ST25TV04K-P datasheet(21/107 Pages) STMICROELECTRONICS

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5.2.2

Passwords and security sessions

ST25TV04K-P provides protection of user memory and system configuration registers. user and host can access

those protected data by opening security sessions with the help of passwords. Access rights is more restricted

when security sessions are closed, and less restricted when security sessions are open.

There is two types of security sessions, as shown in Table 34. Security session type:

Table 34. Security session type

Security session

Open by presenting

Right granted when security session is open, and until it is closed

user

password 1, 2 or 3

(PWD_1,

PWD_2,

PWD_3)

User access to protected user memory as defined in AiSS registers

User write access to password 1, 2 or 3

configuration

password 0

(PWD_0)

User write access to configuration registers

User write access to password 0

1. Password number must be the same as the one selected for protection.

2. Write access to the password number corresponding to the password number presented.

All passwords are 64-bits long, and default factory passwords value is 0000000000000000h.

The ST25TV04K-P passwords management is organized around dedicated set of commands to access the

dedicated registers in system configuration area.

The dedicated password commands are:

•

"Write Password": command (code B1h): see Section 6.4.28 Write password.

•

"Present Password": command (code B3h): see Section 6.4.29 Present password.

User possible actions for security sessions are:

•

Open user security session: "Present Password" command, with password number 1, 2 or 3 and the

valid corresponding password

•

Write password: "Present Password" command, with password number (0, 1, 2 or 3) and the current valid

corresponding password. Then "Write Password" command, with same password number (0, 1, 2 or 3) and

the new corresponding password.

•

Close user security session: "Present Password" command, with a different password number than the

one used to open session or any wrong password. Or remove tag from RF field (POR).

•

Presenting a password with an invalid password number doesn't close the session.

•

Open configuration security session: "Present Password" command, with password number 0 and the

valid password 0.

•

Close configuration security session: "Present Password" command, with a password number different

than 0, or password number 0 and wrong password 0. Or remove tag from field (POR).

•

Presenting a password with an invalid password number doesn't close the session.

Opening any new security session (user or configuration) automatically close the previously open one (even if it

fails).

Caution:

To make the application more robust, it is recommended to use addressed or selected mode during write

password operations to get the traceability of which tags/UID have been programmed

ST25TV04K-P

Data protection

DS12942 - Rev 2

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