ATAES132-SH-ER Atmel, ATAES132-SH-ER Datasheet - Page 14

• 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

3.4.
3.4.1.
3.5.
3.5.1.
3.5.2.
Data Encryption/Decryption
A key can be configured to allow encryption/decryption of small packets of data using AES-CCM with an internally stored key.
The encrypt command encrypts 16 or 32 bytes of plaintext data provided by the host; the encrypted data and MAC are
returned to the host. The decrypt command decrypts 16 or 32 bytes of encrypted data after verifying the MAC; the data is
returned to the host only if the MAC is valid. When these commands are used, none of the data is stored in the internal
EEPROM.
AES-ECB Encryption/Decryption
A key can be configured to allow AES-ECB mode operations using the legacy command. A single AES-ECB operation is
performed using an internally stored key and the 16 byte input packet received with the AES-ECB command. The 16 byte
result is returned to the host. No input or output formatting is performed by this command, and no data is stored in the internal
EEPROM.
Keys
The ATAES132 securely stores sixteen 128 bit keys in the EEPROM. Keys can only be used for the cryptographic functions
enabled in the ZoneConfig, CounterConfig or KeyConfig register bits in the configuration memory. Key values can never be
read from the ATAES132 under any circumstances. Any key can be used with any user zone.
A seventeenth key register in the internal SRAM can be used for session keys.
See section 7.11 for the EncWrite command. See section 7.19 for the lock command.
Key Management
The key registers can be written with plaintext data or with encrypted data before the key memory is locked. After the key
memory is locked, a key register can only be updated if the corresponding KeyConfig register allows updates.
Several key management commands are available for updating or generating the keys:
Limited Use Keys
To prevent exhaustive attacks on the keys, the ATAES132 can be configured to limit the key usage with a monotonic counter.
If a key is configured with a usage counter, then the following steps are performed for any command using that key:
By default, the counters are configured to allow two million counts, allowing two million operations using a key with the usage
limits enabled. Atmel recommends that the customer configure key usage counters at personalization to a smaller number;
the appropriate key usage limit is dependent on the application. See Appendix H for additional information.
1.
2.
3.
4.
5.
1.
2.
3.
An encrypted key provided by the host can be written to an internal key register after validating the MAC. The
Plaintext data provided by the host can be encrypted and returned to the host along with the MAC; this packet can
The internal random number generator can be used to create a key for use as a session key or for storage in an
The contents of the session key register can be encrypted and returned to the host along with the MAC. The
Keys stored in the user memory can be transferred to an internal key register or used as a session key. A user zone
Read the counter from memory to check if the count has reached the maximum count value
If the maximum count has been reached, then the command is not executed and an error code is returned
If the maximum count has not been reached, then the counter is incremented and the command is executed
KeyImport command and KeyLoad command perform this function.
be used as the encrypted key input to another ATAES132 device. The KeyExport command performs this function.
internal key register. The new key can also be encrypted and returned to the host for use as the encrypted key input
to another ATAES132 device. The KeyCompute command and KeyExport command perform this function.
KeyExport command performs this function.
configured as extended key memory can be used to store eight keys. The KeyTransfer command performs this
function.
Atmel ATAES132 Preliminary Datasheet
8760A−CRYPTO−5/11
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