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BACKGROUND OF THE INVENTION
A portion of the disclosure of this patent document contains material which
is subject to copyright protection. The copyright owner has no objection
to the facsimile reproduction by any one of the patent disclosure, as it
appears in the Patent and Trademark Office patent files or records, but
otherwise reserves all copyright rights whatsoever.
A. Field of the Invention
The present invention relates generally to a microprocessor controlled
security system for computers, especially personal computers. More
particularly, it relates to a computer security system accessed by
magnetically encoded cards that allows control of personal computer access
and time usage, internally recorded data and attached peripheral devices.
B. Description of Related Art
With personal computers and their applications becoming more commonplace,
an increasing number of such computers are being placed in multi-user
environments. For example, universities and other educational institutions
often give their students access to many personal computers, and allow the
same computer to be used by any of a number of different students.
Typically, a university or other institution might make personal computers
available in a library for the use of students who are studying or
conducting research.
Similarly, businesses will often make one or more personal computers
available for use by multiple employees, who perform the same or similar
tasks, or who may even perform dramatically different tasks. In either
circumstance, the computer may have any of a variety of built-in or
peripheral features, such as disk drives (floppy disks, hard disks, CD
ROM's, etc.), printers, optical scanners, modems, FAX machines, MIDI
devices, or video devices.
When personal computers are made available for use by multiple individuals,
the organization owning the computer often wants to maintain control of
the access to those computers, and their peripherals. Thus, educational
institutions and businesses may keep their personal computers within
locked rooms and allow entry into the room only by those with
authorization to access the computers.
Organizations having such multi-user computers often seek to allocate the
expenses for each computer's use, either in the organization's accounting
procedures or through actual charges to users. Such charges are either
made directly to the individual users, or are allocated for accounting
purposes in accordance with the tasks performed by those individuals.
Thus, a university may keep track of the students who use computers and
their peripherals by academic department to determine whether more
expenses associated with personal computers should be allocated to one
department or another, or the university may require students or other
users to "pay by the hour" for their actual use of computer time.
Likewise, organizations may want to limit access to certain costly
peripherals, such as laser printers. Business environments have similar
requirements.
Computer-owning institutions could, of course, place each computer within a
locked room (with different rooms having different combinations of
peripherals) and allow students or other users access to those rooms only
for limited and carefully controlled times. However, a simple locked room
is often inadequate to provide proper security for personal computer data
and makes accurate accounting of the individuals who use computers and
their peripherals, and the amount of use by each individual difficult.
Such methods are cumbersome and, in any event, unlikely to be followed
with the consistency necessary for accurate accounting or cost charging.
Another potential multi-use circumstance for personal computers is in a
classroom environment, where one "master" computer, associated with an
instructor, displays its data on the screens of a number of "slave"
computers, each associated with one or more students. These screens and
their internal hard drives can also be driven by the "master computer"
independent of individual computers. In that circumstances, the instructor
often wants control over the activation of the individual computers or
screens so as to fully control the lecture or other educational
environment. Aside from physically disabling the "slave" computers, hard
drives, or screens by, for example, disconnecting the equipment from its
power source, few methods have been traditionally available for allowing
instructors to have such control.
Due to the need for security for personal computer systems, it is not
surprising that considerable effort has been made in the prior art to meet
the needs of computer-owning institutions. Simple password techniques are
perhaps the most familiar, where access is gained by the user by entering
a password into the computer. Password generating machines combined with
computer interfacing devices are also known int he art, one example being
U.S. Pat. No. 4,800,590 issued to Vaughn. Other security techniques
include call and call back systems, security by encoding messages and
data, and "trapdoor" encryption schemes. However, such computer access and
security techniques each have their limitations. Most do not provide for
limited time access, and some are too expensive or impractical for
personal computers or personal computer networks. Additionally, many prior
art methods are not suitable for selective access to peripheral devices
linked together through a peripheral data bus to a master computer.
Accordingly, it is an object of this invention to provide a system for
controlling access to personal computer and peripheral devices to
authorized users.
It is also an object of this invention to provide a computer security
system that is suitable for personal computers, and that is both practical
and of reasonable cost.
A further object of this invention is to provide security for data that is
held within such personal computers, when the data is held within internal
or physically attached hard disks or other data storage devices.
Yet another object of this invention is to provide a means for accurately
recording and accounting for the time used by each computer users on the
equipment. A related object is to provide an ability to disable the
operation of personal computers when their operation is not authorized, or
when the elapsed time used by a computer user reaches a predetermined time
limit.
SUMMARY OF THE INVENTION
These and other objects of this invention are obtained by providing a
microprocessor controlled security system for controlling access to
personal computer video displays, data storage devices, accessories, and
peripherals. The security system includes a magnetic card reading and
encoding device for reading input signals form a magnetically encoded card
which includes at least one magnetically encoded data track. The security
system also includes a microcontroller that processes the input signals
read by the magnetic card reading and encoding device, and responsively
provides component enable and disable signals for computer video displays,
data storage device, computer accessories, and computer peripherals. A
component interface is further provided which enables and disables at
least one component of the computer system in response to the component
enable and disable signals provided by the microcontroller. The security
system further includes indicators which indicate the status of the
security system and the components in response to indicator signals from
the microcontroller.
The microcontroller and reading and encoding device provide the capability
to program time and component access data onto the magnetically encoded
card. The card, once programmed, is inserted into and out of the reading
and encoding device to gain access to the component that corresponds to
the data track that is programmed. Subsequent insertion and removal of the
card disables the component, and the residual time remaining to the user
is written onto the card as it is withdrawn.
Thus, the security system controls access to components of the computer
system depending on the data that is programmed onto the magnetically
encoded card. The computer-owning institution has control of access to
computers and peripheral devices depending on how it chooses to program
and distribute the cards. The system is practical and of relatively low
cost as well.
Control over access to internally stored data is controlled by programming
access and time data onto a card that is designated a hard disk drive
card. Similarly, control over peripheral devices is achieved by
programming the card to gain access to a peripheral device over the
peripheral data bus.
Recording the accounting for time usage is provided by selecting the amount
of time to be programmed onto the time field of the data track on the
card. When the authorized amount of time is nearly up, the user is alerted
by the indicators (audio and/or visual) and the component is disabled at
the expiration of the authorized time.
Other features, objects, and advantages of the invention will become
apparent from the following detailed description of the preferred
embodiment and explanation of practice and use of the system described
below.
BRIEF DESCRIPTION OF THE DRAWINGS
In the detailed description of the preferred embodiment and alternative
embodiments which follows, reference will be made to the accompanying
drawings wherein like numerals in the text refer to like elements of the
various drawings, and in which:
FIG. 1 is a general block diagram of the microprocessor controlled computer
security system of the present invention;
FIG. 2 is an illustration of a bidirectional magnetically encoded card
employed in the present invention;
FIG. 3 is a diagram depicting the environment in which the security system
of FIG. 1 may be employed;
FIG. 4 is a flow diagram depicting the general operation of the preferred
embodiment of the present invention.
FIG. 5 is a detailed circuit diagram of a preferred embodiment of the
present invention shown in FIG. 1;
FIG. 6 is a detailed circuit diagram of an alternative embodiment of the
present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIG. 1, the elements of the microprocessor controlled security
system 10 can be seen in block-diagram form. The system 10 includes a
magnetic card reading and encoding device 12 which reads input signals
from a magnetically encoded card 14 which includes at least one
magnetically encoded data track 16. A microcontroller 18 which includes a
microprocessor processes input signals read by the magnetic card reading
and encoding device 12, and responsively provides component enable or
disable signals to a component interface 20 for enabling or disabling
various components of a computer system such as a printer 22, scanner 24,
MIDI 26, disk drive 28, or internal or external video monitors 30.
The microcontroller 18 further issues indicator signals to various
indicators, such as LED's 32 for indicating to the user the status of the
components and the security system. The operation of the indicators 32 is
controlled by the microcontroller 18. Audio indicators are provided
through an audio circuit 34 which is also controlled by the
microcontroller 18. The microcontroller 18 provides a first indicator
signal to the audio circuit 34 when a certain fraction of computer access
time remains allocated on the time field, for example, 1/60 (at one minute
when 60 minutes was originally authorized). A second indicator signal is
provided when a second fraction, say 1/120, of computer access time
remains allocated in the time field. The indicators give notice to the
user that access time is about to expire, and thereby giving the user a
chance to save his or her files.
The microcontroller 18 has a clock crystal circuit 36 for measuring time
and providing clock inputs to the microcontroller. The microcontroller 18
also is provided with a RAM/ROM computer memory 38 that stores the system
operating code and transitory data.
In one possible embodiment, the magnetic card reading and encoding device
12, microcontroller 28, memory device 38 and interface 20 are incorporated
into the housing of a personal computer, but they may be positioned
external of the computer. In the preferred embodiment, the security system
is installed in a host or master personal computer manufactured by Apple
Computer, and controls access to peripheral devices and remote personal
computers through a bus interface in the external peripheral interface 20.
Referring again to FIG. 1, the magnetic card reading and encoding device 12
is a standard "off-the-shelf" magnetic card reader/encoder. In the
preferred embodiment, the reading and encoding device 12 is the XICO, Inc.
Model 7702SA insertion card reader/encoder peripheral unit, available from
XICO, Inc. 9737 Eton Avenue, Catsworth, Calif. 91311.
The microcontroller 18 in FIG. 1 is preferably a Motorola MC68A701S
Controller 100 microprocessor. The microcontroller 18 is programmed with
resident software (see Appendices) for controlling operation of the
computer security system 10. The particular amount of time to be
programmed on the cards and the choice of which components to be accessed
by the card is made by changing the software for the microcontroller.
Referring now to FIG. 2, the magnetically encoded card 14 is shown as
comprising a bidirectional card that includes two data tracks 40 and 42.
The data tracks 40 and 42 are independently read by the magnetic card
reading and encoding device 12 depending on the direction in which the
card 14 is inserted into the device 12. The data tracks 40 and 42 are
encoded to enable or disable one or more computer system components or
external peripheral accessories, as will be explained below. The card 12
may include a pair of additional data tracks on its reverse side for a
total of four data tracks. Additionally, data tracks 40 and 42 may include
a time field for computer access time accounting purposes. The data tracks
40 and 42 of the magnetically encoded card 14 are encoded by an authorized
system operator by activating a switch 46 connected to the microcontroller
18 (FIG. 1) on selected security systems.
Referring now to FIG. 3, the computer security system of the present
invention is shown installed in a host or master computer 50. The
magnetically encoded card 14 is inserted through a slot 52 to be read by
the magnetic card reading and encoding device 12 (FIG. 1) built into the
host computer 50. Depending on how the card 14 is encoded, the video
display 54 may be disabled or enabled, the internal disk drives (not
shown) may be disabled or enabled, or various peripheral devices such as a
printer 22, scanner 24 or other peripherals 58 may be enabled or disabled.
It is also possible to enable or disable slave PC's 60 or remote central
processing units linked through a peripheral bus to the host computer 50.
The peripheral bus referred to herein will normally be the SCSI (Small
Computer Systems Interface) bus common to personal computers.
In the preferred embodiment, the security system provides restricted access
to host computer 50 by controlling the video display 54 and the hard disk
drive 28 (not shown in FIG. 3). Video display 54 is enabled by inserting
and retracting the magnetically encoded card 14 into and out of the
reading and encoding device 12 such that data track 40 (FIG. 2) is read,
and the hard disk drive 28 is enabled by inserting and retracting the
magnetically encoded card 14 such that data track 42 is read. The video
display 54 and the hard disk drive 28 are disabled by a subsequent
insertion and retraction of data tracks 40 and 42 into and out of the
reading and encoding device 12.
In the preferred embodiment, data tracks 40 and 42 include a time field
allocating a predetermined amount of computer access time. The time field
included in the data track for enabling and disabling the hard disk drive
28 is reduced an amount proportional to the time during which hard disk
drive 28 is enabled. Upon expiration of the access time allocated by the
time field, hard disk drive 28 will be disabled by security system 10.
However, security system 10 provides an audio and visual warning
indicating when there are approximately 2 and 1 minutes of computer access
time remaining in the time field, thereby allowing the user to save any
data before hard disk drive 28 is disabled. Additionally, upon enabling
the hard disk drive 28 by inserting and retracting the card 14 into and
out of the reading and encoding device 12, the device 12 zeros the time
field on the card 14 as the card 14 is retracted from the device 12,
thereby preventing the card 14 from being used to access another computer
protected by a similar computer security system. The card 14 is credited
with any residual computer access time remaining in the time field upon
disabling the hard disk drive 28 by a subsequent insertion and retraction
of the card 14 into and out of the reading and encoding device 12. In the
preferred embodiment, the time field included on the data track for
enabling and disabling video display 54 is not reduced by the computer
security system, as is the time field included on the data track for
enabling the disabling hard disk drive 28. A random number (up to 8 bed
digits) is written to a card that has successfully enabled a component
before the card is completely withdrawn. This insures another card cannot
be used to disable the component.
In an alternative embodiment, the data tracks on the card 14 may be encoded
to enable and disable the disk drives or the video displays of a plurality
of slave computers 60 or monitors 62, or any combination of the external
peripheral equipment stated above. Video display monitors may be
controlled by controlling the video signal, or the video display power
supply. Additionally, the slave computers 60 may also include a computer
security system 10 having magnetically encoded cards 64 encoded to enable
and disable computer components and external peripheral equipment in a
manner as state above with regard to the host computer 50.
Security System Operating Flow Diagram
The operation of a preferred embodiment of the computer security system is
illustrated in the flow diagram of FIG. 4. For simplicity, the external
peripheral interfaces to be enabled or disabled by the security system are
the video display and the hard disk drive of the host computer.
Power is applied to the computer security system upon activation of the
host computer at Step 1. The computer security system performs a hardware
test at Step 2. The test is limited to security system circuitry, aside
from the shot computer power supply from which it derives its power. A
computer security system hardware failure is indicated at Step 3. The
computer security system indicates that the card reading and encoding
device is waiting to read a magnetized card at Step 4. A magnetically
encoded card is inserted into the card reading and encoding device at Step
5. The computer security system determines whether the magnetic card data
track is invalid or unreadable at Step 6 upon insertion of the card into
the card reading and encoding device at Step 5. An unreadable card has
either the wrong address code or has had its magnetic field erased.
The computer security system determines whether the hard drive data track
or the video display data track has been inserted into the card reading
and encoding device at Step 7. Insertion of the video display data track
on the card into the card reading and encoding device will prompt the
computer security system to determine whether the video signal is enabled
at Step 8. If the video is not on, upon retraction of the card from the
card reading and encoding device at Step 9, a disabled video signal is
enabled at Step 10. The computer security system also indicates that the
video display has been enabled. Upon completion of Step 10, the computer
security system indicates that the card reading and encoding device is
awaiting to read a card at Step 4.
If the video is on, upon retraction of the card from the card reading and
encoding device at Step 11, the video signal is disabled at Step 12. The
computer security system also indicates that the video display has been
disabled. The time field on the card is also updated in Step 12. Upon
completion of Step 12, the computer security system indicates that the
card reading and encoding device is waiting to read a card at Step 4.
Insertion of the hard drive data track on the card into the card reading
and encoding device will prompt the computer security system to determine
whether the hard drive is enabled at Step 13. If the hard disk is
disabled, upon retraction of the card from the card reading and encoding
device at Step 14, the time field on the card is set to zero. The computer
security system enables the hard drive at Step 15 and provides an
indication of the enablement before indicating that the card reading and
encoding device is awaiting to read a card at Step 4.
If the hard disk is enabled, upon retraction of the card, at Step 16, any
residual time is credited to the magnetically encoded card, i.e., the time
field is reduced in proportion to the period of time that the disk drive
was enabled. The computer security system disables the disk drive at Step
17 and provides an indication of the disablement before indicating that
the card reading and encoding device is awaiting to read a magnetized card
at Step 4.
As the flow diagram illustrates, it is necessary to insert and retract the
magnetically encoded card into and out of the card reading and encoding
device tow times, once for each data track, to enable both the disk drive
and the video display.
The determination of an invalid or unreadable card at Step 6 prompts the
computer security system to indicate an invalid data track has been
inserted into the card reader at Step 19. The computer security system
then determines whether the program switch is activated at Step 20.
A deactivated program switch prompts the computer security system to return
to Step 4 upon retracting the card at Step 21. If the program switch is
activated, the computer security system is prompted to validate the
magnetic card by programming the data tracks.
Step 22 determines whether the hard disk drive is enabled. An enabled hard
disk drive prompts the security system to validate the data track for
enabling and disabling the video display. The data track is programmed as
the card is retracted from the card reader at Step 23. Upon retracting the
card at Step 23, the computer security system returns to Step 4.
A disabled hard drive prompts the computer security system to validate the
data track for enabling and disabling the hard drive. The data track is
programmed as the card is retracted form the card reading and encoding
device at Step 24. A time field is also programmed onto the data track.
Upon retracting the card at Step 24, the computer security system returns
to Step 4.
As illustrated by Steps 22, 23, and 24 of the flow diagram, it is necessary
to program one data track at a time on a new or expired card, thereby
requiring that the card be inserted and retracted into and out of the card
reading two times to program the video and hard disk data tracks.
Additionally, an incorrect read or write as the magnetic card is retracted
from the card reader, such as may occur in Steps 9, 11, 14, 16, 21, 23,
and 24, is indicated by the security system. The step may be repeated by
reinserting the card into the card reader.
A circuit diagram illustrating the preferred embodiment of the invention is
shown in FIG. 5. The microcontroller 18 unit for the preferred embodiment,
as stated previously, is the Motorola MC68A701S Controller 100. The
microcontroller 18 is a 40 pin device, which contains 2K bytes of
electrically programmable read only memory (EPROM) and 128 bytes of random
access memory (RAM). Of course, other microcontrollers with different size
memories may be suitable for particular applications. The control software
lies in the on-chip EPROM. Power requirements for the microcontroller 18
are 5 V DC .+-.5% at 80 mA. In FIG. 5, the notations "P12", "NMI", etc.
indicate the pins to be connected to the various circuits, power supplies,
and components as shown in the diagram.
A clock circuit 36 is provided to the microcontroller 18. The clock crystal
36a is a 4.9152 MHz crystal. However, the software (see appendices)
provides that if the 4.9152 MHz crystal is unavailable, a 5.0688 MHz
crystal can be used, the crystal not being used is "commented out" of the
software. Bypass capacitors 36b and 36c provide noise and parasytics
immunity.
The microcontroller 18 interfaces with the magnetic card reading and
encoding device 12 through a standard 20-pin flat ribbon cable 70. An
adapter 72 is the intermediary between the microcontroller 18 and the
cable 70. The cable 70 carries power to the reading and encoding device
12, and uses 5 signal lines: Clear to Send (CTS), Transmit Data (XMIT
DATA), Receive Data (RECV DATA), card front detect, and card rear detect.
The predominant mode of communication between the microcontroller 18 and
the reading and encoding device 12 is TTL-level serial ASCII asynchronous
9600 baud, 7 bit word, no parity, 2 stop bits. The reading and encoding
device must be strapped to operate in that mode.
A program switch circuit 74 containing the program switch 46 is provided to
the microcontroller to permit the operator of the computer system to
encode data tracks 40 and 42 of magnetic card 14 upon insertion of the
card 14 into the reading and encoding device 12.
A power-on reset generator circuit 80 is provided to the microcontroller
for supplying the reset voltage/current levels for power-up reset of the
microcontroller 18. The reset generator circuit includes resistors 80a-c,
capacitor 80d, and a 74HCTLSO4 CMOS logic chip shown as invertor network
80e. The output of the logic chip is provided to the RESET pin on
microcontroller 18.
Microcontroller 18 also provides indicator signals to an audio indicator
circuit 34. While other audio indicator circuits are possible, the
preferred embodiment audio circuit incorporates a piezo-electric buzzer 78
responsive to indicator signals from the microcontroller 18. The audio
circuit includes invertor 76a, OR gates 76b and 76c, and associated
resistors 76d-g.
An additional means for indicating the status of the components of the
security system is the LED indicator circuit 82. The red, yellow and green
indicator lights 32a, b, and c, respectively, are responsive to indicator
signals from the microcontroller 18.
The video display for the computer system is enabled or disabled by video
adaptor interface circuit 84. The video adapter interface circuit includes
zener diode 84a, resistors 84b and 84c, transistor 84d, capacitor 84e, and
a two pin adapter 84f having pins on 0.100 inch centers.
An external peripheral interface circuit 20 interfaces between
microcontroller 18 and the hard disk drive, printer, or other external
peripherals of the host computer system, slave computers, or remote
central processing units. The OR gate 88 has as inputs an enable or
disable signal from the microcontroller 18 and the select (SEL) signal
from the peripheral bus. The output of the OR gate is supplied to the
select (SEL) line to the peripheral bus. A 5 pin adapter 89 having 0.100
inch centers provides the output of the interface circuit 20 to the
peripherals along the bus (not shown).
The microcontroller 78, card reading and encoding device 12, and other
system accessories are powered by a power interface circuit 90. The power
interface circuit 90 receives power from the host computer. Typically, the
power is supplied from the power to the host disk drive. A standard two
pin junction 91 having pins on 0.200 inch centers connects between the
host computer and the security system.
An alternative embodiment of the present invention is depicted in circuit
diagram form in FIG. 6. The microcontroller 18, power-on reset generator
circuit 80, LED indicator circuit 82, clock circuit 36, magnetic card
reading and encoding device 12 and adapter 72, and power interface circuit
90 are the same as in the preferred embodiment of FIG. 1. The alternative
embodiment differs in that the microcontroller 18 provides enable/disable
signals to a video tube power interface circuit 100, and enables or
disables the video card by interrupting the power to the tube. In this
embodiment, the external peripheral interface circuit and video adapter
interface circuit are not present. However, it is possible to combine in
one embodiment any two of the three component interface circuits shown in
FIGS. 5 and 6--the video adapter interface circuit 84 (FIG. 5), the
external peripheral interface circuit 20 (FIG. 5), and the video tube
power interface circuit 100 (FIG. 6).
The video tube power interface circuit 100 includes first and second
transistors 102 and 104, a LED indicator light 106 that lights when video
tube disablement is imminent, and the associated resistors. A capacitor
108 is connected between the collector and emitter of the first transistor
102.
The alternative embodiment of FIG. 5 also includes a simple audio indicator
circuit comprising a sound producing device such as a piezo-electric
buzzer 114.
Additional, optional circuitry may be connected up to the microcontroller
18, for example, voice synthesizer or additional RAM or ROM memory
devices. While such optional circuitry is illustrated in conjunction with
the alternative embodiment of FIG. 6, it is to be understood that the
preferred embodiment of FIG. 5 may also incorporate such optional
circuitry. Additionally, various EP ROM chips, each with different
software to provide different accessability of components, may be included
in the preferred and alternative embodiments.
While there has been set forth preferred and alternative embodiments of the
invention, it is to be understood that changes may be made as to the
particular details of the circuitry and software without departure from
the true spirit and scope of the appended claims. For example, there are
modifications which may be made to the indicator circuits such as the
audio circuit. Similarly, other types of visual indicators may be
employed. Additionally, other choices for the microcontroller and reading
and encoding device may be made.
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