anotherexample.java

java rc4 加密 rc4加密算法的一个实现

import java.io.*;
import java.security.MessageDigest;
import java.security.SecureRandom;
import java.security.NoSuchAlgorithmException;

/**
 * @author reikon (Thomas Dixon) 
 * This file is released into public domain. (no license)
 * PLEASE NOTE THAT USING STRINGS FOR PASSPHRASES IS INSECURE!
 * THIS IS DONE AS AN EXAMPLE ONLY!!!
 */
public class AnotherExample {
 
private static boolean decrypt = false;

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		if (args.length == 0)
			usage();
		
		for (int i = 0; i < args.length; i++) {
			if (args[i].equals("-e")) {
				crypt(args[i+1],args[i+2],args[i+3]);
				i+=3;
			} else if (args[i].equals("-d")) {
				decrypt = true;
                crypt(args[i+1],args[i+2],args[i+3]);
                i+=3;
			} else if (args[i].equals("-h")
						|| args[i].equals("-help") 
						|| args[i].equals("--help")) {
				usage();
			} else {
				usage();
			}
		}
	}
	
	private static void crypt(String password, String infile, String outfile) {
        FileInputStream in   = null;
        FileOutputStream out = null;
        
        try {
            in = new  FileInputStream(new File(infile));
        } catch (IOException ioe) {
            System.err.println("File " + infile + " not found... Please check your spelling and try again.\n");
            System.exit(-1);
        }
        
        try {
            if (new File(outfile).exists()) {
                System.out.println("File: " + outfile + " already exists. Overwrite? [Y/n]");
                if ((char)System.in.read() == ('n' | 'N'))
                    System.exit(-1);
            }
            out = new FileOutputStream(new File(outfile));
        } catch (IOException ioe) {
            System.err.println("Unable to create file: " + outfile + ": Ensure you have proper permissions to create this file.");
            System.exit(-1);
        }
        
        // create or read IV
        byte[] sessionIV = new byte[8];
        try {
            if (!decrypt) {
                SecureRandom random = new SecureRandom();
                random.nextBytes(sessionIV);
                out.write(sessionIV);
            } else {
                in.read(sessionIV,0,8);
            }
        } catch (IOException ioe) {
        }
        
        RC4 rc4 = new RC4();
        
        // create the key
        byte[] sessionKey = myKeyGen("SHA1", password.getBytes(), sessionIV, 65000, 160);
        
        try {
            rc4.engineInit(sessionKey);
        } catch (Exception e) {
        }
        
        if (!decrypt) {
            System.out.println("Encrypting...");
        } else {
            System.out.println("Decrypting...");
        }
        
        // initialize the cipher properly
        byte[] dummyBlock = new byte[256];
        for (int i = 0; i < 256; i++)
            dummyBlock[i] = (byte)0x00;
        
        for (int i = 0; i < 16; i++)
            rc4.engineCrypt(dummyBlock,0);
		
        // encipher
        try {
            byte[] rawbuf = new byte[1024];
            int numRead = 0;
            while ((numRead = in.read(rawbuf)) >= 0) {
                byte[] buf = new byte[numRead];
                System.arraycopy(rawbuf,0,buf,0,numRead);
                out.write(rc4.engineCrypt(buf,0));
            }
            in.close();
            out.close();
        } catch (IOException ioe) {
            System.err.println("FATAL: IO Error "+ioe);
            System.exit(-1);
        }
        
        System.out.println("Done");
        
    }
    
    private static byte[] myKeyGen(String mdStr, byte[] password, byte[] keysalt, int iteration, int keysize) {
        // bits to bytes.
        keysize = (keysize / 8);
        MessageDigest md = null;
        try {
            // Get the message digest.
            md = MessageDigest.getInstance(mdStr);
        } catch (NoSuchAlgorithmException e) {
            System.out.println(e);
        }
        
        // concatenate password and salt.
        byte[] pwAndSalt = new byte[password.length+keysalt.length];
        System.arraycopy(password, 0, pwAndSalt, 0, password.length);
        System.arraycopy(keysalt, 0, pwAndSalt, password.length, keysalt.length);
        
        byte[] hash = pwAndSalt;
        // Create the key as md(md(md(md(...(pw+salt))...)
        for (int i = 0; i < iteration; i++) {
            md.update(hash);
            hash = md.digest();
        }
        byte[] key = new byte[keysize];
        
        System.arraycopy(hash, 0, key, 0, keysize);
        
        return key;
    }  

    private static void usage() {
        System.out.println("usage: [-e|-d password /file/to/(en|de)crypt /output/filename] [-h] [--help]");
        System.out.println("ex   : java AnotherExample -e \"apassword\" ./File.txt ./File.enc");
    }
}