NFC RFID product tag reading in mobile app

Implementing NFC/RFID Product Tag Reading in Mobile Applications

NFC in phone — HF RFID at 13.56 MHz. Reads same chips as stationary HF readers: MIFARE Classic/Ultralight, NTAG213/215/216, ICODE SLI, ISO 15693. For reading product tags in retail, authenticity verification, or warehouse operations — built-in NFC works without external equipment. Range — 1–5 centimeters. Not UHF, not mass reading. But works on any modern smartphone.

iOS: CoreNFC

import CoreNFC

class ProductTagReader: NSObject, NFCNDEFReaderSessionDelegate {
    private var session: NFCNDEFReaderSession?
    var onProductFound: ((ProductInfo) -> Void)?

    func startReading() {
        guard NFCNDEFReaderSession.readingAvailable else {
            showError("NFC not available on this device")
            return
        }
        session = NFCNDEFReaderSession(delegate: self, queue: nil, invalidateAfterFirstRead: false)
        session?.alertMessage = "Apply phone to product tag"
        session?.begin()
    }

    func readerSession(_ session: NFCNDEFReaderSession, didDetectNDEFs messages: [NFCNDEFMessage]) {
        for message in messages {
            for record in message.records {
                guard record.typeNameFormat == .nfcWellKnown,
                      let type = String(data: record.type, encoding: .utf8),
                      type == "U" else { continue }

                // URL record in NDEF — standard for product tags
                if let urlString = parseNDEFUrl(record.payload),
                   let url = URL(string: urlString) {
                    fetchProductInfo(from: url)
                }
            }
        }
    }

    func readerSession(_ session: NFCNDEFReaderSession, didInvalidateWithError error: Error) {
        if let nfcError = error as? NFCReaderError,
           nfcError.code != .readerSessionInvalidationErrorFirstNDEFTagRead,
           nfcError.code != .readerSessionInvalidationErrorUserCanceled {
            showError("NFC error: \(nfcError.localizedDescription)")
        }
    }
}

invalidateAfterFirstRead: false — session doesn't close after first read. Useful for sequential checking multiple products without restarting session.

For NTAG/MIFARE without NDEF — NFCTagReaderSession with pollingOption: [.iso14443]:

func tagReaderSession(_ session: NFCTagReaderSession, didDetect tags: [NFCTag]) {
    guard let tag = tags.first else { return }
    session.connect(to: tag) { [weak self] error in
        if let error = error {
            session.invalidate(errorMessage: "Error: \(error.localizedDescription)")
            return
        }
        switch tag {
        case .miFare(let mifareTag):
            let uid = mifareTag.identifier.hexString
            self?.lookupProduct(uid: uid)
        case .iso15693(let isoTag):
            // ICODE SLI for box tags in logistics
            let uid = isoTag.identifier.hexString
            self?.lookupProduct(uid: uid)
        default:
            session.invalidate(errorMessage: "Unsupported tag type")
        }
    }
}

Android: NFC Foreground Dispatch

class ProductScanActivity : AppCompatActivity() {
    private lateinit var nfcAdapter: NfcAdapter
    private lateinit var pendingIntent: PendingIntent
    private lateinit var filters: Array<IntentFilter>

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        nfcAdapter = NfcAdapter.getDefaultAdapter(this)
            ?: run { showNoNfcMessage(); return }

        pendingIntent = PendingIntent.getActivity(
            this, 0,
            Intent(this, javaClass).addFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP),
            PendingIntent.FLAG_MUTABLE
        )
        filters = arrayOf(IntentFilter(NfcAdapter.ACTION_NDEF_DISCOVERED).apply {
            addDataType("*/*")
        })
    }

    override fun onResume() {
        super.onResume()
        nfcAdapter.enableForegroundDispatch(this, pendingIntent, filters, null)
    }

    override fun onPause() {
        super.onPause()
        nfcAdapter.disableForegroundDispatch(this)
    }

    override fun onNewIntent(intent: Intent) {
        super.onNewIntent(intent)
        when (intent.action) {
            NfcAdapter.ACTION_NDEF_DISCOVERED -> handleNdefTag(intent)
            NfcAdapter.ACTION_TAG_DISCOVERED -> handleRawTag(intent)
        }
    }

    private fun handleNdefTag(intent: Intent) {
        val messages = intent.getParcelableArrayExtra(NfcAdapter.EXTRA_NDEF_MESSAGES)
            ?.filterIsInstance<NdefMessage>() ?: return

        messages.flatMap { it.records.toList() }
            .filter { it.tnf == NdefRecord.TNF_WELL_KNOWN && it.type.contentEquals(NdefRecord.RTD_URI) }
            .forEach { record ->
                val url = parseNdefUri(record.payload)
                viewModel.loadProduct(url)
            }
    }
}

Foreground dispatch intercepts NFC tags while app active. Without it, Android shows system app selection dialog.

Tag Formats and What to Store

For authenticity verification: tag stores signed token, app verifies signature with public key offline:

// ECDSA signature verification from tag
func verifyAuthTag(_ signedPayload: Data) -> Bool {
    let publicKey = getEmbeddedPublicKey() // embedded in bundle
    return SecKeyVerifySignature(
        publicKey,
        .ecdsaSignatureMessageX962SHA256,
        productId as CFData,
        signature as CFData,
        nil
    )
}

Timeline

NDEF-URL reading and product info loading: 2–3 days. Custom tag formats with signature verification and offline database: 1–2 weeks.