import java.io.*;import crypt.*;import ortega.*;public class Extract {    private static File f;	    // carrier file    private static byte[] carrier;  // carrier data    private static int[] coeff;     // dct values    private static FileOutputStream fos;   // embedded file (output file)    private static String embFileName;	// output file name    private static String password;    private static byte[] deZigZag = {       0,  1,  5,  6, 14, 15, 27, 28,       2,  4,  7, 13, 16, 26, 29, 42,       3,  8, 12, 17, 25, 30, 41, 43,       9, 11, 18, 24, 31, 40, 44, 53,      10, 19, 23, 32, 39, 45, 52, 54,      20, 22, 33, 38, 46, 51, 55, 60,      21, 34, 37, 47, 50, 56, 59, 61,      35, 36, 48, 49, 57, 58, 62, 63    };    static void usage() {	System.out.println("java Extract [Options] \"image.jpg\"");	System.out.println("Options:");	System.out.println("\t-p password (default: abc123)");	System.out.println("\t-e extractedFileName (default: output.txt)");        System.out.println("\nAuthor: Andreas Westfeld, westfeld@inf.tu-dresden.de");	System.exit(0);    }    public static void main(String[] args) {    	embFileName = "output.txt";	password = "abc123";	try {	    if (args.length < 1)		usage();	    for (int i=0; i<args.length; i++) {		if (!args[i].startsWith("-")) {		    if (!args[i].endsWith(".jpg"))			usage();		    f = new File(args[i]);		    continue;		}		if (args.length < i+1) {		    System.out.println("Missing parameter for switch "+args[i]);		    usage();		}		if (args[i].equals("-e")) {		    embFileName = args[i+1];		} else if (args[i].equals("-p")) {		    password = args[i+1];		} else		    System.out.println("Unknown switch "					    +args[i]+" ignored.");		i++;	    }	    carrier = new byte[(int)f.length()];	    FileInputStream fis = new FileInputStream(f);	    fos = new FileOutputStream(new File(embFileName));	    fis.read(carrier);	    HuffmanDecode hd = new HuffmanDecode(carrier);System.out.println("Huffman decoding starts");	    coeff=hd.decode();System.out.println("Permutation starts");	    F5Random random = new F5Random(password.getBytes());	    Permutation permutation = new Permutation(coeff.length, random);System.out.println(coeff.length+" indices shuffled");	    int extractedByte=0;	    int availableExtractedBits=0;	    int extractedFileLength=0;	    int nBytesExtracted=0;	    int shuffledIndex=0;	    int extractedBit;	    int i;	    int one=0;System.out.println("Extraction starts");	    // extract length information	    for (i=0; availableExtractedBits<32; i++) {		shuffledIndex = permutation.getShuffled(i);		if (shuffledIndex%64 == 0) continue; // skip DC coefficients		shuffledIndex = shuffledIndex-(shuffledIndex%64)+deZigZag[shuffledIndex%64];                if (coeff[shuffledIndex] == 0) continue; // skip zeroes		// rev. 12: skip every second 1 or -1		if (Math.abs(coeff[shuffledIndex]) == 1)		    if (((++one)&1) == 0) continue;		if (coeff[shuffledIndex] > 0)		    extractedBit=coeff[shuffledIndex]&1;		else		    extractedBit=1-(coeff[shuffledIndex]&1);		extractedFileLength |= extractedBit << availableExtractedBits++;	    }	    // remove pseudo random pad	    extractedFileLength ^= random.getNextByte();	    extractedFileLength ^= random.getNextByte()<<8;	    extractedFileLength ^= random.getNextByte()<<16;	    extractedFileLength ^= random.getNextByte()<<24;	    int k = extractedFileLength >> 24;	    k %= 32;	    int n = (1 << k)-1;	    extractedFileLength &= 0x007fffff;System.out.println("Length of embedded file: "+extractedFileLength+" bytes");	    availableExtractedBits = 0;	    if (n>0) {		int startOfN = i;		int hash;		System.out.println("(1, "+n+", "+k+") code used");extractingLoop:		do {		    // 1. read n places, and calculate k bits		    hash = 0;		    int code = 1;		    for (i=0; code<=n; i++) {			// check for pending end of coeff			if (startOfN+i>=coeff.length) break extractingLoop;			shuffledIndex = permutation.getShuffled(startOfN+i);			if (shuffledIndex%64 == 0) continue; // skip DC coefficients			shuffledIndex = shuffledIndex-(shuffledIndex%64)+deZigZag[shuffledIndex%64];			if (coeff[shuffledIndex] == 0) continue; // skip zeroes			// rev. 12: skip every second 1 or -1			if (Math.abs(coeff[shuffledIndex]) == 1)			    if ((++one&1) == 0) continue;			if (coeff[shuffledIndex] > 0)			    extractedBit=coeff[shuffledIndex]&1;			else			    extractedBit=1-(coeff[shuffledIndex]&1);			if (extractedBit==1) {			    hash ^= code;			}			code++;		    }		    startOfN += i;		    // 2. write k bits bytewise		    for (i=0; i<k; i++) {			extractedByte |= ((hash>>i)&1) << availableExtractedBits++;			if (availableExtractedBits == 8) {			    // remove pseudo random pad			    extractedByte ^= random.getNextByte();			    fos.write((byte) extractedByte);			    extractedByte=0;			    availableExtractedBits=0;			    nBytesExtracted++;			    // check for pending end of embedded data			    if (nBytesExtracted==extractedFileLength)				break extractingLoop;			}		    }		} while (true);	    } else {		System.out.println("Default code used");		for (; i<coeff.length; i++) {		    shuffledIndex = permutation.getShuffled(i);		    if (shuffledIndex%64 == 0) continue; // skip DC coefficients		    shuffledIndex = shuffledIndex-(shuffledIndex%64)+deZigZag[shuffledIndex%64];		    if (coeff[shuffledIndex] == 0) continue; // skip zeroes		    // rev. 12: skip every second 1 or -1		    if (Math.abs(coeff[shuffledIndex]) == 1)			if ((++one&1) == 0) continue;		    if (coeff[shuffledIndex] > 0)			extractedBit=coeff[shuffledIndex]&1;		    else			extractedBit=1-(coeff[shuffledIndex]&1);		    extractedByte |= extractedBit << availableExtractedBits++;		    if (availableExtractedBits == 8) {			// remove pseudo random pad			extractedByte ^= random.getNextByte();			fos.write((byte) extractedByte);			extractedByte=0;			availableExtractedBits=0;			nBytesExtracted++;			if (nBytesExtracted==extractedFileLength)			    break;		    }		}	    }	    if (nBytesExtracted<extractedFileLength) {		System.out.println("Incomplete file: only "+		    nBytesExtracted+" of "+extractedFileLength+		    " bytes extracted");	    }	} catch(Exception e) {	    e.printStackTrace();	}    }}