Secure self learning system

Details Secure self learning system Secure self learning system

1995-08-25

2001-02-20

Holloway, III, Edwin C. (Department: 2735)

Communications: electrical

Continuously variable indicating

With meter reading

C340S870030, C340S870030

Reexamination Certificate

active

06191701

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a secure self learning system and method and, in particular, to a secure self learning system and method for remotely controlling systems and devices in security systems.
2. Discussion of the Background
The remote control of systems or devices via ultrasonic, radio frequency or infra red transducers is popular for many applications, including security systems for buildings and vehicles, and remote controlled garage door and gate openers.
Certain unidirectional transmission systems currently in use have two very important security shortcomings:
(a) the codes they transmit are usually fixed; and
(b) the number of possible code combinations is relatively small. Either of these shortcomings can lead to unauthorized access.
The limited number of possible combinations available in most remote control systems makes it possible to transmit all possible combinations in a relatively short time. A hand held microprocessor-based system for this purpose (called a code scanner) can easily be constructed.
In systems using eight DIP switches (256 combinations), this scanning process can typically be accomplished in less than 32 seconds, when trying eight combinations per second. Even in systems using 16 bit keys, yielding 65,536 combinations, only 2¼ hours would be required to try all possible combinations. It should also be noted that the scanner may gain access in far less than this maximum time—the average time would in fact be half of the total time.
An easier way of gaining unauthorized access to a security system is freely available. A unit of this type is advertised as a tool for the “legal repossession of vehicles”.
A remote control transmitter of the type normally used in vehicle security and remote control systems includes a small radio transmitter that transmits a code number on a specific frequency. This code number is normally generated by an integrated circuit encoder. The transmission frequency is usually fixed by legislation within a particular country. Thus it is possible to build a receiver that can receive signals from all such transmitters and to use this together with a circuit which records the transmissions captured by the receiver. Such a device is known as a code or key grabber and can be used to gain access to protected premises or to vehicles with remote control security systems.
Code hopping and rolling code systems are currently available to overcome the limitations of fixed code systems (refer to ZA Patent No. 91/4063 and U.S. Pat. No. 5,103,221). The specifications of these patents describe transmitters which use algorithms to generate a different transmission each time the transmitter is activated. When a code is received and decoded, a decoder responds only if a valid transmission was made. In some cases (refer to ZA Patent No. 91/4063) a special algorithm is used with a stored key to decode an encoded reception. The decoded value is then compared to a stored value to determine if the transmission is legitimate or not.
A disadvantage of code hopping and rolling code systems is the fact that it is difficult to replace or disable lost, stolen or unserviceable transmitters. External equipment is used by a manufacturer or dealer to reprogram and replace a transmitter. An additional security problem may be created during this process.
Ideally a security system should not require dealer intervention when a user needs to add a new transmitter to the system or replace a transmitter. The user should be able to buy a generic replacement transmitter off the shelf and add this transmitter unassisted when convenient. Learning systems provide this capability, in that the decoder can “learn” the new transmitter's identity without having to be reprogrammed from outside using special equipment.
A learning system should however not only enable a user to add a new transmitter to the system, but should also have a means of excluding a previous transmitter from the system, due to the possibility of such a transmitter failing into the wrong hands.
In self learning fixed code systems, the incoming code is stored for future reference by the decoder when it is in a learning mode. Subsequent transmissions are compared with the learned code. Different arrangements to learn new transmitter codes are used. A switch can be used to set the decoder either in a normal operation mode or in a learning mode (U.S. Pat. Nos. 4,750,118 and 4,912,463). In the learning mode, the decoder can learn new valid codes from a transmitter. Similar means is used (refer to U.S. Pat. Nos. 4,931,789 and 5,049,867) to program the decoders to react to a new transmitter code. In another invention (refer to U.S. Pat. No. 5,148,159), a randomly selected fixed code is generated by the decoder and programmed into the associated transmitter. U.S. Pat. No. 4,855,713 describes the use of a hand held programmer to program the new fixed code to be recognized by the decoder. In all of these cases, the transmitted or programmed codes are fixed stored codes. Security threats by means of code grabbing or code generation still exist irrespective of the learning mechanisms employed.
Reference should also be made to the specifications of the following U.S. Pat. Nos: Re 29,525; 4,380,762; 4,385,296; 4,426,637; 4,529,980; 4,534,333; 4,574,247; 4,590,470; 4,596,985; 4,638,433; 4,652,860; 4,686,529; 4,737,770; 4,779,090; 4,835,407; 4,847,614; 4,855,713; 4,878,052; 4,890,108; 4,928,098; 4,951,029; 4,988,992; 5,049,867; 5,055,701.
SUMMARY OF THE INVENTION
The invention provides, in the first instance, a method of operating an encoder which includes the steps of:
storing a serial number;
storing at least one of the following:
a seed; and
a key which is generated using a manufacturer's master key and at least one of the following:
the seed; and
the serial number; and
transferring key generation information selected at least from:
the seed;
the serial number; and
information derived from applying the key and an algorithm to an input value.
The input value may include information selected at least from:
a management code;
a counter value; and
information relating to a command.
In one embodiment the method includes the steps of:
storing a plurality of parameter sets, each parameter set including information selected at least from:
a respective serial number;
a respective seed;
a respective key; and
respective information derived from applying the said respective key and the algorithm to a respective input value;
selecting a parameter set; and
transferring the respective key generation information for the selected parameter set.
Each input value may include information selected at least from:
a respective management code;
a respective counter value; and
information relating to a command.
The encoder may also include provisions for disabling the transmission of key generation information. This facility is useful to prevent an outsider from obtaining the key generation information after the transmitter has been learned by a decoder. The transmission of key generation information can be permanently disabled by a conscious action by the user, or by an automatic process, e.g. when the encoder has been used a predetermined number of times. In the former case manual action can be taken by using a programming action or a specific combination of inputs.
The invention also extends to a method of operating a decoder which includes the steps of:
storing a manufacturer's masterkey;
receiving a signal which contains key generation information selected at least from:
a seed;
a serial number; and
encoded information derived from applying a first key and an algorithm to an input value; and
generating a second key using at least the key generation information and the manufacturer's master key.
The method may include the steps of storing at least one of:
the second key;
the key generation information; and
the serial number.
In one embodiment the received signal includes the encoded information and the method includes the steps of:
decoding the enco

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