ENC424J600-I/ML Microchip Technology, ENC424J600-I/ML Datasheet - Page 134

• Manufacturer Part Number: ENC424J600-I/ML
• Description: IC ETHERNET CTRLR W/SPI 44-QFN
• Manufacturer: Microchip Technology

Specifications of ENC424J600-I/ML

• Package / Case: 44-QFN
• Controller Type: Ethernet Controller
• Interface: SPI
• Voltage - Supply: 3 V ~ 3.6 V
• Current - Supply: 96mA
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Input Voltage Range (max): 5.5 V
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Mounting Style: SMD/SMT
• Operating Supply Voltage: 3 V to 3.6 V
• Supply Current (max): 117 mA
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: AC164132 - BOARD DAUGHTER PICTAIL ETHERNET
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

ENC424J600/624J600
To encrypt a block using CBC mode:
1.
2.
3.
4.
5.
6.
7.
8.
To decrypt a block using CBC mode:
1.
2.
3.
4.
5.
6.
7.
FIGURE 15-3:
DS39935C-page 132
Load the encryption key as described in
Section 15.3.1 “Key Support” .
Set AESOP<1:0> (ECON1<10:9>) to ‘ 01 ’.
Copy the Initialization Value (IV) to TEXTA at
7C20h.
Copy the plaintext message to TEXTB at
7C30h.
Set AESST (ECON1<11>) to initiate the
encryption.
Wait for the hardware to clear AESST.
Read the ciphertext message from TEXTA at
7C20h.
Repeat steps 4-7 for subsequent blocks. The
ciphertext from the previous block automatically
becomes the IV for the following block.
Initialize the decryption key as described in
Section 15.3.1 “Key Support” .
Set AESOP<1:0> to ‘ 10 ’.
Copy the Initialization Value (IV) to TEXTB at
7C30h.
Copy the ciphertext message to TEXTA at
7C20h.
Set AESST to initiate the decyption.
Wait for the hardware to clear AESST.
Read the plaintext message from XOROUT at
7C40h.
DATA
Plaintext
IV
ENCRYPTER
Ciphertext
0
Key
KEY
ENCRYPTION
0
CFB ENCRYPTION AND DECRYPTION
DATA
Plaintext
ENCRYPTER
Ciphertext
1
Key
KEY
1
8.
9.
The context for CBC mode consists of both the AES
encryption key and the ciphertext from the most recent
block. Save the ciphertext from the previous block to be
used as the IV when resuming the operation for
additional blocks.
15.3.3.3
Cipher Feedback mode is similar to CBC in that the
ciphertext becomes the Initialization Vector (IV) for the
subsequent block. However, in CFB mode, only the IV
is encrypted, then XORed with the plaintext to form the
ciphertext. For the second and subsequent blocks, the
ciphertext is passed through the encryption function
again, then XORed with the next plaintext block to
become the ciphertext. Like CBC mode, each
subsequent block depends on the previous block.
Therefore, identical subsequent plaintext blocks will
use a different IV, and therefore, yield different cipher-
text blocks. Figure 15-3 shows the use of CFB mode
for encryption and decryption.
Note:
DATA
ENCRYPTER
IV
If another block is to be decrypted, copy the
ciphertext message from this block to TEXTB at
7C30h. The ciphertext from this block becomes
the IV for the following one.
Repeat steps 4-8 for subsequent blocks.
Plaintext
Only 128-bit CFB mode is natively
supported. Other less common implemen-
tations, including 1-bit and 8-bit CFB
modes, could be accomplished with
support software, but are not detailed here.
Cipher Feedback Mode (CFB)
0
Key
KEY
DECRYPTION
Ciphertext
 2010 Microchip Technology Inc.
0
DATA
ENCRYPTER
Plaintext
Ciphertext
1
Key
KEY
1