Wireless subscription portability

Details Wireless subscription portability Wireless subscription portability

2000-09-20

2001-07-10

Peeso, Thomas R. (Department: 2132)

Electrical computers and digital processing systems: support

System access control based on user identification by...

C713S164000, C713S165000

Reexamination Certificate

active

06260147

ABSTRACT:

TECHNICAL FIELD
This invention relates to wireless voice and data systems, and has particular relation to allowing a subscriber to move his subscription from one wireless terminal to another. The invention thus provides subscription portability, sometimes also called personal mobility.
BACKGROUND ART
A wireless terminal (portable telephone, laptop computer, etc.) cannot be used as such unless its user has subscribed to a wireless communications service, so that the terminal may use that service to communicate with other terminals, both wireless and wireline. This in turn requires the service provider to register and provision that terminal, that is, to recognize that terminal as being entitled to service and to program the terminal with identification and security information that allows it to access the wireless service.
In the wireless service industry the term “registration” has several meanings. Herein the term “registration” will be used to mean an exchange of the information needed to establish the identity of the user of a terminal and to permit access to wireless services.
This registration may be required in two situations. First, when the terminal is originally purchased, it is not registered to anyone. This situation is referred to as initial provisioning. Second, a subscriber may choose to re-register, that is, to transfer his subscription from one wireless terminal to another. This re-registration might be, for example, from his portable telephone to his laptop computer, or from his regular portable telephone to the portable telephone which he has just rented on a trip to a distant city. This re-registration is referred to as subscription portability.
In early wireless systems such as the analog Advanced Mobile Phone Systems (AMPS), provisioning is performed manually by trained personnel at a terminal distribution site. One of these employees manually registers the terminal with the service provider, typically over the landline telephone. The employee enters information into the terminal through the keypad, using secret information which the service provider has made available to him/her, and storing the subscription information permanently in the terminal. This arrangement is expensive because the seller must have extensively trained employees at every retail outlet. Furthermore, the process is not secure, since the secret information is readily available to these employees.
One alternative means for dealing with both initial provisioning and subscription portability is to provide to the user a separate, removable device known as a user identification module (UIM). The service provider provisions identity and security information into the UIM before distributing it to the user. When the user inserts the UIM into a terminal, the terminal reads the necessary identity information from the UIM and thereby acquires the identity of the user's subscription. This means is popular in the Global System for Mobiles (GSM) system. Registering the terminal after insertion of the UIM is an over-the-air process, and involves a three-way transfer of information between the module, a base station operated by the service provider (which has a unique identification number), and the wireless terminal itself (which has a unique Electronic Serial Number, or ESN).
This first alternative means is still not entirely satisfactory. It requires an electronic interface between the module and the wireless terminal and this interface adds cost to the terminal. Further, the interface is open to contamination when the UIM is removed and inserted, and consequently may become unreliable with repeated use.
A second alternative means deals with the initial provisioning but not with subscription portability. This second means requires that, when the subscriber first buys a new telephone, the user dials a special number to reach a customer service representative who can determine the credit of the user and can then program the necessary subscription information into the terminal using over the air messages.
This second alternative means is an improvement over the UIM means in that it requires no special interface in the terminal. This second means, however, is also not entirely satisfactory, because the service provider must still have highly skilled personnel in the customer service center to operate the over-the-air programming equipment. The expensive nature of the customer service process prohibits the subscriber from re-registering a telephone which a friend has loaned to him for a day or two.
The purpose of this invention is to provide a method for initial provisioning and subscription portability that does not require skilled personnel to complete the provisioning and registration process, nor a removable item that the user must physically insert into the terminal.
The procedure described herein requires only that the subscriber enter his/her portable wireless subscription identifier, or user identifier (conventionally, his International Mobile User Identifier, or IMUI) and a password (conventionally, his Personal Identification Number, or PIN) into a wireless terminal. The password may be entered into the terminal in any convenient manner, such as keying a number into a keypad, speaking a phrase (with suitable voice recognition technology) into the microphone, or any other convenient manner. The wireless terminal is then able to contact the service provider using over-the-air signals, obtain necessary subscription information, and automatically reprogram itself—and reprogram the service provider—so that the service provider thereafter recognizes this wireless terminal as being registered to this subscriber. The password must be fairly short—typically four to six digits, as in bank card PINs—because the average subscriber cannot memorize a security code that is sufficiently long (twenty digits or more) to impede a brute-force attack.
It is evident that the password must be protected from compromise during the registration process, otherwise the subscription information would be subject to cloning by fraudulent users who obtain the user identifier and password. Recent advances in cryptography, such as the work of Bellovin and Merritt, cited below, provide techniques for securely verifying that the terminal and wireless network both know the correct password without revealing the password. These techniques also provide means for establishing encryption keys that can be used in the encryption of subscription information exchanged subsequent to the initial password confirmation. The existence of these techniques makes it possible to support registration for initial provisioning and subscription portability without need for removable nor for customer service intervention.
BRIEF DISCLOSURE OF THE INVENTION
Applicant has developed a subscription which is truly portable from one wireless terminal to another, and which uses passwords which are both short and secure.
Whenever a subscriber wishes to register a terminal to his subscription, he enters his user identifier (conventionally, his International Mobile User Identifier, or IMUI) and his password (conventionally, his Personal Identiication Number, or PIN) into the terminal. The terminal generates a public/private key pair and stores it. This key pair is preferably a Diffie-Hellman (D-H) key pair. It optionally concatenates the public key with a random number, and encrypts the (optionally concatenated) number with the password. Any convenient Secure Key Exchange (SKE) method may be used. Several suitable SKE methods are described in Thomas Wu,“The Secure Remote Password Protocol,”
Proc.
1998
Internet Society Network and Distributed System Security Symposium
, San Diego, Calif., March 1998, pp. 97-111, http://jafar.stanford.edu/srp
dss.html, and in David P. Jablon, “Strong Password-Only Authenticated Key Exchange,” of Integrity Sciences, Inc., of Westboro, Mass., USA, Mar. 2, 1997, http://world.std.com/~dpj/speke97.html, the disclosures of which are incorporated herein by reference. The Diffie-Hellman Encrypted Key Exchange (DH-EKE) method of

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