User: loadfix

DeCCS

On: A New DeCSS

/*
* css_descramble.c
*
* Released under the version 2 of the GPL.
*
* Copyright 1999 Derek Fawcus
*
* This file contains functions to descramble CSS encrypted DVD content
*
*/

/*
* Still in progress: Remove the use of the bit_reverse[] table by recoding
* the generation of LFSR1. Finish combining this with
* the css authentication code.
*
*/

#include
#include
#include "css-descramble.h"

typedef unsigned char byte;

/*
*
* some tables used for descrambling sectors and/or decrypting title keys
*
*/

static byte csstab1[256]=
{
0x33,0x73,0x3b,0x26,0x63,0x23,0x6b,0x76,0x3e,0x7e, 0x36,0x2b,0x6e,0x2e,0x66,0x7b,
0xd3,0x93,0xdb,0x06,0x43,0x03,0x4b,0x96,0xde,0x9e, 0xd6,0x0b,0x4e,0x0e,0x46,0x9b,
0x57,0x17,0x5f,0x82,0xc7,0x87,0xcf,0x12,0x5a,0x1a, 0x52,0x8f,0xca,0x8a,0xc2,0x1f,
0xd9,0x99,0xd1,0x00,0x49,0x09,0x41,0x90,0xd8,0x98, 0xd0,0x01,0x48,0x08,0x40,0x91,
0x3d,0x7d,0x35,0x24,0x6d,0x2d,0x65,0x74,0x3c,0x7c, 0x34,0x25,0x6c,0x2c,0x64,0x75,
0xdd,0x9d,0xd5,0x04,0x4d,0x0d,0x45,0x94,0xdc,0x9c, 0xd4,0x05,0x4c,0x0c,0x44,0x95,
0x59,0x19,0x51,0x80,0xc9,0x89,0xc1,0x10,0x58,0x18, 0x50,0x81,0xc8,0x88,0xc0,0x11,
0xd7,0x97,0xdf,0x02,0x47,0x07,0x4f,0x92,0xda,0x9a, 0xd2,0x0f,0x4a,0x0a,0x42,0x9f,
0x53,0x13,0x5b,0x86,0xc3,0x83,0xcb,0x16,0x5e,0x1e, 0x56,0x8b,0xce,0x8e,0xc6,0x1b,
0xb3,0xf3,0xbb,0xa6,0xe3,0xa3,0xeb,0xf6,0xbe,0xfe, 0xb6,0xab,0xee,0xae,0xe6,0xfb,
0x37,0x77,0x3f,0x22,0x67,0x27,0x6f,0x72,0x3a,0x7a, 0x32,0x2f,0x6a,0x2a,0x62,0x7f,
0xb9,0xf9,0xb1,0xa0,0xe9,0xa9,0xe1,0xf0,0xb8,0xf8, 0xb0,0xa1,0xe8,0xa8,0xe0,0xf1,
0x5d,0x1d,0x55,0x84,0xcd,0x8d,0xc5,0x14,0x5c,0x1c, 0x54,0x85,0xcc,0x8c,0xc4,0x15,
0xbd,0xfd,0xb5,0xa4,0xed,0xad,0xe5,0xf4,0xbc,0xfc, 0xb4,0xa5,0xec,0xac,0xe4,0xf5,
0x39,0x79,0x31,0x20,0x69,0x29,0x61,0x70,0x38,0x78, 0x30,0x21,0x68,0x28,0x60,0x71,
0xb7,0xf7,0xbf,0xa2,0xe7,0xa7,0xef,0xf2,0xba,0xfa, 0xb2,0xaf,0xea,0xaa,0xe2,0xff
};

static byte lfsr1_bits0[256]=
{
0x00,0x01,0x02,0x03,0x04,0x05,0x06,0x07,0x09,0x08, 0x0b,0x0a,0x0d,0x0c,0x0f,0x0e,
0x12,0x13,0x10,0x11,0x16,0x17,0x14,0x15,0x1b,0x1a, 0x19,0x18,0x1f,0x1e,0x1d,0x1c,
0x24,0x25,0x26,0x27,0x20,0x21,0x22,0x23,0x2d,0x2c, 0x2f,0x2e,0x29,0x28,0x2b,0x2a,
0x36,0x37,0x34,0x35,0x32,0x33,0x30,0x31,0x3f,0x3e, 0x3d,0x3c,0x3b,0x3a,0x39,0x38,
0x49,0x48,0x4b,0x4a,0x4d,0x4c,0x4f,0x4e,0x40,0x41, 0x42,0x43,0x44,0x45,0x46,0x47,
0x5b,0x5a,0x59,0x58,0x5f,0x5e,0x5d,0x5c,0x52,0x53, 0x50,0x51,0x56,0x57,0x54,0x55,
0x6d,0x6c,0x6f,0x6e,0x69,0x68,0x6b,0x6a,0x64,0x65, 0x66,0x67,0x60,0x61,0x62,0x63,
0x7f,0x7e,0x7d,0x7c,0x7b,0x7a,0x79,0x78,0x76,0x77, 0x74,0x75,0x72,0x73,0x70,0x71,
0x92,0x93,0x90,0x91,0x96,0x97,0x94,0x95,0x9b,0x9a, 0x99,0x98,0x9f,0x9e,0x9d,0x9c,
0x80,0x81,0x82,0x83,0x84,0x85,0x86,0x87,0x89,0x88, 0x8b,0x8a,0x8d,0x8c,0x8f,0x8e,
0xb6,0xb7,0xb4,0xb5,0xb2,0xb3,0xb0,0xb1,0xbf,0xbe, 0xbd,0xbc,0xbb,0xba,0xb9,0xb8,
0xa4,0xa5,0xa6,0xa7,0xa0,0xa1,0xa2,0xa3,0xad,0xac, 0xaf,0xae,0xa9,0xa8,0xab,0xaa,
0xdb,0xda,0xd9,0xd8,0xdf,0xde,0xdd,0xdc,0xd2,0xd3, 0xd0,0xd1,0xd6,0xd7,0xd4,0xd5,
0xc9,0xc8,0xcb,0xca,0xcd,0xcc,0xcf,0xce,0xc0,0xc1, 0xc2,0xc3,0xc4,0xc5,0xc6,0xc7,
0xff,0xfe,0xfd,0xfc,0xfb,0xfa,0xf9,0xf8,0xf6,0xf7, 0xf4,0xf5,0xf2,0xf3,0xf0,0xf1,
0xed,0xec,0xef,0xee,0xe9,0xe8,0xeb,0xea,0xe4,0xe5, 0xe6,0xe7,0xe0,0xe1,0xe2,0xe3
};

static byte lfsr1_bits1[512]=
{
0x00,0x24,0x49,0x6d,0x92,0xb6,0xdb,0xff,0x00,0x24, 0x49,0x6d,0x92,0xb6,0xdb,0xff,
0x00,0x24,0x49,0x6d,0x92,0xb6,0xdb,0xff,0x00,0x24, 0x49,0x6d,0x92,0xb6,0xdb,0xff,
0x00,0x24,0x49,0x6d,0x92,0xb6,0xdb,0xff,0x00,0x24, 0x49,0x6d,0x92,0xb6,0xdb,0xff,
0x00,0x24,0x49,0x6d,0x92,0xb6,0xdb,0xff,0x00,0x24, 0x49,0x6d,0x92,0xb6,0xdb,0xff,
0x00,0x24,0x49,0x6d,0x92,0xb6,0xdb,0xff,0x00,0x24, 0x49,0x6d,0x92,0xb6,0xdb,0xff,
0x00,0x24,0x49,0x6d,0x92,0xb6,0xdb,0xff,0x00,0x24, 0x49,0x6d,0x92,0xb6,0xdb,0xff,
0x00,0x24,0x49,0x6d,0x92,0xb6,0xdb,0xff,0x00,0x24, 0x49,0x6d,0x92,0xb6,0xdb,0xff,
0x00,0x24,0x49,0x6d,0x92,0xb6,0xdb,0xff,0x00,0x24, 0x49,0x6d,0x92,0xb6,0xdb,0xff,
0x00,0x24,0x49,0x6d,0x92,0xb6,0xdb,0xff,0x00,0x24, 0x49,0x6d,0x92,0xb6,0xdb,0xff,
0x00,0x24,0x49,0x6d,0x92,0xb6,0xdb,0xff,0x00,0x24, 0x49,0x6d,0x92,0xb6,0xdb,0xff,
0x00,0x24,0x49,0x6d,0x92,0xb6,0xdb,0xff,0x00,0x24, 0x49,0x6d,0x92,0xb6,0xdb,0xff,
0x00,0x24,0x49,0x6d,0x92,0xb6,0xdb,0xff,0x00,0x24, 0x49,0x6d,0x92,0xb6,0xdb,0xff,
0x00,0x24,0x49,0x6d,0x92,0xb6,0xdb,0xff,0x00,0x24, 0x49,0x6d,0x92,0xb6,0xdb,0xff,
0x00,0x24,0x49,0x6d,0x92,0xb6,0xdb,0xff,0x00,0x24, 0x49,0x6d,0x92,0xb6,0xdb,0xff,
0x00,0x24,0x49,0x6d,0x92,0xb6,0xdb,0xff,0x00,0x24, 0x49,0x6d,0x92,0xb6,0xdb,0xff,
0x00,0x24,0x49,0x6d,0x92,0xb6,0xdb,0xff,0x00,0x24, 0x49,0x6d,0x92,0xb6,0xdb,0xff,
0x00,0x24,0x49,0x6d,0x92,0xb6,0xdb,0xff,0x00,0x24, 0x49,0x6d,0x92,0xb6,0xdb,0xff,
0x00,0x24,0x49,0x6d,0x92,0xb6,0xdb,0xff,0x00,0x24, 0x49,0x6d,0x92,0xb6,0xdb,0xff,
0x00,0x24,0x49,0x6d,0x92,0xb6,0xdb,0xff,0x00,0x24, 0x49,0x6d,0x92,0xb6,0xdb,0xff,
0x00,0x24,0x49,0x6d,0x92,0xb6,0xdb,0xff,0x00,0x24, 0x49,0x6d,0x92,0xb6,0xdb,0xff,
0x00,0x24,0x49,0x6d,0x92,0xb6,0xdb,0xff,0x00,0x24, 0x49,0x6d,0x92,0xb6,0xdb,0xff,
0x00,0x24,0x49,0x6d,0x92,0xb6,0xdb,0xff,0x00,0x24, 0x49,0x6d,0x92,0xb6,0xdb,0xff,
0x00,0x24,0x49,0x6d,0x92,0xb6,0xdb,0xff,0x00,0x24, 0x49,0x6d,0x92,0xb6,0xdb,0xff,
0x00,0x24,0x49,0x6d,0x92,0xb6,0xdb,0xff,0x00,0x24, 0x49,0x6d,0x92,0xb6,0xdb,0xff,
0x00,0x24,0x49,0x6d,0x92,0xb6,0xdb,0xff,0x00,0x24, 0x49,0x6d,0x92,0xb6,0xdb,0xff,
0x00,0x24,0x49,0x6d,0x92,0xb6,0xdb,0xff,0x00,0x24, 0x49,0x6d,0x92,0xb6,0xdb,0xff,
0x00,0x24,0x49,0x6d,0x92,0xb6,0xdb,0xff,0x00,0x24, 0x49,0x6d,0x92,0xb6,0xdb,0xff,
0x00,0x24,0x49,0x6d,0x92,0xb6,0xdb,0xff,0x00,0x24, 0x49,0x6d,0x92,0xb6,0xdb,0xff,
0x00,0x24,0x49,0x6d,0x92,0xb6,0xdb,0xff,0x00,0x24, 0x49,0x6d,0x92,0xb6,0xdb,0xff,
0x00,0x24,0x49,0x6d,0x92,0xb6,0xdb,0xff,0x00,0x24, 0x49,0x6d,0x92,0xb6,0xdb,0xff,
0x00,0x24,0x49,0x6d,0x92,0xb6,0xdb,0xff,0x00,0x24, 0x49,0x6d,0x92,0xb6,0xdb,0xff,
0x00,0x24,0x49,0x6d,0x92,0xb6,0xdb,0xff,0x00,0x24, 0x49,0x6d,0x92,0xb6,0xdb,0xff
};

/* Reverse the order of the bits within a byte.
*/
static byte bit_reverse[256]=
{
0x00,0x80,0x40,0xc0,0x20,0xa0,0x60,0xe0,0x10,0x90, 0x50,0xd0,0x30,0xb0,0x70,0xf0,
0x08,0x88,0x48,0xc8,0x28,0xa8,0x68,0xe8,0x18,0x98, 0x58,0xd8,0x38,0xb8,0x78,0xf8,
0x04,0x84,0x44,0xc4,0x24,0xa4,0x64,0xe4,0x14,0x94, 0x54,0xd4,0x34,0xb4,0x74,0xf4,
0x0c,0x8c,0x4c,0xcc,0x2c,0xac,0x6c,0xec,0x1c,0x9c, 0x5c,0xdc,0x3c,0xbc,0x7c,0xfc,
0x02,0x82,0x42,0xc2,0x22,0xa2,0x62,0xe2,0x12,0x92, 0x52,0xd2,0x32,0xb2,0x72,0xf2,
0x0a,0x8a,0x4a,0xca,0x2a,0xaa,0x6a,0xea,0x1a,0x9a, 0x5a,0xda,0x3a,0xba,0x7a,0xfa,
0x06,0x86,0x46,0xc6,0x26,0xa6,0x66,0xe6,0x16,0x96, 0x56,0xd6,0x36,0xb6,0x76,0xf6,
0x0e,0x8e,0x4e,0xce,0x2e,0xae,0x6e,0xee,0x1e,0x9e, 0x5e,0xde,0x3e,0xbe,0x7e,0xfe,
0x01,0x81,0x41,0xc1,0x21,0xa1,0x61,0xe1,0x11,0x91, 0x51,0xd1,0x31,0xb1,0x71,0xf1,
0x09,0x89,0x49,0xc9,0x29,0xa9,0x69,0xe9,0x19,0x99, 0x59,0xd9,0x39,0xb9,0x79,0xf9,
0x05,0x85,0x45,0xc5,0x25,0xa5,0x65,0xe5,0x15,0x95, 0x55,0xd5,0x35,0xb5,0x75,0xf5,
0x0d,0x8d,0x4d,0xcd,0x2d,0xad,0x6d,0xed,0x1d,0x9d, 0x5d,0xdd,0x3d,0xbd,0x7d,0xfd,
0x03,0x83,0x43,0xc3,0x23,0xa3,0x63,0xe3,0x13,0x93, 0x53,0xd3,0x33,0xb3,0x73,0xf3,
0x0b,0x8b,0x4b,0xcb,0x2b,0xab,0x6b,0xeb,0x1b,0x9b, 0x5b,0xdb,0x3b,0xbb,0x7b,0xfb,
0x07,0x87,0x47,0xc7,0x27,0xa7,0x67,0xe7,0x17,0x97, 0x57,0xd7,0x37,0xb7,0x77,0xf7,
0x0f,0x8f,0x4f,0xcf,0x2f,0xaf,0x6f,0xef,0x1f,0x9f, 0x5f,0xdf,0x3f,0xbf,0x7f,0xff
};

/*
*
* this function is only used internally when decrypting title key
*
*/
static void css_titlekey(byte *key, byte *im, byte invert)
{
unsigned int lfsr1_lo,lfsr1_hi,lfsr0,combined;
byte o_lfsr0, o_lfsr1;
byte k[5];
int i;

lfsr1_lo = im[0] | 0x100;
lfsr1_hi = im[1];

lfsr0 = ((im[4] >8)&0xff] >16)&0xff]>24)&0xff];

combined = 0;
for (i = 0; i >1;
lfsr1_lo = ((lfsr1_lo&1)>7)^(lfsr0>>10)^(lfsr0>>11)^(lfsr0>>1 9);*/
o_lfsr0 = (((((((lfsr0>>8)^lfsr0)>>1)^lfsr0)>>3)^lfsr0)>>7);
lfsr0 = (lfsr0>>8)|(o_lfsr0>= 8;
}

key[4]=k[4]^csstab1[key[4]]^key[3];
key[3]=k[3]^csstab1[key[3]]^key[2];
key[2]=k[2]^csstab1[key[2]]^key[1];
key[1]=k[1]^csstab1[key[1]]^key[0];
key[0]=k[0]^csstab1[key[0]]^key[4];

key[4]=k[4]^csstab1[key[4]]^key[3];
key[3]=k[3]^csstab1[key[3]]^key[2];
key[2]=k[2]^csstab1[key[2]]^key[1];
key[1]=k[1]^csstab1[key[1]]^key[0];
key[0]=k[0]^csstab1[key[0]];
}

/*
*
* this function decrypts a title key with the specified disk key
*
* tkey: the unobfuscated title key (XORed with BusKey)
* dkey: the unobfuscated disk key (XORed with BusKey)
* 2048 bytes in length (though only 5 bytes are needed, see below)
* pkey: array of pointers to player keys and disk key offsets
*
*
* use the result returned in tkey with css_descramble
*
*/

int css_decrypttitlekey(byte *tkey, byte *dkey, struct playkey **pkey)
{
byte test[5], pretkey[5];
int i = 0;

for (; *pkey; ++pkey, ++i) {
memcpy(pretkey, dkey + (*pkey)->offset, 5);
css_titlekey(pretkey, (*pkey)->key, 0);

memcpy(test, dkey, 5);
css_titlekey(test, pretkey, 0);

if (memcmp(test, pretkey, 5) == 0) {
fprintf(stderr, "Using Key %d\n", i+1);
break;
}
}

if (!*pkey) {
fprintf(stderr, "Shit - Need Key %d\n", i+1);
return 0;
}

css_titlekey(tkey, pretkey, 0xff);

return 1;
}

/*
*
* this function does the actual descrambling
*
* sec: encrypted sector (2048 bytes)
* key: decrypted title key obtained from css_decrypttitlekey
*
*/
void css_descramble(byte *sec,byte *key)
{
unsigned int lfsr1_lo,lfsr1_hi,lfsr0,combined;
unsigned char o_lfsr0, o_lfsr1;
unsigned char *end = sec + 0x800;
#define SALTED(i) (key[i] ^ sec[0x54 + (i)])

lfsr1_lo = SALTED(0) | 0x100;
lfsr1_hi = SALTED(1);

lfsr0 = ((SALTED(4) >8)&0xff] >16)&0xff]>24)&0xff];

sec+=0x80;
combined = 0;
while (sec != end) {
o_lfsr1 = lfsr1_bits0[lfsr1_hi] ^ lfsr1_bits1[lfsr1_lo];
lfsr1_hi = lfsr1_lo>>1;
lfsr1_lo = ((lfsr1_lo&1)>7)^(lfsr0>>10)^(lfsr0>>11)^(lfsr0>>1 9);*/
o_lfsr0 = (((((((lfsr0>>8)^lfsr0)>>1)^lfsr0)>>3)^lfsr0)>>7);
lfsr0 = (lfsr0>>8)|(o_lfsr0>= 8;
}
}

Enough said.....