Understanding and Using UNTRACEABLE Mode in ST25TV Tags

[itanuj_KI]

Hello ST Community,

I've been exploring STEVAL-25R200A dev kit using the X-CUBE-NFC10 package-based sample application. Currently, I am testing the UNTRACEABLE mode feature in the ST25TV tag. However, I’m noticing some unexpected behavior and would love to get help and support.

In my case UNTR_CMD = 1b and as per the Table 70 of the specifications, the device (ST25TV tag) should boot in UNTRACEABLE state irrespective of any UNTR_DFT value, and in this state, it should only respond to Get Random Number and Present Password commands. However, in my testing, I’ve found that when UNTR_CMD = 1b and UNTR_DFT = 0, the tag responds to every command which it should not.

This makes me wonder if I’ve understood the UNTRACEABLE mode correctly or not.

Regards,
Tanuj

[Brian TIDAL · Accepted solution]

Hi Tanuj,

make sure to check the Response_flags of the ToggleUntraceable response. It is likely that Error_flag equals 1 due to  something wrong in the ToggleUntraceable request. Make sure to follow section 5.1.3 Password encryption when building the unique valid Password_data value in the ToggleUntraceable command.

Note: the untraceable mode can be exercised with the ST25PC-NFC. Start the ST25R200 Eval Gui and click on the ST25PC-NFC icon:

Once running the ST25PC-NFC, go to the Untraceable mode menu.

Then, you can toggle the untraceable mode and check its behavior.

Rgds

BT