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NTAG215 AUTHLIM BRUTE FORCE LIMIT

I need to protect my NTAG215 from bad password after ten incorrect attempts.

First protected page 04 to 81:

RAW COMMAND: A2 83 04 00 00 04

After to enable brute force protection:

RAW COMMAND: A2 84 82 00 00 00

enter image description here enter image description here

HEX 82 = BIN 10000010

  • PROT = 1
  • CFGLCK = 0
  • RFUI = 0
  • NFC_CNT_EN = 0
  • NFC_CNT_PWD_PROT = 0
  • AUTHLIM = 010 ( 10 attempts )

But after 3 incorrect attempts my NTAG215 seems dead.

NTAG213-216 data sheet: https://www.nxp.com/docs/en/data-sheet/NTAG213_215_216.pdf

I'm doing something incorrectly?

Thanks for help.

#SOLVED ( Thanks to @nanofarad ) enter image description here

Solution

  • authlim is a three-bit number - 010 is not ten attempts, it's binary 10 attempts (meaning 2 attempts), so presumably on the third it locks itself.

    You cannot set 10 attempts using AUTHLIM if AUTHLIM can only represent numbers from zero (binary 000) to seven (binary 111).