US 5,862,225 A · Automatic resynchronization for remote keyless entry systems

Abstract

The present invention teaches a method and system for resynchronizing a remote keyless entry receiver having received a new encrypted message transmitted by the transmitter which does not match a previous encrypted message, also transmitted by the transmitter, and stored in memory. The method comprises a first step of transmitting and receiving a first new follow up encrypted message. Subsequently, the received new encrypted message is re-encrypted, and that result is tested against the received first new follow up encrypted message to determine whether there is a match. In the event both match, a second new follow up encrypted message transmitted and received. At this point, the received re-encrypted new encrypted message is re-encrypted a second time, and that result is tested against the received second new follow up encrypted message to determine whether there is a further match. If a match is made, the received second new follow up encrypted message is decrypted and the command within the received and decrypted second new follow up encrypted message is initiated.

Claims13

Dependent claims

A method of resynchronizing a receiver with a transmitter if the receiver and the transmitter are asynchronous, the receiver having received a new encrypted message, the method comprising the steps:

transmitting and receiving a first new follow up encrypted message;
re-encrypting the received new encrypted message;
testing whether said received first new follow up encrypted message matches the re-encrypted received new encrypted message;
and
if said received first new follow up encrypted message matches the re-encrypted received new encrypted message,
transmitting and receiving a further new follow up encrypted message;
re-encrypting the received re-encrypted new encrypted message;
testing whether said received further new follow up encrypted message matches said received twice re-encrypted new encrypted message;
and
if said received further new follow up encrypted message matches the received twice re-encrypted new encrypted message,
decrypting said received further new follow up encrypted message;
and
initiating a command within said received and decrypted further new follow up encrypted message.

10 more elements

A method of resynchronizing a remote keyless entry receiver with a transmitter, the receiver having received a previous encrypted message, the method comprising the steps:

receiving a new encrypted message from the transmitter;
re-encrypting the previous encrypted message;
testing whether said received new encrypted message matches said re-encrypted previous encrypted message;
if said received new encrypted message matches said re-encrypted previous encrypted message,
decrypting said received new encrypted message;
initiating a command within said decrypted new message;
if said received new encrypted message does not match said re-encrypted previous encrypted message,
re-encrypting said re-encrypted previous encrypted message;
decrementing a counter each time said re-encrypted previous encrypted message is re-encrypted;
if said counter exceeds a count number,
testing whether said received new encrypted message matches said re-encrypted previous encrypted message;
if said received new encrypted message matches said re-encrypted previous encrypted message,
decrypting said received new encrypted message;
initiating said command within said decrypted new message;
if said received new encrypted message does not match said re-encrypted previous encrypted message,
repeating the steps of re-encrypting said re-encrypted previous encrypted message, decrementing the counter, and testing whether said new encrypted message matches said re-encrypted previous encrypted message if said counter exceeds said count number;
if said counter does not exceed said count number,
transmitting and receiving a first new follow up encrypted message;
re-encrypting said received new encrypted message;
testing whether said received first new follow up encrypted message matches said re-encrypted received new encrypted message;
if said received first new follow up encrypted messages matches said re-encrypted received new encrypted message,
transmitting and receiving a further new follow up encrypted message;
re-encrypting said received re-encrypted new encrypted message;
testing whether said received further new follow up encrypted messages matches said received twice re-encrypted new encrypted message;
if said received further new follow up encrypted message matches said received twice re-encrypted new encrypted message,
decrypting said received further new follow up encrypted message;
and
initiating said command within said received further new follow up encrypted message.

25 more elements

A system for resynchronizing a receiver with a transmitter if the receiver and the transmitter are asynchronized, the system comprising:

a first memory device for storing an old encrypted message transmitted by the transmitter and received by the receiver;
a second memory device for storing a new encrypted message transmitted by the transmitter and received by the receiver;
a microcomputer for re-encrypting said old encrypted message, for testing whether said re-encrypted old message matches said new message,
if said new message matches said re-encrypted old message,
for decrypting said new message;
and
for initiating a command within said decrypted new message;
and
if said new message does not match said re-encrypted old message,
for re-encrypting said re-encrypted old message;
for decrementing a counter each time said re-encrypted old message is re-encrypted;
for testing whether said counter exceed a count number;
and
if said count number exceeds said zero,
for testing whether said new message matches said re-encrypted old message;
if said new message matches said re-encrypted old message,
for decrypting said new message;
for initiating said command within said decrypted new message;
and
if said new message does not match said re-encrypted old message,
for repeating the steps of re-encrypting said re-encrypted old message, for decrementing the counter, and for testing whether said new encrypted message matches said re-encrypted old message if said counter exceeds said count number;
and
if said counter number does not exceed zero,
for transmitting and receiving a first new follow up encrypted message;
for re-encrypting said new message;
for testing whether said first new follow up message matches said re-encrypted new message;
and
if said first new follow up encrypted message matches said re-encrypted new message,
for transmitting and receiving a further new follow up encrypted message;
for re-encrypting said re-encrypted new message;
for testing whether said further new follow up message matches said twice re-encrypted new message;
and
if said further new follow up message matches said twice re-encrypted new message,
for decrypting said further new follow up message;
and
for initiating said command within said further new follow up message.

33 more elements

Dependencies are inferred from the claim text.

Automatic resynchronization for remote keyless entry systems

Life of this patent

Automatic resynchronization for remote keyless entry systems

Life of this patent

Abstract

Claims13