Telecommunications – Radiotelephone system – Security or fraud prevention
Reexamination Certificate
1999-03-16
2001-11-20
Maung, Nay (Department: 2681)
Telecommunications
Radiotelephone system
Security or fraud prevention
C455S410000, C455S558000, C455S418000
Reexamination Certificate
active
06321079
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to mobile telephones which operate through a radio network and in particular it relates to a security function for restricting the use of individual mobile telephones to radio networks of selected operators.
2. Description of the Related Art
The mobile telephone for which the invention is provided is a digital radio transceiver programmed to operate under the control of a central processing unit (CPU).
Owing to the variations in pricing policy of network operators, the nominal selling price of mobile telephones is often heavily discounted in favor of a higher call tariff. The possibility exists therefore of a user obtaining at very low or even no cost, a mobile telephone for use on a specified network with a relatively high call tariff. If the mobile telephone were then to be used on a low call tariff network for which the charge for mobile telephones remained at full selling price then both network operators would be deprived of revenue. It is important to network operators therefore that use of mobile telephones be restricted to specified networks.
On GSM (Global System for Mobile communication) networks the restriction of mobile telephones to specified networks is sometimes called ‘network lock’ and this definition of network lock shall be used herein. Network lock for GSM is implemented by ensuring that the mobile telephone will only operate if a SIM (Subscriber Identity Module) belonging to the appropriate network is inserted. The SIM is a smartcard which is attached to the mobile telephone and contains information about the user's subscription (see TS GSM 11.11, ‘Digital Cellular Telecommunications System; Specification of Subscriber Identity Module-Mobile Equipment Interface, published by European Telecommunications Standards Institute).
There is a need for a convenient means to be provided to enable the network operator or the agents of the operator to unlock a mobile telephone, for instance at the end of a service contract. It is preferable that this can be carried out without the participation of the manufacturer. The present method is not conductive to this, since it relies on the administration of secret numbers indexed in accordance with mobile telephone equipment numbers.
SUMMARY OF THE INVENTION
An object of this invention is to facilitate the legitimate unlocking of a telephone mobile telephone from a network and in particular to permit the administration of security codes indexed on SIM card numbers. At the same time it must be very difficult for unauthorized parties to reverse network lock.
According to the invention there is provided a method and means for network operator control of locking and unlocking of a mobile telephone to selected networks, the mobile telephone having a secret number, stored in non volatile memory, and prevision for generating a random number to be used in combination with the secret number stored in the mobile telephone to provide a first function for comparison with a second function generated by the same combination of secret number and random number used to provide said first function.
This invention has two important advantages over the arrangements described in GSM 02.22 (Digital Cellular telecommunications system: personalization of GSM Mobile Equipment, published by European Telecommunications Standards Institute).
Firstly in this invention, the administration of secret numbers is performed on the basis of each SIM and not on the basis of each mobile telephone. Therefore it is convenient for the operator rather than the manufacturer to administer secret numbers, since the operator necessarily maintains a list of SIMs as an essential part of his business (since the SIM contains subscriber information). The operator does not, necessarily, hold a list of mobile telephone serial numbers.
Secondly network locking and unlocking takes place over a standardized interface (the SIM-Mobile Equipment interface), and does not require manual entry or techniques specific to manufacturers.
Mobile telephones may be locked to the network at the time that they are matched with a SIM (which is typically the moment at which they are purchased by the customer and thus attract the operator subsidy). The mobile telephones would then be delivered to the operator or his agent in an unlocked state after the manufacturing process. An unlocked mobile telephone can be used with any network.
Network lock is enforced by embedding a ‘secret’ number into the mobile telephone. Once this number is embedded into the mobile telephone, it will only function with a SIM that has access to this number. This number is embedded in the mobile telephone when the mobile telephone is paired with a SIM.
This secret number can be unique to each SIM-mobile telephone pair, or can be shared by more than one SIM. The secret numbers can be administered by the operator (who in any case has to maintain a record of SIMs), without the need for the manufacturer to be involved. Indeed, the secret number can be pre-programmed into the SIM before it is delivered to the operators agent. Alternatively the secret number can be transmitted to the SIM via the operator's radio network, for example when a call is made after the mobile telephone has been paired with a SIM.
The SIM interface is also used to undo network lock when required. This can be performed by the same SIM that has been paired with the mobile, or any other equipment which connects to the SIM interface with knowledge of the secret number. Unauthorized de-activation of network lock can be protected by whatever security measures the operator deems appropriate, which would typically require knowledge of the ‘secret’ number.
The above and other objects, features and advantages of the present invention will become apparent from the following description with reference to the accompanying drawings which illustrate examples of the present invention.
REFERENCES:
patent: 5668875 (1997-09-01), Brown et al.
patent: 5864757 (1999-01-01), Parker
patent: 5940773 (1999-08-01), Barvesten
patent: 6011976 (2000-01-01), Michaels et al.
Gary Erika A.
Maung Nay
NEC Corporation
Sughrue Mion Zinn Macpeak & Seas, PLLC
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