From: Jiri Baum <jirib@sweeney.cs.monash.edu.au>
Date: Sun, 24 Dec 1995 19:03:42 +0800
To: andr0id@midwest.net (Jason Rentz)
Subject: Re: ex encrypted script
In-Reply-To: <199512202339.RAA05220@cdale1.midwest.net>
Message-ID: <199512241046.VAA06529@sweeney.cs.monash.edu.au>
MIME-Version: 1.0
Content-Type: text/plain


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Hello andr0id@midwest.net (Jason Rentz)
  and Cypherpunks

Dr0id wrote:
> I have several simple scripts that are simple yet handle important realtime
> call proccessing tasks and remote control operations.  These programs are my
> programs but are running on a system that is dialed into by the vendor once
> in a while.  

The problem will be that a superuser can do just about anything...

> Is there a way to encrypt a script yet still allow it to be runnable?  I
...

Well, what's wrong with 
  pgp -f | /bin/sh
? Obviously, it still decrypts before use, and may or may not be
useful depending on your application, but it never has a file with
the unencrypted script around.

> I thought of a few simple protections but they all involve decrypting before
> running.

It depends on what you want to prevent: copying the scripts, running 
them, understanding them, or what?

To prevent copying/running them, you can use the above script, but
you'll have to type in the passphrase each time (checking that noone
is watching you, which is impossible with a determined su).

If you just want them to not understand, obfuscation should suffice.
(But reverse-engineering can still be applied.)


(On the "supply useless source" subthread, it is possible to define
the term "source code" so as to disallow such obfuscation. See the
GNU GPL ("copyleft") licence for an example.)

Adiau

Jiri
- --
If you want an answer, please mail to <jirib@cs.monash.edu.au>.
On sweeney, I may delete without reading!
PGP 463A14D5 (but it's at home so it'll take a day or two)
PGP EF0607F9 (but it's at uni so don't rely on it too much)

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