WO2007050272A2

WO2007050272A2 - Ending a service provider subsidy lock

Info

Publication number: WO2007050272A2
Application number: PCT/US2006/039422
Authority: WO
Inventors: Jin-Yue Chen
Original assignee: Motorola Inc.
Priority date: 2005-10-25
Filing date: 2006-10-06
Publication date: 2007-05-03
Also published as: CN100525522C; WO2007050272A3; CN1956568A

Abstract

The present invention provides a method (300) of operating a wireless communications device (200). A restricted service provider mode is first activated (310), in which communications to and from the device are restricted to a predetermined service provider (250A). A start restricted service provider code is generated using a predetermined data and a restricted service provider mode activation time (320). An end restricted service provider code is generated using the predetermined data and a restricted service provider mode deactivation time (330). The restricted service provider mode is deactivated if the end restricted service provider code corresponds to the start restricted service provider code (335Y).

Description

ENDING A SERVICE PROVIDER SUBSIDY LOCK

FIELD OF THE INVENTION

The present invention relates generally to the field of restricting provision of a service to an electronic device to a particular service provider; especially though not exclusively to a wireless connectivity service provider subsidising the initial cost of the electronic device.

BACKGROUND OF THE INVENTION

In a wireless portable communication device, such as a cellular telephone used in Global System for Mobile Communications ("GSM"), a Subscriber Identification Module ("SIM") card is used to store various information pertaining to a subscriber. Generally, the subscriber is able to use any compatible cellular telephone by inserting the SIM card into the cellular telephone, provided that the subscriber is able to access the SIM card. The subscriber may be locked out of the SIM card if he fails to enter the correct access code such as a password within a predetermined time or within a predetermined number of attempts, or when his contract with the service provider expires. When the subscriber is locked out, the SIM card allows the subscriber to make only an emergency call. After a predetermined lockout period expires, the subscriber may be allowed to re-enter the password, and the phone is placed in a normal operation mode upon successful entry of the password.

In a wireless communication network, a subsidized subscriber generally has an agreement with a subsidizing network service provider for a specified period as defined in the contract. A subsidized wireless portable communication device used in the wireless communication network features a subscriber specific module (such as a SIM card) having a subsidy lock or restricted service provider mode, which prevents the subscriber from making voice or data calls or Short Message Service ("SMS") messages in a network other than that of the subsidizing network service provider. For the subscriber to be able to use the wireless portable communication device in a non- subsidizing network or after the expiration of the contract, the subscriber must enter an access code provided by the subsidizing network service provider to access the SIM card. Otherwise, the subscriber is only allowed to make an emergency call. The access code is generally provided via a voice call to a service centre. In some cases, however, the subsidized wireless portable communication device needs be taken to the service centre for unlocking and/ or renewing of the service contract to avoid disclosure of the access code by the subsidizing network service provider. These arrangements are inconvenient for the subscriber.

Automated methods of unlocking a portable wireless communications device at the end of a network service provider subsidy period are also known. For example the access code for unlocking the device may be sent over the wireless network of the service provider to the portable communications device or phone, for example via an SMS service. However the access code may be intercepted by other parties over the wireless link and used to unlock other phones for which the subsidy period has not yet expired. Therefore such methods do not guarantee the interests of the service provider.

SUMMARY OF THE INVENTION

In general terms in one aspect the present invention provides a method of activating and deactivating a restricted service provider mode in a portable or wireless communications device. The restricted service provider mode may restrict communications with the device to a single service provider, for example a wireless connectivity service provider which has subsidised the cost of the communications device. Activation of this mode can be in response to insertion into the device of a predetermined data such as that contained on an allowable SIM card or other subscriber module which corresponds with the service provider. Typically the device will be pre-programmed to only accept subscriber modules from the subsidizing service provider - a restricted service provider mode, for example by securely storing a service provider password or code for matching with a corresponding password on the subscriber module. Similarly the device will typically also comprise a securely stored access code for deactivating the restricted service provider mode.

Predetermined data is retrieved from the subscriber module and/ or communications device, for example the IMSI and IMEI numbers respectively; and this is used together with a restricted service provider mode activation time to generate a start restricted service provider code. The start or activation time may be the time of generating the code, and may correspond to the start of a subsidy period for example. The start restricted service provider code is stored for later comparison. When a matching end restricted service provider code is generated by the device, the restricted service provider mode is deactivated, and the mobile device may then communicate using other service providers. The end restricted service provider code is generated using the same predetermined data but a restricted service provider mode deactivation or end time, which may correspond to the expiration of the above subsidy period. The restricted service provider mode end time corresponds to the time the end restricted service provider code is generated, and may be "tried" periodically, or only triggered to try after the end of the subsidy period.

By generating codes using predetermined data and timing information on the communications device, a restricted service provider mode such as subsidy lock can be automatically unlocked after a predetermined period for example a subsidy period, without the need for the service provider to send an access, deactivate or unlock code to the device over the insecure wireless network. Similarly no action is required by the user of the device, for example calling the network provider or taking the device to a service centre, making the unlocking function far simpler. In an embodiment the start and end restricted service provider codes are generated by applying an encryption function to the predetermined data and a pseudorandom number which is arranged to be the same at the start and end restricted service provider times. This is achieved by using a time based pseudorandom number generator which has a cycle length equal to the subsidy period. In other words, the pseudorandom sequence of numbers is repeated every cycle, thus starting at the start restricted service provider time and repeated starting at the end restricted service provider time corresponding to the end of the subsidy period. Alternatively the subsidy period may be a multiple of the cycle length in which case the device may be programmed to generate the end restricted service provider code at the end of the subsidy period or after a predetermined number of pseudorandom number cycles.

The encryption of a time based pseudorandom number with the predetermined data provides a secure method of enforcing the subsidy period, making it difficult for an unscrupulous user to attempt to unlock the device prematurely.

In an alternative arrangement, a simple time and date signal may be used, so that after a subsidy period of one year for example, the time and date will be repeated. Such a signal may also be encrypted with the subscriber data to generate a code dependent on the two.

In an embodiment, the predetermined data comprises subscriber data from a SIM or similar type of subscriber module, and which may include user or subscriber specific data such as an International Mobile Subscriber Identity number (IMSI) as well as data specific to the network provider. The predetermined data may also or alternatively include device specific data for example the International Mobile Equipment Identity number (IMEI).

In an embodiment the timing information used for the start restricted service provider time and the end restricted service provider time is derived from wireless network signals associated with the service provider's wireless network. These might include Network Time Protocol (NTP) or Global

Positioning System (GPS) time signals in GSM or Code Division Multiple

Access (CDMA) based networks respectively. Using network based timing to synchronise the device ensures more accurate timing information for use with the unlocking method.

The restricted service provider mode typically restricts uses of the device to a particular subscriber identity module (eg SIM card) associated with the subsidizing network, however the device may be restricted to use of any SIM card associated with the subsidizing network. This is typically implemented by pre-programming the network and/ or SIM card identifiers into the secure memory of the device prior to release of the device to a subscriber.

In another aspect of the present invention there is provided an electronic device, and/ or a computer program which when executed on a suitable processor is, arranged to carry out the methods described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

hi order that the invention may be readily understood and put into practical effect, reference will now be made to an exemplary embodiment as illustrated with reference to the accompanying figures, where like reference numerals refer to identical or functionally similar elements throughout the separate views. The figures together with a detailed description below, are incorporated in and form part of the specification, and serve to further illustrate the embodiments and explain various principles and advantages, in accordance with the present invention where:

Fig. 1 is a schematic block diagram illustrating circuitry of an electronic device in accordance with the invention; Fig. 2 is a schematic block diagram illustrating use of a restricted wireless connectivity service provider in accordance with the invention;

Fig. 3 is a flow diagram illustrating a method of operating an electronic device in accordance with the invention; and

Fig. 4 is a flow diagram illustrating a detailed embodiment of activating and deactivating a restricted (wireless connectivity) service provider mode in accordance with the invention.

Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.

DETAILED DESCRIPTION

Before describing in detail embodiments that are in accordance with the present invention, it should be observed that the embodiments reside primarily in combinations of method steps and apparatus components related to the activation and deactivation of a restricted service provider mode in an electronic device. Accordingly, the apparatus components and method steps have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.

In this document, relational terms such as first and second, top and bottom, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. The terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, device or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by "comprises ...a" does not, without more constraints, preclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element.

It will be appreciated that embodiments of the invention described herein may be comprised of one or more conventional processors and unique stored program instructions that control the one or more processors to implement, in conjunction with certain non-processor circuits, some, most, or all of the functions of activation and deactivation of a restricted service provider mode in an electronic device described herein. The non-processor circuits may include, but are not limited to, a radio receiver, a radio transmitter, signal drivers, clock circuits, power source circuits, and user input devices. As such, these functions may be interpreted as steps of a method for activation and deactivation of a restricted service provider mode in an electronic device. Alternatively, some or all functions could be implemented by a state machine that has no stored program instructions, or in one or more application specific integrated circuits (ASICs), in which each function or some combinations of certain of the functions are implemented as custom logic. Of course, a combination of the two approaches could be used.

Thus, methods and means for these functions have been described herein. Further, it is expected that one of ordinary skill, notwithstanding possibly significant effort and many design choices motivated by, for example, available time, current technology, and economic considerations, when guided by the concepts and principles disclosed herein will be readily capable of generating such software instructions and programs and ICs with minimal experimentation.

Referring to FIG. 1, there is a schematic diagram illustrating an electronic device 100, typically a wireless communications device, in the form of a mobile station or mobile telephone comprising a radio frequency communications unit 102 coupled to be in communication with a processor

103, The electronic device 100 also has a display screen 105. There is also an alert module 115 that typically contains an alert speaker, vibrator motor and associated drivers. The display screen 105, and alert module 115 are coupled to be in communication with the processor 103.

The processor 103 includes an encoder/ decoder 111 with an associated code Read Only Memory (ROM) 112 for storing data for encoding and decoding voice or other signals that may be transmitted or received by the electronic device 100. The processor 103 also includes a micro-processor 113 coupled, by a common data and address bus 117, to the encoder/ decoder 111, a character Read Only Memory (ROM) 114, a Random Access Memory (RAM)

104, static programmable memory 116 and a Removable User Identity Module (RUIM) interface 118. The static programmable memory 116 and a RUIM card 119 (commonly referred to as a Subscriber Identity Module (SIM) card) operatively coupled to the RUIM interface 118 each can store, amongst other things, Preferred Roaming Lists (PRLs), subscriber authentication data, selected incoming text messages and a Telephone Number Database (TND phonebook) comprising a number field for telephone numbers and a name field for identifiers associated with one of the numbers in the name field. The

RUIM card 119 and static memory 116 may also store passwords for allowing accessibility to password-protected functions on the mobile telephone 100.

The micro-processor 113 has ports for coupling to the display screen

105, and the alert module 115. Also, micro-processor 113 has ports for coupling to a microphone 135 and al communications speaker 140 that are integral with the device.

The character Read Only Memory 114 stores code for decoding or encoding text messages that may be received by the communications unit 102.

In this embodiment the character Read Only Memory 114, RUIM card 119, and static memory 116 may also store Operating Code (OC) for the micro- processor 113 and code for performing functions associated with the mobile telephone 100.

The radio frequency communications unit 102 is a combined receiver and transmitter having a common antenna 107. The communications unit 102 has a transceiver 108 coupled to the antenna 107 via a radio frequency amplifier 109. The transceiver 108 is also coupled to a combined modulator/ demodulator 110 that couples the communications unit 102 to the processor 103.

FIG 2 shows a wireless communications system in which a wireless network service provider provides wireless connectivity services to a wireless communications electronic device. A wireless electronics device 200 such as a mobile phone, wireless enabled PDA, laptop or other mobile electronic equipment is connected to a wireless service provider 250A using a wireless air interface 280 comprising radio signals operating according to a predetermined protocol as is known. An alternative wireless service provider 250B is also shown, and the wireless device 200 may have the capabilities to wirelessly connect to a number of such service providers 250.

In order for the wireless electronic device 200 to be able to connect to a service provider 250A or 250B, the service provider needs to be able to recognise the electronic device 200 as belonging to a subscribing customer so that use of the service will be paid for. This is typically achieved with the use of subscriber identity module (SIM) cards 260, or similar subscriber identity modules more generally known as international mobile subscriber identity

(IMSI) cards; including for example the equivalent CDMA network RIUM card. These cards 260 can be bought separately from the electronic device 200, and can be inserted into the wireless device 200 by a user of the device. The IMSI cards 260 comprise data uniquely identifying the purchaser of the card with the service provider 250, This is typically implemented using predetermined data or a subscriber identifier such as an International Mobile Subscriber Identity (IMSI) number which the service provider can cross- reference with further personal data about the subscriber such as their name and address and billing details. The subscriber modules 260 also typically include an identifier to identify the service provider 250 associated with the module 260; for example a system identification code (SID). The subscriber module 260 typically also includes a secure key known also by the corresponding service provider 250 and used by both to encrypt and decrypt communications between them.

In an effort to encourage the take-up of new mobile phone technology and hence the demand for chargeable services, service providers 250 typically subsidise the true cost of the electronic device 200 in return for the user only using the subsidising service provider 250A for a subsidy period, for example

2 years. In order to enforce these restrictions to communicating with only the subsidising service provider 250A, and not an alternative wireless service provider 250B, mobile phones and other wireless electronic devices 200 can be configured or locked such that wireless communications are only possible with the subsidising service provider 250A. This can be achieved by preprogramming the electronic device 200 to require a predetermined service provider password (GID) from the SIM card which only subsidising service provider SIM cards carry, before allowing wireless communications - except emergency calls. This effectively means that the device or phone 200 is locked to a particular service provider 250A, or even a particular SIM card 260A, and therefore must operate in a restricted service provider mode.

An unlocking password or access code is required in order to remove the need for a matching service provider password (GID), and therefore to enable access to another service provider's SIM card 260B or wireless services

250B. This is the access code referred to above which a subscriber must typically call a service provider for, but which in this embodiment is provided automatically to unlock the device or deactivate the restricted service provider mode. As discussed, without the access code, the device or phone only allows emergency calls to be made unless a specific SIM card or SIM cards from a specific service provider 250A are used. The service provider associated with a particular IMSI card can be determined from data stored on the card, for example the provider's unique system identification code (SID). Once a suitable access code has been entered, the mobile phone or wireless device 200 deactivates the restricted service provider mode, and enables interaction with any SIM card 260B. The restricted service provider mode in which the mobile device 200 may only communicate with one (the subsidising) service provider 250A is achieved using a restricted service provider lock functionality 270, which may be implemented as software pre-programmed into and executed by the mobile phone 200 for example. This may simply check that the service provider specific password (GID) on the SIM card matches the one securely stored on the device before allowing more than emergency calls. The restricted service provider lock 270 prevents interaction between the mobile phone 200 and a SIM card 260B from a non-subsidising network or service provider 250B, and only allows this interaction with a SIM card 260A associated with the subsidising service provider 260A. Operation of this type of service provider lock or restricted service provider mode functionality 270 will be known to those skilled in the art. Activation of the restricted service provider mode or lock is typically achieved using a secure setting, flag or bit such as the mobile personalisation bit in the electronic device 200; which ensures that the phone or device checks for a suitable GID before allowing wireless communication using the SIM card. This flag can be unset by providing the correct access code, that is the access code that matches the one pre-programmed and securely stored on the device.

The embodiment provides an alternative to entering an access code to deactivate the restricted service provider mode, and instead uses an automatic lock disable or restricted service provider mode deactivation function 290 to automatically deactivate the restricted service provider mode

(270) after the expiry of the subsidised service period. This can be achieved by providing an access code securely stored on the device 200, or possibly the subscriber module 260, to the restricted service lock 270 part of the device 200, at the end of the service period. Both the access code provided by the lock disable function 290 and that used by the phone or device 200 for matching can be pre-programmed into the device's secure memory. This is a memory area which is only accessible by authorised software modules as is known.

Determination of the end of the subsidised period and hence restricted service provider mode or period is achieved by monitoring a timer 295 or clock signal. Thus at the end of the subsidised service period as measured by the timer 295, the lock disable module 290 deactivates the restricted service provider mode or lock 270, allowing the electronic device 200 to interact with other SIM cards 260B, and hence other service providers 250B. The lock disable module 290 and the restricted service provider mode or lock 270 will typically be implemented in secure software pre-programmed into the device

200.

FIG 3 shows a flow diagram for a method of operating an electronic device 200 such as a mobile phone in order to implement the functionality of the lock disable module 290 and the restricted service provider mode or lock

270. Following power on of the device, the method (300) awaits insertion of a SIM card or another predetermined event (305), and in response to this event activates a restricted service provider mode (310). In the restricted service provider mode, the device 200 may only interact with or use a SIM card from a subsidising network or restricted service provider. Therefore communications to and from the device 200 are restricted to that predetermined service provider. SIM cards or other IMSI cards may be identified as corresponding to the predetermined service provider by querying the SID number of the SIM card, and/ or by checking that the service provider password (GID) is correct.

The method (300) then obtains predetermined data such as the IMEI number from the device itself, and the IMSI number from the SIM card (315). The restricted service provider mode activation time is also noted, for example using a local clock. Alternatively a timer may be set in response to activation of the restricted service provider mode. The method (300) then generates a start restricted service provider code using the predetermined data, and the restricted service provider mode activation time (320). The restricted service provider mode activation time may be used directly, or indirectly for example as an input to a time based pseudorandom number generator as described in more detail below. The code may be generated using an encryption or scrambling function applied to the predetermined data and the restricted service provider mode activation time based parameter.

At a later time, the method (300) then obtains the same predetermined data such as the combination of IMSI and IMEI numbers, as well as a restricted service provider mode deactivation time (325). This restricted service provider mode deactivation time based parameter corresponds to the restricted service provider mode deactivation time parameter and may be a direct time derived for example from the device's on-board clock or the expiry of a timer, or it may be a time based pseudorandom number dependent on the restricted service provider mode deactivation time. The method may perform this step (325) periodically, or only at the end of the subscription period, and perhaps for a number of times after that if initially unsuccessful in deactivating the restricted service provider mode.

The method then generates an end restricted service provider code (330). This is achieved in the same manner as the start restricted service provider code, using the same predetermined data but a different time based parameter. At the expiry of the subsidy period, the restricted service provider mode deactivation time based parameter is arranged to be the same as the time based parameter corresponding to the restricted service provider mode activation time. This may be achieved using a time based pseudorandom number generator with a cycle period corresponding to the duration of the subsidy period.

The newly generated end restricted service provider code and the stored start restricted service provider code are then compared (335). If the two codes do not match (335N), then the method returns to the step of obtaining another restricted service provider mode end or deactivation time (325). Alternatively, the method may simply alert the user to contact the support team at the subsiding service provider. If however the two codes match (335Y), then the restricted service provider mode is deactivated (340), and the device 200 may use other service providers for wireless communications. Deactivation of the restricted service provider mode may be achieved by providing the device's restricted service provider lock software module 270 with a securely stored access code; which if matching that module's own access code, causes it to unset the mobile personalisation bit or similar mechanism in order to unlock the device 200.

FIG 4 illustrates another embodiment for unlocking a communications device or deactivating a restricted service provider mode in a device utilising a time based pseudorandom number generator. The method 400 receives network timing signals 405 such as NTP (network time protocol) signals in a GSM network or GPS timing signals in a CDMA based network. These network or global time signals are used to synchronise a local timer or clock 410 on the device with the network time. The local timer function 410 provides clock or time signals to a time based pseudorandom number generator function (PRNG) 415 which is arranged to generate a series of pseudorandom numbers (KcI, Kc2) in response to the incoming clock signals. The PRNG 415 can be configured to repeat the pseudorandom sequence of numbers after a given number of clock signals or inputs. Therefore by knowing the number of clock inputs or timer signals received over a given period, the PRNG 415 can be configured to repeat a pseudorandom number (PRN) sequence after a predetermined period. In the embodiment, a service or subsidy period 420 is used to configure the PRNG 415 and which corresponds to a subsidy period (eg 2 years) over which a wireless network or service provider subsidises the cost of the device. During this period, the service provider expects the user of the device to only use that service provider for wireless communications.

Those skilled in the art will be familiar with configurable time based pseudorandom number generators 415, which can be implemented in software, firmware, or hardware for example using registers and simple logic in which the pseudorandom number generators 415 are seeded by predefined respective restricted service provider mode activation and restricted service provider mode deactivation times.

The device 200 will typically include one or more types of preprogrammed locks, for example a network or service provider lock which prevents use of the phone on another network, a SIM lock which prevents use of another SIM card with the phone, or a code lock which requires a special password to unlock the phone. The embodiment may be used with any or all of these types of lock, however for simplicity of explanation, only unsetting a code lock is described. Unsetting a code lock also typically has the effect of deactivating any SIM or service provider locks. When a user inserts a new SIM card into a new GSM capable device according to the embodiment 425, the device reads predetermined data, in this embodiment the IMSI from the SIM or other subscriber card and the IMEI or ESN (electronic serial number) from the device 430. As described above, the device may also check the SIM cards GID before allowing use of the inserted SIM. This effectively restricts use of the device to the service provider associated with the SIM card, or in other words activates a restricted service provider mode. With the IMEI and IMSI, the method generates a security key or start restricted service provider code KdI 435 using also the time based pseudorandom number KcI corresponding to the time the SIM card was inserted or the code was generated - the restricted service provider activation time. To generate the key, the predetermined data and pseudorandom number KcI are encrypted according to a predetermined encryption function to produce the initial security key or start restricted service provider code KdI. Thus the security or locking key KdI is dependent on the time the device or phone 200 is first legitimately used, and this is defined as the start of the subscription period or the start restricted service provider mode time.

The security key or start restricted service provider code KdI is then stored in the device or phone's secure memory 440, and wireless communications between the phone and the service provider corresponding to the inserted SIM are allowed or enabled 445. However should another SIM card from another operator or service provider be inserted, the GID will not match the phone's, and so only emergency calls will be allowed. Thus the phone or device 200 enters a restricted service provider mode 445, in which normal or unrestricted wireless communications with only one service provider is allowed - the service provider 250A corresponding to the SIM card and thus the one subsidising the cost of the phone 200.

A count up timer trigger function 450 can be provided, which prevents any further activity associated with the method 400 until the end of the subsidy or service period has been reached. This prevents further generation of security keys for each pseudorandom number generated, as this is battery consumption and computationally expensive. Once the end of the subsidy period has been reached, the counter up timer and trigger step 450 allows movement on to the next method step. This trigger function 450 may simply be implemented by counting the number of pseudorandom numbers provided by the PRNG 415. The method 400 then retrieves the current IMEI and IMSI from the device or phone and SIM card respectively 455. IF a new SIM card has been inserted or for other reasons this predetermined data is different from that gathered when the first SIM card was inserted (430), then the security key or end restricted service provider code generated (Kd2) will be different from the stored security key or start restricted service provider code (KdI); and the device will not be unlocked - the restricted service provider mode will not be deactivated.

A second security key or end restricted service provider code Kd2 is then generated 460, using the predetermined data (455), the same encryption function as used in the first key or start restricted service provider mode deactivation time parameter generation step 435, and the current pseudorandom number or restricted service provider mode deactivation time parameter Kc2 from the PRNG 415. The PRNG 415 is arranged to repeat its sequence of numbers at the end of the service period, and so the pseudorandom number Kc2 (corresponding to the restricted service provider mode deactivation time) provided should be the same as the pseudorandom number KcI (corresponding to the restricted service provider mode activation time) provided for the generation of the first security key or start restricted service provider code KdI. Alternatively, the method may be configured such that one of the following pseudorandom number is the same as KcI, in order to ensure that the device is ready to receive Kc2 and doesn't "miss it" due to some software glitch that holds up gathering of the IMSI or IMEI numbers for example. In another alterative, the service period entered (420) may be much shorter than the actual subsidy period so that the sequence of pseudorandom numbers cycles through a number of times before the count up time trigger is activated. Thus if the appropriate end restricted service provider code Kc2 is missed by the method, it may be only a short period before the pseudorandom numbers (KcI and Kc2) using the restricted service provider mode activation and deactivation times match.

Once the security key generation step 460 has been performed, the generated key Kd2 (the end restricted service provider code) is compared with the stored security key KdI (the start restricted service provider code) generated at the start of the subsidy period 465. If the two keys KdI and Kd2 do not match (465N), then the phone or device remains locked 470. This may then result in a loop back to the security key or end restricted service provider code generation step (460) to try the next PRN. If the two keys KdI and Kd2 match (465Y), then the method reads the access code securely stored on the device 475. A corresponding access code may also be securely stored on the SIM card, and if so this is also read by the method (475).

Assuming the access code(s) provided by the method matches that stored in the pre-programmed restricted service provider lock or mode part

270 of the device 200, the device then unsets a mobile personalisation bit 480, which is provided for all mobile phones and is the setting which enables service provider locking.

This unlocking or deactivating of the restricted service provider mode using the mobile personalisation bit setting enables unrestricted wireless communications with other service providers, for example by inserting corresponding SIM cards. Other mechanisms for deactivating the restricted service provider mode could alternatively be used, as would be understood by those skilled in the art.

From the above, it can be seen that in one embodiment the 103 processor is arranged to generate the start restricted service provider and end restricted service provider codes by applying an encryption function to predetermined data and a pseudorandom number or numbers from the pseudorandom number generator(s) that are seeded by predefined respective restricted service provider mode activation and restricted service provider mode deactivation times. The use of pseudorandom numbers to generate security keys or start and end restricted service provider codes is a simple yet secure way of binding use of the device to a single service provider for a predetermined period of time (the subsidy period); and yet allowing the device to then be unlocked automatically without the transfer of security codes over the insecure air-interface, or user inconvenience. Furthermore not all operators have such OTA functions.

The skilled person will recognise that the above-described device and methods may be embodied as processor control code, for example on a carrier medium such as a disk, CD- or DVD-ROM, programmed memory such as read only memory (Firmware), or on a data carrier such as an optical or electrical signal carrier. For many applications embodiments of the invention will be implemented on a DSP (Digital Signal Processor), ASIC (Application Specific Integrated Circuit) or FPGA (Field Programmable Gate Array). Thus the code may comprise conventional programme code or microcode or, for example code for setting up or controlling an ASIC or FPGA. The code may also comprise code for dynamically configuring re-configurable apparatus such as re-programmable logic gate arrays. Similarly the code may comprise code for a hardware description language such as VHDL (Very high speed integrated circuit Hardware Description Language). As the skilled person will appreciate, the code may be distributed between a plurality of coupled components in communication with one another. Where appropriate, the embodiments may also be implemented using code running on a field- (re)programmable analogue array or similar device in order to configure analogue hardware.

In the foregoing specification, specific a embodiment of the present invention has been described. However, one of ordinary skill in the art appreciates that various modifications and changes can be made without departing from the scope of the present invention as set forth in the claims below. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of present invention. The benefits, advantages, solutions to problems, and any element(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential features or elements of any or all the claims. The invention is defined solely by the appended claims including any amendments made during the pendency of this application and all equivalents of those claims.

Claims

WE CLAIM:

1. A method of operating a wireless communications device, the method comprising: activating a restricted service provider mode in which communications to and from the device are restricted to a predetermined service provider, and generating a start restricted service provider code using a predetermined data and a restricted service provider mode activation time; generating an end restricted service provider code using the predetermined data and a restricted service provider mode deactivation time; and deactivating the restricted service provider mode in response to the end restricted service provider code corresponding to the start restricted service provider code.

2. A method of operating a wireless communications device as claimed in claim 1, wherein the start restricted service provider and end restricted service provider codes are generated by applying an encryption or scrambling function to the predetermined data and a pseudorandom number seeded by respective restricted service provider mode activation and restricted service provider mode deactivation times.

3. A method of operating a wireless communications device as claimed in claim 1, wherein the restricted service provider mode activation and deactivation times are determined from a device clock synchronised with an external wireless communications network clock.

4. A method of operating a wireless communications device as claimed in claim 1, wherein the predetermined data comprises a device identifier and a device user identifier.

5. A method of operating a wireless communications device as claimed in claim 1, wherein the generating an end restricted service provider code step is delayed until the end of a predetermined subscription period starting at the restricted service provider mode activation time.

6. A carrier medium for carrier processor code which when executed on a processor is arranged to carry out the method of claim 1.

7. An electronic device comprising: radio communications circuitry arranged to communicate with a wireless service provider; a processor and memory arranged to activate a restricted service provider mode in which communications to and from the device are restricted to a predetermined service provider, and to generate a start restricted service provider code using a predetermined data and a restricted service provider mode activation time; and the processor and memory further arranged to generate an end restricted service provider code using the predetermined data and a restricted service provider mode deactivation time, and to deactivate the restricted service provider mode in response to the end restricted service provider code corresponding to the start restricted service provider code.

8. An electronic device as claimed in claim 7, further comprising a time based pseudorandom number generator and wherein the processor is arranged to generate the start restricted service provider and end restricted service provider codes by applying an encryption function to the predetermined data and a pseudorandom number from the pseudorandom number generator that is seeded by predefined respective restricted service provider mode activation and restricted service provider mode deactivation times.

9. An electronic device as claimed in claim 7, further comprising a device clock arranged to generate the restricted service provider mode activation and deactivation times, the device clock arranged to synchronise with external wireless communications network timing signals.

10. An electronic device as claimed in claim 7, wherein the device is further arranged to accept a subscriber card comprising at least a part of the predetermined data.

11. A wireless communications device as claimed in claim 7, wherein the processor is further arranged to implement a count up time trigger function arranged to prevent the processor and memory from generating an end restricted service provider code until the end of a predetermined subscription period starting at the restricted service provider mode activation time