Java Card

Hello folks,

I manage to perform authentication to G&D expert3.0 cards (Init-update, then Ext-Auth) to start a secure channel.
My problem is for following commands in same session, I get an 0x6982 for commands sent in a secure channel, below is a piece of code :

applet:

  public boolean select()
   {
      mySecureChannel = GPSystem.getSecureChannel();
      return true;
   }
(...)
  public void process(APDU apdu) throws ISOException
    {
      byte[] buffer = apdu.getBuffer();     
      (....) 
       switch (buffer[ISO7816.OFFSET_INS]) {
          
          case myFunction: 
             // Host has to be authenticated:
             if(mySecureChannel.getSecurityLevel() == SecureChannel.NO_SECURITY_LEVEL)
              ISOException.throwIt(ISO7816.SW_CONDITIONS_NOT_SATISFIED);
           else
           {
             wrappedLength = apdu.setIncomingAndReceive();
             mySecureChannel.unwrap(buffer,ISO7816.OFFSET_CLA,(short)(wrappedLength + 5));    /*<-- Exception thrown HERE*/
             myFunction(apdu); }
(...)

I assume MAC generation on host side is correct as I could reproduce sample sequences and MAC for External Authentication is correct.

Any hints greatly appreciated ! Thanks,

Daniel