When the password check procedure is invoked by a parent procedure (e.g. for service activation, service deactivation, password registration), the network sends to the MS an invoke component of the operation "get password" with "password" as the value of the mandatory GuidanceInfo information element. This invoke component is embedded in a FACILITY message, since the password check procedure is always invoked during an existing transaction. The MS will return to the network the required password in the return result component of the operation. This return result component is embedded in a FACILITY message, see Figure 4.1. If the provided password is right the password check procedure returns to the parent procedure an indication of successful password check.

If no result is returned by the MS for the "Get password" operation invoked by the network, the password check procedure is terminated. If the password value which is returned by the MS does not match the password value registered in the network, the network increments a counter and sends to the MS a Return Error component indicating "Negative Password Check". The counter is reset as soon as the right password is returned. If the served mobile subscriber enters a wrong call barring "password" three consecutive times, the subscription option "control of services" is set to "by the service provider" in the network: thus the network makes the use of password impossible for any subscriber operation. The password check procedure returns to the parent procedure an indication of Password Attempts Violation. The password can be made valid by the service provider only.

The successful procedure consists of three steps:

• the password registration procedure invokes first the password check procedure as it is described above;
• if the password check procedure has returned an indication of successful password check, the network sends secondly to the MS, in an invoke component of the operation "get password" with "new password?" as the value of the mandatory GuidanceInfo information element. This invoke component is embedded in a FACILITY message. The MS will return to the network the required new password in the return result component of the operation. This return result component is embedded in a FACILITY message;
• the network sends thirdly to the MS an invoke component of the operation "get password" with "new password again?" as the value of the mandatory GuidanceInfo information element. This invoke component is embedded in a FACILITY message. The MS will return again to the network the required new password in the return result component of the operation. This return result component is embedded in a FACILITY message.

If the two values of the provided passwords are identical, the network confirms the registration of the new password by sending to the MS the return result component of the operation "register password", with the new password as a mandatory information element, see Figure 4.2.

If the subscription option "control of services" is set to "by the service provider" or if the WPA is greater than 3 an attempt to register a password will be denied by the network (see TS 23.011). If the counter for wrong password attempts is smaller than four, the network will return to the MS an error component with the error value "SS_SubscriptionViolation". If the counter is larger than three, the error value "Password Attempts Violation" is returned. If the password check procedure returns an indication of negative password check, the network will send to the MS a return error component of the operation "register password" with the error value "negativePasswordCheck". If the new password is not repeated twice identically by the mobile subscriber, the network returns to the MS an error component of the "register password" operation with the error value "passwordRegistrationFailure". The diagnostic "newPasswordsMismatch" may be passed as an error parameter. The old password remains registered. If no result is returned by the MS for the "Get password" operation invoked by the network the "register password" procedure is terminated, and the old password remains registered. If the format of a new password which is returned by the MS is invalid (e.g. the value does not belong to the [0000-9999] range), the network sends to the MS an error component of the "register password" operation with the error value "passwordRegistrationFailure". The diagnostic "invalidFormat" may be passed as an error parameter. The old password remains registered.