Here is the DeCSS code:
/*
* Copyright (C) 1999 Derek Fawcus
*
* This code may be used under the terms of Version 2 of the GPL,
* read the file COPYING for details.
*
*/
/*
* These routines do some reordering of the supplied data before
* calling engine() to do the main work.
*
* The reordering seems similar to that done by the initial stages of
* the DES algorithm, in that it looks like it's just been done to
* try and make software decoding slower. I'm not sure that it
* actually adds anything to the security.
*
* The nature of the shuffling is that the bits of the supplied
* parameter 'varient' are reorganised (and some inverted), and
* the bytes of the parameter 'challenge' are reorganised.
*
* The reorganisation in each routine is different, and the first
* (CryptKey1) does not bother of play with the 'varient' parameter.
*
* Since this code is only run once per disk change, I've made the
* code table driven in order to improve readability.
*
* Since these routines are so similar to each other, one could even
* abstract them all to one routine supplied a parameter determining
* the nature of the reordering it has to do.
*/
#include "css-auth.h"
typedef unsigned long u32;
static void engine(int varient, byte const *input, struct block *output);
void CryptKey1(int varient, byte const *challenge, struct block *key)
{
static byte perm_challenge[] = {1,3,0,7,5, 2,9,6,4,8};
byte scratch[10];
int i;
for (i = 9; i >= 0; --i)
scratch[i] = challenge[perm_challenge[i]];
engine(varient, scratch, key);
}
/* This shuffles the bits in varient to make perm_varient such that
* 4 -> !3
* 3 -> 4
* varient bits: 2 -> 0 perm_varient bits
* 1 -> 2
* 0 -> !1
*/
void CryptKey2(int varient, byte const *challenge, struct block *key)
{
static byte perm_challenge[] = {6,1,9,3,8, 5,7,4,0,2};
static byte perm_varient[] = {
0x0a, 0x08, 0x0e, 0x0c, 0x0b, 0x09, 0x0f, 0x0d,
0x1a, 0x18, 0x1e, 0x1c, 0x1b, 0x19, 0x1f, 0x1d,
0x02, 0x00, 0x06, 0x04, 0x03, 0x01, 0x07, 0x05,
0x12, 0x10, 0x16, 0x14, 0x13, 0x11, 0x17, 0x15};
byte scratch[10];
int i;
for (i = 9; i >= 0; --i)
scratch[i] = challenge[perm_challenge[i]];
engine(perm_varient[varient], scratch, key);
}
/* This shuffles the bits in varient to make perm_varient such that
* 4 -> 0
* 3 -> !1
* varient bits: 2 -> !4 perm_varient bits
* 1 -> 2
* 0 -> 3
*/
void CryptBusKey(int varient, byte const *challenge, struct block *key)
{
static byte perm_challenge[] = {4,0,3,5,7, 2,8,6,1,9};
static byte perm_varient[] = {
0x12, 0x1a, 0x16, 0x1e, 0x02, 0x0a, 0x06, 0x0e,
0x10, 0x18, 0x14, 0x1c, 0x00, 0x08, 0x04, 0x0c,
0x13, 0x1b, 0x17, 0x1f, 0x03, 0x0b, 0x07, 0x0f,
0x11, 0x19, 0x15, 0x1d, 0x01, 0x09, 0x05, 0x0d};
byte scratch[10];
int i;
for (i = 9; i >= 0; --i)
scratch[i] = challenge[perm_challenge[i]];
engine(perm_varient[varient], scratch, key);
}
/*
* We use two LFSR's (seeded from some of the input data bytes) to
* generate two streams of pseudo-random bits. These two bit streams
* are then combined by simply adding with carry to generate a final
* sequence of pseudo-random bits which is stored in the buffer that
* 'output' points to the end of - len is the size of this buffer.
*
* The first LFSR is of degree 25, and has a polynomial of:
* x^13 + x^5 + x^4 + x^1 + 1
*
* The second LSFR is of degree 17, and has a (primitive) polynomial
of:
* x^15 + x^1 + 1
*
* I don't know if these polynomials are primitive modulo 2, and thus
* represent maximal-period LFSR's.
*
*
* Note that we take the output of each LFSR from the new shifted in
* bit, not the old shifted out bit. Thus for ease of use the LFSR's
* are implemented in bit reversed order.
*
*/
static void generate_bits(byte *output, int len, struct block const
*s)
{
u32 lfsr0, lfsr1;
byte carry;
/* In order to ensure that the LFSR works we need to ensure that the
* initial values are non-zero. Thus when we initialise them from
* the seed, we ensure that a bit is set.
*/
lfsr0 = (s->b[0] b[1] b[2] & ~7) b[2] & 7);
lfsr1 = (s->b[3] b[4];
++output;
carry = 0;
do {
int bit;
byte val;
for (bit = 0, val = 0; bit > 24) ^ (lfsr0 >> 21) ^ (lfsr0 >> 20) ^ (lfsr0
>> 12)) & 1;
lfsr0 = (lfsr0 > 16) ^ (lfsr1 >> 2)) & 1;
lfsr1 = (lfsr1 > 1) & 1)
combined = !o_lfsr1 + carry + !o_lfsr0;
carry = BIT1(combined);
val |= BIT0(combined) 0);
}
static byte Secret[];
static byte Varients[];
static byte Table0[];
static byte Table1[];
static byte Table2[];
static byte Table3[];
/*
* This encryption engine implements one of 32 variations
* one the same theme depending upon the choice in the
* varient parameter (0 - 31).
*
* The algorithm itself manipulates a 40 bit input into
* a 40 bit output.
* The parameter 'input' is 80 bits. It consists of
* the 40 bit input value that is to be encrypted followed
* by a 40 bit seed value for the pseudo random number
* generators.
*/
static void engine(int varient, byte const *input, struct block *output)
{
byte cse, term, index;
struct block temp1;
struct block temp2;
byte bits[30];
int i;
/* Feed the secret into the input values such that
* we alter the seed to the LFSR's used above, then
* generate the bits to play with.
*/
for (i = 5; --i >= 0; )
temp1.b[i] = input[5 + i] ^ Secret[i] ^ Table2[i];
generate_bits(&bits[29], sizeof bits, &temp1);
/* This term is used throughout the following to
* select one of 32 different variations on the
* algorithm.
*/
cse = Varients[varient] ^ Table2[varient];
/* Now the actual blocks doing the encryption. Each
* of these works on 40 bits at a time and are quite
* similar.
*/
for (i = 5, term = 0; --i >= 0; term = input[i]) {
index = bits[25 + i] ^ input[i];
index = Table1[index] ^ ~Table2[index] ^ cse;
temp1.b[i] = Table2[index] ^ Table3[index] ^ term;
}
temp1.b[4] ^= temp1.b[0];
for (i = 5, term = 0; --i >= 0; term = temp1.b[i]) {
index = bits[20 + i] ^ temp1.b[i];
index = Table1[index] ^ ~Table2[index] ^ cse;
temp2.b[i] = Table2[index] ^ Table3[index] ^ term;
}
temp2.b[4] ^= temp2.b[0];
for (i = 5, term = 0; --i >= 0; term = temp2.b[i]) {
index = bits[15 + i] ^ temp2.b[i];
index = Table1[index] ^ ~Table2[index] ^ cse;
index = Table2[index] ^ Table3[index] ^ term;
temp1.b[i] = Table0[index] ^ Table2[index];
}
temp1.b[4] ^= temp1.b[0];
for (i = 5, term = 0; --i >= 0; term = temp1.b[i]) {
index = bits[10 + i] ^ temp1.b[i];
index = Table1[index] ^ ~Table2[index] ^ cse;
index = Table2[index] ^ Table3[index] ^ term;
temp2.b[i] = Table0[index] ^ Table2[index];
}
temp2.b[4] ^= temp2.b[0];
for (i = 5, term = 0; --i >= 0; term = temp2.b[i]) {
index = bits[5 + i] ^ temp2.b[i];
index = Table1[index] ^ ~Table2[index] ^ cse;
temp1.b[i] = Table2[index] ^ Table3[index] ^ term;
}
temp1.b[4] ^= temp1.b[0];
for (i = 5, term = 0; --i >= 0; term = temp1.b[i]) {
index = bits[i] ^ temp1.b[i];
index = Table1[index] ^ ~Table2[index] ^ cse;
output->b[i] = Table2[index] ^ Table3[index] ^ term;
}
}
static byte Varients[] = {
0xB7, 0x74, 0x85, 0xD0, 0xCC, 0xDB, 0xCA, 0x73,
0x03, 0xFE, 0x31, 0x03, 0x52, 0xE0, 0xB7, 0x42,
0x63, 0x16, 0xF2, 0x2A, 0x79, 0x52, 0xFF, 0x1B,
0x7A, 0x11, 0xCA, 0x1A, 0x9B, 0x40, 0xAD, 0x01};
static byte Secret[] = {0x55, 0xD6, 0xC4, 0xC5, 0x28};
static byte Table0[] = {
0xB7, 0xF4, 0x82, 0x57, 0xDA, 0x4D, 0xDB, 0xE2,
0x2F, 0x52, 0x1A, 0xA8, 0x68, 0x5A, 0x8A, 0xFF,
0xFB, 0x0E, 0x6D, 0x35, 0xF7, 0x5C, 0x76, 0x12,
0xCE, 0x25, 0x79, 0x29, 0x39, 0x62, 0x08, 0x24,
0xA5, 0x85, 0x7B, 0x56, 0x01, 0x23, 0x68, 0xCF,
0x0A, 0xE2, 0x5A, 0xED, 0x3D, 0x59, 0xB0, 0xA9,
0xB0, 0x2C, 0xF2, 0xB8, 0xEF, 0x32, 0xA9, 0x40,
0x80, 0x71, 0xAF, 0x1E, 0xDE, 0x8F, 0x58, 0x88,
0xB8, 0x3A, 0xD0, 0xFC, 0xC4, 0x1E, 0xB5, 0xA0,
0xBB, 0x3B, 0x0F, 0x01, 0x7E, 0x1F, 0x9F, 0xD9,
0xAA, 0xB8, 0x3D, 0x9D, 0x74, 0x1E, 0x25, 0xDB,
0x37, 0x56, 0x8F, 0x16, 0xBA, 0x49, 0x2B, 0xAC,
0xD0, 0xBD, 0x95, 0x20, 0xBE, 0x7A, 0x28, 0xD0,
0x51, 0x64, 0x63, 0x1C, 0x7F, 0x66, 0x10, 0xBB,
0xC4, 0x56, 0x1A, 0x04, 0x6E, 0x0A, 0xEC, 0x9C,
0xD6, 0xE8, 0x9A, 0x7A, 0xCF, 0x8C, 0xDB, 0xB1,
0xEF, 0x71, 0xDE, 0x31, 0xFF, 0x54, 0x3E, 0x5E,
0x07, 0x69, 0x96, 0xB0, 0xCF, 0xDD, 0x9E, 0x47,
0xC7, 0x96, 0x8F, 0xE4, 0x2B, 0x59, 0xC6, 0xEE,
0xB9, 0x86, 0x9A, 0x64, 0x84, 0x72, 0xE2, 0x5B,
0xA2, 0x96, 0x58, 0x99, 0x50, 0x03, 0xF5, 0x38,
0x4D, 0x02, 0x7D, 0xE7, 0x7D, 0x75, 0xA7, 0xB8,
0x67, 0x87, 0x84, 0x3F, 0x1D, 0x11, 0xE5, 0xFC,
0x1E, 0xD3, 0x83, 0x16, 0xA5, 0x29, 0xF6, 0xC7,
0x15, 0x61, 0x29, 0x1A, 0x43, 0x4F, 0x9B, 0xAF,
0xC5, 0x87, 0x34, 0x6C, 0x0F, 0x3B, 0xA8, 0x1D,
0x45, 0x58, 0x25, 0xDC, 0xA8, 0xA3, 0x3B, 0xD1,
0x79, 0x1B, 0x48, 0xF2, 0xE9, 0x93, 0x1F, 0xFC,
0xDB, 0x2A, 0x90, 0xA9, 0x8A, 0x3D, 0x39, 0x18,
0xA3, 0x8E, 0x58, 0x6C, 0xE0, 0x12, 0xBB, 0x25,
0xCD, 0x71, 0x22, 0xA2, 0x64, 0xC6, 0xE7, 0xFB,
0xAD, 0x94, 0x77, 0x04, 0x9A, 0x39, 0xCF, 0x7C};
static byte Table1[] = {
0x8C, 0x47, 0xB0, 0xE1, 0xEB, 0xFC, 0xEB, 0x56,
0x10, 0xE5, 0x2C, 0x1A, 0x5D, 0xEF, 0xBE, 0x4F,
0x08, 0x75, 0x97, 0x4B, 0x0E, 0x25, 0x8E, 0x6E,
0x39, 0x5A, 0x87, 0x53, 0xC4, 0x1F, 0xF4, 0x5C,
0x4E, 0xE6, 0x99, 0x30, 0xE0, 0x42, 0x88, 0xAB,
0xE5, 0x85, 0xBC, 0x8F, 0xD8, 0x3C, 0x54, 0xC9,
0x53, 0x47, 0x18, 0xD6, 0x06, 0x5B, 0x41, 0x2C,
0x67, 0x1E, 0x41, 0x74, 0x33, 0xE2, 0xB4, 0xE0,
0x23, 0x29, 0x42, 0xEA, 0x55, 0x0F, 0x25, 0xB4,
0x24, 0x2C, 0x99, 0x13, 0xEB, 0x0A, 0x0B, 0xC9,
0xF9, 0x63, 0x67, 0x43, 0x2D, 0xC7, 0x7D, 0x07,
0x60, 0x89, 0xD1, 0xCC, 0xE7, 0x94, 0x77, 0x74,
0x9B, 0x7E, 0xD7, 0xE6, 0xFF, 0xBB, 0x68, 0x14,
0x1E, 0xA3, 0x25, 0xDE, 0x3A, 0xA3, 0x54, 0x7B,
0x87, 0x9D, 0x50, 0xCA, 0x27, 0xC3, 0xA4, 0x50,
0x91, 0x27, 0xD4, 0xB0, 0x82, 0x41, 0x97, 0x79,
0x94, 0x82, 0xAC, 0xC7, 0x8E, 0xA5, 0x4E, 0xAA,
0x78, 0x9E, 0xE0, 0x42, 0xBA, 0x28, 0xEA, 0xB7,
0x74, 0xAD, 0x35, 0xDA, 0x92, 0x60, 0x7E, 0xD2,
0x0E, 0xB9, 0x24, 0x5E, 0x39, 0x4F, 0x5E, 0x63,
0x09, 0xB5, 0xFA, 0xBF, 0xF1, 0x22, 0x55, 0x1C,
0xE2, 0x25, 0xDB, 0xC5, 0xD8, 0x50, 0x03, 0x98,
0xC4, 0xAC, 0x2E, 0x11, 0xB4, 0x38, 0x4D, 0xD0,
0xB9, 0xFC, 0x2D, 0x3C, 0x08, 0x04, 0x5A, 0xEF,
0xCE, 0x32, 0xFB, 0x4C, 0x92, 0x1E, 0x4B, 0xFB,
0x1A, 0xD0, 0xE2, 0x3E, 0xDA, 0x6E, 0x7C, 0x4D,
0x56, 0xC3, 0x3F, 0x42, 0xB1, 0x3A, 0x23, 0x4D,
0x6E, 0x84, 0x56, 0x68, 0xF4, 0x0E, 0x03, 0x64,
0xD0, 0xA9, 0x92, 0x2F, 0x8B, 0xBC, 0x39, 0x9C,
0xAC, 0x09, 0x5E, 0xEE, 0xE5, 0x97, 0xBF, 0xA5,
0xCE, 0xFA, 0x28, 0x2C, 0x6D, 0x4F, 0xEF, 0x77,
0xAA, 0x1B, 0x79, 0x8E, 0x97, 0xB4, 0xC3, 0xF4};
static byte Table2[] = {
0xB7, 0x75, 0x81, 0xD5, 0xDC, 0xCA, 0xDE, 0x66,
0x23, 0xDF, 0x15, 0x26, 0x62, 0xD1, 0x83, 0x77,
0xE3, 0x97, 0x76, 0xAF, 0xE9, 0xC3, 0x6B, 0x8E,
0xDA, 0xB0, 0x6E, 0xBF, 0x2B, 0xF1, 0x19, 0xB4,
0x95, 0x34, 0x48, 0xE4, 0x37, 0x94, 0x5D, 0x7B,
0x36, 0x5F, 0x65, 0x53, 0x07, 0xE2, 0x89, 0x11,
0x98, 0x85, 0xD9, 0x12, 0xC1, 0x9D, 0x84, 0xEC,
0xA4, 0xD4, 0x88, 0xB8, 0xFC, 0x2C, 0x79, 0x28,
0xD8, 0xDB, 0xB3, 0x1E, 0xA2, 0xF9, 0xD0, 0x44,
0xD7, 0xD6, 0x60, 0xEF, 0x14, 0xF4, 0xF6, 0x31,
0xD2, 0x41, 0x46, 0x67, 0x0A, 0xE1, 0x58, 0x27,
0x43, 0xA3, 0xF8, 0xE0, 0xC8, 0xBA, 0x5A, 0x5C,
0x80, 0x6C, 0xC6, 0xF2, 0xE8, 0xAD, 0x7D, 0x04,
0x0D, 0xB9, 0x3C, 0xC2, 0x25, 0xBD, 0x49, 0x63,
0x8C, 0x9F, 0x51, 0xCE, 0x20, 0xC5, 0xA1, 0x50,
0x92, 0x2D, 0xDD, 0xBC, 0x8D, 0x4F, 0x9A, 0x71,
0x2F, 0x30, 0x1D, 0x73, 0x39, 0x13, 0xFB, 0x1A,
0xCB, 0x24, 0x59, 0xFE, 0x05, 0x96, 0x57, 0x0F,
0x1F, 0xCF, 0x54, 0xBE, 0xF5, 0x06, 0x1B, 0xB2,
0x6D, 0xD3, 0x4D, 0x32, 0x56, 0x21, 0x33, 0x0B,
0x52, 0xE7, 0xAB, 0xEB, 0xA6, 0x74, 0x00, 0x4C,
0xB1, 0x7F, 0x82, 0x99, 0x87, 0x0E, 0x5E, 0xC0,
0x8F, 0xEE, 0x6F, 0x55, 0xF3, 0x7E, 0x08, 0x90,
0xFA, 0xB6, 0x64, 0x70, 0x47, 0x4A, 0x17, 0xA7,
0xB5, 0x40, 0x8A, 0x38, 0xE5, 0x68, 0x3E, 0x8B,
0x69, 0xAA, 0x9B, 0x42, 0xA5, 0x10, 0x01, 0x35,
0xFD, 0x61, 0x9E, 0xE6, 0x16, 0x9C, 0x86, 0xED,
0xCD, 0x2E, 0xFF, 0xC4, 0x5B, 0xA0, 0xAE, 0xCC,
0x4B, 0x3B, 0x03, 0xBB, 0x1C, 0x2A, 0xAC, 0x0C,
0x3F, 0x93, 0xC7, 0x72, 0x7A, 0x09, 0x22, 0x3D,
0x45, 0x78, 0xA9, 0xA8, 0xEA, 0xC9, 0x6A, 0xF7,
0x29, 0x91, 0xF0, 0x02, 0x18, 0x3A, 0x4E, 0x7C};
static byte Table3[] = {
0x73, 0x51, 0x95, 0xE1, 0x12, 0xE4, 0xC0, 0x58,
0xEE, 0xF2, 0x08, 0x1B, 0xA9, 0xFA, 0x98, 0x4C,
0xA7, 0x33, 0xE2, 0x1B, 0xA7, 0x6D, 0xF5, 0x30,
0x97, 0x1D, 0xF3, 0x02, 0x60, 0x5A, 0x82, 0x0F,
0x91, 0xD0, 0x9C, 0x10, 0x39, 0x7A, 0x83, 0x85,
0x3B, 0xB2, 0xB8, 0xAE, 0x0C, 0x09, 0x52, 0xEA,
0x1C, 0xE1, 0x8D, 0x66, 0x4F, 0xF3, 0xDA, 0x92,
0x29, 0xB9, 0xD5, 0xC5, 0x77, 0x47, 0x22, 0x53,
0x14, 0xF7, 0xAF, 0x22, 0x64, 0xDF, 0xC6, 0x72,
0x12, 0xF3, 0x75, 0xDA, 0xD7, 0xD7, 0xE5, 0x02,
0x9E, 0xED, 0xDA, 0xDB, 0x4C, 0x47, 0xCE, 0x91,
0x06, 0x06, 0x6D, 0x55, 0x8B, 0x19, 0xC9, 0xEF,
0x8C, 0x80, 0x1A, 0x0E, 0xEE, 0x4B, 0xAB, 0xF2,
0x08, 0x5C, 0xE9, 0x37, 0x26, 0x5E, 0x9A, 0x90,
0x00, 0xF3, 0x0D, 0xB2, 0xA6, 0xA3, 0xF7, 0x26,
0x17, 0x48, 0x88, 0xC9, 0x0E, 0x2C, 0xC9, 0x02,
0xE7, 0x18, 0x05, 0x4B, 0xF3, 0x39, 0xE1, 0x20,
0x02, 0x0D, 0x40, 0xC7, 0xCA, 0xB9, 0x48, 0x30,
0x57, 0x67, 0xCC, 0x06, 0xBF, 0xAC, 0x81, 0x08,
0x24, 0x7A, 0xD4, 0x8B, 0x19, 0x8E, 0xAC, 0xB4,
0x5A, 0x0F, 0x73, 0x13, 0xAC, 0x9E, 0xDA, 0xB6,
0xB8, 0x96, 0x5B, 0x60, 0x88, 0xE1, 0x81, 0x3F,
0x07, 0x86, 0x37, 0x2D, 0x79, 0x14, 0x52, 0xEA,
0x73, 0xDF, 0x3D, 0x09, 0xC8, 0x25, 0x48, 0xD8,
0x75, 0x60, 0x9A, 0x08, 0x27, 0x4A, 0x2C, 0xB9,
0xA8, 0x8B, 0x8A, 0x73, 0x62, 0x37, 0x16, 0x02,
0xBD, 0xC1, 0x0E, 0x56, 0x54, 0x3E, 0x14, 0x5F,
0x8C, 0x8F, 0x6E, 0x75, 0x1C, 0x07, 0x39, 0x7B,
0x4B, 0xDB, 0xD3, 0x4B, 0x1E, 0xC8, 0x7E, 0xFE,
0x3E, 0x72, 0x16, 0x83, 0x7D, 0xEE, 0xF5, 0xCA,
0xC5, 0x18, 0xF9, 0xD8, 0x68, 0xAB, 0x38, 0x85,
0xA8, 0xF0, 0xA1, 0x73, 0x9F, 0x5D, 0x19, 0x0B,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x33, 0x72, 0x39, 0x25, 0x67, 0x26, 0x6D, 0x71,
0x36, 0x77, 0x3C, 0x20, 0x62, 0x23, 0x68, 0x74,
0xC3, 0x82, 0xC9, 0x15, 0x57, 0x16, 0x5D, 0x81};