ST STM32F40 Series Reference Manual page 580

RM0090 Cryptographic processor (CRYP)
Bits 7:6 DATATYPE[1:0]: Data type selection
This bitfield defines the format of data entered in the CRYP_DIN register (refer to
Section 20.3.3: Data type).
00: 32-bit data. No swapping of each word. First word pushed into the IN FIFO
(or popped off the OUT FIFO) forms bits 1...32 of the data block, the second
word forms bits 33...64.
01: 16-bit data, or half-word. Each word pushed into the IN FIFO (or popped off
the OUT FIFO) is considered as 2 half-words, which are swapped with each
other.
10: 8-bit data, or bytes. Each word pushed into the IN FIFO (or popped off the
OUT FIFO) is considered as 4 bytes, which are swapped with each other.
11: bit data, or bit-string. Each word pushed into the IN FIFO (or popped off the
OUT FIFO) is considered as 32 bits (1st bit of the string at position 0), which are
swapped with each other.
Bits 19 and 5:3 ALGOMODE[3:0]: Algorithm mode
0000: TDES-ECB (triple-DES Electronic codebook): no feedback between blocks
of data. Initialization vectors (CRYP_IV0(L/R)) are not used, three key vectors
(K1, K2, and K3) are used (K0 is not used).
0001: TDES-CBC (triple-DES Cipher block chaining): output block is XORed with
the subsequent input block before its entry into the algorithm. Initialization
vectors (CRYP_IV0L/R) must be initialized, three key vectors (K1, K2, and K3)
are used (K0 is not used).
0010: DES-ECB (simple DES Electronic codebook): no feedback between
blocks of data. Initialization vectors (CRYP_IV0L/R) are not used, only one key
vector (K1) is used (K0, K2, K3 are not used).
0011: DES-CBC (simple DES Cipher block chaining): output block is XORed with
the subsequent input block before its entry into the algorithm. Initialization
vectors (CRYP_IV0L/R) must be initialized. Only one key vector (K1) is used (K0,
K2, K3 are not used).
0100: AES-ECB (AES Electronic codebook): no feedback between blocks of
data. Initialization vectors (CRYP_IV0L/R...1L/R) are not used. All four key
vectors (K0...K3) are used.
0101: AES-CBC (AES Cipher block chaining): output block is XORed with the
subsequent input block before its entry into the algorithm. Initialization vectors
(CRYP_IV0L/R...1L/R) must be initialized. All four key vectors (K0...K3) are used.
0110: AES-CTR (AES Counter mode): output block is XORed with the
subsequent input block before its entry into the algorithm. Initialization vectors
(CRYP_IV0L/R...1L/R) must be initialized. All four key vectors (K0...K3) are used.
CTR decryption does not differ from CTR encryption, since the core always
encrypts the current counter block to produce the key stream that will be XORed
with the plaintext or cipher in input. Thus, ALGODIR is don't care when
ALGOMODE = 110b, and the key must NOT be unrolled (prepared) for
decryption.
0111: AES key preparation for decryption mode. Writing this value when
CRYPEN = 1 immediately starts an AES round for key preparation. The secret
key must have previously been loaded into the K0...K3 registers. The BUSY bit in
the CRYP_SR register is set during the key preparation. After key processing,
the resulting key is copied back into the K0...K3 registers, and the BUSY bit is
cleared.
1000: Galois Counter Mode (GCM). This algorithm mode is also used for the
GMAC algorithm.
1001: Counter with CBC-MAC (CCM). This algorithm mode is also used for the
CMAC algorithm.
Doc ID 018909 Rev 4 580/1422