Original CoAP Packet
                   +-+-+---+-------+---------------+
                   |v|t|TKL| code  | Message ID    |
                   +-+-+---+-------+---------------+....+
                   | Token                              |
                   +-------------------------------.....+
                   | Options (IEU)            |
                   .                          .
                   .                          .
                   +------+-------------------+ 
                   | 0xFF |
                   +------+------------------------+
                   |                               |
                   |     Payload                   |
                   |                               |
                   +-------------------------------+      
                          /                \ 
                         /                  \
                        /                    \
                       /                      \
     Outer Header     v                        v  Plaintext
  +-+-+---+--------+---------------+          +-------+
  |v|t|TKL|new code| Message ID    |          | code  |
  +-+-+---+--------+---------------+....+     +-------+-----......+
  | Token                               |     | Options (E)       |
  +--------------------------------.....+     +-------+------.....+
  | Options (IU)             |                | 0xFF  |
  .                          .                +-------+-----------+
  . OSCORE Option            .                |                   |
  +------+-------------------+                | Payload           |
  | 0xFF |                                    |                   |
  +------+                                    +-------------------+