I have one stupid question. I have mifare classic tags (1k). I want to hide content of this card (any data stored there). How to do it? What about ndef records?
MFC (MiFare Classic) got reverse engineered completely, so storage should be considered read-write, and clear text, copiable/clonable, etc.
If you can afford encryption of the payload before putting it on the card, you may be able to make data confidential, but not "hide" it: third parties will be able to tell card is not blank, but will not be able to tell what is actually stored.
NDEF wont help you there.