Trying to learn

Amal, you hooked me up with a spiffy NFC/RFID chip at last year’s DECON for a fair price. I haven’t had much chance to play with it until recently (pleanty of healing time for sure :smiley: ). All I have is an android phone to use to tinker with the chip. In the course of tinkering, I write protected it with a password, which I still remember. Now I’m not sure how to remove the password so I can put some data on the chip, or how to provide the password to add data.

I should also mention, I have since used the Dangerous Things support tool to write a blank NDEF to the tag at your suggestion because I had an issue getting error “Store failed. NFC data set is too large!”. I created an account earlier in the year, but it seems the forum no longer recognizes my email address with a + character in it.

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Hey there :slight_smile:

So the password cannot be removed, it can only be set to factory default FF FF FF FF. As you should know, the password is held in memory page E5, so if you set the AUTH0 byte to anything less than E5 then you will have to authenticate first before you can write a new password to page E5.

If you accidentally set any of the lock bytes to lock the user memory or config memory (like the password block, or you accidentally set the CFGLCK bit to 1, then you are screwed. This is why we suggest using the Dangerous NFC app to put the tag into a protected state that disables lock bytes and protects the config pages with a password, but leaves the user writable area open to writing. It’s the perfect middle-of-the-road balance between safety and usability.

Thanks for replying. Though, I am not sure what to do from here based on your response. Are you saying I am screwed?

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When you say you “tinkered around”, I was under the impression you were sending APDU commands to it - i.e. you had a working understanding of memory pages in the xNT and how to “tinker” with them. If you are saying you set the password using our Dangerous NFC app, then you should be ok to write data to your tag still since it does not password protect anything but the config bytes… the user writable memory pages are still wide open. If you’d like to set the password back to factory, then that’s going to require some work with a USB reader or our PN532 reader and some code. We had planned on putting that feature into Dangerous NFC but developer after developer has dropped the project… at the moment we’re still looking for someone who can pick it up and finish it.