ATAES132-SH-ER Atmel, ATAES132-SH-ER Datasheet - Page 67

• Manufacturer Part Number: ATAES132-SH-ER
• Description: EEPROM AES 32Kbit EE I2C
• Manufacturer: Atmel

Specifications of ATAES132-SH-ER

• Rohs: yes
• Maximum Clock Frequency: 1 MHz
• Operating Supply Voltage: 6 V
• Maximum Operating Temperature: - 40 C to + 85 C
• Mounting Style: SMD/SMT
• Package / Case: SOIC-8
• Interface Type: I2C
• Factory Pack Quantity: 2300

7.26.
WriteCompute Command
The WriteCompute command encrypts data and computes the MAC required to execute the EncWrite command on a second
ATAES132 device.
To use this command, the nonce must be identical on both devices (see Section 7.21.1) and the MacCount must have the
same value. Both devices must also contain identical key values, but it is not necessary for the KeyID on the origin device to
match the KeyID on the destination device. In this section, the device which encrypts data and generates the MAC is referred
to as the origin device. The device checking the MAC is referred to as the destination device.
If mode bit 5, 6, or 7 is 1b, then the associated usage counter, SerialNum register value, or the first four bytes of the
SmallZone register must be identical on both devices. The ManufacturingID register must be identical on both devices, since it
is always included in the MAC calculation.
A valid nonce is required to run the WriteCompute command. If the KeyConfig[EKeyID].RandomNonce bit is 1b, then the
nonce must be random.
The value of Param2 in the FirstBlock field must match the count field value.
Table 7-73. Input parameters
Table 7-74. Output parameters
The command and response packet is transmitted as a block beginning with the count and ending with a packet checksum.
This block format is described in Section 6.1.
Opcode
Mode
Param1
Param2
Data1
Data2
Data3
Name
ReturnCode
OutMac
OutData
Name
WriteCompute
Mode
EKeyID
Count
FirstBlock
SecondBlock
InData
16 or 32
(Bytes)
Size
16
1
Notes
Upon success, 0x00 will be returned. Any command execution or validation failure generates a
non-zero error code, per Section 6.3.
The input MAC for the EncWrite command on the destination device
The encrypted data (ciphertext) to be written to the destination device using the EncWrite
command
(Bytes)
1 to 32
Size
16
1
1
2
2
6
Notes
0x16
The value of this field must match the mode field value to be used when
executing the EncWrite command on the destination device
Upper byte is always 0x00. Lower byte is the pointer to the encrypt key.
Legal values: 0x00 to 0x0F, 0xFF.
Upper byte is always 0x00. Lower byte is the number of Data bytes to be
encrypted.
The value of this field must match the first authenticate-only block to be used
when executing the EncWrite command on the destination device
The value of this field must match the second authenticate-only block to be
used when executing the EncWrite command on the destination device. If
mode bits 5, 6, and 7 are 0b, then this field must be present, but is ignored.
Input data to be encrypted (plaintext)
Atmel ATAES132 Preliminary Datasheet
8760A−CRYPTO−5/11
67