Reply To: Desfire Ev1 diverse questions

Forum MIFARE and NFC Reader IC`s Desfire Ev1 diverse questions Reply To: Desfire Ev1 diverse questions

Re: Desfire Ev1 diverse questions

17. August 2018 at 17:51
France's sales rep. are still on vacation, so i am continuing to try and dig my way through this. (till we setup that NDA)

As funny as it may seem, i was able to get like 90% of it working.

I can authenticate.
I can create an AID, and create a file in that AID.
I can change access settings to make it readable only after authentication.

So far, so good!

No the very last bit i am trying to achieve is to encypher the data transfer. For instance, if i am trying to read "Hello World" from the DesFire card, i don't want this string to be "sniffable", if you see what i mean.

So, In the libFreeFare (from which i am inspired) I fond a option to change communication mode from "PLAIN" (0x00) to "ENCIPHERED" (0x03). I did that, and indeed, now I can't read back the correct data, even with correct key.

The problem i get is that I can't get a correct CRC from deciphered data.

My question is more of a programming one: How can start searching for where the problem is? What is the best methodology to try to understand which part is broken?

I've double checked my CRC algorithm, and it's the same i can find in various project on the web, so i don't suspect it's the problem.

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