Abstract:
A device for communicating with other devices to allow them to access applications, comprises: at least a first application; authentication means for authenticating a communicating device; and access control means accessible by a communicating device requesting access to the first application without the communicating device having been authenticated by the authentication means. The device is further arranged to arbitrate whether access of the communicating device to the first application is granted or refused wherein if the arbitration requires an authentication of the communicating device, the access control means instructs the authentication means to authenticate the communicating device.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to the provision of improved security in a device which has services accessible by other devices communicating with the device. It particularly relates to devices which are accessed over a radio interface in accordance with the BLUETOOTH specification (a digital wireless protocol). 
       FIG. 1  illustrates a network  2  of radio transceiver units, including a master unit  4  and slave units  6 ,  8  and  10 , communicating by transmitting and receiving radio packets. There is only one master in a network. The network operates in a time division duplex fashion. The transceiver units are synchronized to a common time frame determined by the master unit  4 . This time frame consists of a series of time slots of equal length. Each radio packet transmitted in the network has its start aligned with the start of a slot and a single packet transmitted in the network at a time. When the master unit is performing point-to-point communication a transmitted radio packet is addressed to a particular transceiver which replies to the master unit by transmitting a radio packet addressed to the master unit in the next available time slot. When the master unit is performing point to multi-point communication a transmitted radio packet is addressed to all transceiver units. Any misalignment between the master and a slave is corrected by adjusting the timing of the slave. 
     The transceivers transmit and receive, in this example, in a microwave frequency band, illustratively 2.4 Ghz. The network reduces interference by changing the frequency at which each radio packet is transmitted. A number of separate frequency channels are assigned each with a bandwidth of 1 MHz, and the frequency may hop at a rate of 1600 hops/s. The frequency hopping of the transceivers communicating in or joining the network is synchronized and controlled by the master unit. The sequence of hopping frequencies is unique for the network and is determined by a unique identification of the master unit. 
     Each transceiver unit has a unique identification, the Unit ID, henceforth referred to as the BLUETOOTH ID. Each BLUETOOTH ID (48-bit IEEE address) is unique for each BLUETOOTH unit. A BLUETOOTH ID of a unit can be found through an enquiry routine over the RF interface to the unit. 
     The network is a radio frequency network suitable for transmitting voice information or data information between transceivers. The transmissions made are of low power, for example 0 to 20 dBm, and the transceiver units can effectively communicate over the range of a few centimeters to a few tens or hundred of meters. 
     Referring to  FIG. 2 , a frame  20  is illustrated. This frame  20  is the common time frame used by the network  2  and controlled by the master unit  4 . The frame illustratively has slots  22  to  29 . The slots designated by even numbers are reserved. Only the master unit can begin transmitting a radio packet aligned with the start of the even numbered slots. The slots designated by odd numbers are reserved. Only radio packets transmitted by a slave, that is radio packets addressed for reception by the master unit can have their start aligned with the start of the odd numbered slots. Each slot is allocated a different one of a sequence of hopping frequencies. It is however, possible for a radio packet to extend over a number of slots and in this case the frequency at which the packet is transmitted remains constant at that allocated to the slot at the start of the packet. A slot has a constant time period and is typically 625 microseconds. 
     Referring to  FIG. 3 , a typical radio packet  30  is illustrated. The radio packet has a start  32  and contains three distinct portions: a first portion contains an Access Code  34 , a second portion contains a Header  36  and a third portion contains a Payload  38 . The Payload  38  has a Payload Header  37 . 
     Referring to  FIG. 4 , a schematic illustration of a transceiver unit is shown. Only as many functional blocks and interconnections are shown in this diagram as are necessary to explain in the following how a transceiver unit and the communication network operates. The transceiver unit  40  contains a number of functional elements including: an antenna  46 , receiver  50 , synchroniser  52 , header decoder  54 , controller  60 , memory  56 , which may include non-transitory machine accessible and readable media, packetiser  42 , clock  68 , frequency hop controller  48  and transmitter  44 . Although these elements are shown as separate elements they may in fact be integrated together and may be carried out in software or in hardware. 
     Data to be transmitted in the payload by the transceiver unit  40  is supplied as data signal  41  to the packetizer  42 . Control information to be transmitted in the payload of a packet is supplied in a payload control signal  87  provided by the controller  60  to the packetizer  42 . The packetizer  42  also receives an access code control signal  69  and a header control signal  71  from controller  60  which respectively control the Access Code  34  and the Header  36  attached to the payload to form the packet. The packetizer  42  places the data or control information into a packet  30  which is supplied as signal  43  to the transmitter  44 . The transmitter  44  modulates a carrier wave in dependence upon the signal  43  to produce the transmitted signal  45  supplied to the antenna  46  for transmission. The frequency of the carrier wave is controlled to be one of a sequence of hop frequencies by a transmission frequency control signal  47  supplied by the frequency hop controller  48  to the transmitter  44 . 
     The antenna  46  receives a radio signal  51  and supplies it to the receiver  50  which demodulates the radio signal  51  under the control of a reception frequency control signal  49  supplied by the frequency controller  48  to produce a digital signal  53 . The digital signal  53  is supplied to the synchronizer  52  which synchronizes the transceiver unit  40  to the time frame of the network. The synchronizer is supplied with an access code signal  81  specifying the Access Code of the packet which the transceiver unit is expecting to receive. The synchronizer accepts those received radio packets with Access Codes which correspond to the expected Access Codes and rejects those received radio packets with Access Codes that do not correspond to the expected Access Code. A sliding correlation is used to identify the presence and the start of the expected Access Code. A sliding correlation is used to identify the presence and the start of the expected Access Code in a radio packet. If the radio packet is accepted then the radio packet is supplied to the header decoder  54  as a signal  55  and a confirmation signal  79  is returned to the controller  60  indicating the packet has been accepted by the synchronizer  52 . The confirmation signal  79  is used by the controller in a slave unit to resynchronize the slave clock to the master clock. The controller compares the time at which a radio packet was received with the time at which the radio packet was expected to be received and shifts its timing to offset the difference. The header decoder  54  decodes the header in the received packet and supplies it to the controller  60  as header signal  75 . The header decoder  54 , when enabled by a payload acceptance signal  77  supplied by the controller  60 , produces a data output signal  57  containing the remainder of the radio packet, the payload  38 . 
     The memory  56  may store applications. 
     The operation of unit can also be understood from  FIG. 5  which illustrates a Bluetooth protocol stack  100 . The stack  100  includes, in order from the bottom up, the basic layers including RF layer  102 , Baseband and Link Control layer  104 , Link Manager Protocol Layer  106  and Logical Link Control and Adaptation Layer (L2CAP)  108 . The layer L2CAP  108  connects with a number of overlying layers  110  including an Internet layer  112  for providing TCP/IP protocol, a Human Interface Device layer  114  for interfacing with the user interface  130  and a RF Communications layer  116  which emulates serial ports of a PC (com1, com2 com3 etc). Each of the layers  112 ,  114  and  116  may connect directly with one or more applications/services  118  and are able to multiplex their output so that data is sent to the correct one of several applications/services. The layer L2CAP  108  may also connect directly to an application or service. 
     In the units currently proposed, the Baseband and Link Control layer  104  enables the physical RF link between units using inquiry and paging to synchronise their clocks and transmission frequencies. The Link Manager Protocol Layer  106 , henceforth referred to as the Link Layer  106 , is responsible for link set-Up between two units including security, control of packet size, connection and power modes. In the proposal the Link Layer  106  responds to the payloads received in Link Management Protocol packets. 
     L2CAP allows higher level protocols to receive the payloads of received L2CAP data packets. The L2CAP protocol may be coupled to application and higher protocol layers and transfers data between either higher level protocols and services and the lower level Link Layer  106 . 
     The payload header  37  of the payload  38  in packets  30  distinguishes L2CAP packets from Link Management Protocol packets. At present, it is required that the Link Management Protocol packets should be filtered out by the Link Layer  106  and not propagated to higher layers. 
     The BLUETOOTH technology should provide security measures both at the application layer and the link layer. Currently, in each BLUETOOTH unit the link layer  106  security measures are standardized. Authentication and encryption routines are implemented in a standard way in each device in the Link Layer  106 . 
     Each unit stores one or more secret authentication link keys for use in communication with another unit or units. Typically a unit will permanently store a link key for each of the units it wishes to communicate with. Each link key is associated with the BLUETOOTH ID of the unit for which it is used to communicate. 
     The stored secret link key is used in an authentication routine to authenticate the identity of the unit being communicated with. The stored shared secret link key is also used to generated an encryption key. The encryption key is derived from but is different to the authentication link key and a new encryption key is generated each time encryption is used by using a random number generator. 
     A challenge response scheme is used to authenticate a unit. A valid pair of units share the same secret link key. A first unit produces a random number and challenges a second unit to authenticate itself by supplying the random number to it. The second unit returns the result of a function which takes as its arguments the BLUETOOTH ID of the second unit, the received random number and the key associated with the first unit but stored in the second unit. The first unit uses the same function to produce a result which if it equals the result received from the second unit authenticates the second device. The function in the first unit takes as its arguments the BLUETOOTH ID of the second unit which has been previously obtained, the random number and the key associated with the second unit but stored in the first unit. 
     The authentication procedure occurs in the Link Layer of each unit. Once authentication has been successfully completed access to the protocol layer, services and applications in the unit is unrestricted. 
     Each time encryption is required a random number is produced and an encryption key is formed from the random number and the authentication key for the link. The encryption process occurs in the Link Layer  106 . 
     If the two devices have not previously communicated there will be no shared link key stored in the devices and it is necessary to ‘pair’ the devices. This may be done by inputting a PIN number into a user interface of the first unit and inputting the same PIN into a user interface of the second unit. The PINs may be used for the calculation of temporary initial authentication link keys until the calculation of a permanent shared secret authentication link key for communication between the devices. 
     One problem with the presently proposed security system is that it is inflexible. Once the link layer  106  has allowed a device access to the layers above it, its access is unrestricted except by specific security features built into the applications themselves. It would be desirable to provide an improved, more flexible, security system. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the present invention there is provide a device for communicating with other devices to allow them to access applications, comprising: at least a first application; authentication means for authenticating a communicating device; access control means accessible by a communicating device requesting access to the first application without the communicating device having been authenticated by the authentication means, and arranged to arbitrate whether access of the communicating device to the first application is granted or refused wherein if the arbitration requires an authentication of the communicating device, the access control means instructs the authentication means to authenticate the communicating device. 
     According to another aspect of the present invention there is provided a device for communicating with other devices to allow them to access applications, comprising: at least first and second applications; authentication means for authenticating a communicating device; first access control means accessible by a communicating device requesting access to the first application without the communicating device having been authenticated by the authentication means, and arranged to arbitrate whether access of the communicating device to the first application is granted or refused wherein if the arbitration requires an authentication of the communicating device, the access control means instructs the authentication means to authenticate the communicating device. second access control means accessible by a communicating device requesting access to the second application without the communicating device having been authenticated by the authentication means, and arranged to arbitrate whether access of the communicating device to the second application is granted or refused wherein if the arbitration requires an authentication of the communicating device, the access control means instructs the authentication means to authenticate the communicating device, wherein the first access control means is accessible by a communicating device requesting access to the second application without the communicating device having been authenticated by the authentication means, and is arranged to provide the access of the communicating device to the second access means. 
     According to another aspect of the present invention there is provided a method of arbitrating the access of a requesting device to a service provided by a providing device comprising: sending a request to access the service from the requesting device to the providing device; receiving the request at the providing device and passing it, without authenticating the requesting device, to an arbitration means interfacing the service; determining, in the arbitration means, whether to grant or refuse access to the first application by the requesting device, wherein if the determination requires an authentication of the requesting device, the authentication is performed during that determination and not previously. 
     Embodiments of the invention provide a flexible security architecture that performs access checks when connection to a service is requested including, if necessary, authentication and encryption at the time of requesting access to application. The access control means may be a multiplexing protocol layer and the authentication means may be the link layer. 
     It is preferable that a device requesting access to a service is authenticated once and not many times. This may be achieved by having the request for access to a service arbitrated once-only, preferably in response to a query from the highest possible multiplexing layer (the one that directly interfaces the service). 
     Access to a service may be arbitrated in dependence on the security requirements of the requested service and/or the trust level of the device requesting access. The security architecture is implemented without changing the basic functions (pairing, authentication, encryption) which remain in the authentication means (link level). 
     According to a further aspect of the present invention there is provided a device for providing services and allowing access by other devices to the provided services, comprising: an interface for communicating with the other devices and receiving requests to access a service therefrom; arbitration means, for determining whether a requesting device communicating through the interface can access a service it has requested access to, arranged to store trust indications in association with requesting devices and arranged to receive from the interface an indication, originating from the other device, identifying the other device, wherein, if the requesting device has a stored trust indication associated therewith no user authorization is required and if the requesting device has no stored trust indication associated therewith user authorization is requirable; and a user interface for providing user authorization. 
     According to a further aspect of the present invention there is provided a device for providing services and allowing access by other devices to the provided services, comprising: an interface for communicating with the other devices and receiving requests to access a service therefrom; arbitration means, for determining whether a requesting device communicating through the interface can access a service it has requested access to, arranged to store trust indications in association with requesting devices and store security indications in association with provided services and arranged to receive from the interface indications, originating from the other device, identifying the other device and the service requested, wherein, if the requesting device has a stored trust indication associated therewith no user authorization is required and if the requesting device has no stored trust indication associated therewith user authorization is required in dependence upon the stored security indication associated with the requested service; and a user interface for providing user authorization. 
     According to the embodiments of the invention, access to services depends upon the trust level of the device which is trying to access the service. A trusted device, once its identity has been verified has access to all the services/applications. A not-trusted device may require user authorization each time it attempts to access a service. Therefore the grant of access of a not-trusted device to one service does not open up the other services to access. Separate user authorization is required to access each of the other services. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a better understanding of the present invention and to understand how the same may be brought into effect reference will now be made by way of example only to accompanying drawings in which: 
         FIG. 1  illustrates a communications network including a master and slave units; 
         FIG. 2  illustrates the time frame of the communications network; 
         FIG. 3  illustrates a radio packet 
         FIG. 4  illustrates a transceiver unit suitable for use as a master or slave; 
         FIG. 5  illustrates a protocol stack used by a transceiver unit; 
         FIG. 6  illustrates a security architecture; 
         FIGS. 7   a  and  7   b  illustrate, respectively, a service database and a device database; 
         FIGS. 8   a  and  8   b  illustrate information flow in the security architecture when access for a not-open service is requested by a trusted and untrusted device respectively 
         FIGS. 9 to 11  are flow diagrams illustrating the arbitration process performed by the controller to determine if a device should access a service. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 6  illustrates a security architecture in accordance with one embodiment of the invention. The Bluetooth protocol stack  100  is illustrated. It includes lower layers including the link layer  106 , a lowest multiplexing protocol layer  108  such as the L2CAP layer, a higher multiplexing protocol layer  110  such as the RFCOMM layer  116  and an application layer  118 . Also illustrated are the User Interface  130 , a security manager  120 , a service database  122  and a device database  124 . 
     The link layer  106  is directly connected to the lowest multiplexing protocol  108 . Access to the higher multiplexing protocol  110  and the applications/services  118  from the link layer can only be achieved via the lowest multiplexing protocol layer  108 . 
     The lowest multiplexing protocol layer  108  is directly connected to the higher multiplexing protocol  110  and also directly connected to application  118   3 . Access to the application  118   3  can be made directly by the lowest multiplexing protocol, whereas access to applications  118   1  and  118   2  can only be made via the higher multiplexing protocol  110  which is directly connected to applications  118   1  and  118   2 . 
     When a packet is received by a unit, the payload of the packet is passed to the lowest multiplexing protocol layer  108 . The payload is not filtered by the link layer  106 . If the received packet is a request to access a service/application, access to that service application is arbitrated. 
     The lowest multiplexing protocol layer  108  sends a query to the security manager asking whether access to a higher entity such as the higher protocol layer  110  or application  18   3  should be given. This query identifies the service/application to which access is required and the BLUETOOTH ID of the device requesting access. The Security Manager determines if access to the next entity should be allowed and may control the Link Layer  106  to enforce authentication. If the querying protocol layer is not directly connected to the requested service, the Security Manager automatically sends a grant signal to the querying protocol layer  108  which then allows access to a higher protocol layer  110 . If the querying protocol layer  108  is directly connected to the requested service  118   3 , the Security Manager arbitrates to determine if access should be allowed. If access is allowed it sends a grant signal to the lowest multiplexing protocol layer  108  which then accesses the application  18   3 . If access is denied, the Security Manager  120  sends a refusal signal to the lowest multiplexing protocol  108  preventing access of the requesting unit to the desired service. 
     The request to access a service (application  118   1  or  118   2 ) received at the higher multiplexing protocol  110  from the lowest multiplexing protocol  108 , causes the layer  110  to send a query to the Security Manager asking whether access to a higher entity such as a higher multiplexing protocol layer (not illustrated) or application  118   1  or  118   2 . This query identifies the service/application to which access is required and BLUETOOTH ID of the device requesting access. If the querying protocol layer is not directly connected to the requested service, the Security Manager automatically sends a grant signal to the querying protocol layer  108  which then allows access to a higher protocol layer. If the querying protocol layer  110  is directly connected to the requested service, the Security Manager arbitrates to determine if access should be allowed. If access is allowed it sends a grant signal to the querying protocol layer  110  which then accesses the requested application. If access is denied, the Security Manager  120  sends a refusal signal to the querying protocol layer  110  preventing access of the requesting unit to the desired service. 
     The lowest multiplexing protocol  108  makes an enquiry to the Security Manager for every received request for access to a service. The request is allowed to progress to a higher layer or service only if access is granted by the Security Manager. Each of the multiplexing protocol layers through which a request to access a service is routed, makes an enquiry to the Security Manager each time a request is received. The request is allowed to progress to a higher layer or service only if access is granted by the Security Manager. No application/service can therefore be accessed by a unit without at least one arbitration by the Security Manager. 
     The Security manger  120  is a software module with interfaces to protocols  108  and  110 , services/applications  118 , the UI  130 , the databases  122  and  124  and the link layer  106 . The security manager controls the link layer and the performance of its standard functions such as authentication, encryption and pairing. The Security Manager knows the identity of the services each of the protocol layers has direct access to. 
     The Security Manager may use its interfaces to the service database  122 , the device database, the link manager and the UI  130  to perform an above-mentioned arbitration. An exemplary service database is illustrated in  FIG. 7   a  and an exemplary device database is illustrated in  FIG. 7   b . When the Security Manager receives a query from the protocol layers or applications it queries the databases  122  and  124 . It accesses the fields associated with the requested application/service from the service database and accesses the fields associated with the BLUETOOTH ID of the requesting unit from the device database  124 . 
     The databases are used to define different security levels for devices and services. Each unit has a device database which stores information about other devices it has previously communicated with. The device database has an entry for each BLUETOOTH ID of the other devices. Each entry has associated fields including a first field to indicate whether that device is trusted or not trusted, a second field for storing the current link key for communication with that devices and a third field to indicate whether there has been a successful authentication with that device in the current session. 
     The trusted field is binary and there are therefore two security levels for devices-trusted and not-trusted. If a first unit records a second unit as trusted in its device database, then that second unit can access all the services of the first unit after authentication. If the first unit records the second unit as not-trusted (untrusted), the second unit may have its access to the services of the first unit restricted in dependence upon the service database in the first unit. 
     Each unit has a service database ( FIG. 7   a ) which stores information about the applications and services in that unit available for access by another unit. The service database has an entry for each available application or service. 
     Each entry has associated fields including a first field to indicate whether that service is open or not open and a second field to indicate whether encryption is required. This security information can be provided by the services/applications to the security manager during a registration procedure. 
     The Security Manager defines three levels of security in relation to a service. What the level is depends upon the security rating of the service (open/not-open) and the security rating of the requesting device (trusted/untrusted). When the security rating of the service is open there is no dependence upon whether the requesting device is trusted or untrusted and the open services are open to all devices. 
     When the security rating of the service is not-open then there is a dependence upon the trust level of the device requesting access. If the requesting device is trusted, then the device requesting access to the service must be authenticated before access to the service is granted. If the requesting device is untrusted, then the device requesting services must be authenticated and then explicit user authorization must be given before access to the service is granted. 
     Referring to the flow diagrams in  FIGS. 9 to 11 , after the Security Manager receives an query ( 200 ) from the multiplexing protocol layers  108  or  110 , it determines whether the querying multiplexing layer is directly connected to (interfaces with) the requested service ( 201 ). If the query from the protocol layer concerns a service to which the protocol layer is not directly connected, but is indirectly connected through higher multiplexing protocol layers, the Security Manager allows the passage of the request to the higher multiplexing protocol layer by sending a grant signal to the querying protocol layer. If the query from the querying protocol layer concerns a service to which the querying protocol layer is directly connected, the Security Manager performs an arbitration to determine if access to the service should be allowed or denied. 
     The arbitration is initiated by the Security Manager accessing ( 202 ) the databases  122  and  124 , identifying whether the requesting device is trusted and identifying whether the requested service is open ( 204 ). 
     If the requested service is an open service, the Security Manager grants access ( 216 ) by sending a grant signal to the querying protocol layer which then accesses the requested application. If the requested service is not an open service the arbitration continues. 
     If the requesting device is trusted, authentication only is required. If authentication of the requesting device has not occurred in this session ( 206 ) (determined from, the 3 rd  field of the entry for the requesting device in the device database), then the security manager instructs the link layer  106  to perform an authentication ( 208 ). Referring to  FIG. 10 , the security manager provides the link layer with the current key (if any) stored in the 2 nd  field of the database entry. The link layer performs the authentication (with pairing if necessary) and informs the security manager if the authentication has been successful. The processes of pairing ( 222 ), checking the link key is current ( 224 ) and creating a link key are implementation dependent and are not described further. If the authentication is unsuccessful the Security Manager sends ( 218 ) a refusal signal to the querying protocol thereby preventing access to the requested service. If the authentication is successful, link layer also returns the current link key for the requesting device. The Security Manager then updates ( 210 ) the device database, placing the current link key in the second field of the database entry and indicating that successful authentication has occurred in this session in the third field of the entry. The Security Manager then determines ( 212 ) whether the requesting device is a trusted device. As the device is trusted the Security Manager sends ( 216 ) a grant signal to the querying protocol thereby allowing access to the service. 
     If the requesting device is not-trusted, authentication and user authorization is required. If authentication of the requesting device has not occurred in this session ( 206 ) (determined from the 3 rd  field of the entry for the requesting device in the device database), then the security manager instructs ( 208 ) the link layer  106  to perform an authentication. The security manager provides the link layer with the current key (if any) stored in the 2 nd  field of the database entry. The link layer performs the authentication (with pairing if necessary) as previously described in relation to  FIG. 10 , and informs the security manager if the authentication has been successful. If the authentication is unsuccessful the Security Manager sends ( 218 ) a refusal signal to the querying protocol thereby preventing access to the service. If the authentication is successful the link layer also returns the current link key for the requesting device and the Security Manager updates the device database ( 210 ), placing the current link key in the second field of the database entry and indicating that successful authentication has occurred in this session in the third field of the entry. The security manager checks ( 212 ) the trusted status of the requesting device. As the device is not-trusted, the security manager then attempts to obtain user authorization ( 214 ) as illustrated in  FIG. 11 . The security manager controls ( 230 ) the UI  130  to indicate to the user that some positive act is required to allow a requesting device access to a service. The service and/or the requesting device may be identified on a screen. The user can agree or disagree to the access. Agreement causes the Security Manager to give ( 216 ) a grant signal to the querying protocol layer thereby allowing access to the requested service. Disagreement causes the Security Manager to give ( 218 ) a rejection signal to the enquiring protocol thereby preventing access to the requested service. The fact that the user authorization has been given is not recorded and access is therefore one time only. The Security Manager, may then as an option, offer ( 232 ) the user the opportunity to change the trust status of the requesting device from untrusted to trusted with subsequent updating ( 234 ) of the device database. 
     If encryption is required in addition to authentication, the Security Manager controls the link layer  106  to perform it, before allowing connection to the application/service requested. 
     The applications/services  118  and the higher multiplexing protocol  110  must register their multiplexing policies with the Security Manager so that it can determine which application/service is directly connected to each protocol layer. 
     The process of accessing a service using a trusted device is further illustrated in  FIG. 8   a . The protocol layer is directly connected to a service.
     1. Connect request to protocol layer   2. If access control occurs at this protocol layer, then send enquiry to Security Manager   3. Security manager looks up service database   4. Security manager looks up device database   5. Security Manager enforces standard authentication (and possibly encryption) in the link layer   6. Security Manager&#39;grants access or link terminated   7. Protocol layer continues to set up the connection by contacting higher protocol layers/services   

     The process of accessing a service using an untrusted devices is further illustrated in | FIG. 8   b . The protocol layer is directly connected to a service.
     1 Connect request to protocol layer   2 If access control occurs at this protocol layer, then send enquiry to Security Manager   3 Security manager looks up service database   4 Security manager looks up device database   5 Security Manager enforces standard authentication (and possibly encryption) in the link layer   6 Security Manager asks for manual user authorization   7 Security manager may update device database (trusted?)   8 Security Manager grants access or link terminated   9 Protocol layer continues to set up the connection by contacting higher protocol layers/services   

     In this embodiment authentication (5) is performed before authorisation (6). It would of course be possible to perform authorisation (6) before authentication (5). 
     The preceding description describes a preferred implementation of the claimed invention in a preferred application, namely a low power radio frequency communications network in accordance with the BLUETOOTH Standard. However, it should be appreciated that other implementations and applications may be utilized without departing from the scope of the invention. 
     In particular, in the embodiment described, whether or not the device authentication is required depends simply on the service requested and the content of the service database, in particular, whether the service is open or not-open. Whether or not user authorization is required is dependent on the service requested and the content of the service database, in particular, whether the service is open or not-open and dependent upon the identity of the device requesting access and the content of the device database, in particular whether the requesting device is trusted or not-trusted. 
     It would of course be possible to make device authentication solely or additionally dependent upon the trust status of the device requesting the service. It would also be possible to make user authorization solely or additionally dependent upon the service requested so that, for example, user authorization is or is not required for a not-trusted device accessing a particular service in dependence on the stored attributes of the service. 
     In the above embodiments, the operation of the security architecture has been described in relation to a device requesting access to a service in the ‘secure’ device. The security architecture may operate in both directions so that information is not sent from the ‘secure’ device to another device without a decision being made by the security manager. A protocol layer, preferably the highest possible multiplexing protocol layer, and the security manager in combination arbitrate whether the information is sent or not. This arbitration may require authentication and/or authorization as described above. 
     While preferred embodiments of the invention have been described in detail, it will be apparent to those skilled in the art that many changes and modifications may be made without departing from the disclosed invention in its broader aspects; and it is intended that the appended claims cover all changes and modifications as fall within the true spirit and scope of the contributions made to the art hereby.