Table 137. Initialization Of Aes_Ivrx Registers In Ccm Mode; Figure 123. Ccm Mode Authenticated Encryption - STMicroelectronics STM32WL5 Series Reference Manual

AES hardware accelerator (AES)
CCM processing
Figure 123
example). This mode is selected by writing 100 into the CHMOD[2:0] bitfield of the AES_CR
register.
(1) Init
AES_IVRx (CTR0)
mask
AES_IVRx (First block B0)
Encrypt
AES_KEYRx (KEY)
(2) Header
AES_DINR (associated
data block B1)
Swap
management
DATATYPE[1:0]
Encrypt
AES_KEYRx (KEY)
Legend
input
output
XOR
The data input to the generation-encryption process are a valid nonce, a valid payload
string, and a valid associated data string, all properly formatted. The CBC chaining
mechanism is applied to the formatted plaintext data to generate a MAC, with a known
length. Counter mode encryption that requires a sufficiently long sequence of counter blocks
as input, is applied to the payload string and separately to the MAC. The resulting ciphertext
C is the output of the generation-encryption process on plaintext P.
AES_IVRx registers are used for processing each data block, AES automatically
incrementing the CTR counter with a bit length defined by the first block B0.
shows how the application must load the B0 data.
Note: The AES peripheral in CCM mode supports counters up to 64 bits, as specified by NIST.
AES_IVR3[31:0]
B0[127:96]
674/1450
describes the CCM implementation within the AES peripheral (encryption

Figure 123. CCM mode authenticated encryption

Counter
increment (+1)
AES_KEYRx (KEY)
AES_DINR (plaintext P1)
Swap
management
AES_DINR (associated
data last block Bu)
Swap
management
DATATYPE[1:0]
Encrypt
AES_KEYRx (KEY)

Table 137. Initialization of AES_IVRx registers in CCM mode

AES_IVR2[31:0]
B0[95:64]
Block 1
AES_IVRx (CTR1)
Encrypt
S1
DATATYPE
[1:0]
DATATYPE
[1:0]
Swap
management
AES_DOUTR (ciphertext C1)
B
u+1
Encrypt
AES_KEYRx (KEY)
AES_IVR1[31:0]
B0[63:32]
RM0453 Rev 5
(3) Payload
AES_IVRx (CTRm)
Counter
increment (+1)
AES_KEYRx (KEY)
AES_DINR (plaintext
last block Pm )
DATATYPE
Swap
management [1:0]
DATATYPE
[1:0]
management
AES_DOUTR
(ciphertext last block Cm)
AES_KEYRx (KEY)
AES_DINR (CTR0)
S0
Encrypt
AES_DOUTR
AES_KEYRx (KEY)
Table 137
AES_IVR0[31:0]
B0[31:0]
RM0453
Block m
Encrypt
Sm
Swap
B
r
Encrypt
MAC (T)
(EncTAG)
(4) Final
MSv42152V2