4 ms·
Many are mentioning digital timestamps. There's a pretty universal physical one, too -- a postmark. So enclose your message and a newspaper front page in an env
by senstax 6y ago
Many are mentioning digital timestamps. There's a pretty universal physical one, too -- a postmark. So enclose your message and a newspaper front page in an envelope addressed to yourself and sealed in a trustable way, and drop it in the mail. But then opening it can only happen once and has to be witnessed.