hammingdistancematchrule.java

基于人工免疫原理的入侵检测系统框架

/*=================
 * Copyright (C) 2001  Dennis Chao
 *
 * Lisys is a program that monitors TCP SYN packets to detect network
 * traffic anomalies.
 *
 * Licensed under the GNU General Public License (GPL), version 2 or
 * higher.  Please see the COPYING and PATENT files included with the 
 * Lisys distribution, which can be found at:
 *
 *   http://www.cs.unm.edu/~judd/lisys/
 *
 * Also, the current text of the GPL can be found at: 
 *
 *   http://www.gnu.org/copyleft/gpl.html
 * 
 * Note that Lisys has NO WARRANTY!
 *=================*/

package edu.unm.cs.lisys.detection.matchrule;

import edu.unm.cs.lisys.debug.*;
import edu.unm.cs.lisys.util.*;
import edu.unm.cs.lisys.detection.bip.*;
import java.util.*;
import java.io.*;

/**========== 
 * HammingDistanceMatchRule.java 
 *   (based on ContiguousMatchesMatchRule.java)
 *
 * Here are the people who have worked on this code, starting with 
 * the most recent:
 *   @author Justin Balthrop <[e-mail]>
 *   @author Dennis Chao <[e-mail]>
 *
 * Hamming distance rule (number of same bits).
 * Permutation masks don't change the result.
 *==========*/

public class HammingDistanceMatchRule implements MatchRule, Serializable
{
    public static void main(String[] args) 
    {
	KnuthRandom random = new KnuthRandom(100);

	for (int i = 0; i < 5; i++) {
	    BinaryInputPattern bip1 = new TCPDump49BitBIP();
	    bip1.constructBinaryString(random);

	    BinaryInputPattern bip2 = new TCPDump49BitBIP();
	    bip2.constructBinaryString(random);
	    System.err.println(bip1.toString());
	    System.err.println(bip2.toString());

	    MatchRule mr = new HammingDistanceMatchRule();
	    int length = mr.match(bip1, bip2);
	    System.err.println("length of match = " + length);
	}
    }

    /**==========
     * match:
     *   @param first binary input pattern to match
     *   @param second binary input pattern to match
     *   @return the number of bits the patterns have in common
     *==========*/
    public int match(BinaryInputPattern first, BinaryInputPattern second)
    {
	BitSet bits1 = (BitSet) first.getBinaryString().clone();
	BitSet bits2 = (BitSet) second.getBinaryString().clone();
	bits1.xor(bits2);
	
	// Now, search for the number of xored bits set to 1.
	int currentMatches = 0;

	for (int i = 0; i < first.getLength(); i++) {
	    boolean bit = bits1.get(i);
	    if (bit != true) {
		currentMatches++;
	    }
	}
	return currentMatches;
    }
}