10

5204AS–CRYPT–7/08

AT88SC0808CA

10.1

Security Fuses

There are three fuses on the device that must be blown during the device personalization pro-

cess. Each fuse locks certain portions of the configuration zone as OTP (One-Time

Programmable) memory. Fuses are designed for the module manufacturer, card manufacturer

and card issuer and should be blown in sequence, although all programming of the device and

blowing of the fuses may be performed at one final step.

11. Communication Security Modes

Communications between the device and host operate in three basic modes. Standard mode is

the default mode for the device after power-up. Authentication mode is activated by a successful

authentication sequence. Encryption mode is activated by a successful encryption activation fol-

lowing a successful authentication.

Note:

1. Configuration data include viewable areas of the Configuration Zone except the passwords:

MDC: Modification Detection Code.

MAC: Message Authentication Code.

12. Security Options

12.1

Anti-Tearing

In the event of a power loss during a write cycle, the integrity of the device’s stored data is recov-

erable. This function is optional: the host may choose to activate the anti-tearing function,

depending on application requirements. When anti-tearing is active, write commands take longer

to execute, since more write cycles are required to complete them, and data is limited to a maxi-

mum of eight bytes for each write request.

Data is written first into a buffer zone in EEPROM instead of the intended destination address,

but with the same access conditions. The data is then written in the required location. If this sec-

ond write cycle is interrupted due to a power loss, the device will automatically recover the data

from the system buffer zone at the next power-up. Non-volatile buffering of the data is done

automatically by the device.

During power-up in applications using Anti-Tearing, the host is required to perform ACK polling

in the event that the device needs to carry out the data recovery process.

Table 11-1.

Communication Security Modes

(1)

Mode

Configuration Data

User Data

Passwords

Data Integrity Check

Standard

Clear

Clear

Clear

MDC

Authentication

Clear

Clear

Encrypted

MAC

Encryption

Clear

Encrypted

Encrypted

MAC