Patent Publication Number: US-9906528-B2

Title: Method and apparatus for providing bootstrapping procedures in a communication network

Description:
RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 11/352,058 filed Feb. 10, 2006, entitled “Method and apparatus for providing bootstrapping procedures in a communication network”, which claims the benefit of the earlier filing date under 35 U.S.C. § 119(e) of U.S. Provisional Application Ser. No. 60/652,235 filed Feb. 11, 2005, entitled “Method and Apparatus For Supporting Authentication in a Radio Communication System,” U.S. Provisional Application Ser. No. 60/671,621 filed Apr. 15, 2005, entitled “Method and Apparatus For Bootstrapping in a Radio Communication System,” and U.S. Provisional Application Ser. No. 60/651,620 filed Feb. 11, 2005, entitled “Using GAA in Legacy CDMA Networks”; the entireties of which are incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to communications, and more particularly, to providing authentication services in a communication system. 
     BACKGROUND OF THE INVENTION 
     Radio communication systems, such as cellular systems (e.g., spread spectrum systems (such as Code Division Multiple Access (CDMA) networks), or Time Division Multiple Access (TDMA) networks), provide users with the convenience of mobility along with a rich set of services and features. This convenience has spawned significant adoption by an ever growing number of consumers as an accepted mode of communication for business and personal uses. To promote greater adoption, the telecommunication industry, from manufacturers to service providers, has agreed at great expense and effort to develop standards for communication protocols that underlie the various services and features. One key area of effort involves authentication. Authentication plays an important role in any communication system to ensure that communication is established between proper users or applications. Unfortunately, implementation of such standards may require modification of other protocols, which may be cost prohibitive, even if technically achievable. 
     Therefore, there is a need for an approach to provide authentication services without requiring altering of extant standard protocols or development of new protocols. 
     SUMMARY OF THE INVENTION 
     These and other needs are addressed by the invention, in which an approach is presented for more effectively performing initial authentication (bootstrapping) in a communication network. 
     According to one aspect of an embodiment of the invention, a method for authenticating comprises establishing a key with a terminal in a communication network according to a key agreement protocol, wherein the terminal is configured to operate using spread spectrum. The method also comprises tying the agreed key to an authentication procedure to provide a security association that supports reuse of the key. Further, the method comprises generating a master key based on the agreed key. 
     According to another aspect of an embodiment of the invention, a method for authenticating comprises establishing a shared key with a network element in a communication network according to a key agreement protocol, wherein the network element is configured to tie the agreed key to an authentication procedure to provide a security association that supports reuse of the key. The method also comprises generating a master key based on the agreed key. 
     According to another aspect of an embodiment of the invention, an apparatus for authenticating comprises an authentication module configured to establish a shared key with a network element in a communication network according to a key agreement protocol, wherein the network element is configured to tie the agreed key to an authentication procedure to provide a security association that supports reuse of the key, the authentication module being further configured to generate a master key based on the agreed key. 
     According to another aspect of an embodiment of the invention, a method for authenticating comprises generating a message for authenticating communication with a network element configured to perform bootstrapping. The method also comprises setting a password field of the message to a function of a secret key, wherein the secret key is encrypted; and specifying key establishment information within a payload of the message, wherein the message is transmitted according to a transport protocol for accessing information over a data network. 
     According to another aspect of an embodiment of the invention, a method for authenticating comprises receiving a message from a terminal, according to a transport protocol for accessing information over a data network, requesting authentication, wherein the message includes a password field that is a function of a secret key and a payload containing key establishment information specifying parameters for determining another secret key. The method also comprises generating a master key based on the secret key. 
     According to another aspect of an embodiment of the invention, an apparatus for authenticating comprises an authentication module configured to generate a message for authenticating communication with a network element configured to perform bootstrapping, and to set a password field of the message to be a function of a secret key, wherein the secret key is encrypted. The message has a payload that includes new key establishment information. The message is transmitted according to a transport protocol for accessing information over a data network. 
     According to another aspect of an embodiment of the invention, a method for authenticating comprises receiving an authentication request specifying a user identity from a terminal. The method also comprises forwarding the user identity to a location register configured to generate, based on the user identity, cryptographic parameters including a random secret data, and a secret data generated from the random secret data according to a cryptographic algorithm. Additionally, the method comprises receiving the generated cryptographic parameters from the location register. The method also comprises generating an authentication vector by converting the cryptographic parameters to key parameters including an authenticating token and an authentication response; and transmitting the authenticating token to a terminal configured to output the authentication vector. Further, the method comprises validating an authentication response from the terminal using the authentication response from the authentication vector; and generating a master key based on the key parameters. 
     According to another aspect of an embodiment of the invention, a method for authenticating comprises generating an authentication request specifying a user identity. The method also comprises transmitting the authentication request to a network element configured to provide bootstrapping, wherein the network element forwards the user identity to a location register configured to generate, based on the user identity, cryptographic parameters including a random secret data, and a secret data generated from the random secret data according to a cryptographic algorithm. The network element generates an authentication vector by converting the cryptographic parameters to key parameters including an authenticating token and an authentication response. Additionally, the method comprises receiving the authenticating token from the network element; and outputting the authentication response based on the authenticating token. Further, the method comprises determining a digest response using the authentication response; transmitting the digest response to the network element for validation; and generating a master key based on the key parameters. 
     According to yet another aspect of an embodiment of the invention, an apparatus comprises an authentication module configured to generate an authentication request specifying a user identity. The apparatus also comprises a transceiver configured to transmit the authentication request to a network element configured to provide bootstrapping, wherein the network element forwards the user identity to a location register configured to generate, based on the user identity, cryptographic parameters including a random secret data, and a secret data generated from the random secret data according to a cryptographic algorithm. The network element generates an authentication vector by converting the cryptographic parameters to key parameters including an authenticating token and an authentication response. The transceiver is further configured to receive the authenticating token from the network element, and the authentication module is further configured to output the authentication vector based on the authenticating token, to determine a digest response using the authentication response, and to generate a master key based on the key parameters upon validation of the digest response by the network element. 
     Still other aspects, features, and advantages of the invention are readily apparent from the following detailed description, simply by illustrating a number of particular embodiments and implementations, including the best mode contemplated for carrying out the invention. The invention is also capable of other and different embodiments, and its several details can be modified in various obvious respects, all without departing from the spirit and scope of the invention. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings in which like reference numerals refer to similar elements and in which: 
         FIG. 1  is a diagram of a radio communication system for supporting a Generic Authentication Architecture (GAA), in accordance with various embodiments of the invention; 
         FIG. 2  is a diagram of an exemplary bootstrapping procedure utilized in the system of  FIG. 1 ; 
         FIG. 3  is a diagram of a bootstrapping procedure utilizing anonymous Transport Layer Security (TLS) with Challenge Handshake Authentication Protocol (CHAP) challenge, according to an embodiment of the invention; 
         FIG. 4  is a diagram of a bootstrapping procedure utilizing server authenticated TLS with CHAP challenge, according to an embodiment of the invention; 
         FIGS. 5 and 6  are diagrams of bootstrapping procedures supporting key exchange parameters in the payload, according to various embodiments of the invention; 
         FIGS. 7 and 8  are diagrams of bootstrapping procedures supporting key exchange parameters that are covered by the hash of the passwords, according to various embodiments of the invention; 
         FIG. 9  is a diagram of a bootstrapping procedure utilizing Cellular Authentication and Voice Encryption (CAVE) with one shared secret data (SSD), according to an embodiment of the invention; 
         FIGS. 10A and 10B  are diagrams of a bootstrapping procedure utilizing CAVE with multiple SSDs, according to an embodiment of the invention; 
         FIG. 11  is a diagram of a bootstrapping procedure utilizing CAVE with HTTP Digest Authentication and Key Agreement Protocol (AKA), according to an embodiment of the invention; 
         FIG. 12  is a diagram of hardware that can be used to implement various embodiments of the invention; 
         FIGS. 13A and 13B  are diagrams of different cellular mobile phone systems capable of supporting various embodiments of the invention; 
         FIG. 14  is a diagram of exemplary components of a mobile station capable of operating in the systems of  FIGS. 13A and 13B , according to an embodiment of the invention; and 
         FIG. 15  is a diagram of an enterprise network capable of supporting the processes described herein, according to an embodiment of the invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     An apparatus, method, and software for providing bootstrapping in a communication system are described. In the following description, for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the invention. It is apparent, however, to one skilled in the art that the invention may be practiced without these specific details or with an equivalent arrangement. In other instances, well-known structures and devices are shown in block diagram form in order to avoid unnecessarily obscuring the invention. 
       FIG. 1  is a diagram of a radio communication system for supporting a Generic Authentication Architecture (GAA), in accordance with various embodiments of the invention. Although the invention is discussed with respect to a radio communication system using spread spectrum technology, it is recognized by one of ordinary skill in the art that various aspects of the invention have applicability to any type of transport network, including wireless systems and wired systems. Also, various embodiments of the invention are described with respect to Diffie-Hellman and HyperText Transfer Protocol (HTTP); however, it is contemplated that other equivalent key exchange protocols and communication protocols that support transfer of representation of resources can be used in practicing the invention. 
     Initial authentication (i.e., bootstrapping) of Third Generation Project Partnership (3GPP) Generic Authentication Architecture (GAA) is based on AKA (Authentication and Key Agreement Protocol). Typically, authentication in CDMA 2000 (Code Division Multiple Access 2000) networks is based on CAVE (Cellular Authentication and Voice Encryption) algorithm, while authentication in CDMA 1× EvDo (Evolution Data only) is based on CHAP (Challenge Handshake Authentication Protocol). For CDMA networks (e.g., CDMA 2000 1× Revision C and subsequent revisions), AKA has been adopted by the Third Generation Project Partnership 2 (3GPP2). 
     Communication system  100  includes one or more mobile stations (MSs)  101  configured to communicate with one or more base station transceiver subsystems (BTSs)  103 . The BTSs  103 , in turn, is served by a base station controller (BSC)  105 , which operates with a network element capable providing a Bootstrapping Server Function (BSF)  107 . The system  100  also includes a Mobile Node Authentication, Authorization and Accounting Service (MN-AAA)  109 , which communicates with a Packet Data Serving Node (PDSN)  111 . 
     The system  100 , according to one embodiment, provides 3GPP generic authentication architecture functionality in CDMA Ev-Do networks. In particular, a bootstrapping mechanism entails establishing a GAA master secret between an MS  101  and the BSF  107 . This master secret, in an exemplary embodiment, is tied to the Challenge Handshake Authentication Protocol (CHAP) based authentication procedure. According to one embodiment of the invention, one such key agreement (i.e., key exchange) method is Diffie-Hellman. This method is further described in Internet Engineering Task Force (IETF) Request For Comment (RFC) 2631, which is incorporated herein by reference in its entirety. 
     In CDMA 1× EvDo networks, for example, the MS  101  is authenticated using CHAP, which is specified in IETF RFC 1994 (which is incorporated herein by reference in its entirety). In the defined CHAP procedure, the network element, PDSN  111 , sends a challenge to the MS  101 , which calculates a response based on the received challenge and a subscriber specific secret that is stored in the  101  MS. The response is sent back to the PDSN  111  together with the subscriber identity. The PDSN  111  forwards the received response and the identity together with the challenge that the PDSN  111  earlier sent to the MS  101  to the MN-AAA  109 . 
     The MN-AAA  109  locates the subscriber specific secret using the identity and verifies that the response sent by the MS  101  equals the response value that the MN-AAA  109  calculated. Depending on the outcome of this verification, the MN-AAA  109  returns either success or failure indication to the PDSN  111 . If the PDSN  111  receives a success message, the MS  101  has successfully been authenticated. 
     It is recognized that the authentication procedure used in CDMA 1× EvDo networks cannot be used directly for GAA because the secret is only known by the MS and the MN-AAA (analogous to Home Subscriber System (HSS) in GAA). Hence, the Bootstrapping Server Function (BSF) (which acts like a PDSN) cannot derive a GAA master key from this CHAP secret as the MN-AAA (analogous to Home Subscriber System (HSS) in GAA architecture) does not provide this secret. 
     According to an exemplary embodiment, after the key has been agreed between the MS  101  and the BSF  107 , the BSF  107  ties the key agreement procedure to the CHAP authentication by deriving the CHAP challenge from the key agreement procedure. A number of approaches can be utilized, according to various embodiments of the invention, to tie the key agreement procedure to CHAP. First, the BSF  107  may derive the challenge from the agreed key. Second, the BSF  107  also derives the challenge from the key agreement messages that were transferred between the BSF  107  and the MS  101 . Third, for example, if a Diffie-Hellman key agreement was performed during a Transport Layer Security (TLS) handshake, then the Finished message can be used to derive the challenge, as the Finished message already contains the Message Authentication Code (MAC) of the TLS handshake messages. 
     When the MS  101  receives the CHAP challenge, the MS  101  validates that the challenge was in deed derived from the key agreement procedure to prevent the man-in-the-middle attack. The MS  101  then calculates a CHAP response and sends the response back to the BSF  107 , which in turn validates the response with the MN-AAA  109 . If the MN-AAA  109  indicates that the CHAP response is correct, then the BSF  107  has authenticated the MS  101 , and the GAA master secret has been established. The GAA master secret can be the agreed key itself, or further derived from that key. 
     Alternatively, to establish the secret between the MS  101  and the BSF  107 , another approach, according to an embodiment of the invention, utilizes a server authenticated transport layer security (TLS) where the BSF is authenticated using a server certificate. In this case, the CHAP challenge does not need to be tied to the master secret as above as the BSF  107  is already authenticated. In these cases (both the original point-to-point protocol (PPP) CHAP authentication and the described GAA related procedures), the MS  101  does not answer to the CHAP challenge if the server (i.e., PDSN  111  or BSF  107 ) has not been authenticated; otherwise, there is a possibility for a man-in-the-middle attack. 
     The invention, according to one embodiment, provides a mechanism to agree on a master secret between the MS  101  and the network server (BSF  107 ), which is bound to authentication of the MS  101  to a backend server (e.g., MN-AAA  109 ). This approach advantageously can be performed such that the backend server is unmodified, while utilizing standardized protocols. 
     Conventional approaches do not support bootstrapping from CHAP authentication in such a way that the resulting security association can be reused with multiple servers, as performed in GAA. One such technique is the Diffie-Hellman-Challenge Handshake Authentication Protocol (DH-CHAP), which describes a specific mechanism to bind CHAP authentication to Diffie-Hellman key agreement by adding new information elements to the CHAP protocol messages between the CHAP initiator and responder (i.e., requiring modification of CHAP). 
     It is assumed, in an exemplary embodiment, that the original PPP CHAP authentication procedure in CDMA 1× EvDo networks has a mechanism to prevent an unauthorized server from sending a CHAP challenge to the MS  101  and receiving a response. Without this mechanism, there is a possibility for a man-in-the-middle attack where the attacker initiates communications with the BSF  107  pretending to be the MS  101 . At the point where the attacker receives the challenge from the BSF  107 , the attacker can forward the challenge to the real MS  101 , thereby pretending to be the PDSN  111 . The MS  101  would calculate the response and send it back to the attacker, who in turn would send it to the BSF  107 . If this is successful, the attacker has successfully created a bootstrapping session and can use the GAA credentials with any Network Application Function (NAF). 
       FIG. 2  is a diagram of an exemplary bootstrapping procedure utilized in the system of  FIG. 1 . Although one user equipment (UE) is shown for the purposes of explanation, it is contemplated that multiple UEs are typically employed. The UEs can also be denoted as mobile devices (e.g., mobile telephone), mobile stations, and mobile communications devices. The UE can also be such devices as personal digital assistants (PDA) with transceiver capability or personal computers with transceiver capability. 
     In step  201 , an UE, such as MS  101 , sends a HTTP Digest message, GET/HTTP/1.1 Authorization: Digest username=“&lt;IMPI&gt;,” to the BSF  107 . In response, the BSF  107 , as in step  203 , sends a 401 Unauthorized message. Next, in step  205 , the UE sends a message that includes a part that is calculated using shared information as a shared password (e.g., response=“&lt;RES used as pwd&gt;”) back to the BSF  107 . Thereafter, the BSF  107  submits, as in step  207 , a  200  OK message, which specifies bootstrapping information. 
     After the bootstrapping procedure both, the MS  101  (e.g., UE) and the BSF  107  have agreed on the key material (Ks), a bootstrapping transaction identifier (B-TID), a key material lifetime. After the bootstrapping procedure, the key material (Ks) can be used to derive further application server specific key materials (Ks_NAFs) that can be used with different servers. Ks_NAF and B-TID may be used in a Ua interface to mutually authenticate and optionally secure traffic between the UE and an application server (i.e., Network Application Function (NAF)). By way of example, the Ks is a 256 b GAA shared secret (in 3GPP GAA Ks=CK∥IK). The NAF can be an application server that uses GAA for user authentication. 
     The bootstrapping procedure (i.e., Ub interface) is defined in 3GPP TS 33.220, entitled “Generic Authentication Architecture (GAA); Generic Bootstrapping Architecture,” and TS 24.109, “Bootstrapping Interface (Ub) and Network Application Function Interface (Ua); Protocol Details”; the entireties of which are incorporated herein by reference. 
       FIG. 3  is a diagram of a bootstrapping procedure utilizing anonymous TLS with CHAP challenge, according to an embodiment of the invention. Under this scenario, the reference points, Ub and Zh are involved, whereby Ub provides mutual authentication between the MS  101  and the BSF  107 , and the Zh supports the exchange of authentication information between the BSF  107  and the MN-AAA  109 . As discussed, traditionally the BSF  107  does not have knowledge of the CHAP secret, as only the MS  101  and the MN-AAA  109  possess such information. The PDSN  111  merely sends the CHAP-Challenge to the MN-AAA  109 , and the MN-AAA  109  returns an identity and a CHAP-response which is computed using the CHAP-challenge and the CHAP secret. MN-AAA  109  can check the CHAP-response and determine either success or failure. Thus, agreement of the GAA secret between the MS  101  and the BSF  107  has to be arrived at by other means. In one embodiment of the invention, the GAA secret is established by means of an unauthenticated key agreement procedure, and the CHAP authentication is tied to the GAA secret by deriving the CHAP challenge from GAA secret, and the MS  101  checks that the GAA secret was used to derive the CHAP challenge. 
     In this example, the MS  101  includes a security (SEC) module to execute the CHAP protocol and a GAA module to support GAA functionalities. In step  301 , the MS  101  employs anonymous TLS with a key exchange algorithm, such as Diffie-Hellman, to establish the GAA secret (denoted as “key”) with the BSF  107 . CHAP can then be run inside the TLS tunnel. Accordingly, in step  303 , the BSF  107  generates a CHAP challenge from the agreed key: Challenge=KDF (key, “chap-challenge”). The key derivation function (KDF), in an exemplary embodiment, is provided according to the GAA. 
     The generic key derivation function, according to the GAA (TS 33.220), is now described. First, a string S is generated by concatenating the input parameters and associated lengths as follows. The length of each input parameter (in octets) is encoded into two-octet string. The number of octets is expressed in input parameter Pi as a number k in the range [0, 65535]. Li is a two-octet representation of the number k, with the most significant bit of the first octet of Li equal to the most significant bit of k, and the least significant bit of the second octet of Li equal to the least significant bit of k. 
     The string S is constructed from n input parameters as follows: 
     S=FC∥P 0 ∥L 0 ∥P 1 ∥L 1 ∥P 2 ∥L 2 ∥P 3 ∥L 3 ∥ . . . ∥Pn∥Ln 
     where 
     FC is single octet used to distinguish between different instances of the algorithm, 
     P 0  is a static ASCII-encoded string, 
     L 0  is the two octet representation of the length of the P 0 , 
     P 1 . . . Pn are the n input parameters, and 
     L 1  . . . Ln are the two-octet representations of the corresponding input parameters. 
     The derived key is equal to HMAC-SHA-256 computed on the string S using the key Key: derived key=HMAC-SHA-256 (Key, S). 
     The CHAP challenge message is then transmitted by the BSF  107  inside the TLS tunnel, as in step  305 , to the GAA module of the MS  101 . In step  307 , the GAA module verifies the received CHAP challenge is generated from the agreed key. The CHAP challenge message is then forwarded to the SEC module, per step  309 . Next, the SEC module calculates the CHAP response, as in step  311 , and transmits the response to the GAA module (step  313 ). The MS  101  then sends, as in step  315 , the CHAP response over the TLS tunnel to the BSF  107 . 
     Thereafter, in step  317 , the BSF  107  sends a Request message according to an authentication protocol (e.g., Remote Authentication Dial In User Service (RADIUS) Access-Request message) to the MN-AAA  109 . RADIUS is detailed in Internet Engineering Task Force (IETF) Request For Comment (RFC) 2865 entitled “Remote Authentication Dial In User Service (RADIUS)” (June 2000), which is incorporated herein by reference in its entirety. The Request message specifies a user (or subscriber) identity, challenge and response. The MN-AAA  109  checks the response, per step  319 , and sends a RADIUS Access-Answer message (including the identity) to the BSF  107  (step  321 ). At this point, the BSF  107  fetches the user&#39;s GBA user security settings (GUS S), as in step  323 . GUSS is a GAA specific user profile data that is related to NAF specific user identities and authorizations stored in the home location register (HLR). GUSS includes BSF  107  specific information element and application-specific user security settings (USSs). In an exemplary embodiment, a USS defines an application and subscriber specific parameter; such parameter includes an authentication part and an authorization part. The authentication part specifies user identities associated with the application, while the authorization part defines user permissions. 
     Further, the BSF  107  sets the GAA master key (Ks=key), generates various bootstrapping parameters (e.g., bootstrapping transaction identifier (B-TID), key material lifetime, etc.), and stores the data from the MN-AAA  109 , per step  325 . Next, the BSF  107 , as in step  327 , sends an OK message over the TLS tunnel; the transmitted message includes, e.g., the B-TID and the key material lifetime. In step  329 , the GAA module sets the GAA master key: Ks=key, and stores the key with the received B-TID and key material lifetime. The MS  101  then sends a message to the BSF  107  to close the TLS tunnel, per step  331 . 
     With the above process, the system of  FIG. 1  provides GAA bootstrapping, such that the MS  101  and the BSF  107  are able to agree on a key, and that key is tied to the CHAP authentication procedure. Compared to Diffie-Hellman (DH)-CHAP, the approach adopted by the system of  FIG. 1  does not require any changes to protocol messages that are already standardized, and can be implemented by appropriate “hook” functions in MS  101  and BSF  107 . Also, DH-CHAP describes one specific way of binding CHAP authentication to D-H key: derive the challenge from the agreed key. The invention, according to various embodiments, provides other methods of indirectly binding the outer key to the inner authentication. 
       FIG. 4  is a diagram of a bootstrapping procedure supporting server authenticated TLS with CHAP challenge, according to an embodiment of the invention. In this alternative embodiment, a server authenticated TLS is used to establish the GAA secret between the MS  101  and the BSF  107 , wherein CHAP is employed inside the TLS tunnel. Specifically, in step  401 , the MS  101  establishes a server authenticated TLS tunnel with the BSF  107 . As before, the TLS key is denoted by ‘key’. Next, in step  403 , the BSF  107  generates a CHAP challenge—which need not be generated from the server authenticated TLS key. The CHAP challenge message is then transmitted by the BSF  107  inside the TLS tunnel, as in step  405 , to the GAA module of the MS  101 . 
     The GAA module then forwards the CHAP challenge to the SEC module, per step  407 . Subsequently, the SEC module calculates the CHAP response, as in step  409 , and transmits the response to the GAA module (step  411 ). The MS  101  then sends the CHAP response over the TLS tunnel to the BSF  107 , per step  413 . 
     In step  415 , the BSF  107  sends a RADIUS Access-Request message to the MN-AAA  109 ; the Request message specifies the identity, challenge and response. The MN-AAA  109  checks the response, per step  417 , and sends a RADIUS Access-Answer message (including the identity) to the BSF  107  (step  419 ). At this point, the BSF  107  fetches the user&#39;s GUSS, as in step  421 . Additionally, the BSF  107  sets the GAA master key (Ks=key), generates various bootstrapping parameters (e.g., bootstrapping transaction identifier (B-TID), key material lifetime, etc.), and stores the data from the MN-AAA  109 , per step  423 . 
     Next, the BSF  107 , as in step  425 , sends an OK message over the TLS tunnel. The transmitted message includes the bootstrapping parameters, e.g., the B-TID and the key material lifetime. In step  427 , the GAA module sets the GAA master key: Ks=key, and stores the key with the received B-TID and key material lifetime. The MS  101  then sends a message to the BSF  107  to close TLS tunnel, per step  429 . 
       FIGS. 5 and 6  are diagrams of bootstrapping procedures supporting key exchange parameters (or key establishment information) in the payload, according to various embodiments of the invention. It is recognized that no conventional approaches exist for providing password protected Diffie-Hellman (i.e., key exchange protocol) within the HyperText Transfer Protocol (HTTP). The processes of  FIGS. 5 and 6  enable use of HTTP Digest and Diffie-Hellman parameters together to provide password protected Diffie-Hellman for use in bootstrapping (e.g., as in the 3GPP2 architecture). That is, approaches are provided for usage of HTTP Digest with password (i.e., shared secret), and the key exchange protocol (e.g., Diffie-Hellman) parameters in HTTP payload and for binding the two together. The password field is set to be a function of the secret key. 
     In accordance with one embodiment of the invention, a HTTP Digest message uses Signaling Message Encryption Key (SMEKEY) or MN-AAA key as a password and mobile identity as the username; the Diffie-Hellman parameters are provided in the HTTP payload. Diffie-Hellman exchange is protected by the password because the quality-of-protection “qop” field in HTTP Digest is set to “auth-int”; consequently, the HTTP payload is included in the digest calculation. In the HTTP payload, the Diffie-Hellman parameters can be transferred as is; alternatively, the HTTP payload can be provided with password protection. This approach advantageously permits existing specifications (e.g., HTTP Digest) to be reused. Also, the approach resembles 3GPP GAA functionality (e.g., HTTP Digest Authentication and Key Agreement Protocol (AKA), Ub interface). Further, the approach, according to various embodiments, can be easily implemented without modifying existing, standardized protocols. 
     The 3GPP GAA may be used without modification to current CDMA 2000 networks. It is recognized, however, that the initial authentication of 3GPP GAA requires adaptation for networks that are based on earlier 3GPP2 releases or in networks that do not support AKA and hence are only adapted for CAVE. Accordingly, a system architecture and process are needed to accommodate CAVE. The system  100 , according to various embodiments, employs conversion functions to map 3GPP2 CAVE authentication to HTTP Digest AKA; this approach is particularly applicable to pre-CDMA 2000 Rev. C systems. 
     HTTP Digest Authentication enables a client to authenticate itself with the server without having to transmit the password in the clear. This can be accomplished by utilizing a “one-way” function or irreversible computation using the password and a random value supplied by the server as input values. HTTP Digest Authentication in the context of AKA is detailed in IETF (Internet Engineering Task Force) Request for Comment (RFC) 3310, entitled “Hypertext Transfer Protocol (HTTP) Digest Authentication Using Authentication and Key Agreement (AKA),” which is incorporated herein by reference in its entirety. 
     For the purposes of illustration, the bootstrapping procedures of  FIGS. 5 and 6  are described with respect to CDMA 1× networks and CDMA 1× EvDo networks, respectively. In an exemplary embodiment, these bootstrapping procedures are based on X.P0028; in which a key difference with X.P0028 is that HTTP Digest variant is used instead of Extensible Authentication Protocol (EAP) between terminal and BSF  107  (which can be considered a Home (H)-AAA). Additionally, password protected Diffie-Hellman can be used. The password (i.e., shared secret) is either Signaling Message Encryption Key (SMEKEY) (CDMA 1×) or MN-AAA Key (CDMA 1× EvDo). A wireless LAN (WLAN) key (WKEY) is generated from the password (which is detailed in X.P0028). Additionally, WKEY is the GAA&#39;s master key (Ks). HTTP Digest is used (as shown in  FIGS. 5 and 6 ). The invention, according various embodiments, describes how CAVE and CHAP can be used in a 3GPP GAA architecture for initial authentication. 
     As shown in  FIG. 5 , a terminal (e.g., mobile station) includes a CAVE module configured to execute the CAVE protocol. Additionally, GAA functionalities are supported by a GAA module. In step  501 , the GAA module generates a HTTP Get message, which is sent to the BSF  107 ; the identity is sent in the first message in the “username” field. This authorization request message, in an exemplary embodiment, includes the fields specified in Table 1, below: 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
             
            
               
                   
                 credentials 
                  = “Digest” digest-response 
               
               
                   
                 digest-response 
                 = 1#( username | realm | nonce | digest-uri 
               
               
                   
                   
                  | response | [ algorithm ] | [cnonce] | 
               
               
                   
                   
                  [opaque] | [message-qop] | 
               
               
                   
                   
                  [nonce-count] | [auth-param] ) 
               
               
                   
                 username 
                  = “username” “=” username-value 
               
               
                   
                 username-value 
                  = quoted-string 
               
               
                   
                 digest-uri 
                  = “uri” “=” digest-uri-value 
               
               
                   
                 digest-uri-value 
                  = request-uri  ; As specified by HTTP/1.1 
               
               
                   
                 message-qop 
                 = “qop” “=” qop-value 
               
               
                   
                 cnonce 
                  = “cnonce” “=” cnonce-value 
               
               
                   
                 cnonce-value 
                  = nonce-value 
               
               
                   
                 nonce-count 
                  = “nc” “=” nc-value 
               
               
                   
                 nc-value 
                  = 8LHEX 
               
               
                   
                 response 
                  = “response” “=” request-digest 
               
               
                   
                 request-digest 
                  = &lt;“&gt; 32LHEX &lt;”&gt; 
               
               
                   
                 LHEX 
                  = “0” | “1” | “2” | “3” | 
               
               
                   
                   
                   “4” | “5” | “6” | “7” | 
               
               
                   
                   
                   “8” | “9” | “a” | “b” | 
               
               
                   
                   
                   “c” | “d” | “e” | “f” 
               
               
                   
                   
               
            
           
         
       
     
     Some of the directives in Table 1 are defined in Table 2: 
     
       
         
           
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                 Directive 
                 Description 
               
               
                   
               
             
            
               
                 response 
                 A string of 32 hex digits to provide proof that the user 
               
               
                   
                 knows the password 
               
               
                 username 
                 The user&#39;s name in the specified realm 
               
               
                 digest-uri 
                 The URI from Request-URI of the Request-Line 
               
               
                 qop 
                 Indicates type of “quality of protection” applied to the 
               
               
                   
                 message 
               
               
                 cnonce 
                 This is specified if a qop directive is sent. The 
               
               
                   
                 cnonce-value is an opaque quoted string value 
               
               
                   
                 provided by the client and used by both client and 
               
               
                   
                 server to avoid chosen plaintext attacks, to provide 
               
               
                   
                 mutual authentication, and to provide some message 
               
               
                   
                 integrity protection. 
               
               
                 nonce-count 
                 This is specified if a qop directive is sent. The nc- 
               
               
                   
                 value is the hexadecimal count of the number of 
               
               
                   
                 requests (including the current request) that the client 
               
               
                   
                 has sent with the nonce value in this request. For 
               
               
                   
                 example, in the first request sent in response to a given 
               
               
                   
                 nonce value, the client sends “nc = 00000001”. The 
               
               
                   
                 purpose of this directive is to allow the server to detect 
               
               
                   
                 request replays by maintaining its own copy of this 
               
               
                   
                 count - if the same nc-value is seen twice, then the 
               
               
                   
                 request is a replay. 
               
               
                 auth-param 
                 This directive allows for future extensions. Any 
               
               
                   
                 unrecognized directive is ignored. 
               
               
                   
               
            
           
         
       
     
     The BSF  107  then generates the RAND, as in step  503 , and responds with a  401  Not Authorized message (step  505 ). Initially, no authorization header is sent to the BSF  107 , and thus, the  401  message is utilized as a response. As shown, the RAND is sent in the “nonce” field (similar to HTTP Digest AKA). RAND and CHAP-Challenge can also be sent in the HTTP payload. Upon receiving the RAND, the GAA module forwards it to the CAVE module, as in step  507 . 
     By way of example, an Authenticate Response Header is provided in Table 3; the associated directives are defined in Table 4. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 3 
               
               
                   
                   
               
             
            
               
                   
                 challenge 
                  = “Digest” digest-challenge 
               
               
                   
                 digest-challenge 
                  = 1#( realm | [ domain ] | nonce | 
               
               
                   
                   
                  [ opaque ] |[ stale ] | [ algorithm ] | 
               
               
                   
                   
                  [ qop-options ] | [auth-param] ) 
               
               
                   
                 domain 
                  = “domain” “=” &lt;“&gt; URI ( 1*SP URI ) &lt;”&gt; 
               
               
                   
                 URI 
                  = absoluteURI | abs_path 
               
               
                   
                 nonce 
                 = “nonce” “=” nonce-value 
               
               
                   
                 nonce-value 
                 = quoted-string 
               
               
                   
                 opaque 
                 = “opaque” “=” quoted-string 
               
               
                   
                 stale 
                 = “stale” “=” ( “true” | “false” ) 
               
               
                   
                 algorithm 
                 = “algorithm” “=” ( “MD5” | “MD5-sess” | 
               
               
                   
                   
                  token ) 
               
               
                   
                 qop-options 
                  = “qop” “=” &lt;“&gt; 1#qop-value &lt;”&gt; 
               
               
                   
                 qop-value 
                  = “auth” | “auth-int” | token 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
             
               
                   
                 TABLE 4 
               
               
                   
                   
               
               
                   
                 Directive 
                 Description 
               
               
                   
                   
               
             
            
               
                   
                 realm 
                 A string to be displayed to users so they know which 
               
               
                   
                   
                 username and password to use. This string can include 
               
               
                   
                   
                 the name of the host performing the authentication and 
               
               
                   
                   
                 the users who might have access. 
               
               
                   
                 domain 
                 A quoted, space-separated list of URIs that define the 
               
               
                   
                   
                 protection space. The client can use this list to 
               
               
                   
                   
                 determine the set of URIs for which the same 
               
               
                   
                   
                 authentication information may be sent: any URI that 
               
               
                   
                   
                 has a URI in this list as a prefix (after both have been 
               
               
                   
                   
                 made absolute) may be assumed to be in the same 
               
               
                   
                   
                 protection space. If this directive is omitted or its 
               
               
                   
                   
                 value is empty, the client is to assume that the 
               
               
                   
                   
                 protection space includes all URIs on the responding 
               
               
                   
                   
                 server. 
               
               
                   
                 nonce 
                 A server-specified data string that can be uniquely 
               
               
                   
                   
                 generated each time a 401 response is made. 
               
               
                   
                 opaque 
                 A string of data, specified by the server, which can be 
               
               
                   
                   
                 returned by the client unchanged in the Authorization 
               
               
                   
                   
                 header of subsequent requests with URIs in the same 
               
               
                   
                   
                 protection space. 
               
               
                   
                 stale 
                 A flag, indicating that the previous request from the 
               
               
                   
                   
                 client was rejected because the nonce value was stale. 
               
               
                   
                   
                 If stale is TRUE (case-insensitive), the client can retry 
               
               
                   
                   
                 the request with a new encrypted response, without 
               
               
                   
                   
                 reprompting the user for a new username and 
               
               
                   
                   
                 password. The server should only set stale to TRUE if 
               
               
                   
                   
                 it receives a request for which the nonce is invalid but 
               
               
                   
                   
                 with a valid digest for that nonce (indicating that the 
               
               
                   
                   
                 client knows the correct username/password). If stale 
               
               
                   
                   
                 is FALSE, or anything other than TRUE, or the stale 
               
               
                   
                   
                 directive is not present, the username and/or password 
               
               
                   
                   
                 are invalid, and new values are obtained. 
               
               
                   
                 algorithm 
                 A string indicating a pair of algorithms used to 
               
               
                   
                   
                 produce the digest and a checksum. 
               
               
                   
                   
               
            
           
         
       
     
     In step  509 , the CAVE module sends the Authentication Response (denoted “AUTHR”) and SMEKEY to the GAA module. The GAA module then, as in step  511 , sets the mobile station password (MS_PW): MS_PW=SMEKEY H 1 ′(MS_PW)·g x  mod p, where x is the secret random number generated by the UE. 
     Next, the GAA module sends, per step  513 , an HTTP message with a payload that includes the client Diffie-Hellman parameters to the BSF  107 . With CAVE, the HTTP payload also contains the AUTHR. The payload is protected by HTTP Digest because qop=auth-int; also HTTP payload is included in HTTP Digest calculation of “response” field. The Diffie-Hellman parameters can be sent as is or can be protected. In step  515 , the BSF  107  transmits an Authentication Request (“AUTHREQ”) message (including AUTHR and RAND) to the home location register/authentication center (HLR/AC), which verifies the RAND/AUTHR and generates the SMEKEY (step  517 ). The SMEKEY is sent to the BSF  107 , per step  519 . 
     The BSF  107 , as in step  521 , sets the base station password: BS_PW=SMEKEY H 1 ′(BS_PW)·g y  mod p, where y is the secret random number generated by the BSF. Subsequently, the BSF  107  generates the GAA master key (Ks) from the BS_PW (in a similar manner to that of WKEY). 
     Next, the BSF  107  then sends an HTTP  200  OK message to the terminal, per step  525 . The server Diffie-Hellman parameters are sent in the HTTP payload, protected by HTTP Digest because qop=auth-int (i.e., also HTTP payload is included in HTTP Digest calculation of “respauth” field). According to one embodiment, an authentication information header is provided in the message of step  525  to indicate the successful authentication, per Table 5 below: 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 5 
               
               
                   
                   
               
             
            
               
                   
                 AuthenticationInfo 
                 = “Authentication-Info” “:” auth-info 
               
               
                   
                 auth-info 
                  = 1#(nextnonce | [ message-qop ] 
               
               
                   
                   
                   | [ response-auth ] | [ cnonce ] 
               
               
                   
                   
                   | [nonce-count] ) 
               
               
                   
                 nextnonce 
                  = “nextnonce” “=” nonce-value 
               
               
                   
                 response-auth 
                  = “rspauth” “=” response-digest 
               
               
                   
                 response-digest 
                 = &lt;“&gt; *LHEX &lt;”&gt; 
               
               
                   
                   
               
            
           
         
       
     
     The message-qop directive indicates the “quality of protection” options applied, whereby the value “auth” indicates authentication, and the value “auth-int” indicates authentication with integrity protection. 
     In step  527 , the GAA module generates the GAA master key, Ks, from the PS_PW (in a similar manner as the procedures for the WKEY). 
     In the case of bootstrapping in the CDMA 1× EvDo, CHAP is utilized (as shown in  FIG. 6 ). Under this scenario, the GAA module issues a HTTP Get message, which is sent to the BSF  107 ; the identity is sent in the first message in the “username” field. The BSF  107  responds, as in step  603 , with a  401  message; in this CHAP case, the CHAP-Challenge is sent in the “nonce” (i.e., field is just random, as in standard HTTP Digest). Next, a CHAP challenge and response is exchanged between the GAA module and the CHAP module (steps  605  and  607 ). In step  609 , the GAA module sets the following parameters: BS_PW=MN-AAA key; H 1 ′(BS_PW)·g x  mod p, where x is the secret random number generated by the UE. 
     At this point, the terminal, using the GAA module, generates and transmits an Authorization message to the BSF  107  (step  611 ); the message specifies the following: Digest nonce=“&lt;RAND&gt;”, response=“&lt;MS_PW used as passwd&gt;”, qop=auth-int, . . . . The HTTP payload includes H 1 ′(MS_PWD)·g x  mod p. In step  613 , the BSF  107  sets the base station password (BS_PW): BS_PW=MN-AAA key; H 1 ′(BS_PW)·g y  mod p, where y is the secret random number generated by the BSF. Also, the BSF  107  generates the GAA master key, Ks, from the BS_PW. 
     Thereafter, the BSF  107  transmits a  200  OK message that specifies H 1 ′(MS_PWD)·g y  mod p, B-TID and key lifetime to the GAA module (step  617 ). In step  619 , the GAA module generates the GAA master key, Ks, from the MS_PWD. The WKEY is set to GAA master secret (Ks). 
       FIGS. 7 and 8  are diagrams of bootstrapping procedures supporting key exchange parameters that are covered by the hash of the passwords, according to various embodiments of the invention. The bootstrapping procedure of  FIG. 7  resembles that of  FIG. 5 ; that is, steps  701 - 711  correspond largely to steps  501 - 511 . Similarly, the procedure of  FIG. 8  follows that of  FIG. 6 , whereby steps  801 - 809  track with steps  601 - 609 . However, under the scenarios of  FIGS. 7 and 8 , the client Diffie-Hellman parameters are covered by the hash of password (i.e., SMEKEY, or MN-AAA Key), which is sent in the “cnonce” field. The hash can be generated based on standard HTTP Digest calculations. 
     With respect to the procedure of  FIG. 7 , in step  713  the message that is transmitted from the GAA module to the BSF  107  includes cnonce=“&lt;H 1 ′(MS_PWD)·g x  mod p&gt;”. Steps  715 - 723  follow steps  515 - 523  of  FIG. 5 . Under the present scenario, in step  725 , the BSF  107  transmits a  200  OK message that specifies nextnonce=“&lt;H 1 ′(BS_PWD)·g y  mod p&gt;”. That is, the server Diffie-Hellman parameters are covered by the hash of password (i.e., SMEKEY, or MN-AAA-KEY) that is sent in the “nextnonce” field. Thereafter, the GAA module generates the GAA master key, Ks, from the PS_PW (step  727 ). 
     As for the bootstrapping procedure of  FIG. 8 , the HTTP message of step  811  includes &lt;H 1 ′(MS_PWD)·g x  mod p&gt; in the cnonce field. Steps  813 - 819  generally track with steps  613 - 619 , with the exception that  200  OK message of step  817  specifies nextnonce=“&lt;H 1 ′(BS_PWD)·g y  mod p&gt;”. 
       FIG. 9  is a diagram of a bootstrapping procedure utilizing CAVE with one shared secret data (SSD), according to an embodiment of the invention. The UE (via the GAA module) provides a SSD generation function and an authentication function, whereby the GAA application requires access to SSD_A_NEW and SSD_B_NEW. In step  901 , the bootstrapping procedure is initiated between the UE and the BSF  107  with submission by the UE of a GET request to the BSF  107 . This GET request includes a user identity, which the BSF  107  forwards to the HLR/AC (step  903 ). The HLR/AC then generates a random SSD (“RANDSSD”) and derives SSD_A and SSD_B using the CAVE algorithm (step  905 ); this information is forwarded to the BSF  107 , per step  907 . The SSD, in an exemplary embodiment, is a 128-bit shared secret data and includes a 64-bit SSD_A key used for authentication and a 64-bit SSD-B key used along with other parameters to generate the encryption mask and private long code. RANDSSD is a 56 bit random challenge generated in HLR/AC. The SSD is a concatenation of the SSD_A key and the SSD_B key. 
     In step  909 , the BSF  107  generates a RAND_CHALLENGE and a pseudo AKA authentication vector. By way of example, the RAND_CHALLENGE is a 32 bit random challenge. To generate the AKA authentication vector, conversion functions are performed, in accordance with an embodiment of the invention, to convert (or map) the CAVE parameters generated in step  905  to AKA parameters. The conversion functions are used to generate a pseudo AKA authentication vector from either one or two sets of CAVE parameters, including RANDSSD, SSD_A, SSD_B, and AUTH_SIGNATURE. 
     As shown in  FIG. 9 , the conversion functions provide for the generation of a key, where SSD_A and SSD_B are concatenated as follows: key=SSD_A∥SSD_B∥SSD_A∥SSD_B. Next, the key, CAVE parameters, and the 3GPP GAA key derivation function (KDF) are used to form a pseudo AKA authentication vector (which includes the RAND, an authentication token (AUTN), a cipher key (CK), an integrity key (IK), and an authentication response (RES)). By way of example, the pseudo AKA authentication vector can be generated as follows: 
     RAND=RANDSSD∥RAND_CHALLENGE∥ZZRAND 
     AUTN=KDF (key, “3gpp2-cave-autn”∥RAND), truncated to 128 bits 
     CK=KDF (key, “3gpp2-cave-ck”∥RAND), truncated to 128 bits 
     IK=KDF(key, “3gpp2-cave-ik”∥RAND), truncated to 128 bits 
     RES=KDF(key, “3gpp2-cave-res”∥AUTH_SIGNATURE), truncated to 128, where ZZRAND is 40 bits long zero valued parameters (for extending the RAND to 128 bits). 
     In step  911 , the BSF  107  sends an HTTP  401  message to the UE (e.g., MS  101 ); the message specifies the RAND and AUTN. Upon receipt of this message, the MS  101  extracts, as in step  913 , the RANDSSD and RAND_CHALLENGE from the received RAND. The MS  101  then generates the SSD_A_NEW key and the SSD_B_NEW key using the RANDSSD. 
     The GAA module, as in step  915 , sends the RANDSSD and the ESN to the SEC module, which acknowledges with an OK message (per step  917 ). The ESN is, for instance, a 32 bits Electronic Cellular Authentication Number of the terminal (or mobile station (MS)). 
     In step  919 , the SSD_A_NEW is used to generate an AUTH_SIGNATURE and pseudo AKA authentication vector. The GAA module sends an AUTH_SIGNATURE message to the SEC module, as in step  921 . The SEC module responds, per step  923 , with an appropriate response (AUTH_SIGNATURE). Next, in step  925 , the GAA module generates the pseudo AKA authentication vector, determines whether the received AUTN equals the generated one, and calculates the Digest response using RES. 
     In step  927 , the UE sends a HTTP message, including RES as the password, to the BSF  107 . In turn, the BSF  107  validates, as in step  929 , the Digest response using the RES, and generates the GAA master key (Ks=CK∥IK), B-TID, key lifetime, etc.; such data is stored. Next, the BSF  107  fetches, as in step  931 , the GUSS; alternatively, this information can be delivered in step  907 . 
     The BSF  107  then sends a  200  OK message, which specifies the B-TID and key lifetime, to the MS  101 , per step  933 . At this point, the MS  101  generates the GAA master key, Ks, which is stored along with the received B-TID and key lifetime (step  935 ). 
       FIGS. 10A and 10B  are diagrams of a bootstrapping procedure utilizing CAVE with multiple SSDs, according to an embodiment of the invention. As with the procedure of  FIG. 9 , the GAA module shown here includes SSD generation and authentication functions; also, the GAA application requires access to SSD_A_NEW and SSD_B_NEW. In this example, as shown in  FIGS. 10A and 10B , for a message sequence, two SSDs and two RANDSSDs may be used to obtain, for example, a 256 bit Generic Bootstrapping Architecture (GBA) share secret (Ks). In step  1001 , the UE sends a GET request to the BSF  107  to initiate the bootstrapping procedure. The user identity from the GET request is forwarded to the HLR/AC, per step  1003 . Next, the HLR/AC generates a RANDSSD and derives a first set of SSD_A and SSD_B (denoted as “SSD_A 1  and SSD_B 1 ”), per step  1005 . The RANDSSD (e.g., “RANDSSD 1 ”) along with SSD_A 1  and SSD_B 1  are transmitted to the BSF  107 , per step  1007 . 
     In steps  1009  and  1011 , the user identity is again forwarded to the HLR/AC, and the HLR/AC generates another set of CAVE parameters: RANDSSD 2 , SSD_A 2 , and SSD_B 2 . These parameters are subsequently forwarded to the BSF  107 , as in step  1013 . 
     In step  1015 , the BSF  107  generates a RAND_CHALLENGE and a pseudo AKA authentication vector. As with the procedure of  FIG. 9 , conversion functions are used to generate a pseudo AKA authentication vector from the CAVE parameters (e.g., RANDSSD 1 , SSD_A 1 , SSD_B 1 , AUTH_SIGNATURE 1 , RANDSSD 2 , SSD_A 2 , SSD_B 2 , and AUTH_SIGNATURE 2 ). 
     A key is generated as follows: key=SSD_A 1 ∥SSD_B 1 ∥SSD_A 2 ∥SSD_B 2 . Next, the key, CAVE parameters, and the GAA key derivation function (KDF) are used to form the pseudo AKA authentication vector. The vector includes the RAND, AUTN, CK, IK, and RES, and, by way of example, is determined as follows: 
     RAND=RANDSSD 1 ∥RANDSSD 2 ∥ZZRAND 
     AUTN=KDF (key, “3gpp2-cave-autn”∥RAND), truncated to 128 bits 
     CK=KDF (key, “3gpp2-cave-ck”∥RAND), truncated to 128 bits 
     IK=KDF(key, “3gpp2-cave-ik”∥RAND), truncated to 128 bits 
     RES=KDF(key, “3gpp2-cave-res”∥AUTH_SIGNATURE 1 ∥AUTH_SIGNATURE 2 ), truncated to 128 bits 
     Server specific data=RAND_CHALLENGE 1 ∥RAND_CHALLENGE 2 , 
     where ZZRAND is 16 bits long zero valued data (used to pad the RAND to 128 bits). 
     In step  1017 , the BSF  107  sends an HTTP  401  message that specifies the RAND, AUTN and the server specific data to the GAA module. Upon receipt of this message, the GAA module extracts the RANDSSD 1 , RANDSSD 2 , RAND_CHALLENGE 1  and RAND_CHALLENGE 2  from the received RAND and the server specific data (step  1019 ). The GAA module then generates the SSD_A_NEW 1  and SSD_B_NEW 1  as well as AUTH_SIGNATURE 1 , per step  1021 . 
     Next, the GAA module forwards an SSD generation message (SSD generation), which includes the RANDSSD 1  and the ESN, to the SEC module. In response, the SEC module acknowledges with an OK message (steps  1023  and  1025 ). 
     Additionally, the GAA module forwards an AUTH_SIGNATURE message to the SEC module (step  1027 ); the AUTH_SIGNATURE message specifies RAND_CHALLENGE 1  and SSD_B_NEW 1 . 
     In step  1029 , the SEC module provides the GAA module with AUTH_SIGNATURE 1 . At this point, the GAA module stores, as in step  1031 , the SSD_A_NEW 1 , SSD_B_NEW 1 , and AUTH_SIGNATURE 1 . 
     Steps  1033 - 1043  essentially correspond to steps  1021 - 1031 , but for the second set of parameters: SSD_A_NEW 2 , SSD_B_NEW 2 , and AUTH_SIGNATURE 2 . 
     In step  1045 , the GAA module generates the pseudo AKA authentication vector, and determines whether the received AUTN equals the generated one. The GAA module also outputs a Digest response based on the RES. 
     Next, the UE sends, as in step  1047 , a HTTP message including RES as the password to the BSF  107 . The BSF  107  validates, as in step  1049 , the Digest response using the RES, and generates the GAA master key (Ks=CK∥IK), B-TID, key lifetime, etc.; the BSF  107  also stores the data. In step  1051 , the BSF  107  fetches the GUSS (which can alternatively be delivered in step  1007 ). 
     The BSF  107  then sends, as in step  1053 , a  200  OK message, which specifies the B-TID and key lifetime, to the UE. Thereafter, the UE generates the GAA master key, Ks, which is stored along with the received B-TID and key lifetime (step  1055 ). 
       FIG. 11  is a diagram of a bootstrapping procedure utilizing CAVE with HTTP Digest AKA, according to an embodiment of the invention. The message sequence, in this bootstrapping procedure, utilizes two SSDs and two RANDSSDs. The user identity is transmitted, as in step  1101 , to the BSF  107  and to the HLR/AC (step  1103 ). In step  1105 , the HLR/AC transmits SSD 1 , SSD 2 , RANDSS 1  RANDSS 2 , and GBA user security settings (GUSS) to the BSF  107 . In response, the BSF  107  generates two RAND_CHALLENGES (i.e., RAND_CHALLENGE 1  and RAND_CHALLENGE 2 ), per step  1107 . In step  1109 , the RANDSSD 1 , RANDSSD 2 , RAND_CHALLENGE 1  and RAND_CHALLENGE 2  are delivered to the UE. 
     The UE then calculates the following: SSD 1 , SSD 2 , AUTH_SIGNATURE 1  and AUTH_SIGNATURE 2  (step  1111 ). SSD 1  is computed from RANDSSD 1 , A-Key and ESN; similarly, SSD 2  is determined from RANDSSD 2 , A-Key and ESN. The AUTH_SIGNATURE 1  is calculated from SSD_A 1  and RAND_CHALLENGE 1 ; and an AUTH_SIGNATURE 2  is calculated from SSD_A 2  and RAND_CHALLENGE 2 . In step  1113 , the UE sends the concatenation of AUTH_SIGNATURE 1  and AUTH_SIGNATURE 2  as the password to the BSF  107 . 
     The key is then generated at the BSF  107 , as in step  1115 , by concatenating CK_UMTS∥IK_UMTS (=SSD_A 1 ∥SSD_A 2 ∥SSD_B 1 ∥SSD_B 2 ). Also, the BSF  107  sends a  200  OK message specifying the B-TID and key lifetime to the UE (step  1117 ). In step  1119 , the UE determines the Ks. 
     One of ordinary skill in the art would recognize that the processes for supporting bootstrapping may be implemented via software, hardware (e.g., general processor, Digital Signal Processing (DSP) chip, an Application Specific Integrated Circuit (ASIC), Field Programmable Gate Arrays (FPGAs), etc.), firmware, or a combination thereof. Such exemplary hardware for performing the described functions is detailed below with respect to  FIG. 12 . 
       FIG. 12  illustrates exemplary hardware upon which various embodiments of the invention can be implemented. A computing system  1200  includes a bus  1201  or other communication mechanism for communicating information and a processor  1203  coupled to the bus  1201  for processing information. The computing system  1200  also includes main memory  1205 , such as a random access memory (RAM) or other dynamic storage device, coupled to the bus  1201  for storing information and instructions to be executed by the processor  1203 . Main memory  1205  can also be used for storing temporary variables or other intermediate information during execution of instructions by the processor  1203 . The computing system  1200  may further include a read only memory (ROM)  1207  or other static storage device coupled to the bus  1201  for storing static information and instructions for the processor  1203 . A storage device  1209 , such as a magnetic disk or optical disk, is coupled to the bus  1201  for persistently storing information and instructions. 
     The computing system  1200  may be coupled via the bus  1201  to a display  1211 , such as a liquid crystal display, or active matrix display, for displaying information to a user. An input device  1213 , such as a keyboard including alphanumeric and other keys, may be coupled to the bus  1201  for communicating information and command selections to the processor  1203 . The input device  1213  can include a cursor control, such as a mouse, a trackball, or cursor direction keys, for communicating direction information and command selections to the processor  1203  and for controlling cursor movement on the display  1211 . 
     According to various embodiments of the invention, the processes described herein can be provided by the computing system  1200  in response to the processor  1203  executing an arrangement of instructions contained in main memory  1205 . Such instructions can be read into main memory  1205  from another computer-readable medium, such as the storage device  1209 . Execution of the arrangement of instructions contained in main memory  1205  causes the processor  1203  to perform the process steps described herein. One or more processors in a multi-processing arrangement may also be employed to execute the instructions contained in main memory  1205 . In alternative embodiments, hard-wired circuitry may be used in place of or in combination with software instructions to implement the embodiment of the invention. In another example, reconfigurable hardware such as Field Programmable Gate Arrays (FPGAs) can be used, in which the functionality and connection topology of its logic gates are customizable at run-time, typically by programming memory look up tables. Thus, embodiments of the invention are not limited to any specific combination of hardware circuitry and software. 
     The computing system  1200  also includes at least one communication interface  1215  coupled to bus  1201 . The communication interface  1215  provides a two-way data communication coupling to a network link (not shown). The communication interface  1215  sends and receives electrical, electromagnetic, or optical signals that carry digital data streams representing various types of information. Further, the communication interface  1215  can include peripheral interface devices, such as a Universal Serial Bus (USB) interface, a PCMCIA (Personal Computer Memory Card International Association) interface, etc. 
     The processor  1203  may execute the transmitted code while being received and/or store the code in the storage device  1209 , or other non-volatile storage for later execution. In this manner, the computing system  1200  may obtain application code in the form of a carrier wave. 
     The term “computer-readable medium” as used herein refers to any medium that participates in providing instructions to the processor  1203  for execution. Such a medium may take many forms, including but not limited to non-volatile media, volatile media, and transmission media. Non-volatile media include, for example, optical or magnetic disks, such as the storage device  1209 . Volatile media include dynamic memory, such as main memory  1205 . Transmission media include coaxial cables, copper wire and fiber optics, including the wires that comprise the bus  1201 . Transmission media can also take the form of acoustic, optical, or electromagnetic waves, such as those generated during radio frequency (RF) and infrared (IR) data communications. Common forms of computer-readable media include, for example, a floppy disk, a flexible disk, hard disk, magnetic tape, any other magnetic medium, a CD-ROM, CDRW, DVD, any other optical medium, punch cards, paper tape, optical mark sheets, any other physical medium with patterns of holes or other optically recognizable indicia, a RAM, a PROM, and EPROM, a FLASH-EPROM, any other memory chip or cartridge, a carrier wave, or any other medium from which a computer can read. 
     Various forms of computer-readable media may be involved in providing instructions to a processor for execution. For example, the instructions for carrying out at least part of the invention may initially be borne on a magnetic disk of a remote computer. In such a scenario, the remote computer loads the instructions into main memory and sends the instructions over a telephone line using a modem. A modem of a local system receives the data on the telephone line and uses an infrared transmitter to convert the data to an infrared signal and transmit the infrared signal to a portable computing device, such as a personal digital assistant (PDA) or a laptop. An infrared detector on the portable computing device receives the information and instructions borne by the infrared signal and places the data on a bus. The bus conveys the data to main memory, from which a processor retrieves and executes the instructions. The instructions received by main memory can optionally be stored on storage device either before or after execution by processor. 
       FIGS. 13A and 13B  are diagrams of different cellular mobile phone systems capable of supporting various embodiments of the invention.  FIGS. 13A and 13B  show exemplary cellular mobile phone systems each with both mobile station (e.g., handset) and base station having a transceiver installed (as part of a Digital Signal Processor (DSP)), hardware, software, an integrated circuit, and/or a semiconductor device in the base station and mobile station). By way of example, the radio network supports Second and Third Generation (2G and 3G) services as defined by the International Telecommunications Union (ITU) for International Mobile Telecommunications 2000 (IMT-2000). For the purposes of explanation, the carrier and channel selection capability of the radio network is explained with respect to a cdma2000 architecture. As the third-generation version of IS-95, cdma2000 is being standardized in the Third Generation Partnership Project 2 (3GPP2). 
     A radio network  1300  includes mobile stations  1301  (e.g., handsets, terminals, stations, units, devices, or any type of interface to the user (such as “wearable” circuitry, etc.)) in communication with a Base Station Subsystem (BSS)  1303 . According to one embodiment of the invention, the radio network supports Third Generation (3G) services as defined by the International Telecommunications Union (ITU) for International Mobile Telecommunications 2000 (IMT-2000). 
     In this example, the BSS  1303  includes a Base Transceiver Station (BTS)  1305  and Base Station Controller (BSC)  1307 . Although a single BTS is shown, it is recognized that multiple BTSs are typically connected to the BSC through, for example, point-to-point links. Each BSS  1303  is linked to a Packet Data Serving Node (PDSN)  1309  through a transmission control entity, or a Packet Control Function (PCF)  1311 . Since the PDSN  1309  serves as a gateway to external networks, e.g., the Internet  1313  or other private consumer networks  1315 , the PDSN  1309  can include an Access, Authorization and Accounting system (AAA)  1317  to securely determine the identity and privileges of a user and to track each user&#39;s activities. The network  1315  comprises a Network Management System (NMS)  1331  linked to one or more databases  1333  that are accessed through a Home Agent (HA)  1335  secured by a Home AAA  1337 . 
     Although a single BSS  1303  is shown, it is recognized that multiple BSSs  1303  are typically connected to a Mobile Switching Center (MSC)  1319 . The MSC  1319  provides connectivity to a circuit-switched telephone network, such as the Public Switched Telephone Network (PSTN)  1321 . Similarly, it is also recognized that the MSC  1319  may be connected to other MSCs  1319  on the same network  1300  and/or to other radio networks. The MSC  1319  is generally collocated with a Visitor Location Register (VLR)  1323  database that holds temporary information about active subscribers to that MSC  1319 . The data within the VLR  1323  database is to a large extent a copy of the Home Location Register (HLR)  1325  database, which stores detailed subscriber service subscription information. In some implementations, the HLR  1325  and VLR  1323  are the same physical database; however, the HLR  1325  can be located at a remote location accessed through, for example, a Signaling System Number 7 (SS7) network. An Authentication Center (AuC)  1327  containing subscriber-specific authentication data, such as a secret authentication key, is associated with the HLR  1325  for authenticating users. Furthermore, the MSC  1319  is connected to a Short Message Service Center (SMSC)  1329  that stores and forwards short messages to and from the radio network  1300 . 
     During typical operation of the cellular telephone system, BTSs  1305  receive and demodulate sets of reverse-link signals from sets of mobile units  1301  conducting telephone calls or other communications. Each reverse-link signal received by a given BTS  1305  is processed within that station. The resulting data is forwarded to the BSC  1307 . The BSC  1307  provides call resource allocation and mobility management functionality including the orchestration of soft handoffs between BTSs  1305 . The BSC  1307  also routes the received data to the MSC  1319 , which in turn provides additional routing and/or switching for interface with the PSTN  1321 . The MSC  1319  is also responsible for call setup, call termination, management of inter-MSC handover and supplementary services, and collecting, charging and accounting information. Similarly, the radio network  1300  sends forward-link messages. The PSTN  1321  interfaces with the MSC  1319 . The MSC  1319  additionally interfaces with the BSC  1307 , which in turn communicates with the BTSs  1305 , which modulate and transmit sets of forward-link signals to the sets of mobile units  1301 . 
     As shown in  FIG. 13B , the two key elements of the General Packet Radio Service (GPRS) infrastructure  1350  are the Serving GPRS Supporting Node (SGSN)  1332  and the Gateway GPRS Support Node (GGSN)  1334 . In addition, the GPRS infrastructure includes a Packet Control Unit PCU ( 1336 ) and a Charging Gateway Function (CGF)  1338  linked to a Billing System  1339 . A GPRS Mobile Station (MS)  1341  employs a Subscriber Identity Module (SIM)  1343 . 
     The PCU  1336  is a logical network element responsible for GPRS-related functions such as air interface access control, packet scheduling on the air interface, and packet assembly and re-assembly. Generally the PCU  1336  is physically integrated with the BSC  1345 ; however, it can be collocated with a BTS  1347  or a SGSN  1332 . The SGSN  1332  provides equivalent functions as the MSC  1349  including mobility management, security, and access control functions but in the packet-switched domain. Furthermore, the SGSN  1332  has connectivity with the PCU  1336  through, for example, a Fame Relay-based interface using the BSS GPRS protocol (BSSGP). Although only one SGSN is shown, it is recognized that that multiple SGSNs  1332  can be employed and can divide the service area into corresponding routing areas (RAs). A SGSN/SGSN interface allows packet tunneling from old SGSNs to new SGSNs when an RA update takes place during an ongoing Personal Development Planning (PDP) context. While a given SGSN may serve multiple BSCs  1345 , any given BSC  1345  generally interfaces with one SGSN  1332 . Also, the SGSN  1332  is optionally connected with the HLR  1351  through an SS7-based interface using GPRS enhanced Mobile Application Part (MAP) or with the MSC  1349  through an SS7-based interface using Signaling Connection Control Part (SCCP). The SGSN/HLR interface allows the SGSN  1332  to provide location updates to the HLR  1351  and to retrieve GPRS-related subscription information within the SGSN service area. The SGSN/MSC interface enables coordination between circuit-switched services and packet data services such as paging a subscriber for a voice call. Finally, the SGSN  1332  interfaces with a SMSC  1353  to enable short messaging functionality over the network  1350 . 
     The GGSN  1334  is the gateway to external packet data networks, such as the Internet  1313  or other private customer networks  1355 . The network  1355  comprises a Network Management System (NMS)  1357  linked to one or more databases  1359  accessed through a PDSN  1361 . The GGSN  1334  assigns Internet Protocol (IP) addresses and can also authenticate users acting as a Remote Authentication Dial-In User Service host. Firewalls located at the GGSN  1334  also perform a firewall function to restrict unauthorized traffic. Although only one GGSN  1334  is shown, it is recognized that a given SGSN  1332  may interface with one or more GGSNs  1334  to allow user data to be tunneled between the two entities as well as to and from the network  1350 . When external data networks initialize sessions over the GPRS network  1350 , the GGSN  1334  queries the HLR  1351  for the SGSN  1332  currently serving a MS  1341 . 
     The BTS  1347  and BSC  1345  manage the radio interface, including controlling which Mobile Station (MS)  1341  has access to the radio channel at what time. These elements essentially relay messages between the MS  1341  and SGSN  1332 . The SGSN  1332  manages communications with an MS  1341 , sending and receiving data and keeping track of its location. The SGSN  1332  also registers the MS  1341 , authenticates the MS  1341 , and encrypts data sent to the MS  1341 . 
       FIG. 14  is a diagram of exemplary components of a mobile station (e.g., handset) capable of operating in the systems of  FIGS. 13A and 13B , according to an embodiment of the invention. Generally, a radio receiver is often defined in terms of front-end and back-end characteristics. The front-end of the receiver encompasses all of the Radio Frequency (RF) circuitry whereas the back-end encompasses all of the base-band processing circuitry. Pertinent internal components of the telephone include a Main Control Unit (MCU)  1403 , a Digital Signal Processor (DSP)  1405 , and a receiver/transmitter unit including a microphone gain control unit and a speaker gain control unit. A main display unit  1407  provides a display to the user in support of various applications and mobile station functions. An audio function circuitry  1409  includes a microphone  1411  and microphone amplifier that amplifies the speech signal output from the microphone  1411 . The amplified speech signal output from the microphone  1411  is fed to a coder/decoder (CODEC)  1413 . 
     A radio section  1415  amplifies power and converts frequency in order to communicate with a base station, which is included in a mobile communication system (e.g., systems of  FIG. 13A or 13B ), via antenna  1417 . The power amplifier (PA)  1419  and the transmitter/modulation circuitry are operationally responsive to the MCU  1403 , with an output from the PA  1419  coupled to the duplexer  1421  or circulator or antenna switch, as known in the art. 
     In use, a user of mobile station  1401  speaks into the microphone  1411  and his or her voice along with any detected background noise is converted into an analog voltage. The analog voltage is then converted into a digital signal through the Analog to Digital Converter (ADC)  1423 . The control unit  1403  routes the digital signal into the DSP  1405  for processing therein, such as speech encoding, channel encoding, encrypting, and interleaving. In the exemplary embodiment, the processed voice signals are encoded, by units not separately shown, using the cellular transmission protocol of Code Division Multiple Access (CDMA), as described in detail in the Telecommunication Industry Association&#39;s TIA/EIA/IS-95-A Mobile Station-Base Station Compatibility Standard for Dual-Mode Wideband Spread Spectrum Cellular System; which is incorporated herein by reference in its entirety. 
     The encoded signals are then routed to an equalizer  1425  for compensation of any frequency-dependent impairments that occur during transmission though the air such as phase and amplitude distortion. After equalizing the bit stream, the modulator  1427  combines the signal with a RF signal generated in the RF interface  1429 . The modulator  1427  generates a sine wave by way of frequency or phase modulation. In order to prepare the signal for transmission, an up-converter  1431  combines the sine wave output from the modulator  1427  with another sine wave generated by a synthesizer  1433  to achieve the desired frequency of transmission. The signal is then sent through a PA  1419  to increase the signal to an appropriate power level. In practical systems, the PA  1419  acts as a variable gain amplifier whose gain is controlled by the DSP  1405  from information received from a network base station. The signal is then filtered within the duplexer  1421  and optionally sent to an antenna coupler  1435  to match impedances to provide maximum power transfer. Finally, the signal is transmitted via antenna  1417  to a local base station. An automatic gain control (AGC) can be supplied to control the gain of the final stages of the receiver. The signals may be forwarded from there to a remote telephone which may be another cellular telephone, other mobile phone or a land-line connected to a Public Switched Telephone Network (PSTN), or other telephony networks. 
     Voice signals transmitted to the mobile station  1401  are received via antenna  1417  and immediately amplified by a low noise amplifier (LNA)  1437 . A down-converter  1439  lowers the carrier frequency while the demodulator  1441  strips away the RF leaving only a digital bit stream. The signal then goes through the equalizer  1425  and is processed by the DSP  1405 . A Digital to Analog Converter (DAC)  1443  converts the signal and the resulting output is transmitted to the user through the speaker  1445 , all under control of a Main Control Unit (MCU)  1403 —which can be implemented as a Central Processing Unit (CPU) (not shown). 
     The MCU  1403  receives various signals including input signals from the keyboard  1447 . The MCU  1403  delivers a display command and a switch command to the display  1407  and to the speech output switching controller, respectively. Further, the MCU  1403  exchanges information with the DSP  1405  and can access an optionally incorporated SIM card  1449  and a memory  1451 . In addition, the MCU  1403  executes various control functions required of the station. The DSP  1405  may, depending upon the implementation, perform any of a variety of conventional digital processing functions on the voice signals. Additionally, DSP  1405  determines the background noise level of the local environment from the signals detected by microphone  1411  and sets the gain of microphone  1411  to a level selected to compensate for the natural tendency of the user of the mobile station  1401 . 
     The CODEC  1413  includes the ADC  1423  and DAC  1443 . The memory  1451  stores various data including call incoming tone data and is capable of storing other data including music data received via, e.g., the global Internet. The software module could reside in RAM memory, flash memory, registers, or any other form of writable storage medium known in the art. The memory device  1451  may be, but not limited to, a single memory, CD, DVD, ROM, RAM, EEPROM, optical storage, or any other non-volatile storage medium capable of storing digital data. 
     An optionally incorporated SIM card  1449  carries, for instance, important information, such as the cellular phone number, the carrier supplying service, subscription details, and security information. The SIM card  1449  serves primarily to identify the mobile station  1401  on a radio network. The card  1449  also contains a memory for storing a personal telephone number registry, text messages, and user specific mobile station settings. 
       FIG. 15  shows an exemplary enterprise network, which can be any type of data communication network utilizing packet-based and/or cell-based technologies (e.g., Asynchronous Transfer Mode (ATM), Ethernet, IP-based, etc.). The enterprise network  1501  provides connectivity for wired nodes  1503  as well as wireless nodes  1505 - 1509  (fixed or mobile), which are each configured to perform the processes described above. The enterprise network  1501  can communicate with a variety of other networks, such as a WLAN network  1511  (e.g., IEEE 802.11), a cdma2000 cellular network  1513 , a telephony network  1515  (e.g., PSTN), or a public data network  1517  (e.g., Internet). 
     While the invention has been described in connection with a number of embodiments and implementations, the invention is not so limited but covers various obvious modifications and equivalent arrangements, which fall within the purview of the appended claims. Although features of the invention are expressed in certain combinations among the claims, it is contemplated that these features can be arranged in any combination and order.