Trouble reading AES enciphered data (DESFire EV1)

[Sander Kalsbeek]

I'm having trouble reading enciphered data in an AES authenticated session. I'm able to select an application, succesfully authenticate and obtain my session key. However, reading data has ben unsuccesful so far.
Using my implementation (an Android app written in Delphi) I'm able to reproduce the results of the example in table 24 of AN094534. However the first 16 bytes of the result in step 9 are garbage when I try to read from a real card, meaning the IV is wrong. Since I don't perform a write action first like in the example, I replaced step 4 of table 24 with step 9 of table 23.
What am I doing wrong here?

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[TapLinx Support]

Hi Sander,

The AN0945 is NDA classified material. Therefore, I cannot talk in detail about the content on a public forum. You can write to me directly at taplinx@nxp.com.

Both examples work properly. You cannot change the order of the calculation steps. The IV is updated and used for the next CMAC or cryptographic operation. If you make a mistake, all following operations will also fail.

The TapLinx team

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[Sander Kalsbeek]

Hi,

I sent and e-mail last wednesday. Can I expect a response this week?

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[TapLinx Support]

Hi Sander,

Sorry, we had public holidays. We will answer as soon as possible.

The TapLinx team

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[Sander Kalsbeek]

Thanks! :)

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