RM0319 Datasheet, PDF (304/368 Pages) STMicroelectronics – SPEAr320S architecture and functionality

Security co-processor (C3)
RM0319
Bit ‘a’ in the above table is used to set the algorithm to use:
Table 92.
Bit 25
a
0
1
DES ECB bit ‘a’ encoding
Operation
DES
3DES
Bit ‘b’ in the above table is used to set the operation to perform:
Table 93.
Bit 24
b
0
1
DES ECB bit ‘b’ encoding
Operation
Encryption
Decryption
Bits 15 to 0 in the first instruction word (cccc in the above table) represent the length in
Bytes of the key.
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 94.
W#
1
2
3
DES CBC START Instruction Bit Encoding
Bit Encoding
xxxx 10ab 001x xxxx cccc cccc cccc cccc
32 bit Source Address for the key
32 bit Source Address for the IV
Bits ‘a’ and ‘b’ in the above table are used to set the algorithm and the operation to perform
and have the same encoding as in the ECB instruction. Bits 15 to 0 in the first instruction
word (cccc in the above table) represent the length in Bytes of the key.
DES APPEND instruction
The DES APPEND instruction can be applied with 2 different modes of operation:
● ECB
● CBC
ECB
The DES APPEND ECB instruction is 3 words long. This instruction is used for passing the
data to process (encrypt or decrypt). The length of the data to process is encoded in the first
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