CODER.BAS -

	The Coder is a file encryption program that allows a user
to protect any sequential file from being read or in the case of
executable files, used by any person not knowing the correct
password.  In its present state, the program does require some
machinations on the part of the user to complete the work of 
encrypting the file and although I make no guarantees that the
encryption is completely uncrackable, it does work well enough
to discourage most prying eyes.  When a file is properly encrypted
and decrypted, the hash total for the file will be the same as before
it was processed.

	To begin, you must know the name of the file to be encrypted.
Run the Coder and enter 'E' to Encode the file.  You must be logged
into the account that contains the file you wish to encrypt.  If you
do not specify an extension for the file name, an extension of .TXT
will be assumed.  You may then enter a six character password.  This
password IS case sensitive and is not recorded anywhere except in your
own mind.  I did not do anything fancy to protect the visibility of the
password while it is being entered.  In order that the program be as
generic as possible, I limited the use of XCALL subroutines.  The program
can be altered as desired to echo dots or asterisks instead of your
password.  As the file is being processed you will see the number of
characters encrypted displayed on your crt screen.  Decoding the file is 
similar, except for entering 'D' to Decode the file.

	In order that the file truly be protected, the following procedures
are necessary.  First, the program doesn't directly alter your file.  It
simply creates an encoded copy of it.  This encrypted file will exist in
your PPN as filename.CDE. If you were decoding the file, the Coder would 
create a file called filename.NRM in your PPN.  The best way to complete 
the encryption is to RENAME/D oldfilename,filename.CDE (or .NRM).  This
results in an erase and a copy that leaves no residual pointers in the 
User File Directory (UFD).  If you want to make sure that nothing exists
in the UFD that could point to your erased unencrypted file, simply issue
a DIRSEQ or DIRSEQ/E command from the AMOS prompt.  Again, I don't
guarentee that it would be impossible to find your unencrypted file, but
this would make it very, VERY difficult. 

	The Coder will run fastest if both STRIP.SBR and FILEIN.SBR are
loaded into either user or system memory.  FILEIN is especially important
because a call is issued to that subroutine for every byte in the file to
be processed.

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