TECH: encrypted computer?

Here's something I've been thinking about:
Is it possible to create a computer system based on encryption?  Could
you have a computer that does not just increase the program counter for
each instruction, but instead jumps around forward and back based on
a combination of an encrypted program and a public key?  Without the
public key, the computer would never know what the next instruction was.
If you try to watch the execution, to figure out the order, you can't
tell if the next address was chosen because it's just next or if it
was chosen as the result of a comparison.  A new encryption/decryption
algorithm would need to be invented so as to securely hide how the
next address was chosen.  Decryption hardware would have to be created
so things run fast enough.  There is lots of other things to be worked
out, but is it possible?

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.

In case it's not clear above, the whole system is based on encryption.
It is not just a matter of the executable being encrypted.  I don't
want the owner to be able to decrypt the executable and run that, he
has to run it encrypted.

Peter Baumbach
baumbach@atmel.com

> 
> 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

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Peter Breton  pbreton@cs.umb.edu          PGP key by finger
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