=============================================================

      WRDENC - DATA ENCRYPTION FOR THE MODEL 200

=============================================================

    This program encrypts a .DO file on the model 200 to keep it from 
prying eyes. The program is 100% machine language, uses a 30 character
password or key, and has a speed of about 1.5K/sec.

    This program is model 200 specific.

=============================================================

PROGRAM INSTALLATION:

    The program is installed by downloading the basic program 
WRDENC.200, and then running it. This program will build the .CO file 
in memory, and then save it with the name WRDENC.CO.

    A data checksum is kept when creating the ML program, but as with 
all ML programs, save everything until you are sure it works, a bad ML
program can clobber your machine.

PROGRAM USAGE:

    The program is real simple, just run it and type in the name of 
the file to encode/decode. (Hitting <ENTER> will take you back to the 
MENU). The program will then say either encoding or decoding, and 
prompt you for a password. After entering the password, the full 
password will be listed in inverse video, and you will be asked to 
continue Y/N. Anything but Y or y will take you back to the FILE: 
prompt, and leave your file untouched. Make sure the password is 
correct. This program works on the file in place, and short of 
deadstarting the machine, this program is one of the fastest ways to 
lose data if you type in a wrong password. The algorithim used is also
one way, once you use a wrong password when trying to decode a file, 
information is lost, and can not be recovered. So, be verrrry careful 
when typing in a password to decode. (Having a copy of the encrypted 
file is suggested).

   The method used to encode the file is position dependant, if a byte
in the file is deleted, everything from that byte on will be trash. 
After the file is encoded, do not touch it.

=============================================================

METHOD USED

    The algorithim used is rather simple, but has the advantage of 
being fast. This is not intended to be an "unbreakable" code. It is 
however hard enough to break to discourage any but a determined 
cryptographer. The password entered is reduced to 3 15 bit seeds for a
  random number generator. The 3 random values from the generator are 
then used as exclusive or and shift masks to the data byte. The high 
bit is then set. Decoding is the same in reverse. The random number 
generator is table based, and machine specific.

=============================================================

Note:

     This is a new program, and  while the program is straight forward
and has worked for everything I have tried, care should be used due to
the nature of the program. The user is solely responsible for the loss
of data, and/or any associated losses they may incur as a result of 
use of this program.

=============================================================

    Any comments/ideas, etc. would be appreciated

    Richard Haw
    [71706,334]

=============================================================