Abstract:
A system and a method for ensuring that the initiation of mobile platform operations using maintenance terminals or other tools is prohibited when maintenance activities are not intended to be performed. The solution involves the incorporation of a manual interlock switch (accessible only to authorized personnel) that blocks activation of certain functions during times when such activation would be hazardous and when no properly authorized person has authorized such activation. No system for performing such a function will respond to a request unless the interlock is enabled. Should such a request be received, the system is required to report a fault, so that an investigation can be made as to the cause of the invalid request.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates generally to maintaining the security of a networked airplane.  
         [0002]     Conventional aircraft are provided with a central maintenance computer function (CMCF). The CMCF encompasses all major avionics, electrical, and mechanical systems installed on the aircraft. The CMCF collects, stores, and displays maintenance information generated by line commandable units. The CMCF also provides a centralized location to initiate system tests. The CMCF has operator interface display and input devices (i.e. multi-purpose control display units (MCDUs)).  
         [0003]     The prior art provides airline mechanics with an electronic maintenance terminal display that displays real-time CMCF data screens via MCDU emulation. A typical maintenance terminal is a laptop PC comprising a cursor control device, a keyboard, an internal hard drive, a floppy diskette drive, a CD-ROM drive, interfaces for brightness and contrast control, and a graphical output printer bus. Using such a maintenance terminal, authorized personnel are able to access maintenance applications that supervise the aircraft&#39;s avionics health status.  
         [0004]     Maintenance performed on airplane systems introduces the possibility of two distinct kinds of hazard: (1) direct hazard to maintenance and other personnel on the ground due to the release of energy (e.g., electrical, hydraulic and mechanical motion); and (2) hazard to flight safety from incorrect software configurations loaded into computing systems during maintenance. Some previous airplanes have relied on physical security controls and procedures to ensure that these hazards are mitigated.  
         [0005]     The Boeing 787 aircraft makes extensive use of networks in the design of maintenance tools and terminals for the airplane, introducing a possibility that a malicious or accidental attack on the network might activate hazardous function unexpectedly or cause the corruption of a system&#39;s software configuration without the authorized operator&#39;s knowledge.  
         [0006]     There is a need for a system and a method for ensuring that the initiation of such operations using maintenance terminals or other tools is prohibited when maintenance activities are not intended to be performed, so that airplane operators can be assured that maintenance functions cannot be unexpectedly activated. Such a system and method should be useful for preventing an attacker from manipulating on-board systems, whether accessed via a wired or a wireless maintenance terminal or tool.  
       BRIEF DESCRIPTION OF THE INVENTION  
       [0007]     The present invention is directed to a system and a method for ensuring that the initiation of mobile platform operations using maintenance terminals or other tools is prohibited when maintenance activities are not intended to be performed. The solution involves the incorporation of a manual interlock switch (accessible only to authorized personnel) that blocks activation of certain functions during times when such activation would be hazardous. No system for performing such a function will respond to a request or instruction unless the interlock is enabled. Should such a request or instruction be received, the system is required to report a fault, so that an investigation can be made as to the cause of the invalid request.  
         [0008]     One aspect of the invention is a system for preventing unauthorized access to a network, comprising a switch disposed within a space that can be secured to block entry by unauthorized persons, the switch being switchable between first and second states for respectively generating a first signal enabling access to the network and a second signal disabling access to the network, the signals being immune from duplication by unauthorized personnel.  
         [0009]     Another aspect of the invention is a method for preventing unauthorized activation of a target function aboard a mobile platform having a network, comprising the following steps: (a) placing a switch within a space aboard said mobile platform that can be secured to block entry by unauthorized persons, said switch being switchable between first and second states and being connected to said network; (b) generating an instruction to activate said target function; (c) activating said target function in response to generation of said instruction while said switch is in said first state; and (d) generating a fault message and not activating said target function in response to generation of said instruction while said switch is in said second state, wherein steps (b) through (d) are performed automatically by components of said mobile platform that communicate via said network.  
         [0010]     A further aspect of the invention is an airplane comprising: a space that can be secured to block entry by unauthorized persons; a switch disposed within said space, said switch being switchable between first and second states; a subsystem for performing a target function; a first software module for activating said subsystem only if an instruction to perform said target function is received while said switch is in said first state; and a second software module for performing a guard function in the absence of tampering, said guard function comprising the steps of sending an instruction to said second software module to perform said target function in response to receipt of a user request to perform said target function while said switch is in said first state, and not sending such an instruction in response to receipt of a user request to perform said target function while said switch is in said second state, wherein said first software module generates a fault message and does not activate said subsystem if an instruction to perform said target function is received from said first software module while said switch is in said second state, said fault message indicating that said guard function has been circumvented or compromised.  
         [0011]     Other aspects of the invention are disclosed and claimed below.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]      FIG. 1  is a flow diagram showing a method for protecting against unauthorized activation of a target function in accordance with one embodiment of the invention.  
         [0013]      FIG. 2  is a block diagram showing a system for protecting against unauthorized activation of a target function aboard a mobile platform in accordance with one embodiment of the invention. 
     
    
       [0014]     Reference will now be made to the drawings in which similar elements in different drawings bear the same reference numerals.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0015]     An embodiment of the invention will now be disclosed. While the particular embodiment disclosed herein is a networked airplane, the inventive concept is applicable to any mobile networked platform.  
         [0016]     In accordance with the disclosed embodiment, a manual interlock switch (accessible only to authorized personnel), which blocks activation of certain maintenance-related functions during times when such activation would be hazardous, is installed on the flight deck of a networked airplane. If a subsystem receives a request or an instruction to perform a maintenance function (e.g., ground testing, data loading or closing circuit breakers), such subsystem will not obey that request or instruction unless the interlock switch is in a state of enablement, indicating that maintenance functions are allowed. If an activation request or instruction is received by a subsystem while the interlock is in a state indicating that maintenance functions are prohibited, then that subsystem is required to report a security breach fault, so that an investigation can be made as to the cause of the invalid activation request.  
         [0017]     One embodiment of the invention is generally depicted in  FIG. 1 . A controlled user interface or guard function  2  serves as a gatekeeper for activation of a target function  4  (e.g., turning on an engine or motor, loading data into a computer, or closing a circuit breaker). The interlock switch, located in a secure space (e.g., the flight deck), is enabled by a manual operation  6  performed by a person authorized to enter that space. The enabled state of the interlock switch indicates that the activation of certain maintenance procedures is allowed. The controlled user interface or guard function  2  receives a user request to activate one of the protected maintenance functions. A decision  12  is then made concerning whether the requested maintenance function is prohibited or allowed by reference to the state of the interlock switch. Under normal conditions (i.e., the guard function has not been compromised), if the interlock switch is not in its state of enablement the guard function will deny (step  14 ) the user request and cause a message to be displayed to the user, which displayed message indicates the reason why the user request was denied (e.g., “requested procedure prohibited at this time”). If the interlock switch is enabled, then the guard function  2  sends a verified request (step  18 ) to the target function  4 .  
         [0018]     In response to receipt of a verified request from the guard function  2 , the target function  4  independently determines whether the requested maintenance function has been enabled by manual operation of the interlock switch (step  20 ). If the interlock switch is not enabled, the request from the guard function  2  is denied (step  22 ) and the target function  4  is not performed. In addition, a message is sent to a central maintenance computing function (CMCF), reporting that a security breach fault has occurred (step  24 ). In response to that fault report, authorized personnel will investigate the reason why the guard function issued a request that a certain maintenance function be performed in the absence of a necessary condition, to with, interlock enablement, and will take appropriate measures to eliminate any potential security failure (step  26 ). Under no circumstances will the request from the guard function be acted upon if the interlock switch is in a state indicating such maintenance functions are currently prohibited. On the other hand, if decision block  20  determines that the interlock switch is enabled, the target function  4  determines whether other safety criteria have been satisfied (step  28 ). If those additional safety criteria are satisfied, the requested maintenance function is performed (step  30 ).  
         [0019]     The architecture of a networked airplane in accordance with another embodiment of the invention is illustrated in  FIG. 2 . In this example, the onboard network of the airplane (or other mobile platform) is accessible from a maintenance terminal  32  via either a wireline or wireless communication pathway. In either case, an airplane interlock in the form of a maintenance enable switch  56  is provided on the flight deck for enabling specific functions, such as data load, circuit breaker access or ground tests.  
         [0020]     In the case of wireless maintenance access, a user may request that a target function be activated by a target application  52 , such user request being inputted using a maintenance terminal  32  that communicates with a wireless access point  34 . The maintenance terminal  32  must authenticate to the airplane. The information received from the maintenance terminal  32  by the wireless access point  34  is sent to an Ethernet router/switch  36 . The Ethernet router/switch  36  comprises multiple “virtual” switches (port-based VLANs), provides isolated subnetworks and supports routing policy implementation. User requests requesting the performance of maintenance functions are routed to a maintenance server  38 , that provides PC display services. The user request is then sent from the maintenance server to an Ethernet/AFDX (Avionics Full Duplex Switched Ethernet) router  40 , which provides customized policy routing. In the case of wired maintenance access, a user may request that the target application  52  activate a target function, such user request being inputted using a maintenance terminal  32 ′ that communicates with maintenance server  38  via the Ethernet/AFDX router  40 .  
         [0021]     In those cases when a person, using either maintenance terminal  32  or  32 ′, requests that a ground test (such as turning on an engine or a motor) be performed, the ground test is initiated by a central maintenance computing function (CMCF)  50 , which sends a verified request to the corresponding target applications (e.g., an engine or motor controller). The user request is sent to the CMCF  50  via the Ethernet/AFDX router  40 , an AFDX switch  42 , and an application executive (APEX)  48  The CMCF  50  is part of an avionics module  44 . The avionics module  44  is designed according to ARINC specifications. The target application may be part of the same avionics module  44  (see target application  52  in  FIG. 2 ), a different avionics module (not shown in  FIG. 2 ), or an avionics system  46  (see target application  52 ′ in  FIG. 2 ). For example avionics system  46  may comprise the flight control electronics system. When the CMCF  50  needs to communicate with a target application  52 ′ within avionics system  46 , the CMCF  50  does so via the AFDX switch  42 .  
         [0022]     In accordance with one implementation, the AFDX end system  46  comprises a network interface card, while the APEX  48  is an application executive that functions as an operating system disposed between the target application  52  and the AFDX end system  46 . For the purpose of conducting ground tests, the CMCF  50  incorporates the guard function previously described with reference to  FIG. 1 , while the target application  52  incorporates the target function (also previously described with reference to  FIG. 1 ). The CMCF  50  is made aware of the state of the maintenance enable switch  56  by a remote data concentrator  54 , which sends data represent the switch state onto the airplane network via the AFDX switch  42 .  
         [0023]     In response to receipt of a user request to activate the target function at a time when the switch  56  is in an enable maintenance state, the CMCF  50  will send a verified request to the target application  52 . In response to receipt of a user request to activate the target function at a time when the switch  56  is in an inhibit maintenance state, the CMCF  50  will deny the user request and not send a verified request to the target application  52 . Furthermore, if the target application  52  receives a request or instruction from the CMCF  50  that the target function be activated at a time when the switch  56  is in an inhibit maintenance state, the target application  52  will send a security breach fault message to the CMCF  50  and will not act upon the request or instruction. Authorized maintenance or security personnel will then investigate the cause of the invalid request received by the target application  52  and take steps to prevent the CMCF  50  from being compromised or bypassed in the future.  
         [0024]     Another maintenance function that can be protected from tampering or sabotage is the loading of data into the aircraft&#39;s onboard computers. In accordance with another embodiment of the invention, in response to a valid user request entered via one of the maintenance terminals, data can be loaded into an onboard computer (i.e., target application  52 ) by an onboard data load function that resides on the maintenance server  38 . The data load function residing on maintenance server  38  incorporates the previously described guard function, while the computer to be programmed with data incorporates the previously described target function.  
         [0025]     In response to receipt of a user request to load data into a target computer at a time when the switch  56  is in an enable maintenance state, the data load application residing on the maintenance server  38  will send a verified request to the target computer (i.e., target application  52  in  FIG. 2 ). In response to receipt of a user request to load data into a target computer at a time when the switch  56  is in an inhibit maintenance state, the data load application residing on the maintenance server  38  will deny the user request and not send a verified request to the target computer (i.e., target application  52  in  FIG. 2 ). Furthermore, if the target computer (i.e., target application  52 ) receives a request or instruction from the maintenance server to allow data loading at a time when the switch  56  is in an inhibit maintenance state, the target computer will send a security breach fault message to the CMCF  50  and not act upon the request or instruction.  
         [0026]     Another maintenance function that can be requested via a maintenance terminal is the testing of circuit breakers. An airplane may be provided with a computing function whereby circuit breakers can be opened and closed electronically via a circuit breaker indicator control panel that is displayed on the screen of the maintenance terminal. A special display application for circuit breakers is downloaded from a server (not shown in  FIG. 2 ) onboard the aircraft to the requesting maintenance terminal. The circuit breaker display application, which is like a browser plug-in, incorporates the previously described guard function. This circuit breaker display application will be the gatekeeper in that it is required to not make invalid requests. If a request to turn a circuit breaker on or off is made at a time when the switch  56  is in an inhibit maintenance state, the circuit breaker application (i.e., target application  52  in  FIG. 2 ) will send a security breach fault message to the CMCF  50  and not act upon the request or instruction.  
         [0027]     It should be readily apparent to a person skilled in the art that multiple maintenance enable switches  56  may be provided on the flight deck, each switch being dedicated to a respective category of maintenance functions or to a respective maintenance function. Alternatively, a single maintenance enable switch in a maintenance inhibit state may be used to prohibit all maintenance functions, including but not limited to ground tests, data load and circuit breaker access.  
         [0028]     While the invention has been described with reference to certain embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for members thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation to the teachings of the invention without departing from the essential scope thereof. Therefore it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.  
         [0029]     In the absence of explicit language in any method claim setting forth the order in which certain steps should be performed, the method claims should not be construed to require that steps be performed in the order in which they are recited.