Figure 498. Ecb Encryption And Decryption Principle - ST STM32G4 Series Reference Manual

AES hardware accelerator (AES)
Chaining modes
The following chaining modes are supported by AES, selected through the CHMOD[2:0]
bitfield of the AES_CR register:
•
Electronic code book (ECB)
•
Cipher block chaining (CBC)
•
Counter (CTR)
•
Galois counter mode (GCM)
•
Galois message authentication code (GMAC)
•
Counter with CBC-MAC (CCM)
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.
1446/2083
CBC).

Figure 498. 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 33.4.8: AES basic
Plaintext block 3
key
Encrypt
Ciphertext block 3
Plaintext block 3
key
Decrypt
Ciphertext block 3
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