RM0319 datasheet(305/368 Pages) STMICROELECTRONICS

305 / 368 page

RM0319

Security co-processor (C3)

Doc ID 022640 Rev 3

305/368

instruction word, the second word represents the Source Address and the third word

represents the Destination Address.

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 data to be processed.

CBC

The DES APPEND CBC 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

instruction word, the second word represents the Source Address and the third word

represents the Destination Address.

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 (Table 92. and Table 93.). Bits 15 to 0

in the first instruction word (cccc in Table 96.) represent the length in Bytes of the key.

Table 95.

DES ECB APPEND Instruction bit encoding

Bit Encoding

xxxx 10ab 100x xxxx cccc cccc cccc cccc

32 bit Source Address for the data

32 bit Destination Address for the data

Bit 25

Operation

0DES

13DES

Bit 24

Operation

Encryption

1Decryption

Table 96.

DES CBC Append Instruction Bit Encoding

Bit Encoding

xxxx 10ab 101x xxxx cccc cccc cccc cccc

32 bit Source Address for the data

32 bit Destination Address for the data

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