Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!uunet!samsung!munnari.oz.au!metro!macuni!sunb!ifarqhar
From: ifarqhar@sunb.mqcc.mq.oz.au (Ian Farquhar)
Newsgroups: comp.sys.amiga.programmer
Subject: Re: Executing a program for bootblock (Was: Locking the Amiga)
Message-ID: <1098@macuni.mqcc.mq.oz>
Date: 15 Jan 91 12:01:54 GMT
References: <6145@berry12.UUCP>
Sender: news@macuni.mqcc.mq.oz
Organization: Macquarie University, Sydney, Australia.
Lines: 45

In article <6145@berry12.UUCP> kutem@rtsg.mot.com (Jon Kutemeier) writes:
>I am looking for two things:
>
>1) How would I alter the bootblock on my harddrive so that it would
>   execute a password protection program upon booting (the program
>   would also reside on the boot partition)?

Last time I asked tech support, they told me that a HD bootblock is
never read, so the answer could be either very easy (because it isn't
worth doing), or very hard ('cause you're in for some heavy hacking.)
This is backed up (no pun intended) as a boot-block virus has never, to
my knowledge, infected a hard disk.

>2) Does anyone have the algorithm for a fairly secure encryption
>   program (as optimal as possible :) )?

DES is around.  Try typing in the source in Andrew Tanenbaum's "Computer
Networks."  DES is moderately secure, in that although the NSA (or
whoever) can almost certainly break it, most people cannot.  However, if
by "optimal" you mean fast, forget software implementations of DES.
They are notoriously slow.  This slowness was one of the reasons UNIX
uses DES to encrypt its passwords.

What else?  RSA or variant.  Again, it will be slow, and you will need
to do a huge amount of integer math on numbers hundreds of digits in
size, and again it is almost certain that the powers-that-be have a fast 
way of factorising primes (which makes this system quite open to attack.)

However, if you are wanting an easy encryption method that could be
coded in little time, have a look at the German enigma machine (also
used in the UNIX crypt (1) command.)  Very simple to implement as arrays
of indexes into other arrays, and could be very fast.  As the NSA is too
paranoid to let this simple encryptor loose on the rest of the world (as
everyone knows that a non-US citizen is a terrorist in the pay of Iraq,
the Soviet Union or the boggie-man), then they don't ship it with UNIX
outside the US.  As such, there are lots of clones, and sources
shouldn't be too hard to find.  The enigma machine is reasonably secure,
though any serious cryptography expert should be able to crack it
moderately easily.

--
Ian Farquhar                      Phone : 61 2 805-9400
Office of Computing Services      Fax   : 61 2 805-7433
Macquarie University  NSW  2109   Also  : 61 2 805-7420
Australia                         EMail : ifarqhar@suna.mqcc.mq.oz.au