Forum › MIFARE general topics and applications › Mifare DESFIRE EV1 CMAC Calculation › Reply To: Mifare DESFIRE EV1 CMAC Calculation
Hi Barış,
I have no bandwidth to debug user code, sorry.
The AN094534 is extremely helpful if you implement the cipher functions. In CMAC function the AES is used two times. First, in sub function generate_subkey(), the IV is always zero (take in mind to explicitly reset the IV). But in the main function you must consider the IV. The intermediate results can span more than one block, therefore you must XOR the blocks with the previous block if you use ECB mode. In CBC mode the AES function manage the IV usually. This depend on your base AES functions.
The TapLinx team
I have no bandwidth to debug user code, sorry.
The AN094534 is extremely helpful if you implement the cipher functions. In CMAC function the AES is used two times. First, in sub function generate_subkey(), the IV is always zero (take in mind to explicitly reset the IV). But in the main function you must consider the IV. The intermediate results can span more than one block, therefore you must XOR the blocks with the previous block if you use ECB mode. In CBC mode the AES function manage the IV usually. This depend on your base AES functions.
The TapLinx team
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