Banks want to use their genuine strong credential for online banking transaction authorization - the debit card. Customers nowadays are usually equipped with a Smartphone and prefer to not carry a card reader in addition. Methods where developed that use the Smartphone to authorize online banking transactions. These methods are vulnerable to Smartphone malware. We present NFC-TAN as a Smartphone method that combines the two requirements: Strong credential debit card and no additional device. We discuss to what extend this solution decreases vulnerability. Moreover, we consider usability, cost, and integration aspects of NFC-TAN.