ST STM32WL55JC Reference Manual page 659

RM0453
23.4.7 AES task suspend and resume
A message can be suspended if another message with a higher priority must be processed.
When this highest priority message is sent, the suspended message can resume in both
encryption or decryption mode.
Suspend/resume operations do not break the chaining operation and the message
processing can resume as soon as AES is enabled again to receive the next data block.
Figure 108
order to send a shorter and higher-priority Message 2.
New higher-priority
message 2 to be
processed
A detailed description of suspend/resume operations is in the sections dedicated to each
AES mode.
23.4.8 AES basic chaining modes (ECB, CBC)
Overview
This section gives a brief explanation of the four basic operation modes provided by the
AES core: ECB encryption, ECB decryption, CBC encryption and CBC decryption. For
detailed information, refer to the FIPS publication 197 from November 26, 2001.
gives an example of suspend/resume operation: Message 1 is suspended in
Figure 108. Example of suspend mode management
Message 1
128-bit block 1
128-bit block 2
128-bit block 3
128-bit block 4
128-bit block 5
128-bit block 6
...
RM0453 Rev 2
AES hardware accelerator (AES)
AES suspend
sequence
AES resume
sequence
Message 2
128-bit block 1
128-bit block 2
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