Security system network

• US 5,001,755 A
• Filed: 03/21/1990
• Issued: 03/19/1991
• Est. Priority Date: 04/19/1988
• Status: Expired due to Fees

• Current Assignee: OLIN Microelectronic Chemicals Incorporated
• Original Assignee: Vindicator Corporation
• Inventors: Skret, Daniel L.
• Primary Examiner(s): Tarcza, Thomas H.
• Assistant Examiner(s): Cain, David
• Application Number:
  US07/497,052
• Time in Patent Office: 363 Days
• Field of Search: 380/37, 380/43, 380/46, 380/25
• US Class Current: 380/46
• CPC Class Codes: H04L 12/403 with centralised control, e.g. polling

Abstract

The present invention uniquely applies data communications network techniques to a security system. A series of slave transponders are coupled via a full duplex bus to a master node. The master node is coupled to other master nodes to form a network. The master node periodically polls its slave transponders to authenticate them. Each transponder has processing capability to give a distributed processing system. Each master node is a gateway which directs transmissions to the appropriate end point. The system uses an accordion-like protocol which can have fields added or deleted in a specific structure to conform the protocol to the particular message being transmitted. The protocol begins with address bytes identifying the destination followed by a control field which identifies the fields which are present. For a broadcast, rather than a point-to-point transmission, a process ID field in the protocol determines what area or function has to be addressed in all units. This area or function can be addressed for a large number of nodes by using this protocol field. The protocol is data transparent, it will handle any type of data. A sequence field allows the protocol to simultaneously handle redundant and non-redundant lines. The protocol allows point-to-point encryption of data and can operate over any media, electrical, optical, RF, etc. The routing algorithm includes an authentication byte attached by a particular transponder node and authenticated by a bus master connected to that node. The bus master substitutes its own authentication byte and sends the transmission along to the next point, where the authentication process is repeated. This allows authentication without requiring decrypting and re-encrypting of the transmission at each intermediate point.

Claims

1. A method for encrypting at least a portion of data transmission between nodes in a security system comprising the steps of:

(a) generating an identical sequence of pseudorandom numbers at both a transmitting and a receiving node;

(b) providing a key identifying a starting position in said sequence to both said transmitting and receiving nodes;

(c) incrementing the position in said sequence at both said transmitting and said receiving nodes for each predetermined portion of data transmission between said nodes;

(d) encrypting segments of said data transmissions using said pseudorandom numbers using said starting position for a first segment corresponding to said first position and using subsequent numbers for succeeding segments corresponding to succeeding portions;

(e) repeating steps (a)-(d) for each pair of nodes such that each node uses a different sequence position for each node it communicates with.

2. The method of claim 1 further comprising the step of using separate keys for transmitting and receiving by each node.

3. The method of claim 1 further comprising the step of using a global key by each node for communications with all nodes.

4. The method of claim 1 further comprising the step of resynchronizing two nodes by transmitting a current key value encrypted using said starting position.

5. The method of claim 1 further comprising the step of including a nonencrypted destination address with said encrypted segments.

6. A method for encrypting at least a portion of data transmissions between nodes in a security system comprising the steps of:

(a) generating an identical sequence of pseudorandom numbers at both a transmitting and a receiving node;

(b) providing a key identifying a starting position in said sequence to both said transmitting and receiving nodes;

(c) incrementing the position in said sequence at both said transmitting and said receiving nodes for each predetermined portion of data transmission between said nodes;

(d) encrypting segments of said data transmissions using said pseudorandom numbers using said starting position for a first segment corresponding to said first position and using subsequent numbers for succeeding segments corresponding to succeeding portions;

(e) repeating steps (a)-(d) for each pair of nodes such that each node uses a different sequence position for each node it communicates with;

(f) using two separate keys at each node for transmitting to and receiving from another node; and

(g) resynchronizing two nodes by transmitting a current key value encrypted using said starting position.

7. A security system for encrypting at least a portion of data transmissions between nodes comprising:

means for generating an identical sequence of pseudorandom numbers at both a transmitting and a receiving node;

means for providing a key identifying a starting position in said sequence to both said transmitting and receiving nodes;

means for incrementing the position in said sequence at both said transmitting and said receiving nodes for each predetermined portion of data transmission between said nodes; and

means for encrypting segments of said data transmissions using said pseudorandom numbers using said starting position for a first segment corresponding to said first position nd using subsequent numbers for succeeding segments corresponding to succeeding portions with each node using a different sequence position for each node it communicates with.

8. The system of claim 7 wherein separate keys are used for transmitting and receiving by each node.

9. The system of claim 7 further comprising a global key used by each node for communications with all nodes.

10. The system of claim 7 further comprising means for resynchronizing two nodes by transmitting a current key value encrypted using said starting position.