AT88SC0404CRF-WA1 ATMEL [ATMEL Corporation], AT88SC0404CRF-WA1 Datasheet - Page 6

• Manufacturer Part Number: AT88SC0404CRF-WA1
• Description: 13.56 MHz CryptoRF EEPROM Memory 4 Kbits
• Manufacturer: ATMEL [ATMEL Corporation]

Security Operations
Antitearing
Password Verification
Authentication Protocol
Encryption
Checksum
Initial Device
Programming
6
AT88SC0404CRF
In the event of a power loss during a write cycle, the integrity of the device’s stored data
may be recovered. This function is optional: the host may choose to activate the
antitearing function depending on application requirements. When antitearing is active,
write commands take longer to execute since more write cycles are required to
complete them. Data writes are limited to 8-byte pages when antitearing is active.
Data is written first to a buffer zone in EEPROM instead of to the intended destination
address, but with the same access conditions. The data is then written to the required
location. If this second write cycle is interrupted due to a power loss, the device will
automatically recover the data from the buffer zone at the next power-up.
Passwords may be used to protect user zone read and/or write access. When a
password is presented using the Check Password command, it is memorized and active
until power is removed unless a new password is presented or a valid DESELECT or
IDLE command is received. Only one password is active at a time, but write passwords
also give read access.
The access to a user zone may be protected by an authentication protocol in addition to
password dependent rights. Passwords are encrypted in authentication mode.
The authentication success is memorized and active as long as the chip is powered,
unless a new authentication is initialized or a valid DESELECT or IDLE command is
received. If the new authentication request is not validated, the card loses its previous
authentication and it must be presented again. Only the last request is memorized.
The data exchanged between the card and the reader during Read, Write, and Check
Password commands may be encrypted to ensure data confidentiality.
The issuer may choose to protect the access to a user zone with an encryption key by
settings made in the configuration memory. In that case, activation of the encryption
mode is required in order to read/write data in the zone.
The encryption activation success is memorized and active as long as the chip is
powered, unless a new initialization is initiated or a valid DESELECT or IDLE command
is received. If the new encryption activation request is not validated, the card will no
longer encrypt data during read operations nor will it decrypt data received during write
or Check Password operations.
The PICC implements a data validity check function in the form of a checksum. The
checksum may function in standard or cryptographic mode. In the standard mode, the
checksum is optional and may be used for transmission error detection. The
cryptographic mode is more powerful since it provides data origin authentication
capability in the form of a Message Authentication Code (MAC). To write data to the
device, the host is required to compute a valid MAC and provide it to the device. If after
an ingoing command the device computes a MAC different from the MAC transmitted by
the host, not only is the command abandoned but the cryptographic mode is also reset.
A new authentication is required to reactivate the cryptographic mode.
CryptoRF is delivered with all security features disabled. To program the polling
response or enable the security features of CryptoRF the device must be personalized
by programming several registers. This is accomplished by programming the
configuration memory using simple write and read commands.
5023CS–CRRF–12/06