I really appreciate your enthusiasm. It is one of the core concepts and passwords seemed to be a good way to explore my FIFO idea in a practical manner. It might well have been done before, but from preliminary searches I could not find anything on it(not that I searched really hard). Due to its simplicity, I suspect it will lend itself to some pretty efficient implementations.<p>I would be interested to hear what other kinds of problems you see it being used for.