Key register
Ouput buffer
(cipher or plain text)
AES core
(encrypt)
128
128
Key in
256
Encryption or Decryption
Temporary register
128
Input buffer
(plain or cipher text)
64
data_out
0
128
AES data out buffer
Counter
+
1
63
Zeroes
IV register
0
63
64
64
128
data_in
AES Functional Description
666
SLAU723A – October 2017 – Revised October 2018
Copyright © 2017–2018, Texas Instruments Incorporated
Advance Encryption Standard Accelerator (AES)
9.2.3.1.5 F8 Mode
shows the F8 feedback mode of operation for encryption and decryption. The input to the
cryptographic core is the result of the XOR operation of the previous cryptographic core output, a constant
IV, and a block counter. The output of the cryptographic core is XORed with the input to create the result.
In this mode, encryption and decryption use the same operations.
Figure 9-6. AES – F8 Mode
9.2.3.1.6 XTS Operation
shows the XTS mode of operation for encryption and decryption. The input to the cryptographic
core is XORed with the IV; the output of the cryptographic core is XORed with the same IV. For
decryption, the cryptographic core operates in reverse, but the XOR operations are the same.