sim-applet/src/org/osmocom/IMSIPseudo/IMSIPseudo.java - imsi-pseudo - Gitiles

 /* Copyright 2020 sysmocom s.f.m.c. GmbH
  * SPDX-License-Identifier: Apache-2.0 */
 package org.osmocom.IMSIPseudo;

 import sim.access.*;
 import sim.toolkit.*;
 import javacard.framework.*;

 public class IMSIPseudo extends Applet implements ToolkitInterface, ToolkitConstants {
 	// DON'T DECLARE USELESS INSTANCE VARIABLES! They get saved to the EEPROM,
 	// which has a limited number of write cycles.

 	private byte STKServicesMenuId;
 	private SIMView gsmFile;
 	static byte[] LUCounter = new byte[] { '0', 'x', ' ', 'L', 'U' };

 	/* Main menu */
 	private static final byte[] title = new byte[] { 'I', 'M', 'S', 'I', ' ', 'P', 's', 'e', 'u', 'd', 'o', 'n', 'y', 'm',
 					   'i', 'z', 'a', 't', 'i', 'o', 'n'};
 	private static final byte[] showLU = new byte[] {'S', 'h', 'o', 'w', ' ', 'L', 'U', ' ', 'c', 'o', 'u', 'n', 't', 'e', 'r'};
 	private static final byte[] showIMSI = new byte[] {'S', 'h', 'o', 'w', ' ', 'I', 'M', 'S', 'I'};
 	private static final byte[] changeIMSI = new byte[] {'C', 'h', 'a', 'n', 'g', 'e', ' ', 'I', 'M', 'S', 'I', ' '};
 	private final Object[] itemListMain = {title, showLU, showIMSI, changeIMSI};

 	/* Change IMSI menu */
 	private static final byte[] enterIMSI = new byte[] {'E', 'n', 't', 'e', 'r', ' ', 'I', 'M', 'S', 'I' };
 	private static final byte[] setDigit1 = new byte[] {'S', 'e', 't', ' ', '1', ' ', 'a', 's', ' ', 'l', 'a', 's', 't', ' ',
 						  'd', 'i', 'g', 'i', 't'};
 	private static final byte[] setDigit2 = new byte[] {'S', 'e', 't', ' ', '2', ' ', 'a', 's', ' ', 'l', 'a', 's', 't', ' ',
 						  'd', 'i', 'g', 'i', 't'};
 	private final Object[] itemListChangeIMSI = {changeIMSI, enterIMSI, setDigit1, setDigit2};

 	private static final byte MI_IMSI = 1;

 	private IMSIPseudo() {
 		gsmFile = SIMSystem.getTheSIMView();

 		/* Register menu and trigger on location updates */
 		ToolkitRegistry reg = ToolkitRegistry.getEntry();
 		STKServicesMenuId = reg.initMenuEntry(title, (short)0, (short)title.length, PRO_CMD_SELECT_ITEM, false,
 						 (byte)0, (short)0);
 		reg.setEvent(EVENT_EVENT_DOWNLOAD_LOCATION_STATUS);
 	}

 	public static void install(byte[] bArray, short bOffset, byte bLength) {
 		IMSIPseudo applet = new IMSIPseudo();
 		applet.register();
 	}

 	public void process(APDU arg0) throws ISOException {
 		if (selectingApplet())
 			return;
 	}

 	public void processToolkit(byte event) throws ToolkitException {
 		EnvelopeHandler envHdlr = EnvelopeHandler.getTheHandler();

 		if (event == EVENT_MENU_SELECTION) {
 			byte selectedItemId = envHdlr.getItemIdentifier();

 			if (selectedItemId == STKServicesMenuId) {
 				showMenu(itemListMain, (byte)4);
 				handleMenuResponseMain();
 			}
 		}

 		if (event == EVENT_EVENT_DOWNLOAD_LOCATION_STATUS) {
 			LUCounter[0]++;
 			showMsg(LUCounter);
 		}
 	}

 	private void showMenu(Object[] itemList, byte itemCount) {
 		ProactiveHandler proHdlr = ProactiveHandler.getTheHandler();
 		proHdlr.init((byte) PRO_CMD_SELECT_ITEM,(byte)0,DEV_ID_ME);

 		for (byte i=(byte)0;i<itemCount;i++) {
 			if (i == 0) {
 				/* Title */
 				proHdlr.appendTLV((byte)(TAG_ALPHA_IDENTIFIER | TAG_SET_CR), (byte[])itemList[i],
 						  (short)0, (short)((byte[])itemList[i]).length);

 			} else {
 				/* Menu entry */
 				proHdlr.appendTLV((byte)(TAG_ITEM | TAG_SET_CR), (byte)i, (byte[])itemList[i], (short)0,
 						  (short)((byte[])itemList[i]).length);
 			}
 		}
 		proHdlr.send();
 	}

 	private void showMsg(byte[] msg) {
 		ProactiveHandler proHdlr = ProactiveHandler.getTheHandler();
 		proHdlr.initDisplayText((byte)0, DCS_8_BIT_DATA, msg, (short)0, (short)(msg.length));
 		proHdlr.send();
 	}

 	private byte[] getResponse()
 	{
 		ProactiveResponseHandler rspHdlr = ProactiveResponseHandler.getTheHandler();
 		byte[] resp = new byte[rspHdlr.getTextStringLength()];
 		rspHdlr.copyTextString(resp, (short)0);
 		return resp;
 	}

 	private byte[] showMsgAndWaitKey(byte[] msg) {
 		ProactiveHandler proHdlr = ProactiveHandler.getTheHandler();
 		proHdlr.initGetInkey((byte)0, DCS_8_BIT_DATA, msg, (short)0, (short)(msg.length));
 		proHdlr.send();

 		return getResponse();
 	}

 	private byte[] prompt(byte[] msg, short minLen, short maxLen) {
 		/* if maxLen < 1, the applet crashes */
 		if (maxLen < 1)
 			maxLen = 1;

 		ProactiveHandler proHdlr = ProactiveHandler.getTheHandler();
 		proHdlr.initGetInput((byte)0, DCS_8_BIT_DATA, msg, (short)0, (short)(msg.length), minLen, maxLen);
 		proHdlr.send();

 		return getResponse();
 	}

 	private void showError(short code) {
 		byte[] msg = new byte[] {'E', '?', '?'};
 		msg[1] = (byte)('0' + code / 10);
 		msg[2] = (byte)('0' + code % 10);
 		showMsg(msg);
 	}

 	/* Convert BCD-encoded digit into printable character
 	 *  \param[in] bcd A single BCD-encoded digit
 	 *  \returns single printable character
 	 */
 	private byte bcd2char(byte bcd)
 	{
 		if (bcd < 0xa)
 			return (byte)('0' + bcd);
 		else
 			return (byte)('A' + (bcd - 0xa));
 	}

 	private byte char2bcd(byte c)
 	{
 		if (c >= '0' && c <= '9')
 			return (byte)(c - '0');
 		else if (c >= 'A' && c <= 'F')
 			return (byte)(0xa + (c - 'A'));
 		else if (c >= 'a' && c <= 'f')
 			return (byte)(0xa + (c - 'a'));
 		else
 			return 0;
 	}

 	/* Convert BCD to string.
 	 * The given nibble offsets are interpreted in BCD order, i.e. nibble 0 is bcd[0] & 0xf, nibble 1 is bcd[0] >> 4, nibble
 	 * 3 is bcd[1] & 0xf, etc..
 	 *  \param[out] dst  Output byte array.
 	 *  \param[in] dst_ofs  Where to start writing in dst.
 	 *  \param[in] dst_len  How many bytes are available at dst_ofs.
 	 *  \param[in] bcd  Binary coded data buffer.
 	 *  \param[in] start_nibble  Offset to start from, in nibbles.
 	 *  \param[in] end_nibble  Offset to stop before, in nibbles.
 	 *  \param[in] allow_hex  If false, return false if there are digits other than 0-9.
 	 *  \returns true on success, false otherwise
 	 */
 	private boolean bcd2str(byte dst[], byte dst_ofs, byte dst_len,
 				byte bcd[], byte start_nibble, byte end_nibble, boolean allow_hex)
 	{
 		byte nibble_i;
 		byte dst_i = dst_ofs;
 		byte dst_end = (byte)(dst_ofs + dst_len);
 		boolean rc = true;

 		for (nibble_i = start_nibble; nibble_i < end_nibble && dst_i < dst_end; nibble_i++, dst_i++) {
 			byte nibble = bcd[(byte)nibble_i >> 1];
 			if ((nibble_i & 1) != 0)
 				nibble >>= 4;
 			nibble &= 0xf;

 			if (!allow_hex && nibble > 9)
 				rc = false;

 			dst[dst_i] = bcd2char(nibble);
 		}

 		return rc;
 	}

 	private byte mi2str(byte dst[], byte dst_ofs, byte dst_len,
 			    byte mi[], boolean allow_hex)
 	{
 		/* The IMSI byte array by example:
 		 * 08 99 10 07 00 00 10 74 90
 		 *
 		 * This is encoded according to 3GPP TS 24.008 10.5.1.4 Mobile
 		 * Identity, short the Mobile Identity IEI:
 		 *
 		 * 08 length for the following MI, in bytes.
 		 *  9 = 0b1001
 		 *	1 = odd nr of digits
 		 *	 001 = MI type = IMSI
 		 * 9  first IMSI digit (BCD)
 		 *  0 second digit
 		 * 1  third
 		 * ...
 		 *  0 14th digit
 		 * 9  15th and last digit
 		 *
 		 * If the IMSI had an even number of digits:
 		 *
 		 * 08 98 10 07 00 00 10 74 f0
 		 *
 		 * 08 length for the following MI, in bytes.
 		 *  8 = 0b0001
 		 *	0 = even nr of digits
 		 *	 001 = MI type = IMSI
 		 * 9  first IMSI digit
 		 *  0 second digit
 		 * 1  third
 		 * ...
 		 *  0 14th and last digit
 		 * f  filler
 		 */
 		byte bytelen = mi[0];
 		byte mi_type = (byte)(mi[1] & 0xf);
 		boolean odd_nr_of_digits = ((mi_type & 0x08) != 0);
 		byte start_nibble = 2 + 1; // 2 to skip the bytelen, 1 to skip the mi_type
 		byte end_nibble = (byte)(2 + bytelen * 2 - (odd_nr_of_digits ? 0 : 1));
 		bcd2str(dst, dst_ofs, dst_len, mi, start_nibble, end_nibble, allow_hex);
 		return (byte)(end_nibble - start_nibble);
 	}

 	private byte[] str2mi(byte str[], byte mi_type)
 	{
 		/* 1 byte of MI length.
 		 * 1 nibble of mi_type.
 		 * str.length nibbles of MI BCD.
 		 * The first MI digit is in the high-nibble of the mi_type, so an odd amount of digits becomes
 		 * (1 + str.length)/2 bytes; an even amount of digits has same amount of bytes with the last
 		 * nibble unused (0xf0). */
 		byte len = (byte)(1 + (byte)(1 + str.length)/2);
 		byte mi[] = new byte[1 + len];
 		mi[0] = len;

 		boolean odd_digits = ((str.length & 1) != 0);
 		mi_type = (byte)(mi_type & 0x07);
 		if (odd_digits)
 			mi_type |= 0x08;
 		mi[1] = (byte)((char2bcd(str[0]) << 4) + mi_type);
 		byte str_i = 1;
 		for (byte bcd_i = 1; bcd_i < len; bcd_i++) {
 			byte data = char2bcd(str[str_i]);
 			str_i++;
 			if (str_i < str.length) {
 				data |= char2bcd(str[str_i]) << 4;
 				str_i++;
 			} else
 				data |= 0xf0;
 			mi[1 + bcd_i] = data;
 		}
 		return mi;
 	}

 	private byte nibble2hex(byte nibble)
 	{
 		nibble = (byte)(nibble & 0xf);
 		if (nibble < 0xa)
 			return (byte)('0' + nibble);
 		else
 			return (byte)('a' + nibble - 0xa);
 	}

 	private byte[] hexdump(byte data[])
 	{
 		byte res[] = new byte[(byte)(data.length*2)];
 		for (byte i = 0; i < data.length; i++) {
 			res[(byte)(i*2)] = nibble2hex((byte)(data[i] >> 4));
 			res[(byte)(i*2 + 1)] = nibble2hex(data[i]);
 		}
 		return res;
 	}

 	private void showIMSI() {
 		/* 3GPP TS 31.102 4.2.2: IMSI */
 		byte[] msg = {'C', 'u', 'r', 'r', 'e', 'n', 't', ' ', 'I', 'M', 'S', 'I', ':', ' ',
 			      ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' '};

 		try {
 			byte IMSI[] = readIMSI();
 			mi2str(msg, (byte)14, (byte)16, IMSI, false);
 			showMsgAndWaitKey(msg);
 		} catch (SIMViewException e) {
 			showError(e.getReason());
 		}
 	}

 	private void handleMenuResponseMain() {
 		ProactiveResponseHandler rspHdlr = ProactiveResponseHandler.getTheHandler();

 		switch (rspHdlr.getItemIdentifier()) {
 		case 1: /* Show LU counter */
 			showMsg(LUCounter);
 			break;
 		case 2: /* Show IMSI */
 			showIMSI();
 			break;
 		case 3: /* Change IMSI */
 			showMenu(itemListChangeIMSI, (byte)4);
 			handleMenuResponseChangeIMSI();
 			break;
 		}
 	}

 	private void handleMenuResponseChangeIMSI() {
 		ProactiveResponseHandler rspHdlr = ProactiveResponseHandler.getTheHandler();
 		switch (rspHdlr.getItemIdentifier()) {
 		case 1: /* enter IMSI */
 			promptIMSI();
 			break;
 		case 2: /* set last digit to 1 */
 			promptIMSI();
 			break;
 		case 3: /* set last digit to 2 */
 			promptIMSI();
 			break;
 		}
 	}

 	private void promptIMSI()
 	{
 		byte[] msg = {'N', 'e', 'w', ' ', 'I', 'M', 'S', 'I', '?'};
 		byte imsi[] = prompt(msg, (short)0, (short)15);
 		byte mi[] = str2mi(imsi, MI_IMSI);
 		showMsgAndWaitKey(hexdump(mi));
 	}

 	private byte[] readIMSI()
 	{
 		gsmFile.select((short) SIMView.FID_DF_GSM);
 		gsmFile.select((short) SIMView.FID_EF_IMSI);
 		byte[] IMSI = new byte[9];
 		gsmFile.readBinary((short)0, IMSI, (short)0, (short)9);
 		return IMSI;
 	}

 	private void writeIMSI(byte mi[])
 	{
 		gsmFile.select((short) SIMView.FID_DF_GSM);
 		gsmFile.select((short) SIMView.FID_EF_IMSI);
 		gsmFile.updateBinary((short)0, mi, (short)0, (short)mi.length);
 	}
 }
	/* Copyright 2020 sysmocom s.f.m.c. GmbH
	* SPDX-License-Identifier: Apache-2.0 */
	package org.osmocom.IMSIPseudo;

	import sim.access.*;
	import sim.toolkit.*;
	import javacard.framework.*;

	public class IMSIPseudo extends Applet implements ToolkitInterface, ToolkitConstants {
	// DON'T DECLARE USELESS INSTANCE VARIABLES! They get saved to the EEPROM,
	// which has a limited number of write cycles.

	private byte STKServicesMenuId;
	private SIMView gsmFile;
	static byte[] LUCounter = new byte[] { '0', 'x', ' ', 'L', 'U' };

	/* Main menu */
	private static final byte[] title = new byte[] { 'I', 'M', 'S', 'I', ' ', 'P', 's', 'e', 'u', 'd', 'o', 'n', 'y', 'm',
	'i', 'z', 'a', 't', 'i', 'o', 'n'};
	private static final byte[] showLU = new byte[] {'S', 'h', 'o', 'w', ' ', 'L', 'U', ' ', 'c', 'o', 'u', 'n', 't', 'e', 'r'};
	private static final byte[] showIMSI = new byte[] {'S', 'h', 'o', 'w', ' ', 'I', 'M', 'S', 'I'};
	private static final byte[] changeIMSI = new byte[] {'C', 'h', 'a', 'n', 'g', 'e', ' ', 'I', 'M', 'S', 'I', ' '};
	private final Object[] itemListMain = {title, showLU, showIMSI, changeIMSI};

	/* Change IMSI menu */
	private static final byte[] enterIMSI = new byte[] {'E', 'n', 't', 'e', 'r', ' ', 'I', 'M', 'S', 'I' };
	private static final byte[] setDigit1 = new byte[] {'S', 'e', 't', ' ', '1', ' ', 'a', 's', ' ', 'l', 'a', 's', 't', ' ',
	'd', 'i', 'g', 'i', 't'};
	private static final byte[] setDigit2 = new byte[] {'S', 'e', 't', ' ', '2', ' ', 'a', 's', ' ', 'l', 'a', 's', 't', ' ',
	'd', 'i', 'g', 'i', 't'};
	private final Object[] itemListChangeIMSI = {changeIMSI, enterIMSI, setDigit1, setDigit2};

	private static final byte MI_IMSI = 1;

	private IMSIPseudo() {
	gsmFile = SIMSystem.getTheSIMView();

	/* Register menu and trigger on location updates */
	ToolkitRegistry reg = ToolkitRegistry.getEntry();
	STKServicesMenuId = reg.initMenuEntry(title, (short)0, (short)title.length, PRO_CMD_SELECT_ITEM, false,
	(byte)0, (short)0);
	reg.setEvent(EVENT_EVENT_DOWNLOAD_LOCATION_STATUS);
	}

	public static void install(byte[] bArray, short bOffset, byte bLength) {
	IMSIPseudo applet = new IMSIPseudo();
	applet.register();
	}

	public void process(APDU arg0) throws ISOException {
	if (selectingApplet())
	return;
	}

	public void processToolkit(byte event) throws ToolkitException {
	EnvelopeHandler envHdlr = EnvelopeHandler.getTheHandler();

	if (event == EVENT_MENU_SELECTION) {
	byte selectedItemId = envHdlr.getItemIdentifier();

	if (selectedItemId == STKServicesMenuId) {
	showMenu(itemListMain, (byte)4);
	handleMenuResponseMain();
	}
	}

	if (event == EVENT_EVENT_DOWNLOAD_LOCATION_STATUS) {
	LUCounter[0]++;
	showMsg(LUCounter);
	}
	}

	private void showMenu(Object[] itemList, byte itemCount) {
	ProactiveHandler proHdlr = ProactiveHandler.getTheHandler();
	proHdlr.init((byte) PRO_CMD_SELECT_ITEM,(byte)0,DEV_ID_ME);

	for (byte i=(byte)0;i<itemCount;i++) {
	if (i == 0) {
	/* Title */
	proHdlr.appendTLV((byte)(TAG_ALPHA_IDENTIFIER \| TAG_SET_CR), (byte[])itemList[i],
	(short)0, (short)((byte[])itemList[i]).length);

	} else {
	/* Menu entry */
	proHdlr.appendTLV((byte)(TAG_ITEM \| TAG_SET_CR), (byte)i, (byte[])itemList[i], (short)0,
	(short)((byte[])itemList[i]).length);
	}
	}
	proHdlr.send();
	}

	private void showMsg(byte[] msg) {
	ProactiveHandler proHdlr = ProactiveHandler.getTheHandler();
	proHdlr.initDisplayText((byte)0, DCS_8_BIT_DATA, msg, (short)0, (short)(msg.length));
	proHdlr.send();
	}

	private byte[] getResponse()
	{
	ProactiveResponseHandler rspHdlr = ProactiveResponseHandler.getTheHandler();
	byte[] resp = new byte[rspHdlr.getTextStringLength()];
	rspHdlr.copyTextString(resp, (short)0);
	return resp;
	}

	private byte[] showMsgAndWaitKey(byte[] msg) {
	ProactiveHandler proHdlr = ProactiveHandler.getTheHandler();
	proHdlr.initGetInkey((byte)0, DCS_8_BIT_DATA, msg, (short)0, (short)(msg.length));
	proHdlr.send();

	return getResponse();
	}

	private byte[] prompt(byte[] msg, short minLen, short maxLen) {
	/* if maxLen < 1, the applet crashes */
	if (maxLen < 1)
	maxLen = 1;

	ProactiveHandler proHdlr = ProactiveHandler.getTheHandler();
	proHdlr.initGetInput((byte)0, DCS_8_BIT_DATA, msg, (short)0, (short)(msg.length), minLen, maxLen);
	proHdlr.send();

	return getResponse();
	}

	private void showError(short code) {
	byte[] msg = new byte[] {'E', '?', '?'};
	msg[1] = (byte)('0' + code / 10);
	msg[2] = (byte)('0' + code % 10);
	showMsg(msg);
	}

	/* Convert BCD-encoded digit into printable character
	* \param[in] bcd A single BCD-encoded digit
	* \returns single printable character
	*/
	private byte bcd2char(byte bcd)
	{
	if (bcd < 0xa)
	return (byte)('0' + bcd);
	else
	return (byte)('A' + (bcd - 0xa));
	}

	private byte char2bcd(byte c)
	{
	if (c >= '0' && c <= '9')
	return (byte)(c - '0');
	else if (c >= 'A' && c <= 'F')
	return (byte)(0xa + (c - 'A'));
	else if (c >= 'a' && c <= 'f')
	return (byte)(0xa + (c - 'a'));
	else
	return 0;
	}

	/* Convert BCD to string.
	* The given nibble offsets are interpreted in BCD order, i.e. nibble 0 is bcd[0] & 0xf, nibble 1 is bcd[0] >> 4, nibble
	* 3 is bcd[1] & 0xf, etc..
	* \param[out] dst Output byte array.
	* \param[in] dst_ofs Where to start writing in dst.
	* \param[in] dst_len How many bytes are available at dst_ofs.
	* \param[in] bcd Binary coded data buffer.
	* \param[in] start_nibble Offset to start from, in nibbles.
	* \param[in] end_nibble Offset to stop before, in nibbles.
	* \param[in] allow_hex If false, return false if there are digits other than 0-9.
	* \returns true on success, false otherwise
	*/
	private boolean bcd2str(byte dst[], byte dst_ofs, byte dst_len,
	byte bcd[], byte start_nibble, byte end_nibble, boolean allow_hex)
	{
	byte nibble_i;
	byte dst_i = dst_ofs;
	byte dst_end = (byte)(dst_ofs + dst_len);
	boolean rc = true;

	for (nibble_i = start_nibble; nibble_i < end_nibble && dst_i < dst_end; nibble_i++, dst_i++) {
	byte nibble = bcd[(byte)nibble_i >> 1];
	if ((nibble_i & 1) != 0)
	nibble >>= 4;
	nibble &= 0xf;

	if (!allow_hex && nibble > 9)
	rc = false;

	dst[dst_i] = bcd2char(nibble);
	}

	return rc;
	}

	private byte mi2str(byte dst[], byte dst_ofs, byte dst_len,
	byte mi[], boolean allow_hex)
	{
	/* The IMSI byte array by example:
	* 08 99 10 07 00 00 10 74 90
	*
	* This is encoded according to 3GPP TS 24.008 10.5.1.4 Mobile
	* Identity, short the Mobile Identity IEI:
	*
	* 08 length for the following MI, in bytes.
	* 9 = 0b1001
	* 1 = odd nr of digits
	* 001 = MI type = IMSI
	* 9 first IMSI digit (BCD)
	* 0 second digit
	* 1 third
	* ...
	* 0 14th digit
	* 9 15th and last digit
	*
	* If the IMSI had an even number of digits:
	*
	* 08 98 10 07 00 00 10 74 f0
	*
	* 08 length for the following MI, in bytes.
	* 8 = 0b0001
	* 0 = even nr of digits
	* 001 = MI type = IMSI
	* 9 first IMSI digit
	* 0 second digit
	* 1 third
	* ...
	* 0 14th and last digit
	* f filler
	*/
	byte bytelen = mi[0];
	byte mi_type = (byte)(mi[1] & 0xf);
	boolean odd_nr_of_digits = ((mi_type & 0x08) != 0);
	byte start_nibble = 2 + 1; // 2 to skip the bytelen, 1 to skip the mi_type
	byte end_nibble = (byte)(2 + bytelen * 2 - (odd_nr_of_digits ? 0 : 1));
	bcd2str(dst, dst_ofs, dst_len, mi, start_nibble, end_nibble, allow_hex);
	return (byte)(end_nibble - start_nibble);
	}

	private byte[] str2mi(byte str[], byte mi_type)
	{
	/* 1 byte of MI length.
	* 1 nibble of mi_type.
	* str.length nibbles of MI BCD.
	* The first MI digit is in the high-nibble of the mi_type, so an odd amount of digits becomes
	* (1 + str.length)/2 bytes; an even amount of digits has same amount of bytes with the last
	* nibble unused (0xf0). */
	byte len = (byte)(1 + (byte)(1 + str.length)/2);
	byte mi[] = new byte[1 + len];
	mi[0] = len;

	boolean odd_digits = ((str.length & 1) != 0);
	mi_type = (byte)(mi_type & 0x07);
	if (odd_digits)
	mi_type \|= 0x08;
	mi[1] = (byte)((char2bcd(str[0]) << 4) + mi_type);
	byte str_i = 1;
	for (byte bcd_i = 1; bcd_i < len; bcd_i++) {
	byte data = char2bcd(str[str_i]);
	str_i++;
	if (str_i < str.length) {
	data \|= char2bcd(str[str_i]) << 4;
	str_i++;
	} else
	data \|= 0xf0;
	mi[1 + bcd_i] = data;
	}
	return mi;
	}

	private byte nibble2hex(byte nibble)
	{
	nibble = (byte)(nibble & 0xf);
	if (nibble < 0xa)
	return (byte)('0' + nibble);
	else
	return (byte)('a' + nibble - 0xa);
	}

	private byte[] hexdump(byte data[])
	{
	byte res[] = new byte[(byte)(data.length*2)];
	for (byte i = 0; i < data.length; i++) {
	res[(byte)(i*2)] = nibble2hex((byte)(data[i] >> 4));
	res[(byte)(i*2 + 1)] = nibble2hex(data[i]);
	}
	return res;
	}

	private void showIMSI() {
	/* 3GPP TS 31.102 4.2.2: IMSI */
	byte[] msg = {'C', 'u', 'r', 'r', 'e', 'n', 't', ' ', 'I', 'M', 'S', 'I', ':', ' ',
	' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' '};

	try {
	byte IMSI[] = readIMSI();
	mi2str(msg, (byte)14, (byte)16, IMSI, false);
	showMsgAndWaitKey(msg);
	} catch (SIMViewException e) {
	showError(e.getReason());
	}
	}

	private void handleMenuResponseMain() {
	ProactiveResponseHandler rspHdlr = ProactiveResponseHandler.getTheHandler();

	switch (rspHdlr.getItemIdentifier()) {
	case 1: /* Show LU counter */
	showMsg(LUCounter);
	break;
	case 2: /* Show IMSI */
	showIMSI();
	break;
	case 3: /* Change IMSI */
	showMenu(itemListChangeIMSI, (byte)4);
	handleMenuResponseChangeIMSI();
	break;
	}
	}

	private void handleMenuResponseChangeIMSI() {
	ProactiveResponseHandler rspHdlr = ProactiveResponseHandler.getTheHandler();
	switch (rspHdlr.getItemIdentifier()) {
	case 1: /* enter IMSI */
	promptIMSI();
	break;
	case 2: /* set last digit to 1 */
	promptIMSI();
	break;
	case 3: /* set last digit to 2 */
	promptIMSI();
	break;
	}
	}

	private void promptIMSI()
	{
	byte[] msg = {'N', 'e', 'w', ' ', 'I', 'M', 'S', 'I', '?'};
	byte imsi[] = prompt(msg, (short)0, (short)15);
	byte mi[] = str2mi(imsi, MI_IMSI);
	showMsgAndWaitKey(hexdump(mi));
	}

	private byte[] readIMSI()
	{
	gsmFile.select((short) SIMView.FID_DF_GSM);
	gsmFile.select((short) SIMView.FID_EF_IMSI);
	byte[] IMSI = new byte[9];
	gsmFile.readBinary((short)0, IMSI, (short)0, (short)9);
	return IMSI;
	}

	private void writeIMSI(byte mi[])
	{
	gsmFile.select((short) SIMView.FID_DF_GSM);
	gsmFile.select((short) SIMView.FID_EF_IMSI);
	gsmFile.updateBinary((short)0, mi, (short)0, (short)mi.length);
	}
	}