title: Access protection for NFC Tags
body: <p>I am extremely new to NFC as a technology and have a very basic question. I am investigating the use of NFC tags in the field of authentication. At a broader level imagine a PKI architecture. A private key resides on the NFC tag, and an app can access it for authentication/signing/validation etc.</p>
  
  <p>I understand that smart cards are the de-facto standards for such things, but the cost of NFC tags is far far less. My question is what level of protection is offered by NFC tags for such a scenario or is NFC tag a good choice for such a design?</p>
  
  <p>Can I somehow ensure that a tag is readable by only a certain device? As in, can another user just use his phone/NFC reader to read the key on the tag? What methods are available to protect/restrict access to the data residing on the NFC tag?</p>