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 Title: |
US4418425:
Encryption using destination addresses in a TDMA satellite communications network
[ Derwent Title ]
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| Country: |
US United States of America
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| Inventor: |
Fennel, Jr., John W.; Olney, MD
Heinz, Jr., Miles T.; Seabrook, MD
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| Assignee: |
IBM Corporation, Armonk, NY
other patents from INTERNATIONAL BUSINESS MACHINES CORPORATION (280070) (approx. 44,393)
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| Published / Filed: |
1983-11-29
/ 1981-08-31
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| Application Number: |
US1981000297607
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| IPC Code: |
Advanced:
H04B 7/15;
H04B 7/212;
H04J 3/00;
H04K 1/00;
H04L 9/00;
H04L 9/18;
H04L 9/36;
Core:
more...
IPC-7:
H04J 3/16;
H04K 1/00;
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| ECLA Code: |
H04L9/00;
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| U.S. Class: |
Current:
380/033;
370/321;
380/261;
Original:
455/027;
370/104;
375/002.2;
178/022.17;
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| Field of Search: |
370/104
375/2.1,2.2
455/026-30,12
178/22.15,22.17
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| Priority Number: |
| 1981-08-31 |
US1981000297607 |
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| Abstract: |
An encryption system is disclosed which is based on channel destination addresses for a time division multiple access (TDMA) satellite communications network. A superframe initialization vector is transmitted from a master station to all other stations in the network. A plurality of frame initialization vectors is sequentially generated at each station in an encryption engine, from the superframe initialization vector, using a key which is common only to authorized users within the network. Each data channel is initialized with encryption bits produced by exclusive ORing the channel destination address and the frame initialization vector for the frame in which that channel is to be transmitted, and then passing the output of the exclusive OR through the encryption engine using either the same key or a second, different key. These encryption bits are combined with the channel data in an exclusive OR circuit for TDMA transmission via the satellite transponder to the receiving stations. The decryption process at the receiving stations parallels the encryption process at the transmitting stations, so that clear-text data is output only at the destination addressed where the intended recipient has the same key as the transmitter. The system enables the synchronization of encryption engines at separate, geographically remote stations and permits the decryption of encrypted channels at anytime within a TDMA frame.
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| Attorney, Agent or Firm: |
Hoel, John E. ;
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| Primary / Asst. Examiners: |
Cangialosi, Sal;
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| INPADOC Legal Status: |
Show legal status actions
Family Legal Status Report
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| Designated Country: |
DE FR GB
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| Family: |
Show 6 known family members
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First Claim:
Show all 6 claims |
Having thus described our invention, what we claim as new, and desire to secure by Letters Patent is:
1. In a TDMA satellite communications network having a master station and a plurality of subsidiary earth stations, each communicating through a satellite transponder in a plurality of TDMA frames grouped into superframes, each said station including a TDMA communications controller having a plurality of input/output ports for transferring channels of data from respective, local data users to a TDMA output to said satellite transponder and transferring said channels of data via a TDMA input from said satellite transponder to said respective local users on a time interleaved basis during periodic TDMA frames, an encryption/decryption system for said network, comprising:
- a superframe initialization vector generator in said master station, having an output connected to said TDMA output thereof, for transmitting a superframe synchronization vector once during each superframe;
- a first encryption engine in each of said stations, having an input connected to said TDMA input thereof, for receiving said superframe synchronization vector and encrypting it with a key, forming a first frame initialization vector prior to a first transmit frame of a transmit superframe, to be used for said first transmit frame;
- a frame initialization vector buffer in each of said stations, having an input connected to said first encryption engine, for storing frame initialization vectors output therefrom;
- a transmit address array buffer in each of said stations, for storing a plurality of destination addresses, each respectively corresponding to each of said plurality of channels of data to be transmitted;
- a first exclusive-OR circuit in each of said stations, having a first input connected to said frame initialization vector buffer and a second input connected to said transmit address array buffer, and an output connected to said input of said first encryption engine, for generating a plurality of channel units of exclusive-OR bits from said first initialization vector and said plurality of destination addresses, each said channel unit corresponding to each of said channels of data to be transmitted;
- said first encryption engine receiving each of said plurality of channel units of exclusive-OR bits and encrypting it with a key, forming a corresponding plurality of channel units of encryption bits;
- a transmit crypto bit buffer in each of said stations, having an alternate A/B storage cycle, with an input connected to said output of said first encryption engine, and an output, for storing said plurality of channel units of encryption bits on a first side during the transmit frame immediately preceding said first transmit frame;
- a second exclusive-OR circuit in each of said stations, having a first input connected to the output of said transmit crypto bit buffer and an output connected to said TDMA output;
- a transmit burst buffer in each of said stations having an alternate A/B storage cycle, with a data input connected to a transmit bus common to the data outputs of all of said ports and an output connected to a second input of said second exclusive-OR circuit, for storing, in clear-text form, said plurality of channels of data on a first side during said transmit frame immediately preceding said first transmit frame;
- said transmit burst buffer bursting said plurality of clear-text data channels from said first side thereof during said first transmit frame, to said second input of said second exclusive-OR circuit synchronously with said transmit crypto bit buffer bursting said plurality of channel units of encryption bits from said first side thereof to said first input of said second exclusive-OR circuit;
- said second exclusive-OR circuit outputting to said TDMA output a resultant plurality of encrypted data channels, each of which is transmitted to said satellite transponder with a corresponding destination address.
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| Background / Summary: |
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| Drawing Descriptions: |
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| Description: |
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| Forward References: |
Show 137 U.S. patent(s) that reference this one
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| Foreign References: |
None
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| Other References: |
S 1792 0125, Int. Conf. on Communications, Denver, Co. (1/14-18/81), pp. 59.4-59.45, "Synchronization Techniques for Mobile Satellite Systems", Hagmann et al.
S 1792 011, Int. Conf. on Comm., Denver, Co. (1/14-18/81), pp. 55.1-55.7, "SS/TDMA Frame Synchonization", Campanella et al.
S 0111 0016, Conf. on Electrncs & Aero. Syst., Wash. D.C. (10/69), "Results of TDMA Equip. Dev. Appl. to Military Systems", pp. 133-137 Epstein et al.
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