EP0100106A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Communications systems and transmitters and receivers including scrambling devices
Assignee: Comsat Corp
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Filing: 1983-07-28
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Granted: —
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Expires: 2003-07-28
Abstract
Abstract Pseudo-random number (PN) sequence generators used in scrambling and descrambling circuits at separate locations are periodically preset to the same start value in order to maintain synchronism, with the preset value being also periodically changed. The preset value can be transmitted to the scrambling and descrambling circuits over a privacy channel once per frame and stored in storage registers (20) associated with each of the scrambling and descrambling circuits (22, 24). The stored starting state values can be loaded into the PN sequence generators (22) as often as desired to maintain proper synchronization, with the stored values themselves being changed at a rate dependent on the desired degree of security.
Inventors
- 👤 Vivek Ragavan
- 👤 William H. Wolfe
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-04 22:57
CPC Classifications
H; H04; H04L; H04L9/00; H04L9/06; H04L9/065; H04L9/0656; H04L9/0662
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
144 words
A communications system comprising: at least one transmitting and at least one receiving station, said transmitting station having a scrambling means of the type including first generator means (12) for generating a scrambling sequence commencing with a starting state and mixing means (14) for scrambling data in accordance with said scrambling sequence, said receiving station having descrambling means of the type including second generator means (22) for generating a descrambling sequence commencing with said starting state and mixing means (24) for descrambling received data in accordance with said descrambling sequence, said first and second generating means being arranged to generate identical sequences commencing from identical starting states; characterized by means for periodically setting both said first and second generating means to identical starting states, and by means (10,20) for periodically changing the starting state to which said first and second generating means are set.
Claim 2
Dependent Claim
144 words
A communications system comprising: at least one transmitting and at least one receiving station, said transmitting station having a scrambling means of the type including first generator means (12) for generating a scrambling sequence commencing with a starting state and mixing means (14) for scrambling data in accordance with said scrambling sequence, said receiving station having descrambling means of the type including second generator means (22) for generating a descrambling sequence commencing with said starting state and mixing means (24) for descrambling received data in accordance with said descrambling sequence, said first and second generating means being arranged to generate identical sequences commencing from identical starting states; characterized by means for periodically setting both said first and second generating means to identical starting states, and by means (10,20) for periodically changing the starting state to which said first and second generating means are set.
Claim 3
Dependent Claim
83 words
A system as claimed in claim 1 characterized in that said means for periodically changing comprises: a first storage register (10) at said transmitting station for storing said starting state; a second storage register (20) at said receiving station for storing said starting state, the contents of said first and second storage registers being set into said first and second generating means, respectively, in response to a start signal; and means for periodically changing the contents of said first and second storage registers.
Claim 4
Dependent Claim
58 words
A system as claimed in claim 2 characterized in that said means for periodically changing the contents of said first and second storage registers comprises means for periodically generating a new starting state value, said new starting state value being transmitted in an unscrambled state to at least said receiving station for storage by said second storage register.
Claim 5
Dependent Claim
60 words
A system as claimed in claim 3, characterized by a TDMA system having a reference station in addition to said transmitting and receiving stations, said means for periodically generating a new starting state value being located at said reference station and said new starting state value being transmitted in an unscrambled state to both of said transmitting and receiving stations.
Claim 6
Dependent Claim
27 words
A system as claimed in claim 3 or 4 characterized by means other than said scrambling means for encrypting said new starting state value prior to transmission.
Claim 7
Dependent Claim
141 words
A communications system in which original data to be transmitted is provided at a transmitting station to a scrambler (12,14), the output of said scrambler comprising scrambled data and being transmitted to a receiving station, the received scrambled data being provided at said receiving station to a descrambler (22,24) for recovery of said original data, characterized in that each of said scrambler and descrambler comprises: storage register means (10,20) for receiving and storing a periodically changing starting state value; a PN sequence generator (12,22) for generating a PN sequence commencing from a sequence start value, the PN sequence generators in each of said scrambler and descrambler generating the same PN sequence for any given sequence start value; and means for synchronously loading the starting state values from each storage register into their respective PN sequence generators as said sequence start values.
Claim 8
Dependent Claim
141 words
A communications system in which original data to be transmitted is provided at a transmitting station to a scrambler (12,14), the output of said scrambler comprising scrambled data and being transmitted to a receiving station, the received scrambled data being provided at said receiving station to a descrambler (22,24) for recovery of said original data, characterized in that each of said scrambler and descrambler comprises: storage register means (10,20) for receiving and storing a periodically changing starting state value; a PN sequence generator (12,22) for generating a PN sequence commencing from a sequence start value, the PN sequence generators in each of said scrambler and descrambler generating the same PN sequence for any given sequence start value; and means for synchronously loading the starting state values from each storage register into their respective PN sequence generators as said sequence start values.
Claim 9
Dependent Claim
64 words
A transmitting or receiving station for use in the system of any one of the preceding claims, characterized by: storage register means (10:20); generator means (12;22) arranged to generate a scrambling sequence from a variable starting state; means for loading the content of said register means into said generator means as said start value; and means for changing the content of said register means.
References Cited (Backward Citations)
No citation records indexed.
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