Cryptography – Communication system using cryptography – Wireless communication
Reexamination Certificate
1999-03-09
2002-11-26
Peeso, Thomas R. (Department: 2132)
Cryptography
Communication system using cryptography
Wireless communication
C380S030000, C713S168000
Reexamination Certificate
active
06487294
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a secure satellite communications system that provides private communications by utilizing public encryption procedures and private decryption procedures.
2. Description of the Related Art
“Satellite communications” refers to communications via an orbiting communications satellite. In active satellite communications systems, a transponder-equipped satellite is positioned in a geostationary orbit to provide broadcast, navigation, communications, or similar services to a service area or areas. A service area is defined as the geographic region in which an earth station can receive signals from or send signals to the satellite economically. The satellite carries communications equipment that relays signals to and from ground stations while the satellite orbits high above earthbound relay stations. Broad coverage results and that attracts mobile service where users may roam over a service area as large as the continental United States.
Existing mobile satellite communications networks provide very good communications capabilities to their users but not much communications security. Parties other than the mobile satellite communications network users and their intended correspondents can easily intercept the radio signals carrying the communications and extract the content carried by those signals. The minimal security features of a typical mobile satellite communications network are (1) separate over-the-air IDs for the forward direction (to the mobile user) and return direction (from the mobile user) and (2) scrambling used for single carrier per channel communications in the forward direction (because the forward direction downlink is available over a large portion of the earth's surface and since it is intended for mobile terminals with small antennas it is a high power transmission from the satellite and thus relatively easy to receive).
The communications security shortcomings of a typical mobile satellite communications network are (1) single carrier per channel communications in the return direction use only a “default” scrambling vector, thus no coding security is afforded in the return direction; (2) no security of the data broadcast on the common signaling channel is provided; (3) no security is given to the return direction slotted-ALOHA call request channels; (4) a party that can receive both forward and return direction satellite downlinks can use the information extracted from the return direction to “decode” the forward direction traffic and thus listen to both sides of the call; and, (5) even if the mobile satellite communications network user uses end-to-end encryption (such as STU-III) certain call information such as the service address (telephone number) called and the over-the-air terminal IDs are not protected and thus vulnerable to analysis.
The related art is represented by the following patents of interest.
U.S. Pat. No. 4,200,770, issued on Apr. 29, 1980 to Martin E. Hellman et al., describes a cryptographic apparatus and method. Hellman et al. do not suggest a secure satellite communications system according to the claimed invention.
U.S. Pat. No. 4,306,111, issued on Dec. 15, 1981 to Shyue-Ching Lu et al., describes a public-key cryptosystem. Lu et al. do not suggest a secure satellite communications system according to the claimed invention.
U.S. Pat. No. 4,405,829, issued on Sep. 20, 1983 to Ronald L. Rivest et al., describes a public-key cryptosystem. Rivest et al. do not suggest a secure satellite communications system according to the claimed invention.
U.S. Pat. No. 4,688,250, issued on Aug. 18, 1987 to Donald G. Corrington et al., describes a method and apparatus for effecting a key change via a cryptographically protected link. Corrington et al. do not suggest a secure satellite communications system according to the claimed invention.
U.S. Pat. No. 4,887,296, issued on Dec. 12, 1989 to Donald R. Horne, describes a cryptographic system for a direct broadcast satellite system. Horne does not suggest a secure satellite communications system according to the claimed invention.
U.S. Pat. No. 5,144,667, issued on Sep. 1, 1992 to Russell W. Pogue, Jr. et al., describes a method of positively authenticating a remote unit through cryptographic techniques. Pogue, Jr. et al. do not suggest a secure satellite communications system according to the claimed invention.
U.S. Pat. No. 5,159,633, issued on Oct. 27, 1992 to Kenji Nakamura, describes a multimedia network system. Nakamura does not suggest a secure satellite communications system according to the claimed invention.
U.S. Pat. No. 5,371,794, issued on Dec. 6, 1994 to Whitfield Diffie et al., describes a method and apparatus for providing a secure communication link between a mobile wireless data processing device and a base (fixed node) data processing device which is coupled to a network. Diffie et al. do not suggest a secure satellite communications system according to the claimed invention.
U.S. Pat. No. 5,675,653, issued on Oct. 7, 1997 to Douglas V. Nelson, Jr., describes a real time digital encryption system. Nelson, Jr. does not suggest a secure satellite communications system according to the claimed invention.
U.S. Pat. No. 5,724,428, issued on Mar. 3, 1998 to Ronald L. Rivest, describes a block encryption algorithm with data-dependent rotations. Rivest does not suggest a secure satellite communications system according to the claimed invention.
U.S. Pat. No. 5,745,578, issued on Apr. 28, 1998 to Amer Aref Hassan et al., describes a method and apparatus for establishing a key sequence for secure communication through a communication channel between a first transceiver and a second transceiver. Hassan et al. do not suggest a secure satellite communications system according to the claimed invention.
U.S. Pat. No. 5,748,734, issued on May 5, 1998 to Semyon Mizikovsky, describes a circuit and method for generating cryptographic keys. Mizikovsky does not suggest a secure satellite communications system according to the claimed invention.
European Patent document 0 232 043, published on Aug. 12, 1987, describes a method and apparatus for scrambling a digital signal. European '043 does not suggest a secure satellite communications system according to the claimed invention.
Great Britain Patent document 2,278,518, published on Nov. 30, 1994, describes a method and apparatus for establishing an encrypted data transfer link between a transmitter and a receiver. Great Britain '518 does not suggest a secure satellite communications system according to the claimed invention.
Great Britain Patent document 2,279,541, published on Jan. 4, 1995, describes an authentication system for a mobile communication system. Great Britain '541 does not suggest a secure satellite communications system according to the claimed invention.
International Patent document WO 93/1161, published on Jun. 10, 1993, describes an encryption system for transmitting confidential data from a transmitting device. International '161 does not suggest a secure satellite communications system according to the claimed invention.
Japan Patent document 2-248131, published on Oct. 3, 1990, describes a key sharing method based on identification information. Japan '138 does not suggest a secure satellite communications system according to the claimed invention.
Japan Patent document 3-82237, published on Apr. 8, 1991, describes an open public key cryptographic signal verification system. Japan '237 does not suggest a secure satellite communications system according to the claimed invention.
Japan Patent document 3-169138, published on Jul. 22, 1991, describes a key sharing method based on identification information. Japan '138 does not suggest a secure satellite communications system according to the claimed invention.
An article entitled
“A METHOD FOR OBTAINING DIGITAL SIGNATURES AND PUBLIC-KEY CRYPTOSYSTEMS
” by R. L. Shivest, A. Shamir, and L. Adleman, published in February, 1978, in
Communications of the ACM,
Vol.
Litman Richard C.
Peeso Thomas R.
Zand Kambiz
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