import org.bouncycastle.crypto.engines.*;
import org.bouncycastle.crypto.modes.*;
import org.bouncycastle.crypto.params.*;
// 壹個簡單的例子說明了如何使用Bouncy Castle
// 加密API來執行對任意數據的DES加密
public class Encryptor {
private BufferedBlockCipher cipher;
private KeyParameter key;
// 初始化加密引擎.
// 數組key的長度至少應該是8個字節.
public Encryptor( byte[] key ){
/*
cipher = new PaddedBlockCipher(
new CBCBlockCipher(
new DESEngine() ) );
*/
cipher = new PaddedBlockCipher(
new CBCBlockCipher(
new BlowfishEngine() ) );
this.key = new KeyParameter( key );
}
// 初始化加密引擎.
// 字符串key的長度至少應該是8個字節.
public Encryptor( String key ){
this( key.getBytes() );
}
// 做加密解密的具體工作
private byte[] callCipher( byte[] data )
throws CryptoException {
int size =
cipher.getOutputSize( data.length );
byte[] result = new byte[ size ];
int olen = cipher.processBytes( data, 0,
data.length, result, 0 );
olen += cipher.doFinal( result, olen );
if( olen < size ){
byte[] tmp = new byte[ olen ];
System.arraycopy(
result, 0, tmp, 0, olen );
result = tmp;
}
return result;
}
// 加密任意的字節數組，以字節數組的方式返回被加密的數據
public synchronized byte[] encrypt( byte[] data )
throws CryptoException {
if( data == null || data.length == 0 ){
return new byte[0];
}
cipher.init( true, key );
return callCipher( data );
}
// 加密壹個字符串
public byte[] encryptString( String data )
throws CryptoException {
if( data == null || data.length() == 0 ){
return new byte[0];
}
return encrypt( data.getBytes() );
}
// 解密壹個字節數組
public synchronized byte[] decrypt( byte[] data )
throws CryptoException {
if( data == null || data.length == 0 ){
return new byte[0];
}
cipher.init( false, key );
return callCipher( data );
}
// 解密壹個字符串
public String decryptString( byte[] data )
throws CryptoException {
if( data == null || data.length == 0 ){
return "";
}
return new String( decrypt( data ) );
}
}
下邊的代碼演示如何使用上邊的Encryptor類來加密解密數據
import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;
import javax.microedition.rms.*;
import org.bouncycastle.crypto.*;
import java.math.BigInteger;
public class CryptoTest extends MIDlet {
private Display display;
private Command exitCommand = new Command( "Exit", Command.EXIT, 1 );
private Command okCommand = new Command( "OK", Command.OK, 1 );
private Encryptor encryptor;
private RecordStore rs;
/** 構造函數*/
public CryptoTest() {
}
private void initialize() {
}
public void startApp() {
initialize();
if( display == null ){ // first time called...
initMIDlet();
}
}
public void pauseApp() {
}
public void destroyApp(boolean unconditional) {
exitMIDlet();
}
private void initMIDlet(){
display = Display.getDisplay( this );
// 打開名為"test3"的RecordStore
try {
rs = RecordStore.openRecordStore( "test3",
true );
} catch( RecordStoreException e ){
}
display.setCurrent( new AskForKey() );
}
public void exitMIDlet(){
try {
if( rs != null ){
rs.closeRecordStore();
}
} catch( RecordStoreException e ){
}
notifyDestroyed();
}
private void displayException( Exception e ){
Alert a = new Alert( "Exception" );
a.setString( e.toString() );
a.setTimeout( Alert.FOREVER );
display.setCurrent( a, new AskForKey() );
}
class AskForKey extends TextBox
implements CommandListener {
public AskForKey(){
super( "Enter a secret key:", "", 8, 0 );
setCommandListener( this );
addCommand( okCommand );
addCommand( exitCommand );
}
public void commandAction( Command c,
Displayable d ){
if( c == exitCommand ){
exitMIDlet();
}
String key = getString();
if( key.length() < 8 ){
Alert a = new Alert( "Key too short" );
a.setString( "The key must be " +
"8 characters long" );
setString( "" );
display.setCurrent( a, this );
return;
}
encryptor = new Encryptor( key );
try {
if( rs.getNextRecordID() == 1 ){
display.setCurrent(
new EnterMessage() );
} else {
byte[] data = rs.getRecord( 1 );
String str =
encryptor.decryptString( data );
Alert a =
new Alert( "Decryption" );
a.setTimeout( Alert.FOREVER );
a.setString(
"The decrypted string is '" +
str + "'" );
display.setCurrent( a, this );
}
} catch( RecordStoreException e ){
displayException( e );
} catch( CryptoException e ){
displayException( e );
}
}
}
class EnterMessage extends TextBox
implements CommandListener {
public EnterMessage(){
super( "Enter a message to encrypt:", "",
100, 0 );
BigInteger bigInt = new BigInteger("199999");
setCommandListener( this );
addCommand( okCommand );
}
public void commandAction( Command c,
Displayable d ){
String msg = getString();
try {
byte[] data =
encryptor.encryptString( msg );
rs.addRecord( data, 0, data.length );
} catch( RecordStoreException e ){
displayException( e );
} catch( CryptoException e ){
displayException( e );
}
display.setCurrent( new AskForKey() );
}
}
}