Encoder and decoder microchips and remote control devices for secure unidirectional communication

• US 6,175,312 B1
• Filed: 12/04/1992
• Issued: 01/16/2001
• Est. Priority Date: 05/29/1990
• Status: Expired due to Term

• Current Assignee: Microchip Technology Incorporated
• Original Assignee: Microchip Technology Incorporated
• Inventors: Bruwer, Frederick Johannes, Smit, Willem, Kühn, Gideon Jacobus
• Primary Examiner(s): Holloway, III, Edwin C.
• Application Number:
  US07/985,929
• Time in Patent Office: 2,965 Days
• Field of Search: 340/825.3, 340/825.31, 340/825.34, 340/825.2, 340/825.21, 340/825.56, 340/825.69, 340/825.72, 235/382.5, 307/10.2, 307/10.5, 361/172, 702/56, 380/23, 380/262, 380/274
• US Class Current: 340/5.1
• CPC Class Codes: G06Q 20/341 Active cards, i.e. cards including their own processing means, e.g. including an IC or chip
• CPC Class Codes: G06Q 20/4097 using mutual authentication between devices and transaction partners
• CPC Class Codes: G07C 2009/0023 with encription of the transmittted data signal
• CPC Class Codes: G07C 2009/00769 with data transmission performed by wireless means
• CPC Class Codes: G07C 2009/00928 for garage doors
• CPC Class Codes: G07C 2209/06 Involving synchronization or resynchronization between transmitter and receiver; reordering of codes
• CPC Class Codes: G07C 9/00182 operated with unidirectional data transmission between data carrier and locks
• CPC Class Codes: G07F 7/1008 Active credit-cards provided with means to personalise their use, e.g. with PIN-introduction/comparison system

Abstract

Encoder and decoder microchips suitable for use in secure unidirectional remote control devices. The encoder microchip includes circuits for performing and encoding function on an identification number embedded in the microchip and a combination of a characterization number and a stepping counter value, so as to generate a transmission value which is only decidable by a related decoding function having access to the same identification number. The decoder microchip includes circuits for decoding the transmission value into a decoded characterization number and a decoded counter value and circuits for comparing the decoded counter value with a decoded counter value range. The encoder and decoder microchips are also provided with means for synchronizing the decoder microchip with a particular encoder microchip which has generated a synchronization command.

Claims

1. A system comprising an encoder microchip and a decoder microchip, wherein the encoder microchip comprises:

a circuit in which a first identification number is stored,

a circuit in which a counter value is stored,

a first logic circuit to change the value of the counter value only when the encoder microchip is operated, and

a non-linear encoding circuit to encode the counter value using the first identification number to generate a transmission value decodable to provide the counter value;

wherein the decoder microchip comprises;

a circuit in which a second identification number is stored;

a circuit in which the transmission value from the encoder microchip is received;

a circuit in which the transmission value is decoded using the second identification number to generate from the transmission value a decoded counter value;

a circuit in which a second decoded counter value obtained from a transmission value of a previous transmission is stored; and

a circuit in which signals are scanned to identify signals conforming to a specific format.

2. An encoder microchip comprising:

a circuit in which an identification number is stored;

a circuit in which a counter value is stored;

a first logic circuit to change the value of the counter value only when the encoder microchip is operated; and

a non-linear encoding circuit to encode the counter value using the identification number to generate a transmission value decodable to provide the counter value.

3. The encoder microchip of claim 2, wherein the transmission value is only decodable by using the identification number.

4. The encoder microchip of claim 2, further comprising:

a circuit to modulate the transmission value; and

a circuit to transmit the modulated transmission value to a matched receiver remote control device.

5. An encoder microchip as claimed in claim 2, further comprising:

a second logic circuit to form a unit number selected from the group consisting of information representing a command, information representing an input value, information representing a transmitter number and a constant value; and

wherein the non-linear encoding circuit encodes the counter value and the unit number using the identification number to generate the transmission value.

6. An encoder microchip as claimed in claim 5, wherein the non-linear encoding circuit generates the transmission value decodable to provide the counter value and the unit number.

7. A decoder microchip comprising:

a circuit in which an identification number is stored;

a circuit in which at least a first counter value is stored;

an output circuit;

an input logic circuit to receive data;

a circuit in which the received data using the identification number is decoded to generate a second counter value;

a circuit in which the second counter value is compared with the first counter value;

a circuit in which the output circuit is activated if a comparison shows that the second counter value is within a defined range of the first counter value; and

a circuit in which information relating to the second counter when the output circuit is activated is stored.

8. A decoder microchip according to claim 7, further comprising:

a circuit in which signals are received; and

a circuit in which the received signals are scanned to identify and act on values of valid format.

9. A decoder microchip according to claim 7, wherein the output circuit, when activated, provides an indication of information contained in an accepted decoded transmission value.

10. A decoder microchip according to claim 7, wherein the activator circuit activates the output circuit only when the second counter value is within a forward range of the first counter value.