Secure mobile telephone system
First Claim
1. In a radio frequency mobile telephone communications system having a central station and a plurality of remote stations, each said central and remote station comprising signalling apparatus for establishing one of a plurality of information transmission channels between said central station and a particular remote station and information transmission for exchanging information between said central station and particular remote station over the established information channel, the improvement comprising:
- first means in said central station for enciphering information signals sent to said particular remote station in accordance with a first code unique to said particular remote station;
second means in said particular remote station for detecting the receipt of an information signal sent from said central station which was enciphered with said first code; and
third means in said particular remote station responsive to the detection of receipt of an enciphered information signal by said second means for enciphering with a second code an information signal and sending said enciphered information signal from said remote station to said central station.
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Accused Products
Abstract
A communications system including a central station and a plurality of remote stations, for example, a mobile telephone system, is disclosed in which communications channel establishing signalling transmissions between the central and remote stations are conducted in a clear (unenciphered) mode and subsequent voice transmissions between the central and remote stations are conducted in a secure (enciphered) mode. Each remote station has a unique code assigned thereto which is used by it to at least decipher incoming enciphered voice transmissions from the central station and by the central station to encipher outgoing voice transmissions to the remote station. The unique code may also be used by the remote station to encipher outgoing voice transmissions and by the central station to decipher incoming voice transmissions from the remote station. Alternatively all remote station outgoing voice transmissions may be enciphered with a code common to all remote stations which code is used by the central station for deciphering incoming voice transmissions. The central station can automatically, or in response to a specific request for secure service, switch its equipment to the secure mode upon completion of communications channel establishing signalling transmissions between it and a remote station and can control remote station switching to the secure mode by sending an enciphered voice transmission to the remote station which responds to receipt thereof by switching to the secure mode.
79 Citations
28 Claims
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1. In a radio frequency mobile telephone communications system having a central station and a plurality of remote stations, each said central and remote station comprising signalling apparatus for establishing one of a plurality of information transmission channels between said central station and a particular remote station and information transmission for exchanging information between said central station and particular remote station over the established information channel, the improvement comprising:
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first means in said central station for enciphering information signals sent to said particular remote station in accordance with a first code unique to said particular remote station; second means in said particular remote station for detecting the receipt of an information signal sent from said central station which was enciphered with said first code; and third means in said particular remote station responsive to the detection of receipt of an enciphered information signal by said second means for enciphering with a second code an information signal and sending said enciphered information signal from said remote station to said central station. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A central station for use in a radio frequency mobile telephone communications system containing central station and a plurality of remote stations comprising:
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first means for generating signalling signals for establishing one of a plurality of predetermined communications paths with a selected remote mobile station; second means for enciphering information signals directed to said selected remote mobile station in accordance with a code unique to said selected remote mobile station; third means responsive to address signals from said remote mobile station identifying said selected remote mobile station for generating and supplying said unique code to said second means; and fourth means coupled to said first, second and third means for first sending signalling signals generated by said first means to said selected remote mobile station and for thereafter sending information signals enciphered by said second means to said selected remote station in accordance with said unique code as supplied by said third means. - View Dependent Claims (16, 17)
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18. A method of communicating between a central station and plurality of remote mobile stations in a radio frequency mobile telephone communication system comprising the steps of:
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(a) establishing a sending and receiving information communications path between the central station and a selected one of the remote mobile stations in response to unenciphered signalling communications between the central stations and the selected remote station over one of a predetermined plurality of communication paths,; and (b) sending and receiving enciphered information over the communications path between the central station and the selected remote mobile station, said information being enciphered at the central station in accordance with a code unique to the selected remote mobile station and being applied to the communication path by the central station in response to establishment of the communicating path or in response to receipt by the central station of an unenciphered signal from said selected remote mobile station requesting secure service. - View Dependent Claims (19, 20)
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21. A radio frequency mobile telephone communications system comprising a base station and a plurality of remote stations;
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said base station comprising; means for establishing clear voice communication with a telephone communications system, means for establishing a clear information transmission channel with a selected one of said remote stations, and means responsive to the establishment of said clear information transmission channel with a selected remote station for selectively enciphering and deciphering voice transmissions to and from said selected remote station in accordance with at least one predetermined code uniquely assigned to said selected remote station; each of said remote stations comprising; means for establishing a clear information transmission channel with said base station, means responsive to the establishment of a clear information channel with said base station for selectively enciphering and deciphering voice transmissions to and from said base station in accordance with at least one predetermined code uniquely assigned to said remote station. - View Dependent Claims (22, 23, 24, 25)
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26. In a radio frequency mobile telephone communication system including a base station and a plurality of mobile stations in which unenciphered communication between a mobile station and the base station may be received and understood by each of the other mobile stations, the improvement wherein:
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(a) each of said plurality of mobile stations includes; (i) means of sending to the base station an unenciphered request for secure communication, (ii) means responsive to receipt of an encoded communication from the base station to encode subsequent transmissions to the base station in a code unique to the mobile station, and (iii) means responsive to receipt of an encoded communication for decoding subsequently received transmission from the base station encoded in said unique code; and (b) wherein said base station includes; (i) means for receiving an unenciphered request for secure communications from a mobile station, (ii) means for identifying from the request the particular mobile station and for determining the code unique thereto, (iii) means for transmitting an encoded communication signal to the mobile station in said unique code, (iv) means for decoding subsequently received transmissions from the mobile station in said unique code, and (v) means for encoding subsequent transmissions to said mobile station in said unique code; whereby the base station and one of the plurality of mobile stations may communicate using a code unique to that mobile station in response to an unenciphered request by the mobile station for secure communications.
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27. In a method of communicating between the base station and one of a plurality of remote mobile stations in a radio frequency mobile telephone system, the improvement comprising the steps of:
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(a) establishing non-secure communications between the base station and one of the mobile stations; (b) transmitting in the clear from the mobile station to the base station a request for secure communication service; (c) transmitting an acknowledging signal from the base station to the mobile station in a code unique to the mobile station; and (d) encoding all subsequent communication. - View Dependent Claims (28)
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Specification