/*
 * Enigma.java - ENIGMA implementation
 *
 * Copyright (c) 1998, Charles McManis, All Rights Reserved.
 *
 * Permission to use, copy, modify, and distribute this software
 * and its documentation for NON-COMMERCIAL purposes and without
 * fee is hereby granted provided that this copyright notice
 * appears in all copies.
 *
 * CHUCK MCMANIS MAKES NO REPRESENTATIONS OR WARRANTIES ABOUT THE
 * SUITABILITY OF THE SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING
 * BUT NOT LIMITED TO THE IMPLIED WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, OR NON-INFRINGEMENT. CHUCK MCMANIS
 * SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE AS A RESULT
 * OF USING, MODIFYING OR DISTRIBUTING THIS SOFTWARE OR ITS DERIVATIVES.
 */

import javacard.framework.*;

/**
 * This class implements a 3 rotor Enigma encryption engine. When
 * installed in an iButton it gives the button a rudimentary encryption
 * capability.
 */
public class Enigma extends Applet {
    // The enigma "class" byte
    final static byte EN_CLA = (byte) 0x85;

    // Set the key.
    final static byte EN_INS_KEY = (byte) 0x01;

    // Reset the rotors to the key.
    final static byte EN_INS_RESET = (byte) 0x02;

    // Run a series of bytes through the rotors.
    final static byte EN_INS_ENCRYPT = (byte) 0x03;

   // APDU header stuff used during applet selection
   final static byte SELECT_CLA = 0x00;
   final static byte SELECT_INS = (byte) 0xA4;

    /*
     * These are the three rotors used in our simulated ENIGMA.
     * They are fixed values, generated by the GenRotors utility.
     */
    static byte rotor1[] = {
        '8','E','7','d','V','6','c','x','q','h','A','5','r','F','u','Y',
        'U','K','m','T','l','W','w','Z','n','Q','M','b','4','t','i','2',
        'o','e','N','s','O','g','3','L','I','/','p','G','y','+','R','9',
        'P','z','a','1','D','J','X','k','B','v','j','0','H','f','C','S'
    };
    static byte rotor2[] = {
        'w','9','p','i','K','N','4','/','j','7','3','r','M','D','u','2',
        's','q','h','T','g','A','8','G','x','f','O','1','E','P','+','V',
        'y','H','n','Z','Y','X','a','Q','m','0','S','k','e','5','b','B',
        '6','W','C','t','L','c','U','o','F','R','d','v','J','z','I','l'
    };
    static byte rotor3[] = {
        'p','b','5','Y','N','S','T','F','w','m','2','g','D','1','O','i',
        'K','7','4','B','M','j','9','P','z','A','Z','X','h','t','I','+',
        'U','v','L','/','W','s','e','y','n','0','l','k','q','6','G','c',
        'E','C','r','H','8','f','o','u','d','Q','R','J','3','V','x','a'
    };

    static byte char_map[] = {
      'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P',
      'Q','R','S','T','U','V','W','X','Y','Z','a','b','c','d','e','f',
      'g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v',
      'w','x','y','z','0','1','2','3','4','5','6','7','8','9','+','/'
    };

    static byte reflector[] = {
        '2','3','f','a','5','6','s','H','7','y','b','w','+','9','h','W',
        'l','Z','c','i','U','o','P','d','/','R','D','K','S','X','n','C',
        'z','O','T','x','1','Q','m','e','V','4','0','r','G','8','v','u',
        'L','j','J','g','q','k','A','B','p','E','F','I','t','N','M','Y'
    };

    private byte key[] = new byte[3];

    /* the rotor stack used by the Enigma */
    private Rotor rotors;

    public Enigma() {
	// workaround for a JiB bug. 
	Rotor.setMaps(char_map, reflector);
        rotors = new Rotor((short) 13, rotor1);
        rotors = new Rotor(rotors, (short) 7, rotor2);
        rotors = new Rotor(rotors, (short) 3, rotor3);
	register();
    }

    /* Install the Enigma machine in the ring */
    public static void install(APDU apdu) {
	new Enigma();
    }

    /* Generic select, always accept */
    public boolean select(APDU apdu) {
	return true;
    }

    byte test[];
    private void error(APDU apdu, short err) {
	if (test == null)
	    test = new byte[5];
	test[0] = (byte) 'E';
	test[1] = (byte) (((err >> 12) & 0xf) + '0');
	if (test[1] > '9') test[1] += 7;
	test[2] = (byte) (((err >> 8) & 0xf) + '0');
	if (test[2] > '9') test[2] += 7;
	test[3] = (byte) (((err >> 4) & 0xf) + '0');
	if (test[3] > '9') test[3] += 7;
	test[4] = (byte) ((err & 0xf) + '0');
	if (test[4] > '9') test[4] += 7;
	apdu.setOutgoing();
	apdu.sendBytesLong(test, (short) 0, 
					(short) test.length);
    }

    /* Dispatch a request from the host applet. */
    public void process(APDU apdu) throws ISOException {
	byte buffer[] = apdu.getBuffer();

        // process is called on applet selection but we don't do anything in this applet
        if ((buffer[ISO.OFFSET_CLA] == SELECT_CLA) && (buffer[ISO.OFFSET_INS] == SELECT_INS))
            return;

	if (buffer[ISO.OFFSET_CLA] != EN_CLA) {
	    error(apdu, (short)0x1000);
	    return;
	}

	switch (buffer[ISO.OFFSET_INS]) {
	    default:
		 error(apdu, (short)0x1001);
  	         return;
	    case EN_INS_KEY:
		setKey(apdu);
		break;
	    case EN_INS_RESET:
		rotorReset(apdu);
		break;
	    case EN_INS_ENCRYPT:
		encrypt(apdu);
		break;
	}
    }

    private void rotorReset(APDU apdu) {
	rotors.set(key);
    }

    private void setKey(APDU apdu) throws ISOException {
	byte b[] = apdu.getBuffer();
	short bytesRead = apdu.setIncomingAndReceive();
	
	if (b[ISO.OFFSET_LC] != 3) {
	    error(apdu, (short) 0x2000);
	    return;
	}
	for (short i = 0; i < 3; i++) {
	    key[i] = b[ISO.OFFSET_CDATA+i];
	}
        rotors.set(key);
    }

    private byte buf[];

    void encrypt(APDU apdu) throws ISOException {
	byte b[] = apdu.getBuffer();
        byte c;
	short bytesRead = apdu.setIncomingAndReceive();
	short len;

	if ((buf == null) || (buf.length < bytesRead)) {
	    buf = new byte[bytesRead];
	} 
	len = bytesRead;
	for (int i = 0; i < len; i++) {
	    rotors.rotate();
	    buf[i] = rotors.encrypt(b[ISO.OFFSET_CDATA+i]);
	}
	apdu.setOutgoing();
	apdu.sendBytesLong(buf, (short) 0, len);
    }
}