Figure 102. Ecb Encryption And Decryption Principle - STMicroelectronics STM32WL5 Series Reference Manual

AES hardware accelerator (AES)
Note: The chaining mode may be changed only when AES is disabled (bit EN of the AES_CR
register cleared).
Principle of each AES chaining mode is provided in the following subsections.
Detailed information is in dedicated sections, starting from
chaining modes (ECB,
Electronic codebook (ECB) mode
Legend
ECB is the simplest mode of operation. There are no chaining operations, and no special
initialization stage. The message is divided into blocks and each block is encrypted or
decrypted separately.
Note: For decryption, a special key scheduling is required before processing the first block.
650/1450
CBC).

Figure 102. ECB encryption and decryption principle

Plaintext block 1
key
Encrypt
Ciphertext block 1
Plaintext block 1
key
input
output
key
scheduling
Ciphertext block 1
Encryption
Plaintext block 2
key
Encrypt
Ciphertext block 2
Decryption
Plaintext block 2
key
Decrypt Decrypt
Ciphertext block 2
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Section 23.4.8: AES basic
Plaintext block 3
key
Encrypt
Ciphertext block 3
Plaintext block 3
key
Decrypt
Ciphertext block 3
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