Loadstar 128 #32/q32side2.d64/t.codemeister

Text File | 1992-01-01 | 9.0 KB | 185 lines

                       C O D E M E I S T E R    1 2 8

                      Program and Text by Ray Parrish


    CODEMEISTER 128 is a program that will apply a code to any PETASCII
text file and print it to the screen, disk or the printer.  Before I go on
about the program, I would like to explain the method of coding used.  To
start, pick a word without any repeating letters, like COMPUTER.  Write it
down with the remaining letters of the alphabet following it, in order.
Then write the normal alphabet underneath, like so:

      C O M P U T E R A B D F G H I J K L N Q S V W X Y Z
      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

    To encode the message, find the letter in the bottom row, and replace
it with the corresponding letter in the top row.  LOADSTAR would become
FICPNQCL. Decoding is the same process in reverse.  This process is very
time-consuming, so we let the computer do the work.

    In addition to encoding and decoding text, CODEMEISTER shows off the
use of INSTR in a number of ways.  Those familiar with the BRANCHER
function in LS 64's Toolboxes will see its parallel here.  To create a set
of "hotkeys," use the command like this:

     10 getkeya$:oninstr("hotkeys",a$)goto100,200,300
     20 goto10

    Line 10 checks the last key pressed to see if it is a hotkey.  If not,
it tries again.  If it is, then it branches according to the list of GOTOs.
Another use is for creating flipped-case strings.  See the section of the
BASIC code that asks for the codeword.  The last use of INSTR is in the
coding/decoding process.  It checks the incoming byte to see if it is a
letter.  If not, it passes through unaffected.  If it is a letter, upper or
lowercase, then INSTR is used to code the byte.

    Now for the actual program itself.  Upon startup, it checks the last
device used by polling location 186.  The hotkeys are shown in white
reverse video.  If the selected destination is PRINTER or SCREEN, the
destination drive does not matter.  If you are using a printer connected by
GEOCABLE (or a similar device connected to the user port), then select
SCREEN, turn the printer on, then press "O" again to select the printer.
Once your preferences are in order, choose whether to encode or decode. The
codeword MUST be all lowercase with no repeating letters.  The program
won't let you enter a codeword with a letter appearing more than once.

 NOTE: If you just press RETURN at the "codeword" prompt, it will use Bob
Markland's RANDOM 2-254 from LS 128 #31 to completely scramble the whole
alphabet.  It's as if you had entered a codeword 26 letters long without a
repeated letter.  More on this in FENDER'S POSTMUMBLE below.

 NOTE II: The ML for handling parallel printing is found at $1300.  Load it
with

   35 BLOAD"chrout.1300",u(dv),b0,p4864

  To send a character, use SYS4864,(ASCII character code)

    Then you will be presented with a file requestor (courtesy of Travis
Parker).  If the directory has more than 20 or so files, you can press the
STOP key to stop the file you want from scrolling off the screen.  To
select a file, move the cursor to the desired file and press RETURN.  Be
sure the file is a text file.  Using a program or non-text file would
probably create garbage and force you to break out and rerun the program.
If you want to change disks, select the "Blocks free" line, the header, or
a file listed as 0 blocks long.  If you want to exit here, press return on
a blank line.

    After that, if the selected destination is DISK, you will be asked to
provide a destination file.  If the destination is the printer, CODEMEISTER
goes right to coding/decoding.  If you want to make sure that it's encoding
or uncoding correctly, set the output to SCREEN first.  Once you're
satisfied that it's working properly, then do it for real to disk or
printer.  You can stop the process prematurely by pressing the STOP key.
This part of the program would gain considerable speed if compiled.

    Other errors abort the program with a report of the error.

    That's all there is to it!  This program can be useful if you want to
apply mild encryption to your text.  Or maybe you can use it to study the
use of INSTR.

 FENDER'S POSTMUMBLE:  I liked the simplicity of this program when I first
saw it and the more I worked with it the more I saw its potential.
Obviously, it's a straightforward "encryptor" for text.  Ray calls it
"mild" encryption, because it's not one of the many incredibly tricky
techiques of encryption that have been invented.

 Ray suggested entering a 26-letter codeword to get the "best" encryption,
but that seemed to me to be a lot of work, and it wouldn't be all that easy
to make sure there were no duplicated letters.  So I immediately thought of
Bob Markland's RANDOM 2-254 from last issue.  It's perfect for scrambling
26 letters without a repetition.  It's simple to use.  Just:

  34 bload"random 2-254",u(dv),b0,p2816

to load the ML into place at 2816.  RANDOM 2-254 is completely relocatable
and can be bloaded anywhere in free RAM in Bank 0.  Then, to randomize the
numbers from 1 to 26, do this:

  500 poke176,0:poke177,11:poke178,26:sys2816

The location of the ML (in lobyte/hibyte format) is POKEd into 176/177.
Then the number of items to be randomized is POKEd into 178.  Then SYS to
the start of the ML.  This scrambles the numbers from 1 to 26 and places
them in the 26 bytes immediately following the ML routine at ADDR+94.
CODEMEISTER required a 26-character string of the scrambled letters and
line 504 of the program provides it:

  504 lc$="":fori=1to26:lc$=lc$+chr$(64+peek(2816+94+i)):next

 That's how randomizing was added.  It provides the best encryption
possible with this technique but since it's a random string, if you don't
write it down, you can't "uncode" it.  And the program doesn't show you the
random string!  So don't use RANDOM 2-254 if you want the computer to
uncode your message.

 By the way, Ray used the more proper term, "decode" but I changed it to
"uncode" because I wanted to use D for Destination drive.

 The only way to get text into CODEMEISTER is to have it in a PETASCII text
file on disk.  It is assumed you will create this text with a word
processor.  Using the RANDOM 2-254 method of encoding you could have a
bunch of quotes or quips in files on a disk and set the Output to PRINTER
and print out some Cryptoquotes or Cryptoquips for your friends to solve.
You've undoubtedly seen these types of puzzles in newspapers and
magazines.

 You couldn't use Ray's "mild" form of encryption because it often leaves
some letters alone without changing them.  One of the laws of Cryptoquotes
is that a letter CANNOT stand for itself.  RANDOM 2-254 scrambles the
letters quite well, but it merely randomizes them; it doesn't check to make
sure that EVERY letter has moved somewhere else.  So the following line has
been added:

505 fori=1to26:ifmid$(lc$,i,1)=mid$(la$,i,1)theni=26:next:goto500:elsenext

to make the program call RANDOM 2-254 over and over until it comes up with
an encryption that hasn't left any letters in their original places.  la$
is defined early in the program as:

 abcdefghijklmnopqrstuvwxyz

 Jim Weiler, my compatriot across the hall, is often called "Dugym Qycfyl"
(pronounced "duggum quickfill") by his friends.  He came up with that name
by creating an "alphabet wheel" on his Apple computer years ago.  If you
take the name, James Weiler, and shift the alphabet six letters so that A
is G, B is H, C is I, etc. you get Dugym Qycfyl.  It's like this:

    U V W X Y Z A B C D E F G H I J K L M N O P Q R S T
    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

He tried all 25 possible shifts and shifting six created the most
interesting encryption of his name.  CODEMEISTER allows you to do the same
thing.  Have your name in a file on disk.  Then pick any letter, say "R",
and enter this as your codeword:

   rstuvwxyz

This will do the same as shifting everything nine characters on the
alphabet wheel.  Since you're using the alphabet, you don't have to
remember the whole codeword to uncode it later, just remember the letter
you started with.

 I'm fascinated by little word games like this -- which is why my
POSTMUMBLE is now longer than Ray's whole documentation.  The program is in
BASIC, and in my opinion, fast enough without compiling.  Maybe you can
come up with some new use for CODEMEISTER?  Or maybe some nifty new
features for it?  If it had an input box, for instance, you could enter
text to be encrypted, instead of having to get it from disk.  Send me your
ideas and maybe we can come up with a CODEMEISTER II somewhere down the
road.

 Finally, Travis Parker's routine to display a directory on screen as a
file requestor is very much like the one I've been using for a few years.
Bob Markland is working on a sophisticated machine language file requestor
for the C-128 but until he gets it done, I think Travis' routine does the
job quite well.  He uses TRAP to allow you to stop the scrolling of a large
directory with the STOP key.  It's not foolproof, but it works just dandy.

                    \\\\\ R - Run   RETURN - Menu \\\\\