unusable keys in ntag 424 dna

[zahra2023]

Hi,

I am developing an app for R/W on Ntag424 DNA and I don’t use any hardware (as NFC Reader) so I myself config the NFC and run commands . The problem is that I am facing issues with the keys becoming unusable after a while of working on tags and returning null. According to section 7.4, Failed Authentications Counter, in the AN12196 PDF, it would be possible that the problem is :

"TotFailCtr (2 bytes)
– Increases by 1 on each unsuccessful authentication
– Decreases by value defined with TotFailCtrDecr
– when TotFailCtrLimit is reached, related key cannot be used for Authentication anymore"

BR.

[KellyLi]

Hello @zahra2023 

For your issue, below is the part of the log for your reference, which could be helpful to you.

BR

kelly

[zahra2023]

Thanks for your reply @KellyLi , but I want to know the reason of my problem (why the keys become unusable after a while). Now I can run authentication and other commands except the one I posted here: https://community.nxp.com/t5/NFC/SetConfiguration-Command-return-error/td-p/1743977

I would really appreciate if you could help me.

BR.

[KellyLi]

Hello @zahra2023 

Since you are not designing based on one hardware, where are your keys stored? In general, the key used for authentication is stored at the end of the card reader。 So is this what's causing your KEY to be unstable?

BR

kelly