AT88SC0404CA-MJTG Atmel, AT88SC0404CA-MJTG Datasheet - Page 17

• Manufacturer Part Number: AT88SC0404CA-MJTG
• Description: CRYPTOMEM 4KBIT 4 ZONE MOD J TWI
• Manufacturer: Atmel
• Series: CryptoMemory®r

Specifications of AT88SC0404CA-MJTG

• Format - Memory: EEPROMs - Serial
• Memory Type: EEPROM
• Memory Size: 4K (512 x 8)
• Speed: 4MHz
• Interface: I²C, 2-Wire Serial
• Voltage - Supply: 2.7 V ~ 3.6 V
• Operating Temperature: 0°C ~ 70°C
• Package / Case: M2 J, Smart Card Module
• Operating Temperature (max): 70C
• Operating Temperature (min): 0C
• Operating Temperature Classification: Commercial
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

6.1.3. Data Encryption
6.1.4. Encrypted Checksum (Message Authentication Code, MAC)
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Atmel
the confidentiality of data during read-write accesses and verify password operations. To enable encryption, the host
must generate a challenge using the session encryption key generated from the authentication activation step. The
host then needs to call the Verify CRYPTO command again with the device still in active authentication mode. The
session encryption key must belong to the active authentication key set. The host may enable encryption at any time
after which data content of communication between host and device user zones becomes encrypted. If a user zone
configuration in the Access Register requires encryption, however, then the host must enter encryption mode and must
encrypt all data content to and from the zone in the remainder of the active encryption session in order to communicate
with the zone. CryptoMemory does not encrypt system zone data except for password and password attempt counters.
Passwords and password attempt counters require encryption during active authentication or encryption modes.
Each successful entry into encryption mode renders the mode active for the current key set until the next call to the
Verify CRYPTO command or device reset. Only one key set may be active at anytime. Unsuccessful calls of the Verify
CRYPTO command exits both encryption and authentication modes and decrements the value of the authentication
attempts counter (AAC) register. Decrementing AAC to $00 permanently disables the corresponding key set and
permanently renders the corresponding user zone(s) under protection inaccessible. Activating encryption is similar in
process to activating authentication with the exception that the session encryption key replaces the secret seed. The
process uses the Verify Encryption variant of the Verify CRYPTO command (see Section
Section
Figure 7. Encryption Activation Process from Active Authentication Mode
CryptoMemory implements a data validity check function in the form of an encrypted checksum. This checksum
provides a bi-directional data integrity check and data origin authentication capability in the form of a Message
Authentication Code (MAC): only the host/device that carried out a valid authentication is capable of computing a valid
MAC. When writing data to the CryptoMemory device in authentication or encryption communication modes, the host
must send a valid checksum immediately following the write command. If the checksum is invalid, the device rejects the
write command and resets the device security privileges. The host must reinitiate entry into authentication and, if
applicable, encryption modes to continue. The use of checksum is optional when reading data. Calls to the read
checksum command resets device security so its use is recommended only at the completion of all data read
operations from the device.
Atmel AT88SC0104/0204/0404/0808/CA
®
CryptoMemory
10.3, Command Set
Session Key, Cryptogram
CryptoMemory Device
Compute Challenge A
Compute Challenge B
Verify Challenge A
Enable Encryption
®
allows the use of encryption between a host system and the CryptoMemory device to protect
)
Command/Communications
Read Config Zone
Verify Encryption
Session Key, Cryptogram
Generate Random Number
Compute Challenge A
Compute Challenge B
Read Challenge B
Verify Challenge B
Host Logic
8.2, Command Set
8664C–CRYPT–01/10
and