mukti wrote:
> I want to know whether there is a crypto building block which doesn't allow
> someone to open an encrypted message before a certain date.
The way I'd do this is to split up the encryption key with a shared
secret scheme, then give the shares to a number of trusted third
parties, who agree to release the shares at the agreed-upon time and
no sooner. If they all decide to cheat on their agreement, then you
lose, although if the fraction over your threshold decide to stay
honest, then you win even if the rest cheat.
It sounds like there might be a business in this. It's relatively
straightforward to implement, and there don't seem to be any
excruciatingly difficult issues of trust and policy, just whether or
not the trusted third party is going to follow the agreement.
Raph
