ST STM32F207 series - Figure 202. AES-CBC Mode Encryption

Cryptographic processor (CRYP) RM0033
518/1381 RM0033 Rev 9
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 202. 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].
IN FIFO
AEA, encrypt
P, 1 2 8 b i t s
OUT FIFO
O, 128 bits
plaintext P
ciphertext C
swapping
+
IV=[IV1 IV0]
(2)
128
I, 128 bits
AHB2 data write
(before CRYP
is enabled)
O is written
back into IV
at the same time
as it is pushed
into the OUT FIFO
swapping
C, 128 bits
DATATYPE
DATATYPE
K 0...3
(3)
128, 192
or 256
Ps, 128 bits
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