AS_Cryptographic co-processor (C3)
RM0082
384/844
Doc ID 018672 Rev 1
21.8.5 ECB
The DES START ECB instruction is 2 words long. This instruction is used to set the key for
the following operations. The length of the key is encoded in the first instruction word, while
the second word represents the Source Address for the key.
Bit ‘a’
in the above table is used to set the algorithm to use:
Bit ‘b
’ in the above table is used to set the operation to perform:
Bits 15 to 0
in the first instruction word (cccc in the above table) represent the length in
Bytes of the key.
21.8.6 CBC
The DES START CBC instruction is 3 words long. This instruction is used to set the key and
the initialization vector for the following operations. The length of the key is encoded in the
first instruction word, the second word represents the Source Address for the key and the
third word represents the Source Address for the Initialization Vector.
Table 317.
DES ECB start instruction bit encoding
W#
Bit Encoding
1
xxxx01ab 000x xxxx cccc cccc cccc cccc
2
(32 bit Source Address for the key)
Table 318.
DES ECB bit ‘a’ encoding
Bit 25
a Operation
0
DES
1
3DES
Table 319.
DES ECB bit ‘b’ encoding
Bit 24
b Operation
0
Encryption
1
Decryption
Table 320.
DES CBC START Instruction Bit Encoding
W#
Bit Encoding
1
xxxx 10ab 001x xxxx cccc cccc cccc cccc
2
32 bit Source Address for the key
3
32 bit Source Address for the IV