 Typically, to minimize costs, systems integrators will choose a relatively cheap card such as a MIFARE Classic and concentrate security efforts in the back office.Additional encryption on the card, transaction counters, and other methods known in cryptography are then employed to make cloned cards useless, or at least to enable the back office to detect a fraudulent card, and put it on a blacklist.Systems that work with online readers only (i.e., readers with a permanent link to the back office) are easier to protect than systems that have offline readers as well, for which real-time checks are not possible and blacklists cannot be updated as frequently.