Datasheet

Figure 13-9. AES - CBC-MAC Authentication Mode
Input buffer
(plain text)
AES core
(encrypt)
Authentication
result (TAG)
Key register
128
128
256
data_in
data_out
Key in
IV register
128
128
Temporary buffer
128
128
GCM Operation
Figure 13-10 on page 974 shows one round of a GCM 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. After the encryption/decryption,
the ciphertext is XORed with the intermediate authentication result. The XORed result is used as
input for the polynomial multiplication to create the next (intermediate) authentication result. For
more information about the GCM protocol, see the section called “GCM Protocol
Operation” on page 975.
973June 18, 2014
Texas Instruments-Production Data
Tiva
™
TM4C129ENCPDT Microcontroller