For that, you play a flat fee that depends on the duration of storage and the size of the message. For an extra fee, you can waive cancellation of a message. The message will not be cancelled, even if you yourself demand it at a later time, even if you fully authenticate yourself through other means. The message is delivered to a group of people rather than a single person. The message is printed and sent to its recipients on paper in addition to electronic delivery.
Dead man switch When the message is established, a second key is passed to the client.