Mejf

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

public class CDeCrypt {

    public static void main(String[] args) {
        if (args.length < 2) {
            System.err
                    .println("Usage: java CDeCrypt <keyfile> <cryptfile> [<outdirectory>]\n"
                            + "The decrypted file will get its original name and weill be placed in the optional <outdirectory>.");
            System.exit(-1);
        }

        File key = new File(args[0]);
        File crypt = new File(args[1]);
        File outDir = new File(args.length > 2 ? args[2] : ".");

        decrypt(key, crypt, outDir);
    }

    private static void decrypt(File key, File crypt, File outDir) {
        try {
            DataInputStream k = new DataInputStream(new FileInputStream(key));
            DataInputStream c = new DataInputStream(new FileInputStream(crypt));

            int mNameLen = k.readInt();
            StringBuilder sb = new StringBuilder();
            while (mNameLen > 0) {
                sb.append(k.readChar());
                mNameLen--;
            }
            String mName = sb.toString();
            File mFile = new File(outDir, mName);

            DataOutputStream m = new DataOutputStream(new FileOutputStream(
                    mFile));

            System.out.print("Decrypting " + crypt + " using key " + key
                    + " to file " + mFile + " ... ");

            int b;
            while ((b = k.read()) >= 0) {
                m.write(b ^ c.read());
            }

            k.close();
            c.close();
            m.close();

            System.out.println("done!");
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

}