Figure 209. Aes-Cbc Mode Encryption - ST STM32F40 Series Reference Manual

Cryptographic processor (CRYP)
block of data.) The AES-CBC decryption process continues in this manner until the last
complete ciphertext block has been decrypted. Ciphertext representing a partial data
block must be decrypted in a manner specified for the application.

Figure 209. AES-CBC mode encryption

1. K: key; C: cipher text; I: input block; O: output block; Ps: plain text before swapping (when decoding) or
after swapping (when encoding); P: plain text; IV: Initialization vectors.
2. IVx=[IVxR IVxL], R=right, L=left.
3. If Key size = 128 => Key = [K3 K2].
If Key size = 192 => Key = [K3 K2 K1]
If Key size = 256 => Key = [K3 K2 K1 K0].
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DATATYPE
AHB2 data write
(before CRYP
is enabled)
(2)
IV=[IV1 IV0]
128, 192
or 256
(3)
K 0...3
O is written
back into IV
at the same time
as it is pushed
into the OUT FIFO
DATATYPE
Doc ID 018909 Rev 4
IN FIFO
plaintext P
P, 128 bits
swapping
Ps, 128 bits
128
+
I, 128 bits
AEA, encrypt
O, 128 bits
swapping
C, 128 bits
OUT FIFO
ciphertext C
RM0090
ai16072b