2

AT88SC153

1016D–SMEM–04/04

The embedded authentication protocol allows the memory and the host to authenticate

each other. When this device is used with a host that incorporates a microcontroller

(e.g., AT89C51, AT89C2051, AT90S1200), the system provides an “anti-wiretapping”

configuration. The device and the host exchange “challenges” issued from a random

generator and verify their values through a specific cryptographic function included in

each part. When both agree on the same result, the access to the memory is permitted.

Figure 2. Security Methodology

Memory Access

Depending on the device configuration, the host might carry out the authentication pro-

tocol and/or present different passwords for each operation, read or write. Each user

zone may be configured for free access for read and write or for password-restricted

access. To insure security between the different user zones (multiapplication card),

each zone can use a different set of passwords. A specific attempts counter for each

password and for the authentication provides protection against “systematic attacks.”

When the memory is unlocked, the two-wire serial protocol is effective, using SDA and

SCL. The memory includes a specific register providing a 32-bit data stream conforming

to the ISO 7816-10 synchronous answer-to-reset.