What is an assertion?
An assertion is a signed statement in which a participant affirms something. Assertions are signed by users (operating nodes) or the servers that provide the service (postoffices). Assertions make it easy to police all the participants actions in a communication. Each time a message moves, the party moving the message signs an assertion. That way it is always clear who did what. The assertions are added to the message and also sent back to the sender. In the end, both sender and recipient have the message and all the assertions. The message status changes when the assertions are added to it. The user interface shows whether the assertions have arrived. When they arrive and all is OK, The corresponding ball turns green. If there is something wrong, the balls will turn red. If the assertion has not yet arrived, we do not know whether all is good or whether something is wrong, the ball is then yellow.
