I don't disagree with your posting in general. I will note one thing: "Steven M. Bellovin" <[EMAIL PROTECTED]> writes: > A transit system has to move people. For all that the New York City > Metrocard works, it's slower than a contactless wireless system.
As a consultant, I happen to have a lot of ID badges. I've used contactless systems for entry at several firms on a regular basis. I've experienced the equivalent of "re-swipe" problems even with the contactless systems -- that is, I've been forced to wave the card past the reader more than once. I'm told that similar issues can be found in other RFID systems. Although I will not disagree that the only important criterion for a transit system is "will we maximize overall economic efficiency with this design choice", I'm still far from certain that contactless is always going to be faster. It could in theory be faster -- whether that theory can be reduced to practice is a different question. (As an aside, I'll also point out that, in the NYC transit system, it is fairly rare that the "rate limiting step" is the speed of turnstile reads. Far more often, limited space on stairwells, limited numbers of turnstiles (which are used both for entry and exit), etc., seem to be the limiting factor on how fast people can flow onto and off of the platforms.) I want repeat that I don't disagree with you that all of this is about economics first, and the security level and costs have to take that into consideration. We are in violent agreement there. A $100 but "perfect" entry token is going to be worthless for most transit systems, and an attack that costs a system a few dollars a year at most is unlikely to be worth closing. (Indeed, the Metrocard system isn't perfect, in that you can clone cards -- you just can't steal more than a trivial sum before the card will be turned off, so no one bothers.) My main point here was, in fact, quite related to yours, and one that we make over and over again -- innovation in such systems for its own sake is also not economically efficient or engineering smart. If an existing system works reasonably well and you can use it off the shelf without paying development and other costs, why not use it? I find the fact that nearly every city in the world seems to have a custom designed electronic fare system somewhat peculiar -- I'm not surprised that several such systems might exist, but surely every city in the world does not need to sink the costs of custom development of an entire fare system. The Dutch apparently sunk vast sums into the development of a brand new fare card system -- one questions what requirements could not have been met with one of the several hundred existing systems. -- Perry E. Metzger [EMAIL PROTECTED] --------------------------------------------------------------------- The Cryptography Mailing List Unsubscribe by sending "unsubscribe cryptography" to [EMAIL PROTECTED]