NFCのトピックNtag424DNA tag issue

Ntag424DNA tag issue

long19890829 — Wed, 27 Nov 2019 14:18:01 GMT

Hi,

I'm learning the Ntag424DNA, and I get a problem as below:

1.when I try to decrypt the SDMENCFileData (page 13th of the flie AN12196) refer to the Table4 step by step, and I can get the same data with the Table4 from the step 1 to step 15, but the last step(16), I get the different data "9254fb0561f7a8d030ee6e83487e2487" which is not same with the application note. In my understanding, the step 16 is a standard AES128 CBC arithmetic, the key is SDMMetaReadKey ="00000000000000000000000000000000", the iv is IVe="7B3F3CFC39D3B7FF5868636E38AF7C3A", and the encrypted msg is SDMENCFileData = "94592FDE69FA06E8E3B6CA686A22842B". Therefore, the decrypted msg should be "9254fb0561f7a8d030ee6e83487e2487" rather than "78787878787878787878787878787878". Could you help me to confirm any mistake in my understanding and calculation.

2.Leakage Resilient Primitive (LRP). We don't kown how to achieve the LRP arithmetic even your application note AN12304 is very in detail, could you give me the demo code (source code) to achieve the LRP for our reference since we are not good at the arithmetic. Thank you very much!

Have a great day !

Long Zhu

Re: Ntag424DNA tag issue

Jonathan_Iglesias — Tue, 03 Dec 2019 20:41:41 GMT

Hi long zhu,

Hope you are doing great,

please check the following, I believe there is an error on the names,

please use:

data = 94592FDE69FA06E8E3B6CA686A22842B

key= 8097D73344D53F963B09E23E03B62336

IV = 7B3F3CFC39D3B7FF5868636E38AF7C3A

for examples about LRP, you can check our NFCreaderlibrary the latest version have added the DESFire light and NTAG42xdna please go to:

NxpRdLib > comps > phalMfNtag42XDna > src> Sw > phalMfNtag42XDna_Sw.c there you can find the APIs that detect when the authentication method is LRP.

Jonathan

Re: Ntag424DNA tag issue

long19890829 — Tue, 10 Dec 2019 13:12:29 GMT

Hi Jonathan，

Thanks for your reply! I still confused about the step 14 and 15 of Table18 in Section 6.9 Change NDEF File Settings of AN12196. I don't know how to get the data Cmd.SetConfiguration C-APDU=905F000019022F81A62EB50A5DD4B8A003BDD10F712A0E62908FC6BAE05300 from the step 14, could you show me the calculation process in detail. Thank you very much!

Long Zhu

Re: Ntag424DNA tag issue

long19890829 — Tue, 10 Dec 2019 13:17:17 GMT

Hi Jonathan，

Long Zhu

Re: Ntag424DNA tag issue

Jonathan_Iglesias — Tue, 10 Dec 2019 16:17:55 GMT

Hi long zhu,

this is explained in the datasheet section 10.7.1 ChangeFileSettings,

Jonathan

Re: Ntag424DNA tag issue

long19890829 — Tue, 10 Dec 2019 17:01:06 GMT

Hi Jonathan，

I know the format of APDU command, and the Data =022F81A62EB50A5DD4B8A003BDD10F712A0E62908FC6BAE053 is composed of 3 parts:

cmdHeader = 02 (FileNo),

encrypted cmdData = 2F81A62EB50A5DD4B8A003BDD10F712A,

cMac = 0E62908FC6BAE053.

My confusion is that how can I work out the encrypted cmdData and CMac refer to the Table 18 of AN12196, I need know the detail calculation procedure from step 14 to step 15. Thanks!

Long Zhu