


                         ROTTY! v1.10  (c)1994 Brian Spencer
                         - - - - - - - - - - - - - - - - - -

       If you have any questions or comments concerning this or any of my
       forthcoming projects, feel free to contact me:

                 Brian Spencer
                 54 Highland Avenue
                 Barrie, Ontario
                 L4M 1N3  CANADA

                 1:252/503.2 (FidoNet)


       DISCLAIMER & LICENCE

       NO GUARANTEE OR WARRANTY TO THE FITNESS OF THIS PROGRAM IS MADE.
       USE ONLY AT YOUR OWN RISK!

       You are permitted to use this program without any monetary
       compensation to me.  However, I could always use some
       encouragement, so if you *want* to do something, send me a
       postcard.  If you are an employer, I could use a real job.  :-}

       This package, which includes the following files:

                 ROTTY.COM      Main executable
                 ROTTY.TXT      The file you're reading now
                 FILE_ID.DIZ    Description for Bulletin Board Systems

       may be distributed under these terms:  a) The files listed above
       must all be included and may not be altered in any way; and, b)
       There is no conspicuous charge for this package.  This package may
       NOT be distributed as part of another package without my written
       permission.


       BACKGROUND AND INSTRUCTIONS

       You are probably asking yourself, "What *is* rot13"?  Rot13 is a
       simple form of text-based encryption.  More precisely it is a
       substitution cipher, or a Caesar Cipher.  If you took the letters
       of the English alphabet and rotated them 13 positions (the
       carry-over is wrapped around), then you would have something like
       the following:

            the letters:
                 a b c d e f g h i j k l m n o p q r s t u v w x y z
            become:
                 n o p q r s t u v w x y z a b c d e f g h i j k l m

       What makes this cipher unique is that if you repeat the above
       process, you will return with the original message.  The algorithm
       is a mathematical congruence.


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       Why use rot13?  Obviously it isn't going to provide any challenge
       for cryptanalysists.  Rather, it is used to provide a very easy,
       yet effective, mask of possibly offensive text that is broadcast.
       It is most often used in newsgroups on Usenet.  If someone WANTS to
       read the disguised text, then they can decode it.

       Using rot13 has been made fast, efficient, and painless with ROTTY!
       (Trust me, you don't want to do this with just paper and pen)  On
       the command line prompt, type:

                 ROTTY <filespec> [filespec]...

       Actually, don't type that.  Enter ROTTY alone on a line to get
       brief instructions on it's syntax.  All the program needs is at
       least one parameter - a filename.  You can enter as many filenames
       as you want, with or without wildcards.  ROTTY! will then proceed
       to encrypt/decrypt the file(s).  The original file(s) will be
       replaced with their enrypted/decrypted counterparts.  Remember, you
       can reverse this process by running the program over the same files
       again.  Sound easy?  You bet!

       If you're feeling particularly industrial, try using ROTTY! with
       some tool of telecommunications, such as an offline reader or a
       point system.


       NOTES OF INTEREST

            * Written entirely in ANSI C as a personal excercise.  The
            source code could be compiled on any other platform

            * Compiled with Borland's Turbo C++ for DOS 3.0, (c) 1987,
            1993 Borland International, Inc.  All rights reserved

            * Using the tiny memory model, ROTTY! will consume no more
            than a whopping 64 kilobytes of RAM

            * Should run on the lowest common-denominator of PC ever made

            * For speed and efficiency, I upgraded the output file's
            buffer to 16 kilobytes - your drive heads will thank you for
            it


       HISTORY

            (v1.00) - First release - too pleased with myself to think
            anything could go wrong...

            (v1.10) - Thanks to andrew graham's suggestion, I replaced
            redundant mathematics with a lookup table, which speeds up the
            process; Made cosmetic changes to program and documentation



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