Communications: electrical – Selective – Intelligence comparison for controlling
Reexamination Certificate
2000-03-23
2002-07-16
Holloway, III, Edwin C. (Department: 2635)
Communications: electrical
Selective
Intelligence comparison for controlling
C340S005310, C341S035000, C070S278400
Reexamination Certificate
active
06420958
ABSTRACT:
BACKGROUND OF THE INVENTION
Mechanical combination locks such as those found on safes, vaults, cabinets and other high security enclosures are well known and subject to a number of attacks, such as by drilling, manipulation, and operation by dialer controlled by a computer.
Recently an electronic combination lock for such enclosures has been invented which provides the opportunity to greatly increase the level of security afforded by the lock, while at the same time overcomes many of the shortcomings of the prior art mechanical locks.
A dial type combination lock relies on the rotation of a dial to positions represented by numbers on the dial to rotate mechanical elements within the lock, such that the wheels of the mechanism align to allow a bar to drop into the wheels and retract the lock bar or bolt, allowing the enclosure to be opened.
The electronic combination lock does not have the equivalent mechanical elements and, therefore, can not be attacked in the same manner. For example, the mechanical lock may be drilled to permit the insertion of an optical device into the lock mechanism to observe the positions of the wheels and thus their alignment which permits the opening of the enclosure without the knowledge of the combination.
The electronic lock cannot be drilled for a similar purpose since the electronic lock mechanism will not reveal the position of any element which would be helpful for the attacker to observe and which would give the attacker any information as to the steps needed to unlock the device.
The mechanical lock has a fixed position of internal elements relative to the dial and thus may be observed with the movements of the dial repeated by the attacker, at a later time.
The electronic lock does not have a fixed dial to number position relation and thus observation of the movement of the dial is much more difficult if not impossible.
Dialers exist which may be attached to the knob of a dial on a combination lock and which dial combinations under the control of a computer. As each combination fails, the computer then continues to dial other combinations to eventually unlock the lock.
With a combination lock of the mechanical type and sufficient time,a dialer is particularly effective.
The electronic combination locks are dependent upon electronic pulses being generated to indicate to the electronic controls, that the dial is being rotated and in which direction. The pulses may be generated by conventional pulse generation means when a voltage supply is provided to power the pulse generator.
Alternatively, pulses may be generated by the operation of the lock and the voltage pulses provide a power source for the operation of the lock.
This type of power source eliminates the need for a separate power source for the system, such as a battery or other external voltage supply.
With the control of the device by a series of voltage pulses, the use of the pulses may be used to further control functions of the lock.
SUMMARY OF THE INVENTION
The electronic combination lock disclosed and described herein is a combination lock having a dial which has no divisions or markings relating to the numbers of the combination thereon. The rotation of the dial drives a generator which produces electrical pulses. The voltage pulses serve as a power source for the electronics of the lock and to further indicate to the microprocessor the speed and direction of rotation of the dial.
Through a random number generator, the micro processor generates a psuedo-random number which is then displayed on a display which is mounted in proximity to the dial.
The rotation of the dial of the lock is accomplished in a manner very closely related to the manner of the rotation of the dial of a conventional mechanical combination lock.
When the numbers of the combination have been entered through dial rotation, the microprocessor compares the combination with the authorized combination; if the same, a signal is sent to the motor that will engage the latch with the bolt retractor and connect the bolt through mechanical connections, to the dial so that when the dial is further rotated in the proper direction the bolt will be retracted and the enclosure is then opened.
The microprocessor is controlled by a coded program. The ability to control the microprocessor with a microcoded control program is a major advantage in that the several functions and features may be added to make the lock mechanism and the enclosure more secure.
In order for a dialer to be effective, the relationship between the dial rotation and the numbers entered must be correllated so that a 3.6 degree rotation of the dial increments or decrements the entry number by one unit for a 100 unit dial. The generation of a random number within the microprocessor at the beginning of each number entry operation and the use of that random number as the starting point for the sequence of numbers displayed, eliminates the correllation of the number being displayed and eventually entered, and the dial position.
When the dial is rotated, the generator creates pulses and these pulses are received by and counted by the microprocessor. As the pulses are accumulated, the pulses are also timed and the speed of rotation of the dial is determined. As the speed of the rotation of the dial varies, the rate of change of the displayed numbers is changed. This is accomplished so that at a high rate of rotation the displayed numbers may change at a high rate while at the lower rates of rotation, the rate of change of the displayed numbers may be by single units at a slower rate with respect to the amount of dial rotation. Further the number of degrees the dial must be turned to effect the change of the displayed number will vary so that there is no consistent amount of rotation required to change the displayed number by one unit. This aspect of the lock also acts to foil the use of a computer controlled dialer.
The timing capabilities of the lock provides the opportunity to determine the time used in the entering of the combination. If the total time of entry is either too short, indicating that the lock is under attack by a device rather than a human hand, or if the time to enter the combination is too long, indicating that the operation of the lock is being attacked by other than a person having knowledge of an authorized combination, the lock is prevented from opening even if the authorized combination is subsequently entered.
As the connection between the dial and the generator is mechanical and, therefore, a predictable one, the number of pulses received by the microprocessor indicates the rotational displacement of the dial. The rotational movement of the dial by the hand of a human being is such that the dial is generally turned less than 360 degrees and then the dial is stopped while the operator releases the dial and acquires a new grasp of the dial. The stopping of the dial acts to allow a timer to run and if the stop period is less than a predetermined period that is related to human reaction time, the stop of the dial is not recognized as a stop of the dial. When the dial is rotated more than 480 degrees or 1.33 revolutions without a recognized stop, the lock is probably under attack by a device or at the very least by an unconventional dialing technique and the lock will not open even, if the authorized combination is entered.
Dialers are capable of reversing directions of the dial in very short times and depend upon speed to open a combination lock in a reasonably short time period without detection. This lock requires the dial be stopped or stationary for a short time periodically. One of those times occurs as the dial is reversed to enter the number just dialed and to start access to the next number to be entered. The timing of the stopped period of the dial insures both that a dialer is not being used and it extends the time that is necessary to open the lock by dialing all possible combinations until the lock is unlocked by the proper combination. If the dial is reversed in less than the predetermined time period required to detect a stop
Harvey Michael P.
Miller J. Clayton
C&M Technology, Inc.
Holloway III Edwin C.
Wood Herron & Evans L.L.P.
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