Encrypt/Decrpyt Information File
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by Ed Watkeys

November 4th, 1990

Encrpyt/Decrypt is an application which allows you to gain fairly good security.  It was written in ZBASIC by Zedcor, Inc.  Copy this program freely; if you find it useful please send me $10 at:

Ed Watkeys III
1616 Upper State Road
North Wales, PA 19454

By the time you read this, I should be able to be reached on America Online at EdWatkeys.  Please send your suggestions.

ED encrypts files in the following manor:

1. Uses the key as random number seed.
2. Takes random numbers and processes them through a third degree polynomial.
3. Uses the bottom eight bits to XOR with a byte of data.

While this is no DES, but it works rather well when you aren't sending war plans or anything of that nature.  If your security needs are that pressing, DO NOT USE THIS PROGRAM!

Each byte of the file is processed in the above manor until it is complete.  You specify a source and a destination file, which ED reads from and writes to, respectively.  The prefix should be set to the folder in which ED is run, because ED needs to find the run-time file(s).

Oh yes, when you enter the key, it should be a 16 bit signed integer (-32768 to 32767, if I remember correctly).

As far as plans for future versions, go, I think it would be nice if the program could encrpyt batches of files with the same key, instead of requiring the user to go through the process however many times.  Also, if ShrinkIt (the only NuFX program I know of) would include an option for encrpyting files or putting some sort of password protection, there would be no use for this program.  Unfortunately, the last time I checked, ShrinkIt has about two bytes of memory before it steps on the ProDOS global page, so this could be a problem.  Perhaps I'll write a version which will encrpyt files inside of a NuFX archive, although I've looked at the NuFX file format file, and it looks pretty imposing.