The operation of the protocol of mutual recognition is very complex. Put simply, it works like this:
the reader generates the magnetic field and the card is fed;
2) The card responds with a binary code always the same for all the cards that signals "is a card within the reader." If there are two cards simultaneously, the system is designed to generate a collision voluntary and stop the transaction;
3) The reader sends a recognition code, this code is usually written on a card (SAM type cards for mobile phones) inside the POS: the latter, in the case of opening, they have a system that automatically deletes the card in response to any attempt to clone it. The codes are usually written by the manufacturer;
4) the card scans the code with the mutual recognition algorithm, if the algorithm decodes the code in a positive way sends its code to the reader;
5) The reader decodes the code with the same algorithm on the card and if positive, sends the command to start the transaction;
6) the card receives the command to start the transaction and sends it, encrypting it with the algorithm of mutual recognition, the data contained therein;
7) the reader receives the data, decodes them and ends the communication off the magnetic field;
8) POS processes the information derived by the reader as if he had obtained through the classic "swiping".
As you can see, communication is very complex (much more complex than the ISO 15693 where the reader wonders who is in the field, and the tags respond with their own serial) but it is also extremely safe is practically impossible to read the electromagnetic field with a 'another player, as the latter does not disturb the first making possible communications.
As part of the worldwide deployment of contactless technology for payments not exist a single standard: at present, in Europe, Mastercard chose the communication protocol ISO 14443 type C (in the previous articles I explained the type A and type B, type C is called PayPass system): This specific type using the standard 14443 data transfer by adopting, however, as the communication protocol to mutual recognition, thus obtaining the same degree of safety Felica card but greater compatibility with RFID equipment and software currently on the market.