SLAU723A October 2017 – October 2018 MSP432E401Y , MSP432E411Y
Figure 9-4 shows the counter feedback (CTR/ICM) mode of operation. This operation encrypts the IV. The output of the cryptographic core (encrypted IV) is XORed with the data, therefore creating the output result.
The IV is built out of two components: a fixed part and a counter part. The counter part is incremented with each block. The counter width is selectable per context and can be 16, 32, 64, 96, or 128 bits wide. In this mode, encryption and decryption use the same operation.
NOTE
The value for n can be 1, 2, 3, or 4 for CTR mode and is ½ for ICM mode.