Time Locks-- Re: Delayed self-encrypting messages

[Rick Busdiecker]

    Date: Fri, 10 Jun 94 16:13:03 CDT
    From: dfloyd at runner.jpl.utsa.edu (Douglas R. Floyd)
    
    Anyone have any better ideas for a secure crypto way of doing this? ;)
    
Create your message.  Using PGP, generate a new key pair.  Use the
public key to encrypt the message, then throw it away.  Send the
secret key along with the message.  Have the signature for the secret
key be the NYT headline for the day on which you want the data to be
available :-)

Stepping back from the details of various crypto approaches, I think
that the problem is that you want a locking mechanism to be based on
data.  Since you want a time lock, the data has to be directly
associated with time.  For this to work, you need to create data that
is unknowable until a certain time.  If the data is known to you,
you've come full circle: you're new goal is your original goal.  If
the data is not known to you, it needs to be something which the other
party cannot deduce prior to the expiration of your time lock.  To be
confident that no one could deduce this information, a prerequisite
would have to be that you couldn't deduce it, that is, it wouldn't be
something that you could use as part of an encryption.

I think that this problem ultimately requires a trust based mechanism.

			Rick