Re: Converting Commodore text files to The Numerica Format?


<a7yvm109gf5d1@xxxxxxxxxxx> wrote ...

> Well, the "encryption" is still trivial if you just increment the key
> byte for every character. The fun starts if you use a more complex
> algorithm for the key, like a LFSR. You can implement this in a few
> lines of boolean logic. Of course, key distribution is still a problem.
> But as a way to have fun with a few lines of BASIC on a Commie, it
> sounds like something to do this weekend if it rains!

Yep, XOR is a good way to encrypt a file using a BASIC program. Not too long
ago I ported a QBasic encryption program to C128 BASIC 7.0 If Paul is
interested, I can email him a copy of the C128 PRG file.

Encryption is really pretty secure using the program I converted. A password
supplied by the user is encrypted by a key coded into the program before use.
Then after each use the password is encrypted again. For example, is an 8
character password is used, the password is re-encrypted after each 8
characters from the file are processed.

De-bugging the program drove me crazy, until I realized that some of the
characters in the encrypted file were CHR$(0) causing decryption to fail.
Easy to fix once I figured out what the problem was. (QBasic does not have
the C= BASIC CHR$(0) bug.)

Oh well, enough rambling. Paul, let me know if you want me to email a copy
of the BASIC 7.0 program to you.
--
Best regards,

Sam Gillett

Change is inevitable,
except from vending machines!




.

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