SLAU723A October 2017 – October 2018 MSP432E401Y , MSP432E411Y
Figure 9-11 shows one round of a CCM (counter with CBC-MAC) operation for encryption and decryption. A 32-bit counter is used as IV (as it is for CTR mode). The data is encrypted in the same way as in CTR mode, by XORing the cryptographic core output with the input. Immediately after the encryption operation, the plaintext is XORed with the intermediate authentication result. The XOR result is used as input for a second encryption operation to calculate the next (intermediate) authentication result.