Seite 6: Listing 2

Inhaltsverzeichnis

Listing 2: MiniCrypt.java – einfaches Programm zur Verschlüsselung von Dateien

import java.io.*;
import java.util.*;

public class MiniCrypt {
    final static int BUFLEN=1024*1024;

    public MiniCrypt(String[] args) throws Exception {
        Random r=null;
        byte[] buffer=new byte[BUFLEN];

        for (String s: args) {
            if (r==null) {
                int seed=s.hashCode();
                r=new Random(seed);
                System.out.printf("Password \"%s\" has hashCode: 
                   %d\n", s, seed);
                continue;
            }
            FileInputStream fis=new FileInputStream(s);
            FileOutputStream fos=new FileOutputStream(s+".crypt");
            int rb;

            while ((rb=fis.read(buffer, 0, BUFLEN))>0) {
                for (int i=0;i<rb;i++) {
                    int code=buffer[i] & 0xff;
                    code ^= ~r.nextInt();
                    buffer[i] = (byte)(code & 0xff);
                }
                fos.write(buffer, 0, rb);
            }
            fis.close();
            fos.close();
        }
    }

    public static void main(String[] args) {
        if (args.length>1) {
            try {
                new MiniCrypt(args);
            } catch(Exception e) {
                System.err.println("Exception caught: "+e.getMessage());
                System.exit(1);
            }
        } else {
            System.err.println("usage: java "+MiniCrypt.class.getName()+"
                password file ...");
        }
    }
}