> Never seen a fob or smartcard that has memory which is written with every individual transaction. Actually every SIM card does this. At least when used by a

> Never seen a fob or smartcard that has memory which is written with every individual transaction. Actually every SIM card does this. At least when used by a phone to join a mobile network, a SIM writes some timestamp or counter to persistent internal memory. This caused a funny case of SIM cards with very limited lifetime for a German provider (I think it was Congstar), who had a problem in its network that caused frequent authentications of handsets, thereby having them chew through the write cycles of their SIM cards way faster than projected for normal use. The cards became "dead" afterwards. If I remember correctly, all chip enabled payment cards also have a transaction counter that is updated on every successful transaction.