Is it possible to create a timestamp that is so hard to fake, that it could be used as proof or simply strong evidence in a court of law, that something was not created after a certain point in time?
The file could be anything; a word document, an image, an audio file, a software specific file, ie. PSD.
Some ways I think might work are by uploading it to a reputable cloud or social networking site but what if by some twist of fate the large company goes bust and I can no longer prove it?
What is the most secure, hardest-to-fake, longest lasting (not likely to become invalid anytime soon) way to prove that a digital file was not created after a certain point in time?
It could still be possible to fake, but preferably by some highly advanced means that makes it unlikely.
The use case I'm essentially envisioning is:
A simple 'your word against theirs' situation.
Against all sane advice, I create a file on a pay-if-you-like-it basis, with no written contract. They like it and use it, but don't pay.
I want to sue them with very strong evidence that I created the file before them (if they're trying to argue that they made it themselves - like a simple branded word template).
I'm not looking for advice from a legal standpoint, but expertise about timestamps, and how to create one with strong authenticity (I think).