Cryptographic system for direct broadcast satellite network

Claim 2

The system of Claim 1, characterized in that said address number encrypting means (22) comprises the Data Encryption Standard algorithm.

Claim 3

The system of Claim 1, characterized in that said common key encrypting means (16) comprises a block cipher algorithm.

Claim 4

The system of Claim 1, characterized in that said means (16) for forming an individual encrypted common key for each receiver node comprises means for selecting each receiver node in sequence, for generating the individual key for the selected receiver node and means for generating the encrypted common key for the selected receiver node using the generated individual key for the selected receiver node.

Claim 5

The system of Claim 1, characterized in that said distributing means comprises means for generating a data stream, said data stream comprising said encrypted information and addressed portions, each of said addressed portions comprising the address number and individualized encrypted common key for an addressed receiver node.

Claim 6

The system of Claim 5, characterized in that said information to be communicated comprises a digitized signal and is distributed by a composite television signal including video signal portions and horizontal blanking intervals and further characterized in that said data stream is inserted into said horizontal blanking intervals.

Claim 7

The system of Claim 1, characterized in that each receiver node has a unique individual key stored therein (28) and further comprising means for receiving said encrypted information, means for receiving the individualized encrypted common key for that nodes means (26) for decrypting the received individualized encrypted common key using the stored individual key and.means (24) for decrypting said received encrypted information using said decrypted common key.

Claim 8

The system of Claim 7, characterized in that said encrypted common key decrypting means (26) comprises a block cipher algorithm.

Claim 9

The system of Claim 1, further characterized by means (14) for periodically changing said common key.

Claim 10

The system of Claim 1, characterized in that said information encrypting means (12) comprises a stream cipher algorithm.

Claim 11

The system of Claim 7, characterized in that information decrypting means (12) comprises a stream cipher algorithm.

Claim 12

A three key cryptographic system for secure distribution of information from a transmission node to a plurality of receiver nodes wherein a first key is known only to the transmission node and each receiver node has a unique address number and a pre-stored second key, the transmission node characterized by means (22) for generating the second key for a selected receiver node by encrypting the address number for the selected node with the first key, means (14) for generating a third key, means (12) for encrypting the information to be distributed with said third key, means (16) for encrypting said third key for use by said selected receiver node with said generated second key, means for distributing said encrypted information to all of said receiver nodes, and means for distributing said encrypted third key to said selected receiver node.

Claim 13

The system of Claim 12, characterized in that each of said receiver nodes comprises means for receiving said encrypted information, means for receiving said encrypted third key for that receiver node, means (26) for decrypting said received encrypted third key with the stored second key, and means (24) for decrypting said received encrypted information with said decrypted third key.

Claim 14

The system of Claim 12, characterized in that said second key generating means (22) comprises a Data Encryption Standard algorithm.

Claim 15

The system of Claim 12, characterized in that said third key encrypting means (16) comprises a block cipher algorithm.

Claim 16

The system of Claim 13, characterized in that said third key decryption means (16) comprises a block cipher algorithm.

Claim 17

The system of Claim 12, characterized in that said third key generating means (14, 16) comprises means (14) for periodically changing said third key.

Claim 18

The system of Claim 12, characterized in that said information encryption means (12) comprises a stream cipher algorithm.

Claim 19

The system of Claim 13, characterized in that said information decrypting means (12) comprises a stream cipher algorithm.

Claim 20

The system of Claim 12, characterized in that the stored second key is unique for each receiver node.

Claim 21

The system of Claim 12, characterized in that the stored second key for each receiver node is a function of the address number of that receiver node.

Claim 22

A three key cryptographic method for secure information distribution from a transmission node to a plurality of receiver nodes wherein a first key is known only to the transmission node and each receiver node has a unique address number and a pre-stored unique second key which is a function of its address number, the method characterized by the steps of generating the second key for a selected receiver unit by encrypting the address number for the selected unit with the first key, generating a third key, encrypting the information to be distributed with the third key, encrypting the third key with the generated second key, distributing the encrypted information to all receiver nodes, distributing the encrypted third key to the selected receiver node; receiving the distributed encrypted information and the encrypted third key at the selected receiver node, and decrypting the received encrypted information using the received encrypted third key and the stored second key for the selected receiver node.

Claim 23

The method of Claim 22, characterized in that the step of decrypting the received encrypted information comprises the steps of decrypting the encrypted third key using the stored second key for the selected receiver node and decrypting the encrypted information using the decrypted third key.

Claim 24

The method of Claim 22, characterized in that the step of generating the second key comprises the step of encrypting the address number for the selected receiver node with the first key through the Data Encryption Standard algorithm.

Claim 25

The method of Claim 22, characterized in that the step of encrypting the third key comprises encrypting the third key with the second key through a block cipher algorithm.

Claim 26

The method of Claim 22, characterized in that the step of encrypting the information comprises the step of encrypting the information with said third key through a stream cipher algorithm.

Claim 27

The method of Claim 23, characterized in that the step of decrypting the third key comprises the step of decrypting the third key using the stored second key for the selected receiver node through a block cipher algorithm.

Claim 28

The method of Claim 22, characterized in that the step of decrypting the information comprises the step of decrypting the information with the decrypted third key through a stream cipher algorithm.

Claim 29

Apparatus for encrypting digitized signals in a direct broadcast satellite communications system including a transmission node and a plurality of receiver nodes, each receiver node-having an address number-and a pre-stored signature key which is a function of its address number, the apparatus characterized by: means (14) for generating a common key; means (12 for encrypting the digitized signals with said common key; means (18, 20, 22) for generating the signature key for a selected unit; said signature key generating means comprising: a master key (20) and means (22) for encrypting the address number of said selected receiver node using the master key; means (16) for encrypting said common key for use by the selected receiver node using the generated signature key for that receiver node; means for distributing the encrypted digitized signals and the encrypted common key for said selected receiver node to said selected receiver node by means of a data stream comprising a first portion containing the encrypted digitized signals and receivable by all receiver nodes and a second portion comprising a plurality of sub-portions, each of said sub-portions comprising the encrypted common key for a different receiver node and receivable only by the receiver node having the address number upon which the encrypted common key therein is based.

Claim 30

A cryptographic method for secure distribution of information from a transmission node to first and second receiver nodes, each receiver node having a unique address number, the method characterized by the steps of: generating a common key; encrypting the information to be distributed using said common key; generating a different individual key for each receiver node using a master key and encrypting the address number for each receiver node with the master kay; forming an individualized encrypted common key for each receiver node by encrypting the common key using the generated individual key for that receiver node; and distributing the information to all receiver nodes and the individualized encrypted common key for each receiver node to that receiver node.