How NFC readers works?

Question

Hi I am android developer. I already build android NFC reader and writer and beam. So using writer i can write simple data on NFC tags and with the help of reader I can read data from tag. Using beam I can transmit data between two NFC enabled devices. So till now everything works fine. Now I want to work on NFC payments. I am working on android platform. So my question is that how NFC readers works which are use for payments. Are they work on Beam or our device act as nfc tag for NFC readers and it simply reads data from device.Mean how on device side I conform that this reader is for payments or something else. I read about HCE of android it helps a lot for understanding concept. But I am bit confuse regarding readers concepts and there working scenarios. Is there any one can help me out to understand this things, Need Help. Thank you.

Answer 1

When you talk about payments I assume you refer to payments based on well-known credit card schemes like AmEx, Discover, JCB, MasterCard, VISA, etc. Their payment protocols are standardized in EMVCo. Note that there are other (not that wide-spread) payment schemes that use different approaches.

For the contactless protcols of EMV-based payment cards, they typically follow the following scheme:

• ISO/IEC 14443 anti-collision and activation (either Type A or Type B)
• ISO/IEC 14443-4 transport protocol
• ISO/IEC 7816-4 APDUs
• Payment scheme specific command-sets (the reader side for those command sets is standardized in EMVCo's EMV Contactless Specifications for Payment Systems, seperated in 5 different kernels for different credit/debit card schemes)

(In Android's reader/writer mode NFC API terminology, "ISO/IEC 14443 anti-collision and activation (either Type A or Type B)" would be NfcA or NfcB and the combination of "ISO/IEC 14443 anti-collision and activation (either Type A or Type B)" and "ISO/IEC 14443-4 transport protocol" would be IsoDep.)

So the payment terminal (e.g. POS) implements the reader side for the above protocol stack. The user-side payment device (e.g. plastic credit card, mobile phone with virtual credit card) implements the card-side of these protocols.

So to your questions:

• Beam (or NFC's peer-to-peer mode) is not involved in these payment card schemes.

• NFC's reader/writer mode (as implemented on Android devices) is mostly capable of implementing the payment terminal side of these schemes.

• I don't like the term "act as NFC tags" in that context. NFC tags (as defined by the NFC Forum) are pure data containers with read (and optional write) access, where NDEF messages can be stored on. Payment cards, however, are (contactless) smartcards with processing capabilities (i.e. they execute program code), secure data storage and cryptographic capabilities. Besides freely readable static data, they typically also contain program logic that processes requests from the reader side and they also contain secret keys (that can never be read from the card by conventional means) used for signature generation over payment transactions, etc.

• Android's HCE facility permits developers to implement the above protocol stack on an Android device. So with HCE and Android device can be put in a mode where it acts as a contactless smartcard and interprets ISO/IEC 7816-4 smartcard commands (APDUs).