_buffer[4-i] = p_css->disc.pi_key2[i];
214 /* Send key2 to LU */
215 if( ioctl_HostSendKey2( p_css, p_buffer ) < 0 )
217 intf_ErrMsg( "css error: failed sending key2 to LU" );
221 intf_WarnMsg( 3, "css info: authentication established" );
223 memcpy( p_css->disc.pi_challenge, p_css->disc.pi_key1, KEY_SIZE );
224 memcpy( p_css->disc.pi_challenge+KEY_SIZE, p_css->disc.pi_key2, KEY_SIZE );
225 CSSCryptKey( 2, p_css->disc.i_varient, p_css->disc.pi_challenge,
226 p_css->disc.pi_key_check );
228 intf_WarnMsg( 1, "css info: received Session Key" );
230 if( p_css->i_agid < 0 )
235 /* Test authentication success */
236 switch( CSSGetASF( p_css ) )
242 intf_WarnMsg( 3, "css info: already authenticated" );
246 intf_WarnMsg( 3, "css info: need to get disc key" );
249 /* Get encrypted disc key */
250 if( ioctl_ReadKey( p_css, p_buffer ) < 0 )
252 intf_ErrMsg( "css error: could not read Disc Key" );
256 /* Unencrypt disc key using bus key */
257 for( i = 0 ; i < 2048 ; i++ )
259 p_buffer[ i ] ^= p_css->disc.pi_key_check[ 4 - (i % KEY_SIZE) ];
261 memcpy( p_css->disc.pi_key_check, p_buffer, 2048 );
263 /* Test authentication success */
264 switch( CSSGetASF( p_css ) )
270 intf_WarnMsg( 3, "css info: successfully authenticated" );
274 intf_WarnMsg( 3, "css info: no way to authenticate" );
278 intf_ErrMsg( "css error: CSS decryption is disabled in this module" );
280 #endif /* HAVE_CSS */
285 /*****************************************************************************
286 * CSSEnd : frees css structure
287 *****************************************************************************/
288 void CSSEnd( css_t * p_css )
294 #endif /* HAVE_CSS */
297 /*****************************************************************************
298 * CSSGetKey : get title key.
299 *****************************************************************************
300 * The DVD should have been opened and authenticated before.
301 *****************************************************************************/
302 int CSSGetKey( css_t * p_css )
306 * Title key cracking method from Ethan Hawke,
307 * with Frank A. Stevenson algorithm.
308 * Does not use any player key table and ioctls.
312 title_key_t p_title_key[10];
314 boolean_t b_encrypted;
315 boolean_t b_stop_scanning;
320 int i_registered_keys;
321 int i_total_keys_found;
325 memset( p_title_key, 0, 10 );
326 memset( &pi_key, 0, 10 );
329 i_registered_keys = 0 ;
330 i_total_keys_found = 0 ;
333 /* Position of the title on the disc */
334 i_title = p_css->i_title;
335 i_pos = p_css->i_title_pos;
337 //fprintf( stderr, "CSS %d start pos: %lld\n", i_title, i_pos );
340 i_pos = lseek( p_css->i_fd, i_pos, SEEK_SET );
341 i_bytes_read = read( p_css->i_fd, pi_buf, 0x800 );
343 /* PES_scrambling_control */
344 if( pi_buf[0x14] & 0x30 )
350 for( i = 2 ; i < 0x30 ; i++ )
352 for( j = i ; ( j < 0x80 ) &&
353 ( pi_buf[0x7F - (j%i)] == pi_buf[0x7F-j] ) ; j++ );
355 if( ( j > i_best_plen ) && ( j > i ) )
363 if( ( i_best_plen > 20 ) && ( i_best_plen / i_best_p >= 2) )
365 i = CSSCracker( 0, &pi_buf[0x80],
366 &pi_buf[0x80 - ( i_best_plen / i_best_p) *i_best_p],
367 (dvd_key_t*)&pi_buf[0x54],
372 for( j=0 ; j<i_registered_keys ; j++ )
374 if( memcmp( &(p_title_key[j].pi_key),
375 &pi_key, sizeof(dvd_key_t) ) == 0 )
377 p_title_key[j].i_occ++;
378 i_total_keys_found++;
385 memcpy( &(p_title_key[i_registered_keys].pi_key),
386 &pi_key, sizeof(dvd_key_t) );
387 p_title_key[i_registered_keys++].i_occ = 1;
388 i_total_keys_found++;
390 i = CSSCracker( i, &pi_buf[0x80],
391 &pi_buf[0x80 - ( i_best_plen / i_best_p) *i_best_p],
392 (dvd_key_t*)&pi_buf[0x54], &pi_key);
395 /* Stop search if we find one occurence of the key
396 * I have never found a DVD for which it is not enough
397 * but we should take care of that */
398 if( i_registered_keys == 1 && p_title_key[0].i_occ >= 1 )
405 i_pos += i_bytes_read;
406 } while( i_bytes_read == 0x800 && !b_stop_scanning);
411 "css info: found enough occurencies of the same key." );
416 intf_WarnMsg( 3, "css warning: this file was _NOT_ encrypted!" );
420 if( b_encrypted && i_registered_keys == 0 )
422 intf_ErrMsg( "css error: unable to determine keys from file" );
426 for( i = 0 ; i < i_registered_keys - 1 ; i++ )
428 for( j = i + 1 ; j < i_registered_keys ; j++ )
430 if( p_title_key[j].i_occ > p_title_key[i].i_occ )
432 memcpy( &pi_key, &(p_title_key[j].pi_key), sizeof(dvd_key_t) );
433 k = p_title_key[j].i_occ;
435 memcpy( &(p_title_key[j].pi_key),
436 &(p_title_key[i].pi_key), sizeof(dvd_key_t) );
437 p_title_key[j].i_occ = p_title_key[i].i_occ;
439 memcpy( &(p_title_key[i].pi_key),&pi_key, sizeof(dvd_key_t) );
440 p_title_key[i].i_occ = k;
446 intf_WarnMsg( 1, "css info: key(s) & key probability" );
447 intf_WarnMsg( 1, "----------------------------------" );
449 for( i=0 ; i<i_registered_keys ; i++ )
452 intf_WarnMsg( 1, "%d) %02X %02X %02X %02X %02X - %3.2f%%", i,
453 p_title_key[i].pi_key[0], p_title_key[i].pi_key[1],
454 p_title_key[i].pi_key[2], p_title_key[i].pi_key[3],
455 p_title_key[i].pi_key[4],
456 p_title_key[i].i_occ * 100.0 / i_total_keys_found );
458 if( p_title_key[i_highest].i_occ * 100.0 / i_total_keys_found
459 <= p_title_key[i].i_occ*100.0 / i_total_keys_found )
466 /* The "find the key with the highest probability" code
467 * is untested, as I haven't been able to find a VOB that
468 * produces multiple keys (RT)
470 intf_WarnMsg( 3, "css info: title %d, key %02X %02X %02X %02X %02X",
471 i_title, p_title_key[i_highest].pi_key[0],
472 p_title_key[i_highest].pi_key[1],
473 p_title_key[i_highest].pi_key[2],
474 p_title_key[i_highest].pi_key[3],
475 p_title_key[i_highest].pi_key[4] );
477 memcpy( p_css->pi_title_key,
478 p_title_key[i_highest].pi_key, KEY_SIZE );
485 #endif /* HAVE_CSS */
488 /*****************************************************************************
489 * CSSDescrambleSector
490 *****************************************************************************
491 * sec : sector to descramble
492 * key : title key for this sector
493 *****************************************************************************/
494 int CSSDescrambleSector( dvd_key_t pi_key, u8* pi_sec )
497 unsigned int i_t1, i_t2, i_t3, i_t4, i_t5, i_t6;
498 u8* pi_end = pi_sec + 0x800;
500 /* PES_scrambling_control */
501 if( pi_sec[0x14] & 0x30)
503 i_t1 = ((pi_key)[0] ^ pi_sec[0x54]) | 0x100;
504 i_t2 = (pi_key)[1] ^ pi_sec[0x55];
505 i_t3 = (((pi_key)[2]) | ((pi_key)[3] << 8) |
506 ((pi_key)[4] << 16)) ^ ((pi_sec[0x56]) |
507 (pi_sec[0x57] << 8) | (pi_sec[0x58] << 16));
509 i_t3 = i_t3 * 2 + 8 - i_t4;
513 while( pi_sec != pi_end )
515 i_t4 = pi_css_tab2[i_t2] ^ pi_css_tab3[i_t1];
517 i_t1 = ( ( i_t1 & 1 ) << 8 ) ^ i_t4;
518 i_t4 = pi_css_tab5[i_t4];
519 i_t6 = ((((((( i_t3 >> 3 ) ^ i_t3 ) >> 1 ) ^
520 i_t3 ) >> 8 ) ^ i_t3 ) >> 5) & 0xff;
521 i_t3 = (i_t3 << 8 ) | i_t6;
522 i_t6 = pi_css_tab4[i_t6];
524 *pi_sec = pi_css_tab1[*pi_sec] ^( i_t5 & 0xff );
535 #endif /* HAVE_CSS */
540 /* Following functions are local */
542 /*****************************************************************************
543 * CSSGetASF : Get Authentification success flag
544 *****************************************************************************
547 * 0 if the device needs to be authenticated,
549 *****************************************************************************/
550 static int CSSGetASF( css_t *p_css )
552 int i_oldagid = p_css->i_agid, i_asf = 0;
554 for( p_css->i_agid = 0 ; p_css->i_agid < 4 ; p_css->i_agid++ )
556 if( ioctl_LUSendASF( p_css, &i_asf ) == 0 )
558 intf_WarnMsg( 3, "css info: %sauthenticated", i_asf ? "":"not " );
560 p_css->i_agid = i_oldagid;
565 /* The ioctl process has failed */
566 intf_ErrMsg( "css error: GetASF fatal error" );
568 p_css->i_agid = i_oldagid;
572 /*****************************************************************************
573 * CSSCryptKey : shuffles bits and unencrypt keys.
574 *****************************************************************************
575 * Used during authentication and disc key negociation in CSSInit.
576 * i_key_type : 0->key1, 1->key2, 2->buskey.
577 * i_varient : between 0 and 31.
578 *****************************************************************************/
579 static void CSSCryptKey( int i_key_type, int i_varient,
580 u8 const * pi_challenge, u8* pi_key )
582 /* Permutation table for challenge */
583 u8 ppi_perm_challenge[3][10] =
584 { { 1, 3, 0, 7, 5, 2, 9, 6, 4, 8 },
585 { 6, 1, 9, 3, 8, 5, 7, 4, 0, 2 },
586 { 4, 0, 3, 5, 7, 2, 8, 6, 1, 9 } };
588 /* Permutation table for varient table for key2 and buskey */
589 u8 ppi_perm_varient[2][32] =
590 { { 0x0a, 0x08, 0x0e, 0x0c, 0x0b, 0x09, 0x0f, 0x0d,
591 0x1a, 0x18, 0x1e, 0x1c, 0x1b, 0x19, 0x1f, 0x1d,
592 0x02, 0x00, 0x06, 0x04, 0x03, 0x01, 0x07, 0x05,
593 0x12, 0x10, 0x16, 0x14, 0x13, 0x11, 0x17, 0x15 },
594 { 0x12, 0x1a, 0x16, 0x1e, 0x02, 0x0a, 0x06, 0x0e,
595 0x10, 0x18, 0x14, 0x1c, 0x00, 0x08, 0x04, 0x0c,
596 0x13, 0x1b, 0x17, 0x1f, 0x03, 0x0b, 0x07, 0x0f,
597 0x11, 0x19, 0x15, 0x1d, 0x01, 0x09, 0x05, 0x0d } };
600 { 0xB7, 0x74, 0x85, 0xD0, 0xCC, 0xDB, 0xCA, 0x73,
601 0x03, 0xFE, 0x31, 0x03, 0x52, 0xE0, 0xB7, 0x42,
602 0x63, 0x16, 0xF2, 0x2A, 0x79, 0x52, 0xFF, 0x1B,
603 0x7A, 0x11, 0xCA, 0x1A, 0x9B, 0x40, 0xAD, 0x01 };
605 /* The "secret" key */
606 u8 pi_secret[5] = { 0x55, 0xD6, 0xC4, 0xC5, 0x28 };
612 u8 i_lfsr0_o; /* 1 bit used */
613 u8 i_lfsr1_o; /* 1 bit used */
626 for (i = 9; i >= 0; --i)
627 pi_scratch[i] = pi_challenge[ppi_perm_challenge[i_key_type][i]];
629 i_css_varient = ( i_key_type == 0 ) ? i_varient :
630 ppi_perm_varient[i_key_type-1][i_varient];
633 * This encryption engine implements one of 32 variations
634 * one the same theme depending upon the choice in the
635 * varient parameter (0 - 31).
637 * The algorithm itself manipulates a 40 bit input into
639 * The parameter 'input' is 80 bits. It consists of
640 * the 40 bit input value that is to be encrypted followed
641 * by a 40 bit seed value for the pseudo random number
645 /* Feed the secret into the input values such that
646 * we alter the seed to the LFSR's used above, then
647 * generate the bits to play with.
649 for( i = 5 ; --i >= 0 ; )
651 pi_tmp1[i] = pi_scratch[5 + i] ^ pi_secret[i] ^ pi_crypt_tab2[i];
655 * We use two LFSR's (seeded from some of the input data bytes) to
656 * generate two streams of pseudo-random bits. These two bit streams
657 * are then combined by simply adding with carry to generate a final
658 * sequence of pseudo-random bits which is stored in the buffer that
659 * 'output' points to the end of - len is the size of this buffer.
661 * The first LFSR is of degree 25, and has a polynomial of:
662 * x^13 + x^5 + x^4 + x^1 + 1
664 * The second LSFR is of degree 17, and has a (primitive) polynomial of:
667 * I don't know if these polynomials are primitive modulo 2, and thus
668 * represent maximal-period LFSR's.
671 * Note that we take the output of each LFSR from the new shifted in
672 * bit, not the old shifted out bit. Thus for ease of use the LFSR's
673 * are implemented in bit reversed order.
677 /* In order to ensure that the LFSR works we need to ensure that the
678 * initial values are non-zero. Thus when we initialise them from
679 * the seed, we ensure that a bit is set.
681 i_lfsr0 = ( pi_tmp1[0] << 17 ) | ( pi_tmp1[1] << 9 ) |
682 (( pi_tmp1[2] & ~7 ) << 1 ) | 8 | ( pi_tmp1[2] & 7 );
683 i_lfsr1 = ( pi_tmp1[3] << 9 ) | 0x100 | pi_tmp1[4];
685 i_index = sizeof(pi_bits);
690 for( i_bit = 0, i_val = 0 ; i_bit < 8 ; ++i_bit )
693 i_lfsr0_o = ( ( i_lfsr0 >> 24 ) ^ ( i_lfsr0 >> 21 ) ^
694 ( i_lfsr0 >> 20 ) ^ ( i_lfsr0 >> 12 ) ) & 1;
695 i_lfsr0 = ( i_lfsr0 << 1 ) | i_lfsr0_o;
697 i_lfsr1_o = ( ( i_lfsr1 >> 16 ) ^ ( i_lfsr1 >> 2 ) ) & 1;
698 i_lfsr1 = ( i_lfsr1 << 1 ) | i_lfsr1_o;
700 i_combined = !i_lfsr1_o + i_carry + !i_lfsr0_o;
702 i_carry = ( i_combined >> 1 ) & 1;
703 i_val |= ( i_combined & 1 ) << i_bit;
706 pi_bits[--i_index] = i_val;
707 } while( i_index > 0 );
709 /* This term is used throughout the following to
710 * select one of 32 different variations on the
713 i_cse = pi_varients[i_css_varient] ^ pi_crypt_tab2[i_css_varient];
715 /* Now the actual blocks doing the encryption. Each
716 * of these works on 40 bits at a time and are quite
720 for( i = 5, i_term = 0 ; --i >= 0 ; i_term = pi_scratch[i] )
722 i_index = pi_bits[25 + i] ^ pi_scratch[i];
723 i_index = pi_crypt_tab1[i_index] ^ ~pi_crypt_tab2[i_index] ^ i_cse;
725 pi_tmp1[i] = pi_crypt_tab2[i_index] ^ pi_crypt_tab3[i_index] ^ i_term;
727 pi_tmp1[4] ^= pi_tmp1[0];
729 for( i = 5, i_term = 0 ; --i >= 0 ; i_term = pi_tmp1[i] )
731 i_index = pi_bits[20 + i] ^ pi_tmp1[i];
732 i_index = pi_crypt_tab1[i_index] ^ ~pi_crypt_tab2[i_index] ^ i_cse;
734 pi_tmp2[i] = pi_crypt_tab2[i_index] ^ pi_crypt_tab3[i_index] ^ i_term;
736 pi_tmp2[4] ^= pi_tmp2[0];
738 for( i = 5, i_term = 0 ; --i >= 0 ; i_term = pi_tmp2[i] )
740 i_index = pi_bits[15 + i] ^ pi_tmp2[i];
741 i_index = pi_crypt_tab1[i_index] ^ ~pi_crypt_tab2[i_index] ^ i_cse;
742 i_index = pi_crypt_tab2[i_index] ^ pi_crypt_tab3[i_index] ^ i_term;
744 pi_tmp1[i] = pi_crypt_tab0[i_index] ^ pi_crypt_tab2[i_index];
746 pi_tmp1[4] ^= pi_tmp1[0];
748 for( i = 5, i_term = 0 ; --i >= 0 ; i_term = pi_tmp1[i] )
750 i_index = pi_bits[10 + i] ^ pi_tmp1[i];
751 i_index = pi_crypt_tab1[i_index] ^ ~pi_crypt_tab2[i_index] ^ i_cse;
753 i_index = pi_crypt_tab2[i_index] ^ pi_crypt_tab3[i_index] ^ i_term;
755 pi_tmp2[i] = pi_crypt_tab0[i_index] ^ pi_crypt_tab2[i_index];
757 pi_tmp2[4] ^= pi_tmp2[0];
759 for( i = 5, i_term = 0 ; --i >= 0 ; i_term = pi_tmp2[i] )
761 i_index = pi_bits[5 + i] ^ pi_tmp2[i];
762 i_index = pi_crypt_tab1[i_index] ^ ~pi_crypt_tab2[i_index] ^ i_cse;
764 pi_tmp1[i] = pi_crypt_tab2[i_index] ^ pi_crypt_tab3[i_index] ^ i_term;
766 pi_tmp1[4] ^= pi_tmp1[0];
768 for(i = 5, i_term = 0 ; --i >= 0 ; i_term = pi_tmp1[i] )
770 i_index = pi_bits[i] ^ pi_tmp1[i];
771 i_index = pi_crypt_tab1[i_index] ^ ~pi_crypt_tab2[i_index] ^ i_cse;
773 pi_key[i] = pi_crypt_tab2[i_index] ^ pi_crypt_tab3[i_index] ^ i_term;
779 /*****************************************************************************
780 * CSSCracker : title key decryption by cracking
781 *****************************************************************************
782 * This function is called by CSSGetKeys to find a key
783 *****************************************************************************/
784 static int CSSCracker( int i_start,
785 unsigned char * p_crypted,
786 unsigned char * p_decrypted,
787 dvd_key_t * p_sector_key,
790 unsigned char pi_buffer[10];
791 unsigned int i_t1, i_t2, i_t3, i_t4, i_t5, i_t6;
793 unsigned int i_candidate;
798 for( i = 0 ; i < 10 ; i++ )
800 pi_buffer[i] = pi_css_tab1[p_crypted[i]] ^ p_decrypted[i];
803 for( i_try = i_start ; i_try < 0x10000 ; i_try++ )
805 i_t1 = i_try >> 8 | 0x100;
807 i_t3 = 0; /* not needed */
810 /* iterate cipher 4 times to reconstruct LFSR2 */
811 for( i = 0 ; i < 4 ; i++ )
813 /* advance LFSR1 normaly */
814 i_t4 = pi_css_tab2[i_t2] ^ pi_css_tab3[i_t1];
816 i_t1 = ( ( i_t1 & 1 ) << 8 ) ^ i_t4;
817 i_t4 = pi_css_tab5[i_t4];
818 /* deduce i_t6 & i_t5 */
822 i_t6 = ( i_t6 + 0xff ) & 0x0ff;
830 i_t6 = pi_css_tab4[ i_t6 ];
831 /* feed / advance i_t3 / i_t5 */
832 i_t3 = ( i_t3 << 8 ) | i_t6;
838 /* iterate 6 more times to validate candidate key */
839 for( ; i < 10 ; i++ )
841 i_t4 = pi_css_tab2[i_t2] ^ pi_css_tab3[i_t1];
843 i_t1 = ( ( i_t1 & 1 ) << 8 ) ^ i_t4;
844 i_t4 = pi_css_tab5[i_t4];
845 i_t6 = ((((((( i_t3 >> 3 ) ^ i_t3 ) >> 1 ) ^
846 i_t3 ) >> 8 ) ^ i_t3 ) >> 5 ) & 0xff;
847 i_t3 = ( i_t3 << 8 ) | i_t6;
848 i_t6 = pi_css_tab4[i_t6];
850 if( ( i_t5 & 0xff ) != pi_buffer[i] )
860 /* Do 4 backwards steps of iterating t3 to deduce initial state */
862 for( i = 0 ; i < 4 ; i++ )
865 i_t3 = ( i_t3 >> 8 );
866 /* easy to code, and fast enough bruteforce
867 * search for byte shifted in */
868 for( j = 0 ; j < 256 ; j++ )
870 i_t3 = ( i_t3 & 0x1ffff) | ( j << 17 );
871 i_t6 = ((((((( i_t3 >> 3 ) ^ i_t3 ) >> 1 ) ^
872 i_t3 ) >> 8 ) ^ i_t3 ) >> 5 ) & 0xff;
880 i_t4 = ( i_t3 >> 1 ) - 4;
881 for( i_t5 = 0 ; i_t5 < 8; i_t5++ )
883 if( ( ( i_t4 + i_t5 ) * 2 + 8 - ( (i_t4 + i_t5 ) & 7 ) )
886 (*p_key)[0] = i_try>>8;
887 (*p_key)[1] = i_try & 0xFF;
888 (*p_key)[2] = ( ( i_t4 + i_t5 ) >> 0) & 0xFF;
889 (*p_key)[3] = ( ( i_t4 + i_t5 ) >> 8) & 0xFF;
890 (*p_key)[4] = ( ( i_t4 + i_t5 ) >> 16) & 0xFF;
899 (*p_key)[0] ^= (*p_sector_key)[0];
900 (*p_key)[1] ^= (*p_sector_key)[1];
901 (*p_key)[2] ^= (*p_sector_key)[2];
902 (*p_key)[3] ^= (*p_sector_key)[3];
903 (*p_key)[4] ^= (*p_sector_key)[4];
909 #endif /* HAVE_CSS */