If it is possible, software piracy is given a major blow with such a system. Have any particular program encrypted with a different private key for each customer. Compile the name of the purchaser into the program code, and then tracing illegal copies to the leak is trivial.
There seem to be some problems with the above scheme: 1) Suppose I buy a legal copy of some software and give it to a friend, along with the information he needs to run it. To prove piracy, someone would have to check the files on his/her hard disk. Surely this is an invasion of privacy no cypherpunk would tolerate. 2) Suppose that somehow a pirated copy of the software was discovered, and traced back to me. This still does not provide any kind of case against me, since it is not clear whether or not I gave the information away (it could have been stolen off my hard drive while at a repair shop, or by a house guest, or...). To argue otherwise implies making the software owners liable if the software sold to them is pirated. Of course, these are legal, not technical objections to your scheme. Peter ------------------------------------------------------------------------- Peter Breton pbreton@cs.umb.edu PGP key by finger =========================================================================