I'm not sure about the speed argument. My city uses stored-value cards based on Mifare Classic and Mifare Plus (depending on the type of the ticket). If you liv

I'm not sure about the speed argument. My city uses stored-value cards based on Mifare Classic and Mifare Plus (depending on the type of the ticket). If you live here and use the public transit with any regularity, you don't stop when you're going through the turnstile. The card validation isn't instant by any means, but it takes just enough time that you can plop your card on the reader as soon as you can reach it and keep walking, and it'll be done by the time you need to rotate the thingy that's in your way. On most stations, the bottleneck isn't the turnstiles, it's the escalators. On the security side, yeah, someone did exploit those Mifare key extraction vulnerabilities and make an app to clone cards and restore dumps. The system collates all data every night so if you mess with your ticket, it'll get banned. So you're getting one day of free rides at most, and forfeit the remaining balance and the cost of the card itself.