Specifically how do you keep others from cheating and saying that an event happened in the past when it actually happened in the present?
You need a trusted time-notary who will sign or publish hashes of the event in a manner which is hard to undo (e.g in a major news-paper). This is a known art.
A related but harder problem is time-delayed release of information.
If you can predict the future cost/CPU speed then you can create a problem which can’t be solved with current technology at a reasonable price. The future isn’t predictable enough to do this over the longer term.
If you have a large enough transmitter/receiver, you can transmit they key to distant astral bodies and wait for the reflection. However if this became routine, spy sats might intercept the transmissions.
You can launch a pair of notary space probes and have them bounce an encrypted key stream between them with lasers for a specified period of time (using space as a storage device) before sending decrypts back. If the sats were moving away from earth at significant speed due to VEEGA like alignment windows, it might be a long time before these sats could ever be destroyed.
--
Julian Assange |If you want to build a ship, don't drum up people
|together to collect wood or assign them tasks and
proff@iq.org |work, but rather teach them to long for the endless
proff@gnu.ai.mit.edu |immensity of the sea. -- Antoine de Saint Exupery