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AES Functional Description
625
SWRU543–January 2019
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Advance Encryption Standard Accelerator (AES)
CCM Operation
Figure 17-11 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.
Figure 17-11. AES - CCM Operation
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