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AT88SC3216CRF

5005CS–CRRF–12/06

Security Operations

Antitearing

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.

Password Verification

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.

Authentication Protocol

The access to a user zone may be protected by an authentication protocol in addition to

password dependent rights. Passwords are encrypted in authorization 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.

Encryption

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.

Checksum

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.

Initial Device

Programming

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.