Secure television transmission system

• US 4,070,693 A
• Filed: 03/10/1977
• Issued: 01/24/1978
• Est. Priority Date: 08/08/1975
• Status: Expired due to Term

• Current Assignee: Westinghouse Electric Corporation (Paramount Global (f/k/a ViacomCBS Inc.))
• Original Assignee: Westinghouse Electric Corporation (Paramount Global (f/k/a ViacomCBS Inc.))
• Inventors: Shutterly, Harold B.
• Primary Examiner(s): Buczinski, S. C.
• Application Number:
  US05/776,329
• Time in Patent Office: 320 Days
• Field of Search: 179/1.5 S, 325/32, 178/22, 178/113, 358/119, 358/120, 358/123, 358/259
• US Class Current: 380/215
• CPC Class Codes: H04N 7/088 the inserted signal being digital
• CPC Class Codes: H04N 7/1696 by changing or reversing the order of active picture signal portions

Abstract

A system for transmitting a secure television image is as disclosed. At the transmitter each line of the television image is digitized to generate a series of digital numbers representing the complete video line. The digital numbers representing the picture portion of each scan line are cyclically rotated by a random amount leaving the synchronizing portion unchanged. The digital numbers are converted to an analog signal which is filtered to generate a composite signal with the picture portion of each line cyclically shifted by a random amount. At the receiver the signal is digitized and the picture portion of each line is rotated to restore the picture portions of each line to their original position. The process of rotation is identical to that used at the transmitter except that the amount of rotation must be adjusted to restore all portions of the picture portion of the signal to their original position. The degree of security resulting from this system depends on the complexity of the system used to determine the random rotation of the individual scan lines.

Claims

1. Apparatus for scrambling a signal, said signal including a plurality of first lines with each first line comprising a synchronization portion followed in time by a first data portion, said data portion comprising at least sequentially occurring first and second data segments.data storage apparatus having first and second storage locations with each of said locations having sufficient storage capacity to store data representing at least one line of said signal;

2. storage control apparatus for alternately storing data representing selected lines of said signal;

3. read control apparatus for alternately reading said stored data from said first and second storage locations to produce a modified line corresponding to each of said first lines, each modified line consisting of a synchronization portion and third and fourth data segments sequentially following said synchronization portion;

with

a. said synchronization portion being substantially identical to the synchronization portion of the corresponding said first line;

b. said third data segments being substantially identical to said second data segments;

c. said fourth data segments being substantially identical to said first data segments; and

4. apparatus for randomly varying the length of said first and second data segments to produce said scrambled signal.

2. Apparatus for secure transmission and reception of a signal, said signal including a plurality of first lines with each first line comprising a synchronization portion followed in time by a first data portion, said data portion comprising at least sequentially occurring first and second data segments, comprising:

1. first data storage means having first and second storage locations with each location having sufficient storage capacity to store data representing at least one line of said signal;

2. control apparatus for alternately storing data representing selected lines of said signal in and alternately reading data representing selected lines of said signal from said first and second storage locations to produce modified lines corresponding to each of said first lines, each modified line consisting of a synchronization portion and third and fourth data segments sequentially following said synchronization portion;

wherein

a. said synchronization portion is substantially identical to the synchronization portion of the corresponding first line;

b. said fourth data segment being substantially identical to said first data segment; and

3. apparatus for selectively varying the length of said first and second data segments to produce a scramble signal;

4. apparatus for transmitting said scrambled signal;

5. apparatus for receiving said scrambled signal and for alternately storing selected lines by said scrambled signal in second data storage means having first and second storage locations with each location having sufficient storage capacity to store data representing at least one line of said scrambled signal; and

6. read apparatus for alternately reading data from said first and second storage locations of said second data storage means to produce a second signal, said second signal being substantially identical to said first signal.

3. Apparatus for scrambling a signal, said signal including a plurality of first lines with each first line comprising a synchronization portion followed in time by a first data portion, said data portion comprising at least sequentially occurring first and second data segments.data storage apparatus having first and second storage locations with each of said location having sufficient storage capacity to store data representing at least one line of said signal;

2. storage control apparatus for alternately storing data in and reading said stored data from said first and second storage locations to produce a modified line corresponding to each of said first lines, each modified line consisting of synchronization portion and a second data portion with,

a. said synchronization portion being substantially identical to the synchronization portion of the corresponding said first line;

b. said second data portion being substantially identical to said first data portion with said first and second data segments interchanged;

3. apparatus for varying the length of said first and second segments in predetermined manner to produce said scrambled signal.