package com.mpaa.decss;
import java.io.*;
/**
 * Title: LinearFeedbackShiftRegisterPair.java
 * Description: Sort of based on JDeCSS Java code originally written by Gavin Hall (www.tweakmonkey.freeserve.co.uk)
 * The title key cracker is based on Frank Stevenson's work describing various ways to break CSS and a close 
 * examinination of VobDec code.
 *
 * This version has been brought to you by DiatriBe.
 *
 * Note: There is no attempt to do DVD drive authentication in this code. You should first play the DVD 
 * with a software player (only for a second, unless you want to watch the whole movie). Once this is done, 
 * then authentication has completed. The VOB files can now be copied!
 * @author DiatriBe
 * @version 1.0
 */
public class CSSDescrambler
{
	LinearFeedbackShiftRegisterPair feedbackRegisterPair = new LinearFeedbackShiftRegisterPair();
	TitleKey titleKey;
	File inputVobFile;
	File outputVobFile;
	/**
	 * Default constructor.
	 *
	 * @param titleKey the 40 bit key used for the decryption.
	 * @param inputVobFile the source MPEG file. This can be the file that is directly on the DVD (once the drive has
	 * been authenticated, files can be copied directly from it).
	 * @param outputVobFile the file to write the decrpyted stream into.
	 */
	public CSSDescrambler(TitleKey titleKey, File inputVobFile, File outputVobFile)
	{
		this.titleKey = titleKey;
		this.inputVobFile = inputVobFile;
		this.outputVobFile = outputVobFile;
	}
	/**
	 * This method will descramble a file passed in to the constructor as inputVobFile to the file passed in as outputVobFile,
	 * using the title key.
	 */
	public void descramble()
	{
		try
		{
			DataInputStream reader = new DataInputStream(new BufferedInputStream(new FileInputStream(inputVobFile)));
			DataOutputStream writer = new DataOutputStream(new BufferedOutputStream(new FileOutputStream(outputVobFile)));
			long fileSize = inputVobFile.length();
			long bytesRead = 0;
			int[] sector = new int[2048];
			for (int block = 0; bytesRead < fileSize; block++) { for (int index = 0; index < 2048; index++) sector[index] = reader.readUnsignedByte(); bytesRead += 2048; if ((block % 1000) == 0) System.out.println("Decrypting block " + block); if ((sector[0x14] & 0x30) != 0) // PES scrambling control { sector = descrambleSector(sector); sector[0x14] &= 0x8F; } for (int index = 0; index < 2048; index++) writer.writeByte(sector[index]); } reader.close(); writer.flush(); writer.close(); } catch (FileNotFoundException fnfe) { System.out.println("The imput file '" + inputVobFile.getName() + "' could not be found."); } catch (Exception ex) { System.out.println("There was an error encountered while trying to decrypt '" + inputVobFile.getName() + "' to '" + outputVobFile.getName() + "'"); ex.printStackTrace(); } } /** * This method does the actual descrambling of a single sector. The title key is used to decrypt the data. * * @param sector int array (2048) containing an encrypted DVD sector. * @return returns the decrypted sector as a int array (2048). */ private int[] descrambleSector(int[] sector) { MirrorBitsTable mirrorTable = MirrorBitsTable.getInstance(); feedbackRegisterPair.setRegisters(titleKey); // feedbackRegisterPair.useClassic(true); int[] salt = { sector[0x54], sector[0x55], sector[0x56], sector[0x57], sector[0x58] }; feedbackRegisterPair.salt(salt); int carry = 0; for (int index = 128; index < 2048; index++) { feedbackRegisterPair.clockOneByte(); int cipherStreamOutput = feedbackRegisterPair.getLfsr17Output(true) + feedbackRegisterPair.getLfsr25Output(false) + carry; int tableSubstitution = SubstitutionTable.getAt(sector[index]); sector[index] = (cipherStreamOutput ^ tableSubstitution) & 0xFF; carry = cipherStreamOutput>> 8;
		}
		return sector;
	}
	/**
	 * This is the main method for the prgram that will be executed when the program is started.
	 *
	 * @param args command line arguments.
	 */
	public static void main(String[] args)
	{
		if (args.length != 2)
		{
			System.out.println("Wrong number of arguments (" + args.length + ") passed!");
			System.out.println("Format is CSSDescrambler 'input file name' 'output file name'");
			return;
		}
		File inputFile = new File(args[0]);
		System.out.println();
		System.out.println("Descrambling file '" + args[0] + "' to '" + args[1] + "'");
		System.out.println();
		System.out.println("Blocks in input file = " + (inputFile.length() / 2048));
		System.out.println();
		TitleKeyCracker titleKeyCracker = new TitleKeyCracker(inputFile);
		if (titleKeyCracker.attackKey())
		{
			TitleKey titleKey = titleKeyCracker.getTitleKey();
//			TitleKey titleKey = new TitleKey(0xA7, 0x07, 0xBF, 0x53, 0x84);
			System.out.println("Title key found is = " + titleKey.toString());
			System.out.println();
			System.out.println("Descrambling started.");
			CSSDescrambler cssDescrambler = new CSSDescrambler(titleKey, inputFile, new File(args[1]));
			long startTime = System.currentTimeMillis();
			cssDescrambler.descramble();
			long endTime = System.currentTimeMillis();
			System.out.println("Descrambling finished. Elapsed time = " + ((endTime - startTime) / 1000) + " sec");
		}
		else
			System.out.println("\n Unable to descramble file because title key attack failed");
	}
}
</div><div class="naked_ctrl">
<form action="/index.cgi/larger-text" method="get" name="gate">
<p><a href="http://altstyle.alfasado.net">AltStyle</a> によって変換されたページ <a href="http://www.cs.cmu.edu/~dst/DeCSS/Gallery/DiatriBe/CSSDescrambler.java">(-&gt;オリジナル)</a>
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