Figure 200. Aes-Ecb Mode Encryption - ST STM32F207 Series Reference Manual

Cryptographic processor (CRYP)
ECB decryption, AES-CBC encryption and AES-CBC decryption.This reference manual
only gives a brief explanation of each mode.
AES Electronic codebook (AES-ECB) mode
• AES-ECB mode encryption
Figure 200
In AES-ECB encryption, a 128- bit plaintext data block (P) is used after bit/byte/half-
word swapping (refer to
The input block is processed through the AEA in the encrypt state using the 128, 192 or
256-bit key. The resultant 128-bit output block (O) is used after bit/byte/half-word
swapping as ciphertext (C). It is then pushed into the OUT FIFO.
•
AES-ECB mode decryption
Figure 201
To perform an AES decryption in the ECB mode, the secret key has to be prepared (it is
necessary to execute the complete key schedule for encryption) by collecting the last
round key, and using it as the first round key for the decryption of the ciphertext. This
preparation function is computed by the AES core. Refer to
to perform an encryption or a decryption
In AES-ECB decryption, a 128-bit ciphertext block (C) is used after bit/byte/half-word
swapping as the input block (I). The keying sequence is reversed compared to that of
the encryption process. The resultant 128-bit output block (O), after bit/byte or half-
word swapping, produces the plaintext (P).
1. K: key; C: cipher text; I: input block; O: output block; P: plain text.
2. If Key size = 128: Key = [K3 K2].
If Key size = 192: Key = [K3 K2 K1]
If Key size = 256: Key = [K3 K2 K1 K0].
516/1381
illustrates the AES Electronic codebook (AES-ECB) mode encryption.
Section 19.3.3: Data type on page
illustrates the AES Electronic codebook (AES-ECB) mode encryption.

Figure 200. AES-ECB mode encryption

DATATYPE
128/192
or 256
K 0...3 (1)
DATATYPE
RM0033 Rev 9
522) as the input block (I).
Section 19.3.6: Procedure
for more details on how to prepare the key.
IN FIFO
plaintext P
P, 128 bits
swapping
I, 128 bits
AEA, encrypt
swapping
C, 128 bits
OUT FIFO
ciphertext C
RM0033
ai16071b