Cryptography – Communication system using cryptography – Symmetric key cryptography
Reexamination Certificate
1999-12-14
2004-12-07
Meislahn, Douglas (Department: 2137)
Cryptography
Communication system using cryptography
Symmetric key cryptography
C380S260000
Reexamination Certificate
active
06829357
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to communication systems that utilize encrypted data communication, and is particularly directed to size reduction for encrypted data communication signals of a remote convenience system.
BACKGROUND OF THE INVENTION
Communication systems that engage in transmission of encrypted data (e.g., information) are known in the art. One example of a communication system that utilizes data encryption is a remote convenience system, which permits remote control of certain functions. Within the remote convenience system, data that conveys security code(s), command(s), and the like is encrypted for transmission via signal. Only an authorized receiver decrypts and responds to the signal. Also, the encryption prevents unauthorized remote control of the certain remote convenience functions.
One example type of a remote convenience system is for remotely controlling vehicle functions. Other example types of remote convenience systems include garage door opener systems and entry light activation systems. Focusing on the remote convenience vehicle systems, remotely controlled vehicle functions include locking and unlocking of one or more vehicle doors. A remote convenience system that permits remote locking and unlocking is commonly referred to as a remote keyless entry system.
Known remote convenience vehicle systems include a receiver/controller unit mounted in an associated vehicle and a portable hand-held transmitter unit located remote from the receiver/controller unit. The transmitter unit is provided with one or more manually actuatable switches. Each switch is associated with a vehicle function to be performed. The transmitter unit includes circuitry that responds to the actuation of one of the switches to provide a message package. The message package includes a remote function command, a security code, and a sequence counter. The message package is transmitted to the receiver in the form of a digital signal.
In order to ensure that the contents of the message package cannot be understood by any receiver other than the intended authorized receiver, the digital bits of the signal are partially or completely encrypted by the transmitter. In order for the receiver to act upon the requested function, the signal is decrypted, a security code compared, and the like. As an extra level of security, the encryption methodology for the communication is changed routinely. Specifically, the transmitter and the receiver utilize a sequence counter arrangement. With each transmission from the transmitter, the sequence counter is adjusted. Upon receipt at the receiver, adjustment is made to the sequence counter value, accordingly. Thus, the receiver utilizes the sequence counter value to recognize a transmitted signal from the authorized transmitter.
As the sophistication of the remote convenience vehicle systems has increased, so has the number of bits that are typically transmitted via the signal. It is to be appreciated that increases in the number of transmitted data bits results in an increase in the possibility of corruption of the data.
SUMMARY OF THE INVENTION
In accordance with one aspect, the present invention provides a transmitter. The transmitter includes means for providing a message package. Means encrypts a first fraction of the message package using a second fraction of the message package as an encryption key. Means outputs a signal that conveys the encrypted first fraction of the message package.
In accordance with another aspect, the present invention provides a receiver that includes means for receiving an encrypted signal. Means decrypts the signal using a decryption key. Means assembles a message package using the decryption key as part of the message package.
In accordance with another aspect, the present invention provides a communication system that includes means for providing a message package. Means encrypts a first fraction of the message package using a second fraction of the message package as an encryption key. Means outputs a signal that conveys the encrypted first fraction of the message package. Means receives the signal. Means decrypts the signal using a decryption key. Means reassembles the message package using the decryption key as the second fraction of the message package.
In accordance with yet another aspect, the present invention provides a remote convenience system for remotely controlling a convenience function. The system includes portable transmitter means for outputting a signal containing remote control message information. Receiver/controller means receives the signal and controls performance of a function in accordance with the remote control message. The remote control message includes first and second fractions. The transmitter means includes encryption means for encrypting the first fraction of the remote control message using a second fraction of the remote control message as an encryption key.
In accordance with still another aspect, the present invention provides a remote convenience system for remotely controlling a convenience function. The system includes portable transmitter means for outputting a signal containing remote control message information. Receiver/controller means receives the signal and controls performance of a function in accordance with the remote control message. The remote control message includes first and second information portions. The signal contains the first portion and a first part of the second portion that are encrypted. The receiver/controller means includes decryption means for decrypting the first portion and the first part of the second portion using a decryption key. The receiver/controller means includes means for assembling a decrypted message using the decryption key as the second part of the second portion.
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Schneier, Bruce, Applied Cryptography, 1996, John Wiley & Sons, Inc., 2nd ed., pp. 206-207 and 209.
Alrabady Ansaf Ibrahem
Juzswik David Leonard
Meislahn Douglas
Tarolli, Sundheim Covell & Tummino L.L.P.
TRW Inc.
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