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Key Register
IV Register
Input Buffer
(plain text)
Ouput Buffer
(cipher text)
AES Core
(encrypt)
128
128
128
128
Key in
data_in
data_out
128
256
Encryption
Key Register
IV Register
Input Buffer
(cipher text)
Ouput Buffer
(plain text)
AES Core
(decrypt)
128
128
128
Key in
data_in
data_out
128
256
128
Key Register
128
Decryption
Key Register
AES Core
(encrypt)
256
128
Output Buffer
(cipher text)
Key In
data_out
128
data_in
Input Buffer
(plain text)
Key Register
AES Core
(decrypt)
256
128
Output Buffer
(plain text)
Key In
data_out
128
data_in
Input Buffer
(cipher text)
Encryption
Decryption
AES Functional Description
664
SLAU723A – October 2017 – Revised October 2018
Copyright © 2017–2018, Texas Instruments Incorporated
Advance Encryption Standard Accelerator (AES)
Figure 9-2. AES – ECB Feedback Mode
9.2.3.1.2 CBC Feedback Mode
shows the CBC feedback mode of operation, where the input data is XORed with the IV before
it is passed to the basic cryptographic core. The output of the cryptographic core passes directly to the
output buffer and becomes the next IV.
The operation is reversed for decryption, resulting in an XOR at the output of the cryptographic core. The
input cipher text of the current operation is the IV for the next operation.
Figure 9-3. AES – CBC Feedback Mode
9.2.3.1.3 CTR and ICM Feedback Modes
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.