I am new to java card development. I have been trying to use RSA encryption in my Applet. I finally got the encryption working but the decryption is showing Illegal Use Error. Any kind of help is appreciated.
public class RSAsample extends Applet{
byte[] rsaPublic = new byte[4];
byte[] rsaPrivate = new byte[4];
byte[] rsaPublicMod = new byte[4];
RSAPrivateKey pri ;
RSAPublicKey pub ;
private final static byte INS_ENCRYPT = (byte) 0x20;
private final static byte INS_DECRYPT = (byte) 0x30;
KeyPair pair ;
private RSAsample() {
super();
register();
}
public static void install(byte bArray[], short bOffset, byte bLength)
throws ISOException {
new RSAsample();
}
public boolean select() {
pair = new KeyPair(KeyPair.ALG_RSA, (short) 512);
pair.genKeyPair();
pri = (RSAPrivateKey) pair.getPrivate();
pub = (RSAPublicKey) pair.getPublic();
return super.select();
}
public void deselect() {
super.deselect();
}
public void process(APDU apdu) throws ISOException {
byte[] buffer = apdu.getBuffer();
switch(buffer[ISO7816.OFFSET_INS])
{
case INS_ENCRYPT:
encrypt(apdu);
break;
case INS_DECRYPT:
decrypt(apdu);
break;
}
}
private void decrypt(APDU apdu) {
byte[] buffer = apdu.getBuffer();
byte byteRead = (byte)(apdu.setIncomingAndReceive());
short size = 0;
try{
Cipher cipher = Cipher.getInstance(Cipher.ALG_RSA_PKCS1, false);
cipher.init(pri, Cipher.MODE_DECRYPT);
size = cipher.doFinal(buffer, ISO7816.OFFSET_CDATA, (short)byteRead, buffer,
(short) 0);
}
catch(CryptoException e)
{
switch(e.getReason())
{
case CryptoException.ILLEGAL_USE:
ISOException.throwIt(ISO7816.SW_DATA_INVALID);
break;
case CryptoException.ILLEGAL_VALUE:
ISOException.throwIt(ISO7816.SW_FILE_INVALID);
break;
case CryptoException.INVALID_INIT:
ISOException.throwIt(ISO7816.SW_FILE_NOT_FOUND);
break;
case CryptoException.NO_SUCH_ALGORITHM:
ISOException.throwIt(ISO7816.SW_FILE_INVALID);
break;
case CryptoException.UNINITIALIZED_KEY:
ISOException.throwIt(ISO7816.SW_FILE_FULL);
break;
default:
ISOException.throwIt(ISO7816.SW_FUNC_NOT_SUPPORTED);
break;
}
}
apdu.setOutgoing();
apdu.setOutgoingLength(size);
apdu.sendBytes((short)0, size);
}
private void encrypt(APDU apdu) {
byte[] buffer = apdu.getBuffer();
byte byteRead = (byte)(apdu.setIncomingAndReceive());
short size = 0;
try{
Cipher cipher = Cipher.getInstance(Cipher.ALG_RSA_PKCS1, false);
cipher.init(pub, Cipher.MODE_ENCRYPT);
size = cipher.doFinal(buffer, ISO7816.OFFSET_CDATA, (short)byteRead, buffer,
(short) 0);
}
catch(CryptoException e)
{
switch(e.getReason())
{
case CryptoException.ILLEGAL_USE:
ISOException.throwIt(ISO7816.SW_DATA_INVALID);
break;
case CryptoException.ILLEGAL_VALUE:
ISOException.throwIt(ISO7816.SW_FILE_INVALID);
break;
case CryptoException.INVALID_INIT:
ISOException.throwIt(ISO7816.SW_FILE_NOT_FOUND);
break;
case CryptoException.NO_SUCH_ALGORITHM:
ISOException.throwIt(ISO7816.SW_FILE_INVALID);
break;
case CryptoException.UNINITIALIZED_KEY:
ISOException.throwIt(ISO7816.SW_FILE_FULL);
break;
default:
ISOException.throwIt(ISO7816.SW_FUNC_NOT_SUPPORTED);
break;
}
}
apdu.setOutgoing();
apdu.setOutgoingLength(size);
apdu.sendBytes((short)0, size);
}
}
Also if this is wrong can you share a sample code using RSA Encryption and Decryption.