Get response & slow performance

Question

Internal authenticate method when the RSA 2K RSA key is used returns 256 bytes. The applet does not support the extended length. Because of it, the internal authenticate method returns 255 in the first launch. After the get response is called and the rest (1 byte) is returned. Get response function lasts unexpectedly slow. More than 300 ms. This code handle get response:
if (apdu.getCurrentState() != APDU.STATE_OUTGOING) {
                    apdu.setOutgoing();
               apdu.setOutgoingLength(length);
               apdu.sendBytesLong(tmpBuffer.data, remainingDataOffset, length);I am aware that in order to return the rest of the message, the array has to be iterated on the appropriate position (255). Is there any way how this can be optimized under the prerequisite that the extended length is not used?

Answer 1

This is just the extract of my code. There is a part of code in which I am checking if the command is GET RESPONSE.
Can you see in this code what makes the get response acts slow. In the second launch, only one bate is resturned. This
byte is at the offset 255 of the tmpBuffer.data variable
Extract from the process method:
The instance variables:
private static final byte INS_GET_RESPONSE = (byte) 0xC0;
private byte[] remainingDataLength;
     private byte[] remainingDataOffset;
     The constructor:
remainingDataLength = JCSystem.makeTransientByteArray((short) 2,
                    JCSystem.CLEAR_ON_DESELECT);
          remainingDataOffset = JCSystem.makeTransientByteArray((short) 2,
                    JCSystem.CLEAR_ON_DESELECT);
byte[] buffer = apdu.getBuffer();
          byte ins = buffer[OFFSET_INS];
          if (ins == INS_GET_RESPONSE) {
               if (Util.getShort(remainingDataLength, (short) 0) <= 0) {
                    ISOException.throwIt(SW_CONDITIONS_NOT_SATISFIED);
               sendData(apdu, Util.getShort(remainingDataLength, (short) 0));
               return;
          else {
               Util.setShort(remainingDataOffset, (short) 0, (short) 0);
               Util.setShort(remainingDataLength, (short) 0, (short) 0);
          }The called sendData method:
private void sendData(APDU apdu, short length) {
          short remainingDataOffsetTmp = Util.getShort(remainingDataOffset, (short) 0);
          short remainingDataLengthTemp = Util.getShort(remainingDataLength, (short) 0);
          if (length > RESPONSE_LENGTH) {
               if (apdu.getCurrentState() != APDU.STATE_OUTGOING) {
                    apdu.setOutgoing();
               apdu.setOutgoingLength(RESPONSE_LENGTH);
               apdu.sendBytesLong(tmpBuffer.data, remainingDataOffsetTmp, RESPONSE_LENGTH);
               remainingDataOffsetTmp += RESPONSE_LENGTH;
               remainingDataLengthTemp = (short) (length - RESPONSE_LENGTH);
               Util.setShort(remainingDataOffset, (short) 0, remainingDataOffsetTmp);
               Util.setShort(remainingDataLength, (short) 0, remainingDataLengthTemp);
               ISOException
                         .throwIt((short) (ISO7816Ext.SW_MORE_DATA + ((remainingDataLengthTemp > RESPONSE_LENGTH) ? RESPONSE_LENGTH
                                   : remainingDataLengthTemp)));
          else if (length > 0 && length <= RESPONSE_LENGTH) {
               if (apdu.getCurrentState() != APDU.STATE_OUTGOING) {
                    apdu.setOutgoing();
               apdu.setOutgoingLength(length);
               apdu.sendBytesLong(tmpBuffer.data, remainingDataOffsetTmp, length);
               Util.setShort(remainingDataOffset, (short) 0, (short) 0);
               Util.setShort(remainingDataLength, (short) 0, (short) 0);
     }