ATAES132-SH-EQ-T Atmel, ATAES132-SH-EQ-T Datasheet - Page 106

• 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

I.2.
I.3.
MacFlag
To prevent spoofing of the MAC value, a flag byte is included in each MAC calculation. MacFlag provides information about
the state of the device during the MAC calculation.
Table I-34.
MAC Generation
The following example shows how the integrity MAC is calculated for an authentication operation requiring up to 14 bytes of
authenticate-only data. This operation involves three passes through the AES crypto engine, all three using the same key. If
there are more than 14 bytes of authenticate-only data, then another pass through the AES crypto engine is required.
There are two passes through the AES crypto engine in CBC mode to create the cleartext MAC. The inputs to the crypto
engine for those blocks are labeled B0 and B1, and the outputs are B’0 and B’1 respectively.
There is one additional pass through the AES crypto engine in CTR mode to create the key block that is used to encrypt the
MAC. The input to the crypto engine for this block is labeled A0 and the output is A’0. A’0 is the MAC sent to the system as the
output parameter of the Auth command.
Input integrity MACs for Auth, counter, KeyCompute, and lock are also calculated using this procedure. If the input MAC does
not match A’0, then the command returns an AUTH error.
Bit #
3-7
B0 is composed of the following 128 bits:
B1 is the XOR of B’0 with the following 128 bits:
B’1 is the cleartext MAC, which must be encrypted before being sent to the system
A0 is composed of the following 128 bits:
A’0 is XOR’d with the cleartext MAC (B’1) and sent to the system
0
1
1 byte flag, fixed value of b0111 1001
12 byte nonce, as generated by the nonce command
1 byte MacCount, 1 for first MAC generation
2 byte length field – always 0x00 00 for authentication only
2 byte length field, size of authenticate-only data
14 byte data to be authenticated only
1 byte flag, fixed value of b0000 0001
12 byte nonce, as generated by ATAES132 during nonce command
1 byte MacCount, 1 for first MAC generation
2 byte counter field – always 0x00 00 for A0
Definition of the MacFlag bits
Name
Random
Input
Zero
Notes
If 1b, then the nonce command was run with the RNG enabled and the nonce is
If 0b, the nonce value has been sent to the device by the system and may not be unique
This bit is 1b for MAC values that are sent to the device as inputs
This bit is 0b for MAC values output by the ATAES132
All bits must be 0b
guaranteed to be unique
Atmel ATAES132 Preliminary Datasheet
8760A−CRYPTO−5/11
106