Disable desfire random uid

Hello. My FlexDF is set to random uid. Can i disable the extra layer of security?

This application note explains the UID structure. I’m not sure which byte you need to change to disable RID (UID0 = 0x08?). Check out page 5. You may need a more powerful tool like NFC Shell to achieve something like this.

Also, how did this happen? I have a flexDF and it didn’t ship like that. I’m under the impression that RIDs are only available as 4 bytes, so if yours is 7 bytes it might not be the card configuration, it might be the reader application.

I’m pretty busy today, but I’ll check back in tomorrow.

Libnfc have a tool to enable it

But not disable it?

No i cant find how to disable random uid if possible


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I looked at all the datasheets I could get my hands on, and while they mention the RID functionality, they don’t explain how to configure it at all. This libfreefare GitHub lists that once you configure RID it can’t be undone =/ I’m not sure about that though. I’ll keep looking into it.

When you scan your flexDF with Taginfo, does it give you a changing UID that is only 4 bytes long, and the first byte is always 80?


Hmm yes it is