ATAES132-SH-EQ-T Atmel, ATAES132-SH-EQ-T Datasheet - Page 36

• Manufacturer Part Number: ATAES132-SH-EQ-T
• Description: EEPROM AES 32Kbit EE SPI
• Manufacturer: Atmel

Specifications of ATAES132-SH-EQ-T

• Rohs: yes
• Maximum Clock Frequency: 10 MHz
• Operating Supply Voltage: 6 V
• Maximum Operating Temperature: - 40 C to + 85 C
• Mounting Style: SMD/SMT
• Package / Case: SOIC-8
• Interface Type: SPI
• Factory Pack Quantity: 4000

7.7.
DecRead Command
The DecRead command is used to check the OutMAC generated by an EncRead command on a second ATAES132 device.
If the MAC matches, then the 1 to 16 bytes of data is returned to the host in the DecRead response.
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 the 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 in the SecondBlock field, must match the values on the origin device. 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 DecRead command. If the KeyConfig[DKeyID].RandomNonce bit is 1b, then the nonce
must be random.
Table 7-32. Input parameters
Table 7-33. 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
Data4
Name
ReturnCode
OutData
Name
DecRead
Mode
DKeyID
Count
FirstBlock
SecondBlock
InMac
InData
(Bytes)
1 to 16
Size
1
Notes
Upon success, 0x00 will be returned. Any command execution or validation failure generates a
non-zero error code, per Section 6.3.
Decrypted (plaintext) output data
(Bytes)
Size
16
16
16
1
1
2
2
6
Notes
0x17
The value of this field must match the mode field value used when executing
the EncRead command on the origin device.
Upper byte is always 0x00. Lower byte is the pointer to the decrypt key.
Legal values: 0x00 to 0x0F, 0xFF.
Upper byte is always 0x00. Lower byte is the number of data bytes to be
decrypted.
The value of this field must match the first authenticate-only block used when
executing the EncRead command on the origin device.
The value of this field must match the second authenticate-only block used
when executing the EncRead command on the origin device. If mode bits 5, 6,
and 7 are 0b, then this field must be present, but is ignored
Integrity MAC for the input data
Input data (ciphertext) to be decrypted
Atmel ATAES132 Preliminary Datasheet
8760A−CRYPTO−5/11
36