Dynamic url ntag 424 dna

[Daniel1515151]

Hi 

can someone explain how can I make a url on ntag 424 DNA in nxp ntagxplorer?

I need a url something like this:

https://domain.com?uid=XXX&cmac= XXX

where uid is random every card read and cmac is the encoded uid,

I need this later check on my backend to check the cmac (encoding uid with private key)

Please help I can pay 

[Daniel1515151]

And how can i prevent when someone scan the card 100 times in 1 second? I want max 1 scan for 1 second is this possible to secure?

[Daniel_Gutierrez]

Hello @Daniel1515151, Good Day!

Thank you very much for your interest in our products.

The type of message you refer is a URL that includes mirrored data form the NTAG's memory attached as ASCII encoded text at the end of the URL.  Some of these mirrored values can be the card's UID, an NFC counter (taps) and the CMAC, which is a Message Authentication Code unique for each time communication between the card and an NFC device takes place.

The card's UID is a Unique Identifier that is programmed and locked during production, and it can be encrypted along with the counter, and attached to the URL once it is encrypted. Please refer to section 3.4.2.1 and 3.4.2.2 of the NTAG 424 DNA Application Note to learn about the encryption process, and how you may handle decryption using a backend server that knows the keys that were used.

You may also find a guide to enable Mirroring features for NTAG424 using NFC TagWriter App by NXP in section 4 of the TagWriter User Manual.

My best regards,
Daniel.

[Daniel1515151]

Thanks!
But yet i have another question.


How can I in nxp tag xplorer secure the tag so that:

1. Any user can change URL using NDEF (public access)
2. Only admin (using key) can change the offsets configuration in URL

3. No one can retrieve the private key or change the card configuration. 

In short i want allow users to change the URL by using NDEF, but any other configuration staff is possible only with authenticating.

PS
Can you explain what this options in screenshot below do? Why I have options to select 00,01,02,03,04,0E,0F what is this?

[Daniel_Gutierrez]

Hello @Daniel1515151, Good Day!

Unfortunately, TagXplorer PC is no longer supported, and its content is made available for historical reference only. Please consider using our recommended software such as  RFIDDiscover and NFC TagWriter App by NXP.

However, you may refer to section 4.16.1 of the TagXplorer Quick start-up guide, as you may find useful information on how to enable the mirroring features previously mentioned.

The values you refer correspond to the possible values for the SMD Keys, which, in order to enable mirroring features, should be other than 0F as mentioned in section 4 of the TagWriter User Manual.

The activation and deactivation sequence and timings are defined by the ISO/ IEC14443-4 and the ISO/IEC 7816-4 protocols please refer to section 8.1.1 the NTAG 424 DNA Data Sheet for further details.

My best regards,
Daniel.

[Daniel1515151]

Thanks!

I have this done, but I still need to limit the reading frequency.

For example, a single user can scan the NFC tag 20 times per second, and I want to prevent this. Can I set a limit to allow a maximum of 1 scan per second?

I need that the tag data for reading is public

[Daniel_Gutierrez]

Hello @Daniel1515151, Good Day!

Please consider checking out the specification of the timing parameters defined by the ISO/ IEC14443-4 and the ISO/IEC 7816-4 protocols (section 8.1.1 NTAG 424 DNA  Data Sheet). However, you could take a look at section 9.3.1 of the same document to find out about the Read Counter Mirroring feature of the tag, since this a value that stores the times the tag has been read, and you can set a limit to it in order to limit the number of reads that can be done with a single device. Please take a look at section 9.3.2 for further details.

My best regards,
Daniel.

[Daniel1515151]

Fine, but is this possible to make this on andorisd app? In tag writer?
I want to only limit reads per secons to 1/sec.

[Daniel_Gutierrez]

Hello @Daniel1515151, Good Day!

The Read Counter Limit feature for NTAG424 DNA is available for setting in the NFC TagWriter App by NXP, you can find the steps to do so in section 4.4 of the TagWriter User Manual.

My best regards,
Daniel.