# Patent

## Title
Field programming of a mobile station with subscriber identification and related information

## Abstract

Apparatuses and methods for field programming a private security key into a mobile station are described herein. The methods may include a server initially accepting in a wireless network a connection from a mobile station that is without a factory programmed subscriber identification module (SIM). The server may then collaborate with the mobile station to field program the mobile station with an international mobile subscriber identification (IMSI) and a private security key (Ki).

## Background
TECHNICAL FIELD
Embodiments of the present invention relate to the field of wireless communication, more specifically, to methods and apparatuses for field provisioning of mobile stations with subscriber identification and related information.
BACKGROUND
In certain types of wireless networks, such as Global System for Mobile Communications (GSM) networks, service providers of such networks use subscriber identity module (SIM) in the form of removable smart card also known as Universal integrated Circuit Card (UICC) in mobile devices to identify and authenticate a subscriber/user. As is well-known, a SIM will typically include various types of information including subscriber identification/credentials, billing relationship, roaming support, and so forth.
Typically, the SIMs are provided directly to the end users by the service providers, and the information endowed in the SIMs are factory programmed. A SIM that is provided to an end user or subscriber will include a subscriber identity known as IMSI (International Mobile Subscriber Module) and a unique 128-bit private security key (known as Ki), programmed into the SIM when the SIM is manufactured. IMSI is used to identify the subscriber to the service provider during initial call establishment. A copy of the pre-programmed Ki is also typically stored at a Home Location Register (HLR) in the service provider network. The Ki is used to calculate the response to the challenges made in the authentication phase, and is also used to create the 64-bit encryption key (Kc) for encryption of user traffic during a call/session.
As briefly described above, a unique Ki is programmed into a SIM card before the SIM card is distributed to a user/subscriber. Since a matching Ki also needs to be programmed in the operator's HLR, the SIM card distributed to the subscriber is operator specific. This creates a challenge in retail distribution model of mobile devices since the purchasers of such devices needs to also have an operator specific SIM in the device before being able to connect to the corresponding network. Ideally, the retail distribution model should allow a device be sold to the end user without any embedded service provider specific image (i.e., service provider programs or data). Further, once a user decides to subscribe to a particular service provider, the device should be able to be provisioned over-the-air with the operator specific image and user credentials.



BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments of the present invention will be readily understood by the following detailed description in conjunction with the accompanying drawings. To facilitate this description, like reference numerals designate like structural elements. Embodiments of the invention are illustrated by way of example and not by way of limitation in the figures of the accompanying drawings.
FIG. 1 illustrates a process for a mobile station and a server to collaboratively field program the mobile station with a private security key (Ki), in accordance with various embodiments of the present invention;
FIG. 2 illustrates a wireless network process that generally corresponds to process of FIG. 1, in accordance with various embodiments of the present invention;
FIG. 3 illustrates an exemplary device designed to communicate in a wireless network, in accordance with various embodiments of the present invention; and
FIG. 4 illustrates an exemplary provisioning server, in accordance with various embodiments of the present invention.



DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS OF THE INVENTION
In the following detailed description, reference is made to the accompanying drawings which form a part hereof wherein like numerals designate like parts throughout, and in which is shown by way of illustration embodiments in which the invention may be practiced. It is to be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the present invention. Therefore, the following detailed description is not to be taken in a limiting sense, and the scope of embodiments in accordance with the present invention is defined by the appended claims and their equivalents.
Various operations may be described as multiple discrete operations in turn, in a manner that may be helpful in understanding embodiments of the present invention; however, the order of description should not be construed to imply that these operations are order dependent.
For the purposes of the instant description, the phrase “A/B” means A or B. For the purposes of the instant description, the phrase “A and/or B” means “(A), (B), or (A and B).” For the purposes of the instant description, the phrase “at least one of A, B and C” means “(A), (B), (C), (A and B), (A and C), (B and C) or (A, B and C).” For the purposes of the instant description, the phrase “(A)B” means “(B) or (AB),” that is, A is an optional element.
The description may use the phrases “in various embodiments,” or “in some embodiments,” which may each refer to one or more of the same or different embodiments. Furthermore, the terms “comprising,” “including,” “having,” and the like, as used with respect to embodiments of the present invention, are synonymous.
According to various embodiment of the present invention, apparatuses and methods are provided that enable a mobile station (MS) of a wireless network, in cooperation or collaboration with a provisioning server (or simply “server”), to field program the MS with at least an IMSI and an associated private key (Ki). For the embodiments, once the IMSI is field programmed into the MS, the IMSI may be used by the MS to identify a subscriber to a wireless service provider whenever the MS attempts to connect to the wireless service provider for wireless service. The Ki that is field programmed into the MS, in contrast, may be for use by the MS to authenticate the subscriber to the wireless service provider when the MS is attempting to establish a connection with the wireless service provider as well as for use by the MS to generate an encryption key (Kc) needed to encrypt communication to be sent from the MS to the wireless service provider after a connection has been established with the wireless network. A mobile station may be any one of a number of mobile devices capable of communicating wirelessly such as a desktop computer, a laptop computer, a handheld computer, a tablet computer, a cellular telephone, a pager, an audio and/or video player (e.g., an MP3 player or a DVD player), a gaming device, a video camera, a digital camera, a navigation device (e.g., a GPS device), a wireless peripheral (e.g., a printer, a scanner, a headset, a keyboard, a mouse, etc.), a medical device (e.g., a heart rate monitor, a blood pressure monitor, etc.), and so forth.
In accordance with various embodiments of the present invention, the MS and the server may use particular equations in order to symmetrically calculate matching security keys (Ki) at the MS and at the provisioning server. The words “symmetrical” or “symmetrically” as used herein is in reference to the ability to identically generate or reproduce the same value at different network devices or locations. By employing such methods, man-in-the middle attacks (in which a third party may intercept a Ki being programmed over the air) may be advantageously avoided, and the MS may be safely and securely field programmed with a Ki. For example, in some embodiments of the present invention, the MS may calculate a Ki using the equation Ki=(GB mod p)A mod P, while the server may symmetrically calculate a copy of the Ki that matches the Ki calculated by the MS using the equation Ki=(GB mod p)A mod P. The variables A, B, G, and P will be described in greater detail below.
FIG. 1 illustrates a process in which a mobile station (MS) of a wireless network, in cooperation with a provisioning server, may be securely field programmed with a Ki in accordance with various embodiments of the present invention. The wireless network may be any one or more of a variety of wireless networks including, for example, a Worldwide Interoperability for Microwave Access (WiMAX) network, a GSM network, a 2G/3G network, and so forth. As will be described, the left side of the process 10 may be performed by the MS, while the right side of the process 10 may be performed by the provisioning server or simply “server.” The process 10, however, may begin when the MS and the server collaboratively establishes a secured and encoded channel between the MS and the server at 12. Note that prior to the establishment of the secured and encoded channel, the MS may be an MS without a factory programmed SIM. Thus, in order to establish the secured and encoded channel, the server may need to accept a connection from the mobile station without a factory programmed SIM. The secured and encoded channel may be established using, for example, Secure Socket Layer/Transport Security (SSL/TLS) security and digital certificate (X.509 key) exchanges and RSA (Ronald L. Rivest, Adi Shamir, and Len M. Adleman) authentication
The server may then send or allocate to the MS, using the secured channel, a security identity and a very large prime number P using the secured channel at 14. The security identity, in some instances, may be an IMSI provided from an IMSI pool comprising of unused and available IMSIs, which the server may maintain or have access to. Alternatively, instead of the server providing the large prime number P, the prime number P may be preprovisioned in the MS, e.g., factory installed in the MS. In either case, the value for the large prime number P may be “known” by both the MS and the server.
The MS may then determine the numerical values for A and G at 16. The value for G may be preprovisioned in the MS or may be derived using the IMSI. Note that since the IMSI may be sent by the server and is, therefore, also available to the server, the server may also be able to identically generate the same value for G. For example, suppose both the MS and the server knows to use the same equation (e.g., G=(IMSI)3+5) to derive the value for G, then so long as both have IMSI, G may be symmetrically determinable at both ends. If the value for G is pre-provisioned in the MS (e.g., factory programmed), then the server may already know the value of G or at least have access to it. Thus, in either case, whether G is determined by the MS using the IMSI or in the case where G is preprovisioned into the MS, the value for G may be symmetrically determinable by both the MS and the server.
With respect to A, the MS may select a large numerical value for A that is greater than the numerical value of G. The MS may randomly select or generate using the digital certificate (X.509 key) a value for A. The MS may then calculate GA mod P based on the previously determined values for G, A, and P at 18. The MS may then send the results of the GA mod P calculation to the server using the secured channel to facilitate the server to symmetrically calculate a matching Ki at 20. Since the Ki symmetrically calculated at the server may be identical to the Ki calculated at the MS, the Ki calculated at the server may be referred to herein as a matching Ki or a copy of the Ki.
Referring now to the right side of the process 10, after the secured and encoded channel has been established at 12, the server may then determine the values for B and G at 22. The value for G may already be known to the server as previously indicated, when for example, the value of G is pre-provisioned in the MS. Alternatively, the value for G may be derived from the IMSI assigned to the MS, which the server may have provided to the MS. With respect to the value for B, the server may select a very large numerical value for B. The server may select a value for B that may be randomly selected or use the digital certificate (X.509) to derive a value for B.
After determining the values for G and B, the server may then calculate GB mod P (recall that the prime number P is known by the server) at 24. The server may then send to the MS the results of the GB mod P calculation. The results of the GB mod P calculation provided by the server (as indicated by the dashing arrow line originating from ref. 26) may then be used by the MS to calculate a value for a Ki using the equation Ki=(GB mod p)A mod P at 28. Correspondingly and symmetrically, the server may calculate, based on the results of the GA mod P calculations received from the MS (as indicated by the dashing arrow line originating from ref. 20) and using the equation Ki=(GA mod p)B mod P, a value for a local copy of the Ki that matches the value of the Ki generated by the MS at 32. The value or the Ki calculated by the MS may then be used and/or saved to a memory device at 30. Similarly, the copy of the Ki generated by the server may be written to HLR/HSS (Home Location Register/Home Subscription Server) at 34.
Referring to FIG. 2 illustrating a wireless network process that generally corresponds to the above described process 10, in accordance with various embodiments of the present invention. The wireless network may be, although not limited to, a WiMAX network. As can be seen, corresponding and matching Ki values may be symmetrically calculated at the MS and at the server by calculating for (GB mod p)A mod P at the MS, and calculating for (GA mod p)B mod P at the server.
To summarize the above, a value for Ki may be symmetrically determined at both the MS and the server by the following equation:

Ki=(GB mod p)A mod P=GA mod p)B mod P,where

    
    
        P=large prime number—may be preprovisioned at the MS or sent to the MS by the server. If preprovisioned at the MS, then server also has access to it.
        A=large number—MS may randomly select it or use its security key (X.509 key) to generate it.
        B=large number—server may randomly select it or use the security key (X.509) key to generate it.
        G=smaller value than A—may be preprovisioned in the MS or derived from the IMSI identically by the MS and the server.
    
    


Thus, the numerical values for the variables A and B may be provided by the MS and server, respectively, while the numerical values for G and P may be symmetrically obtainable by both the MS and the server
FIG. 3 illustrates an exemplary device designed to communicate in a wireless network in accordance with various embodiments of the present invention. For the embodiments, the device 50 may be a mobile station and may include, among other things, one or more processors 52, a storage medium 54, a transceiver 56, and one or more omnidirectional or directional antennas 58, coupled together as shown Additional components not depicted may also be included in the device 50 such as a user interface, input/output (I/O) device, an additional memory device for storing, for example, Ki, and so forth.
The various components of the device 50 may be employed to execute the MS operations previously described in order to enable the device 50 to be field programmed with an IMSI and a Ki. For example, the transceiver 56 using the one or more omnidirectional or directional antennas 58 may be designed to transmit signals over, and receive signals from the wireless network. The storage medium 54, which may be a memory device such as a computer readable storage medium, may store programming instructions to be operated by the one or more processors 52 to enable the device 50 to cooperate with a server of the wireless network and allow the server to field program the device 50 with an IMSI and an associated private key (Ki) as described before. The programming instructions may be further adapted to be operated by the one or more processors 52 to perform the other previously described MS operations (as depicted, e.g., on the left side of FIG. 1) including, for example, sending the results of the GA mod P calculations to the server and calculating (GB mod p)A mod P to obtain the value for Ki.
FIG. 4 illustrates an exemplary provisioning server in accordance with various embodiments of the present invention. For the embodiments, the server 60 may include, among other things, one or more processors 62 and a storage medium 64. The storage medium 64 may be an article of manufacture such as a computer readable storage medium having stored therein a plurality of programming instructions configured to program the server 60 to enable the server 60 to perform the various server operations described earlier. For instance, the programming instructions may program the server 60 to enable the server 60 to collaborate with a mobile station to field program the mobile station with an IMSI and Ki, and to generate a local copy of the Ki that matches the Ki of the mobile station.
The programming instructions may be further adapted to enable the server 60 to perform the other previously described server operations including, for example, accepting a connection from an MS without a factory programmed SIM, sending the results of GB mod P calculation to the MS, and calculating (GA mod p)B mod P to symmetrically calculate a local copy of the Ki that matches the Ki field programmed into the MS as previously described.
Although certain embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a wide variety of alternate and/or equivalent embodiments or implementations calculated to achieve the same purposes may be substituted for the embodiments shown and described without departing from the scope of the present invention. Those with skill in the art will readily appreciate that embodiments in accordance with the present invention may be implemented in a very wide variety of ways. This application is intended to cover any adaptations or variations of the embodiments discussed herein. Therefore, it is manifestly intended that embodiments in accordance with the present invention be limited only by the claims and the equivalents thereof.

## Claims

1. An apparatus, comprising:
a transceiver to transmit signals over, and receive signals from a wireless network;
one or more processors coupled to the transceiver; and a storage medium coupled to the one or more processors, the storage medium having stored therein programming instructions, that when executed by at least one of the one or more processors, enable the apparatus to:
facilitate establishment of a secured wireless communication channel with a server of the wireless network;
cooperate with the server to allow the server to field program, over the secured wireless communication channel, a subscriber identification module (SIM), which has not been factory programmed with a private key (Ki), with an international mobile subscriber identification (IMSI) and the private key (Ki), the IMSI for use by the apparatus to identify a subscriber to a wireless service provider when the apparatus attempts to connect to the wireless service provider for wireless service, and the Ki for use by the apparatus to authenticate the subscriber to the wireless service provider when attempting to establish a connection with the wireless service provider as well as for use by the apparatus to generate an encryption key (Kc) to encrypt communication to be sent from the apparatus to the wireless service provider after a connection has been established; and
receive from the server a prime number (P) over the secured wireless communication channel, the prime number (P) to facilitate calculation of the Ki, wherein the programming instructions, when executed by at least one of the one or more processors, further enable the apparatus to receive from the server results of a GB mod P calculation, and to symmetrically calculate Ki that matches another Ki associated with the server by calculating for (GB mod p)A mod P, where A and B are numerical values to be provided by the apparatus and server, respectively, and G is a numerical value symmetrically determinable by both the apparatus and the server.

2. The apparatus of claim 1, wherein the programming instructions, when executed by at least one of the one or more processors, further enable the apparatus to receive the IMSI from the server.

3. The apparatus of claim 2, wherein the programming instructions, when executed by at least one of the one or more processors, further enable the apparatus to derive a value for G using the IMSI.

4. The apparatus of claim 3, wherein the programming instructions, when executed by at least one of the one or more processors, further enable the apparatus to exchange with the server a digital certificate and select a value for A by randomly selecting a value for A that is greater than G or using the digital certificate to select a value for A that is greater than G.

5. The apparatus of claim 4, wherein the programming instructions, when executed by at least one of the one or more processors, further enable the apparatus to send to the server through the secured wireless communication channel results of a GA mod P calculation to facilitate symmetrical calculation of the other Ki associated with the server.

6. The apparatus of claim 1, wherein the programming instructions, when executed by at least one of the one or more processors, further enable the apparatus to save the Ki into a memory device.

7. A method, comprising:
facilitating, by a server of a wireless network, establishment of a secured wireless communication channel with a mobile station, the mobile station having subscriber identification module (SIM), which has not been factory programmed with a private key (Ki); and
collaborating by the server with the mobile station to field program, over the secured wireless communication channel, the mobile station with an international mobile subscriber identification (IMSI) and the private key (Ki), the IMSI for use by the mobile station to identify a subscriber to a wireless service provider when the mobile station attempts to connect to the wireless service provider for wireless service, and the Ki for use by the mobile station to authenticate the subscriber to the wireless service provider when attempting to establish a connection with the wireless service provider as well as for use by the mobile station to generate an encryption key (Kc) to encrypt communication to be sent from the mobile station to the wireless service provider after a connection has been established;
wherein said collaborating comprises sending, by the server to the mobile station over the secured wireless communication channel, a prime number (P) to facilitate the mobile station in calculating the Ki, selecting, by the server, a value for B and calculating GB mod P, where G is numerical value symmetrically determinable by both the server and the mobile station; and
sending, by the server, the results of the GB mod P calculation to the mobile station to facilitate the mobile station in the calculation of the Ki.

8. The method of claim 7, wherein said collaborating comprises sending, by the server, the IMSI to the mobile station.

9. The method of claim 7, wherein: said facilitating, by the server, establishment of a secured wireless communication channel with the mobile station includes exchanging with the mobile station a digital certificate; and said selecting, by the server, a value for B comprises randomly selecting a value for B or using the digital certificate to generate a value for B.

10. The method of claim 7, further comprising:
receiving, by the server from the mobile station, a quantity GA mod P calculated by the mobile station; and
symmetrically calculating, by the server, a local copy of Ki that matches the Ki calculated by the mobile station, by calculating for (GA mod P)B mod P, where A and B are numerical values provided by the mobile station and server, respectively, and G is a numerical value symmetrically determinable by both the mobile station and the server.

11. The method of claim 10, further comprising deriving, by the server, a value for G using the IMSI.

12. The method of claim 10, wherein:
said facilitating, by the server, establishment of a secured wireless communication channel with the mobile station includes exchanging with the mobile station a digital certificate; and
said selecting, by the server, a value for B comprises randomly selecting a value for B or using the digital certificate to select a value for B.

13. The method of claim 7, further comprising writing, by the server, the Ki to a Home Location Register (HLR).

14. An article of manufacture, comprising:
a storage medium;
a plurality of programming instructions stored in the storage medium that, when executed, enable the apparatus to:
facilitate establishment of a secured wireless communication channel with a mobile station, the mobile station having a subscriber identification module (SIM), which has not been factory programmed with a private key (Ki);
collaborate with the mobile station to field program, over the secured wireless communication channel, the mobile station with an international mobile subscriber identification (IMSI) and the private key (Ki), the IMSI for use by the mobile station to identify a subscriber to a wireless service provider when the mobile station attempts to connect to the wireless service provider for wireless service, and the Ki for use by the mobile station to authenticate the subscriber to the wireless service provider when attempting to establish a connection with the wireless service provider as well as for use by the mobile station to generate an encryption key (Kc) to encrypt communication to be sent from the mobile station to the wireless service provider after a connection has been established,
send a prime number (P) over the secured wireless communication channel to facilitate the mobile station in calculating the Ki,
wherein the plurality of programming instructions, when executed, enable the apparatus to select a value for B and to calculate GB mod P, where G is a numerical value symmetrically determinable by both the apparatus and the mobile station, and to send the results of the GB mod P calculation to the mobile station to facilitate the mobile station in the calculation of the Ki.

15. The article of claim 14, wherein the plurality of programming instructions, when executed, enable the apparatus to receive from the mobile station a quantity GA mod P calculated by the mobile station, and to symmetrically calculate a local copy of Ki that matches the Ki calculated by the mobile station, by calculating for (GA mod P)B mod P, where A and B are numerical values provided by the mobile station and the apparatus, respectively, and G is a numerical value symmetrically determinable by both the mobile station and the apparatus.

16. A system, comprising:
an omnidirectional antenna;

a transceiver coupled to the omnidirectional antenna to transmit signals over, and receive signals from a wireless network;
one or more processors coupled to the transceiver; and
a storage medium coupled to the one or more processors, the storage medium having stored therein programming instructions, that when executed by at least one of the one or more processors, enable the system to:
facilitate establishment of a secured wireless communication channel with a server of the wireless network;

enable the system to cooperate with the server to allow the server to field program, over the secured wireless communication channel, a subscriber identification module (SIM), which has not been factory programmed with a private key (K;), with an international mobile subscriber identification (IMSI) and the private key (K;), the IMSI for use by the system to identify a subscriber to a wireless service provider when the system attempts to connect to the wireless service provider for wireless service, and the K; for use by the system to authenticate the subscriber to the wireless service provider when attempting to establish a connection with the wireless service provider as well as for use by the system to generate an encryption key (Kc) to encrypt communication to be sent from the system to the wireless service provider after a connection has been established;
receive from the server a prime number (P) over the secured wireless communication channel, the prime number (P) to facilitate calculation of the Ki;
wherein the programming instructions, when executed by at least one of the one or more processors, further enable the system to receive from the server results of a GB mod P calculation, and to symmetrically calculate Ki that matches another Ki associated with the server by calculating for (GB mod p)A mod P, where A and B are numerical values to be provided by the system and the server,
respectively, and G is a numerical value symmetrically determinable by both the system and the server.

17. The Apparatus of claim 1, wherein the secured wireless communication channel is established using Secure Socket Layer/Transport Security (SSL/TLS) security.

18. The apparatus of claim 17, wherein the secured wireless communication channel is further established using digital certificate (X.509 key) exchanges and a Rivest-Shamir-Adleman (RSA) authentication.