FidesmoCrypto

BaseCardlet.java

package com.fidesmo.javacard.example;

import javacard.framework.*;
import javacard.security.*;

public abstract class BaseCardlet extends Applet implements ISO7816 {
        KeyPair kp;
        Signature sig;

        BaseCardlet(byte[] buffer, short offset, byte length) {
            kp = newKey();
            kp.genKeyPair();
            sig = newSig();
            sig.init(kp.getPrivate(), Signature.MODE_SIGN);
            register();
        }

        protected abstract KeyPair newKey();
        protected abstract Signature newSig();
        protected abstract void sendPublicKey(APDU apdu, short p1);
        protected abstract void signData(APDU apdu);

        public void process(APDU apdu) {
            if (this.selectingApplet()) {
                return;
            }

            byte[] apduBuffer = apdu.getBuffer();
            byte cla = apduBuffer[ISO7816.OFFSET_CLA];
            byte ins = apduBuffer[ISO7816.OFFSET_INS];
            short lc = (short) apduBuffer[ISO7816.OFFSET_LC];
            short p1 = (short) apduBuffer[ISO7816.OFFSET_P1];
            short p2 = (short) apduBuffer[ISO7816.OFFSET_P2];

            switch (ins) {
                case 0x00:
                    if (p1 == 0x00) {
                        sendPublicKeyType(apdu);
                    } else {
                        sendPublicKey(apdu, p1);
                    }
                    return;
                case 0x01:
                    signData(apdu);
                    return;
                default:
                    ISOException.throwIt(ISO7816.SW_INS_NOT_SUPPORTED);
            }
        }

        private void sendPublicKeyType(APDU apdu) {
            PublicKey pk = kp.getPublic();
            apdu.getBuffer()[0] = pk.getType();
            apdu.setOutgoingAndSend((short) 0, (short) 1);
        }
}

ExampleCardlet.java

package com.fidesmo.javacard.example;

import javacard.framework.*;
import javacard.security.KeyBuilder;
import javacard.security.KeyPair;
import javacard.security.RSAPublicKey;
import javacard.security.Signature;

public class ExampleCardlet extends BaseCardlet {

    private static final short SCRATCHPAD_SIZE = 256;

    private byte[] scratchpad = JCSystem.makeTransientByteArray(SCRATCHPAD_SIZE, JCSystem.CLEAR_ON_DESELECT);

    public ExampleCardlet(byte[] buffer, short offset, byte length) {
        super(buffer, offset, length);
    }

    public static void install(byte[] bArray, short bOffset, byte bLength) {
        new ExampleCardlet(bArray, bOffset, bLength);
    }

    protected KeyPair newKey() {
        return new KeyPair(KeyPair.ALG_RSA, KeyBuilder.LENGTH_RSA_2048);
    }

    protected Signature newSig() {
        return Signature.getInstance(Signature.ALG_RSA_SHA_PKCS1, false);
    }

    protected void sendPublicKey(APDU apdu, short cmd) {
        switch (cmd) {
            case 0x01:
                sendRSAPublicKeyExp(apdu);
                return;
            case 0x02:
                sendRSAPublicKeyMod(apdu);
                return;
            default:
                ISOException.throwIt(ISO7816.SW_INCORRECT_P1P2);
        }
    }

    private void sendRSAPublicKeyMod(APDU apdu) {
        RSAPublicKey pk = (RSAPublicKey) kp.getPublic();
        short len = pk.getModulus(scratchpad, (short) 0);
        Util.arrayCopyNonAtomic(scratchpad, (short) 0, apdu.getBuffer(), (short) 0, len);
        apdu.setOutgoingAndSend((short) 0, len);
    }

    private void sendRSAPublicKeyExp(APDU apdu) {
        RSAPublicKey pk = (RSAPublicKey) kp.getPublic();
        short len = pk.getExponent(scratchpad, (short) 0);
        Util.arrayCopyNonAtomic(scratchpad, (short) 0, apdu.getBuffer(), (short) 0, len);
        apdu.setOutgoingAndSend((short) 0, len);
    }

    protected void signData(APDU apdu) {
        short len = sig.sign(apdu.getBuffer(), ISO7816.OFFSET_CDATA, apdu.getBuffer()[ISO7816.OFFSET_LC], scratchpad, (short) 0);
        Util.arrayCopyNonAtomic(scratchpad, (short) 0, apdu.getBuffer(), (short) 0, len);
        apdu.setOutgoingAndSend((short) 0, len);
    }
}