[sci.crypt] simple two-key encryption

dean@mind.UUCP (Dean Radin) (11/20/86)

Anyone know of a simple scheme or program suitable for a microcomputer 
and written in a language like C or Basic whereby data can be encrypted
with one key and later decrypted with another key?

The application is a computer-based experiment on a Macintosh.  
I need to ensure to some reasonable degree that any data produced 
during the experiment is not alterable or even readable by a clever 
person who might be able to disassemble a compiled program to discover the
encrypting key.  Later I would like to decrypt the data
using a key known only to me.