Abstract:
A method and related system is disclosed for integrating a positioning system into the key management structure and within the information security boundary of an End Cryptographic Unit (ECU). This integration enables key management security rules written to include the ECU&#39;s trusted physical location and trusted time in determining if and with which key a message should be encrypted or decrypted. Only appropriate messages for a bounded geographic area would be decrypted and received by the ECU. The trusted positioning system allows extending functionality to allow position-enhanced authentication capabilities. Outgoing messages are cryptographically bound with the ECU&#39;s trusted position information as well as an accurate time stamp.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to management of keys to cryptographic communication devices. More particularly, embodiments of the present invention relate to a system and method for position-based management of cryptographic keys relieving a user of manual key management as the user position changes. 
     BACKGROUND OF THE INVENTION 
     Traditionally, cryptographic key management is a manual human operation. A user of an End Cryptographic Unit (ECU) must first input a key via a fill device connected to the ECU or through a graphic user interface to the ECU. Secondly, the user must select the correct key via graphic user interface to communicate with other communications devices using the same key for accurate encryption and decryption of secure communication. 
     On occasion, cryptographic communications may be of critical importance during an operational event. Manual human action, subject to error, may select an inaccurate or wrongly entered key and inhibit such vital communication. Further, a specific key for communication may be reliant on a user&#39;s position where the specific position of the user determines the correct key to be used. In this case, manual human selection of an inaccurate key may inhibit successful secure communication. 
     Consequently, a need exists for a more automated form of cryptographic key management, including a position-based method of key management. 
     SUMMARY OF THE INVENTION 
     Accordingly, an embodiment of the present invention is directed to a method for position-based cryptographic key management, the method comprises associating a cryptographic module within an information security boundary with a positioning system within the information security boundary, the cryptographic module having a cryptographic engine and a list of security rules, the positioning system configured for reception of at least a positioning signal and a timing signal, receiving and storing a plurality of cryptographic keys, associating at least one of the plurality of cryptographic keys with a known position to create a first security rule, associating at least one of the plurality of cryptographic keys with a known time window to create a second security rule, receiving a positioning signal and a time signal via the positioning system, determining a trusted position and a trusted time based on the positioning signal, determining: if the trusted position is in proximity with the known position, and if the trusted time is within the known time window, applying at least one of: the first security rule and the second security rule as an appropriate security rule, and the associated at least one of the plurality of cryptographic keys based on the determining, and encrypting and decrypting communication via the cryptographic module based on the applied security rule and the at least one associated plurality of cryptographic keys. 
     Embodiments of the present invention provide for a cryptographic module further configured for encrypting and decrypting secure communication and an information security boundary further configured as a perimeter within which all information is trusted. 
     Additional embodiments of the present invention provide a positioning system further configured for receiving positioning signals and determining a position based on the received signals and the known position includes a bounded geographical area defined on each side by a border. 
     Additional embodiments of the present invention provide an appropriate security rule comprising at least one security rule from the list of security rules and encrypting and decrypting communication via the cryptographic module comprises an encryption preceding a communication transmission and a decryption following a communication reception. 
     Additional embodiments of the present invention provide a system for position-based cryptographic key management, the system comprising an end cryptographic unit, the end cryptographic unit having an information security boundary, a cryptographic module within the information security boundary of the end cryptographic unit, the cryptographic module including a cryptographic engine and a list of security rules, a positioning system within the information security boundary of the end cryptographic unit, the positioning system configured for receiving and decoding a plurality of positioning signals and a plurality of timing signals, a key fill device configured for loading a plurality of keys, the cryptographic engine configured for storing the plurality of keys, a transmitter/receiver, the transmitter/receiver configured for sending and receiving signals to and from the cryptographic engine and an offboard ECU, wherein the cryptographic module is configured for: receiving a positioning input from the positioning system, receiving a timing input from the positioning system, receiving and storing a plurality of keys from the key fill device, determining a security rule appropriate for use from the list of security rules based on the positioning input, the timing input and at least one key of the plurality of keys, encrypting and decrypting a communication between a user and the transmitter/receiver based on the security rule appropriate for use. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not necessarily restrictive of the invention as claimed. The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and together with the general description, serve to explain the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The numerous advantages of the present invention may be better understood by those skilled in the art by reference to the accompanying figures in which: 
         FIG. 1  is an overview an exemplary physical layer of an embodiment of the present invention; 
         FIG. 2  is a diagram of multiple networks requiring a keyed cryptographic communications device exemplary of an embodiment of the present invention; 
         FIG. 3  is a diagram of multiple ground based networks requiring a keyed cryptographic communications device exemplary of an embodiment of the present invention; and 
         FIG. 4  is a flow diagram of a method for position-based cryptographic key management representative of an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will now be made in detail to the presently preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. 
     The following description presents certain specific embodiments of the present invention. However, the present invention may be embodied in a multitude of different ways as defined and covered by the claims. In this description, reference is made to the drawings wherein like parts are designated with like numerals throughout. 
     Embodiments of the present invention provide for a method for position-based management for cryptographic keys. More specifically, embodiments herein provide for a trusted position input as one of the inputs within an information security boundary of a cryptographic communications system. 
     Platforms within which embodiments of the present invention may operate may vary. One embodiment of the present invention may operate on an aircraft whereas an additional embodiment may function in an ECU as mounted on a tracked vehicle. One embodiment may function as incorporated within a radio configured for a human on foot. An airborne embodiment as exemplarily used herein serves not to limit the scope of the invention to a fighter sized aircraft but offer one example of the present invention. It is contemplated herein embodiments of the present invention may function within a variety of platforms, on a plurality of radios usable by a plurality of moving entities. 
     Embodiments of the present invention may employ a plurality of security rules to determine which key to use for encryption and decryption of communication information. For example, a time coupled with a key or a position coupled with a key are one example of a security rule. A cryptographic engine acting under commands of the present invention may make key selection decisions based on one or more security rules. 
     Embodiments of the present invention provide a system and method for auto-key selection based on time and location. A set of keys may expire at a specific time where if an expired key were manually selected, cryptographic communication would not be possible. Embodiments herein further provide for position-based automatic key selection where the cryptographic module performs auto key selection based on user position. 
     Additionally, embodiments of the present provide for loading a plurality of keys which may cover a plurality of known time windows and a plurality of geographical regions. For example, a time based key may be in operation from 1401Z to 1500Z another time based key may become operational from 1501Z to 1600Z. Keys may be loaded to the ECU to cover as much time as needed by the operator. Additionally, a position key may cover an area based on latitude and longitude or other geographic reference. A defined geographic area may require a first key whereas an adjacent defined geographic area may require a second key. As time progresses and the user of the ECU may traverse from the defined geographic area to the adjacent defined geographic area, embodiments of the present invention select and place into operation the required key for the defined geographic area. 
     Referring to  FIG. 1 , an overview an exemplary physical layer of an embodiment of the present invention is shown. Aircraft  110  may act as the desired platform upon which embodiments of the present invention may be mounted and employed. System  100  comprises, within information security boundary  120 , trusted elements of an ECU. One trusted element is cryptographic module  122  which houses security rules  124  and a cryptographic engine  126 . Additionally, positioning system  140  also lies within the information security boundary  120 . Outside information security boundary  120  are key fill device  150 , transmitter/receiver  130  with associated antenna  132 , user  128  and positioning system receiver antenna  142 . 
     Positioning System  140  may receive signals from a plurality of positioning systems usable by embodiments of the present invention. For example, reception of a ground based signal, an airborne based positioning signal, and a satellite based positioning signal may function within the scope of the present invention. Additionally, a combination of the above signals may enable system  100  to operate within the scope of this disclosure. It is contemplated herein; embodiments of the present invention may employ a variety of positioning systems receiving a plurality of positioning signals. For example, a Global Positioning System (GPS) signal and a Global Navigation Satellite System (GNSS) signal may be examples of satellite based signals usable by embodiments of the present invention. 
     Also, an onboard positioning systems may fall within the scope of the present invention. For example, system  100  may use an onboard inertial positioning system configured for embodiments of the present invention. 
     In addition, a time signal may be received and usable by embodiments of the present invention. A ground based, airborne based and satellite based timing signal may accompany the positioning signal or be a stand-alone timing signal. It is contemplated herein; system  100  may function with the accuracy of the received time signal to incorporate the received time signal within one or more of the security rules  124 . This time signal incorporation within the information security boundary  120  may, for example, assist embodiments of the present invention to aid in replay attack prevention. 
     Security rules  124  may function as the rules within which cryptographic engine  126  must operate. For example, as cryptographic engine  126  determines which key to employ in a geographic area, cryptographic engine  126  consults security rules  124  to determine which key or set of keys to use. 
     Cryptographic engine  126  operates as the encryption and decryption device to allow encrypted communication between user  128  and a second user via transmitter/receiver  130 . Cryptographic engine  126  receives trusted inputs from the sources and determines which of the security rules  124  to use for encrypted communication. 
     Transmitter/receiver  130  may function as a well-known transceiver, sending and receiving signals to additional transceivers within range. For example, user  128  may transmit a signal intending for the signal to be encrypted. Cryptographic engine  126  receives the signal and consults with security rules to determine the proper security rule to use for the user position and the time. Cryptographic engine  126  then encrypts the signal and transmits the encrypted signal to transmitter/receiver  130  for transmission via antenna  132 . 
     Embodiments of the present invention place the positioning system  140  within the information security boundary  120  of the ECU. Once within the information security boundary  120 , a trusted positioning system  140  may enable the ECU to autonomously alternate between required keys based on position. A user  128  may operate hands off conducting encrypted communication without being required to manually select a specific time-based or position-based key. 
     The trusted positioning and timing source within the information security boundary  120  allows additional function of the cryptographic engine  126  within an ECU. One additional function an embodiment of the present invention may provide is an enhancement to message authentication. A trusted time/position may augment the message&#39;s authenticity, proving that the sender is where they claim to be when the message is sent, in addition to their identity. Authentication methods make use of various data integrity functions, such as hashing, and the trusted time/position may contribute additional content to the authentication method usable within the scope of method  100 . 
     Embodiments of the present invention may leverage the time space position of the ECU (and platform thereon) to ensure trusted communication. For example, a specific platform may be in one position at a first time. The same platform may be at a second position at a second time. The trusted positioning and time reference within the information security boundary enables embodiments of the present invention trusted status with respect to other ECUs within the network. For example an operation radio may be configured with embodiments of the present invention to enable position-based security rules. An exemplary Single Channel Ground and Airborne Radio System (SINCGARS) radio may be configured with one embodiment of the present invention to enable position based security rules. 
     Referring to  FIG. 2 , diagram of multiple networks requiring a keyed cryptographic communications device exemplary of an embodiment of the present invention is shown. Aircraft  110  may follow path  220  along points  222 ,  224 ,  226 , and  228  en route to destination  230 . Satellite  210  provides positioning and timing signals  212  receivable by positioning system  140  onboard aircraft  110 . Along the route  220 , aircraft  110  may encounter a first network  240  within which secure communications may be desired. Further along route  220 , aircraft  110  may encounter second network  250  within which secure communications may be desired. A border  242  indicates the break between where aircraft  110  may communicate with first network and where aircraft  110  may communicate with second network  250 . 
     Embodiments of the present invention provide for a position-based input to the ECU onboard aircraft  110  to allow autonomous key selection and appropriate security rules  124  use. As aircraft  110  is within first network  240 , system  100  selects an appropriate key selection and security rule  124  for use. While aircraft  110  is within second network  250 , system  100  selects another appropriate security rule  124  and key for secure communication. 
     Referring to  FIG. 3 , diagram of multiple ground based networks requiring a keyed cryptographic communications device exemplary of an embodiment of the present invention is shown. Aircraft  110  may traverse first network  240 , second network  250  and a third area  260  while en route between point  222  and destination  230 . Within first network  240 , ground station  340  may be a node to which aircraft  110  may desire encrypted communication. Similarly, within second network  250 , ground station  350  may desire secure communication with aircraft  110 . 
     With aircraft  110  in position  310 , a first key is required to securely communicate in first network  240  with ground station  340 . At position  312 , aircraft may communicate in first network  240  with ground station  340  via the first key and also communicate in second network  250  with ground station  350  via a second key. In position  314 , aircraft  110  may communicate in network  250  only with ground station  350  via the second key. In position  316 , no ground stations are available for aircraft  110  to communicate with so a third key for communication in third network  260  may be appropriate. 
     Embodiments of the present invention may automatically select the appropriate key and associated appropriate security rule at each position based on trusted positioning system  140 . The trusted positioning system  140  accurately determines position and time based on reception and process of satellite based signals  212 . While aircraft  110  moves between networks, system  100  selects the appropriate key, the appropriate security rule and automatically enables position-based cryptic communication for the operator  128 . 
     Further, system  100  selects the appropriate key and appropriate security rule  124  based on the trusted time input from the positioning system  140 . 
     Additionally, system  100  stores keys for future use. For example, once aircraft  110  traverses path  220  to destination  230 , aircraft  110  may be required to egress along path  220  to point  222 . System  100  maintains a plurality of keys and is able to select the appropriate key and security rule for each network along the egress path. Further, system  100  may enable an operator  128  store a sufficient number of keys to cover a number of days of operations. Theater and local rules dependent, a supervisor or commander may authorize storage of an unlimited number of keys within a memory associated with cryptographic engine  126 . 
     Embodiments of the present invention may provide a variety of applications based on trusted positioning information and trusted time information. One such application may include an ECU maneuvering between Continental US and Outside the Continental US or between Strategic and Tactical environments. The ECU in these situations would assure that only properly structured keys would be used to encrypt/decrypt. The integration of the positioning data into the ECU information security boundary may leverage the high assurance of an embeddable cryptographic engine requiring high-assurance cryptographic processing. 
     Further, a multichannel, programmable cryptographic engine providing Multiple Independent Levels of Security (MILS) may benefit from inclusion of system  100  trusted positioning information within the information security boundary. 
     Referring to  FIG. 4 , a flow diagram of a method for position-based cryptographic key management representative of an embodiment of the present invention is shown. Method  400  begins at step  402  with associating a cryptographic module within an information security boundary with a positioning system within the information security boundary, the cryptographic module having a cryptographic engine and a list of security rules, the positioning system configured for reception of at least a positioning signal and a timing signal, and at step  404 , receiving and storing a plurality of cryptographic keys, and at step  406 , associating at least one of the plurality of cryptographic keys with a known position to create a first security rule, and at step  408 , associating at least one of the plurality of cryptographic keys with a known time window to create a second security rule. Method  400  continues at step  410 , receiving a positioning signal and a time signal via the positioning system, and at step  412 , determining a trusted position and a trusted time based on the positioning signal, and at step  414 , determining: if the trusted position is in proximity with the known position; and if the trusted time is within the known time window, and at step  416 , applying at least one of: the first security rule and the second security rule as an appropriate security rule, and the associated at least one of the plurality of cryptographic keys based on the determining, and finally at step  418 , encrypting and decrypting communication via the cryptographic module based on the applied security rule and the at least one associated plurality of cryptographic keys. 
     CONCLUSION 
     Specific blocks, sections, devices, functions, processes and modules may have been set forth. However, a skilled technologist will realize that there are many ways to partition the system, and that there are many parts, components, processes, modules or functions that may be substituted for those listed above. 
     While the above detailed description has shown, described and pointed out the fundamental novel features of the invention as applied to various embodiments, it will be understood that various omissions and substitutions and changes in the form and details of the system illustrated may be made by those skilled in the art, without departing from the intent of the invention. The foregoing description details certain embodiments of the invention. It will be appreciated, however, that no matter how detailed the foregoing appears, the invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiment is to be considered in all respects only as illustrative and not restrictive and the scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.