code: private void authenticatePacketHMCSHA1(RawPacket pkt, int rocIn) {
  		ByteBuffer buf = pkt.getBuffer();
  		buf.rewind();
  		int len = buf.remaining();
  		buf.get(tempBuffer, 0, len);
  		mac.update(tempBuffer, 0, len);
  		rbStore[0] = (byte) (rocIn >> 24);
  		rbStore[1] = (byte) (rocIn >> 16);
  		rbStore[2] = (byte) (rocIn >> 8);
  		rbStore[3] = (byte) rocIn;
  		mac.update(rbStore, 0, rbStore.length);
  		mac.doFinal(tagStore, 0);
  	}
docs: Authenticate a packet. Calculated authentication tag is returned.
  
  @param pkt
  the RTP packet to be authenticated
  @param rocIn
  Roll-Over-Counter