I was thinking about the way git allows to edit the timestamp on commits, and how you can rewrite (public) history that way.
I then drifted from that to "can we prove someone did an action at time X a posteriori? " to prevent these rewrites.
And surprisingly, my brain found little or no ways to prove an action was taken on time, with no way of doctoring that afterwards.
I assume that we can't just ask a trusted server's log on date/time involved for connection as proof, and have to rely on a crypto-thingy to prove "we were there",
I thought about a trusted server sending a hash/key dependent on time when it was contacted, so that you would have to query the server and "be there on time" to get the code. But this is silly, as anyone could record these hashes by hitting the server often enough.
Any computation based on the exact date time would also be broken of course, which leaves me at a loss.
My actual questions now :
- Is such a problem actually important for some ? Important enough for someone else to solve it / take a stab ?
- What did I miss ? Any insight ?