(A less obvious problem with the scheme is that the store could use surveillance cameras to identify which tapes the customer selected, but I chose to ignore that problem.)

An other way to cheat would be also to process the returns faster... In the US (California?), since a well known case, (sorry, no bibliographically correct reference is at hand here) it is illegal for video stores to disclose rental records anyway. [Knowledgeable videomaniacs are welcome to fill in detailed references and whether it is illegal to collect such records, or just to misuse them. I seem to remember also that video stores cannot market their customer lists (as mailing lists). Before I spread anymore rumors, anybody knows the details? (It's probably no use asking somebody in a video store, they would be the last ones to know :-) a problem of our current legal system...] In any event, the case of concern when trying to build protocols and hardware for anonymous video rental is when the store personel is dishonnest. There is little point in trying to postpone this consideration. Pierre Uszynski pierre@shell.portal.com