Abstract:
A method and system for correlating control surface finger pressures to identifying biometric characteristics of a user from a computer input device, such as a mouse. Pressure sensors attached to a computer mouse sense the biometric characteristics, which are correlated to identifying biometric characteristics using a correlation model. The correlation model is derived from a registration process in which a baseline biometric attribute-to-identity correlation is rendered based on statistical analysis of registration signals generated by users. During routine use, the correlation model is use to continuously authenticate the identity of the user from surface finger pressures on the computer mouse.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to biometric devices used to identify people and, more particularly, to a biometric device that can continuously authenticate every input the user makes using the device based on a correlational analysis of sensor signals from the device. 
   2. Description of Prior Art 
   Unauthorized data entry and computer operation is a major computer security problem that yearly costs in the millions of dollars of damage and millions of person-hours to correct. Authenticating the identity of an authorized computer user is a necessary part of computer use. Insuring that a person is authorized to use a computer can be done in three different ways. The first method is by the use of something a person carries, such as a token, key or smart card (e.g., U.S. Pat. Nos. 6,247,644 &amp; 6,268,788). The second method is by the use of something a person knows, such as a password or personal identification code. The third method is by the use of a person&#39;s unique physical or behavioral attributes. A physical attribute would be like a finger print or facial feature. A behavioral attribute might be the way a person moves or speaks, such as a person&#39;s gait when walking or speech patterns. This third method of using physical or behavioral attributes of the person is called biometrics. Most computer security systems use one or more methods to authenticate the user&#39;s identity, but biometrics is the most resistant to theft, since it is part of a person&#39;s attributes. 
   Biometric devices that measure fingerprints (e.g., U.S. Pat. No. 6,125,192), voice (e.g., U.S. Pat. No. 5,913,196), irises (e.g., U.S. Pat. No. 6,554,705), and facial images (e.g., U.S. Pat. No. 6,554,705) are available. All biometric devices require initial registration of the user&#39;s attribute that are measured by the sensors of the biometric device. Upon initial use to authenticate the identity of the user, current biometric devices extract a feature set from sensors which are correlated to an existing user database acquired during user registration. These devices require training, are time consuming, can be difficult to use, can require extra equipment, can be expensive and are so inconvenient that user identity authentication is done only upon initial use. 
   Handheld writing devices that use pressure as a biometric is possible (e.g., U.S. Pat. Nos. 5,774,571, 6,539,101), but they are not commonly used as input devices to a computer and is not commonly available. Also, these devices are primarily for one time identification applications. 
   There are some devices designed to authenticate a computer user that are built into a computer mouse to identify the computer user such as by using a thumb or index fingerprint (e.g., U.S. Pat. Nos. 5,991,431 &amp; D440,568). These devices reduce the cumbersome nature of a separate piece of equipment for identification, but these devices are designed primarily to provide authentication upon initial use and require training on the placement of the finger. Another problem with many of the previously described biometric devices is that they rely primarily on the signal from a single sensor. A sensor flaw or signal distortion from that sensor would reduce the reliability of the user identity authentication system. 
   There are devices similar to the invention with different stipulated uses for the signals from sensor on a computer mouse. Both U.S. Pat. No. 6,190,314 (i.e., A “Computer Input Device with Biosensors for Sensing User Emotions”) and a paper by Qi and Picard (Qi, Y. and Picard, R. W., “Context-sensitive Bayesian Classifiers and Application to Mouse Pressure Pattern Classification”, Proceedings of the International Conference on Pattern Recognition, August 2002, Quéébec City, Canada) stipulate the use of sensors on a computer mouse to detect emotions. Neither stipulate the use of the sensor signals for identification or continuous authentication of the user. 
   Continuous authentication of the identity of a computer user is one of the best ways to use biometrics to prevent unauthorized use of a computer system. An example of continuous authentication is a guard constantly watching who is using a computer, using facial features as the unique biometric identifying attribute. Continuous authentication can prevent an unauthorized person from slipping in and using the computer system after the initial authentication of the identity of the authorized user. 
   The invention senses the pressures a user applies to the computer mouse during routine use. The sensors for the invention are incorporated into the structure of a computer mouse. After the initial registration of the user, there is no training and no special finger placement required, the user simply uses the computer mouse. Authentication of the user can occur within a few clicks and can be continuous as long as the user provides input to the computer with the mouse. Multiple sensors within the mouse provide a unique multidimensional measure of the user&#39;s attributes. The invention resolves the shortcomings of previous inventions by: not requiring training, having a brief period for initial registration of the user&#39;s identity, being easy to use, not requiring extra equipment, using multiple pressure sensors located at critical stress points and providing continuous authentication of the user&#39;s identity. 
   OBJECTS AND ADVANTAGES 
   It is therefore an object of the invention to analyze the signals produced by multiple pressure sensors to authenticate the identity of the user. 
   It is another object of the invention to continuously authenticate the identity of the user of the invention. 
   It is another object of the invention to have multiple sensors on the invention to eliminate the dependency on a single sensor. 
   It is another object of the invention to eliminate the need for training or the use of special procedures for identity authentication. 
   It is another object of the invention to provide rapid identity authentication. 
   BRIEF SUMMARY OF THE INVENTION 
   In accordance with the present invention, there is provided a computer input device with multiple pressure sensors. A possible embodiment of the computer input device would be a computer mouse with sensors placed on the base and on the lever of each of two finger push buttons. A method for correlating pressures applied to a computer input device and authenticating the identity of the user. The method includes a procedure for initially registering the unique pressure attributes of the computer user on the device using one or more pressure sensors. Also, the method includes using the pressure attributes collected during registration to at least one correlational model. The correlational model is used to authenticate the identity of the user. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
     A complete understanding of the present invention may be obtained by reference to the accompanying drawings, when considered in conjunction with the subsequent, detailed description, in which: 
       FIG. 1  is a schematic diagram view of a system for correlating physiological attributes of a computer user to the identity of the user; 
       FIG. 2  is a perspective top view of a bottom half computer mouse case showing the internal placement of the bottom case pressure sensor; 
       FIG. 3  is a cross sectional side view of a computer mouse showing the button cover, button cover support structure, button cover post and push button when the computer mouse button is not depressed; 
       FIG. 4  is a cross sectional side view of a computer mouse showing the button cover, button cover support structure, button cover post and push button when the computer mouse button is depressed; 
       FIG. 5  is a schematic diagram view of a set of sensor input to the system; 
       FIG. 6  is a graphic view of a pressure sensor signal as it changes through the stages; 
       FIG. 7  is a schematic view of an algorithm, showing the logic of the registration module diagram; 
       FIG. 8  is a graphic view of a pressure wave signal from a single pressure sensor of three different users before digitization of the pressure wave signal; and 
       FIG. 9  is a schematic diagram view of an algorithm, showing the logic of the continuous authentication module. 
   

   For purposes of clarity and brevity, like elements and components will bear the same designations and numbering throughout the FIGURES. 
   DETAILED DESCRIPTION OF THE INVENTION 
   Referring initially to  FIG. 1 , a schematic diagram is shown, generally designated the system  14 , that includes two computer systems which are the authentication computer  40  and task computer  44 . The task computer  44  consists of one or more input devices, such as a computer mouse  12  and a keyboard  34 , to input data to the task computer  44  via mouse to computer cable  24  and keyboard to computer cable  32 . The authentication computer  40  consists of one or more input devices, such as a keyboard  34 , to input data to the authentication computer  40  via keyboard to computer cable  32 . The authentication computer  40  also consists of a sensor electronics module  28  that receives conditions and amplifies signals from a plurality of pressure sensors in the computer mouse  12  via the mouse to electronics cable  22 . The conditioned signal from the sensor electronics module  28  is sent to the authentication computer  40  via the electronics to computer cable  30 . The authentication computer  40  is connected to the task computer  44  via the authentication to task computer cable  42 . 
   The authentication computer  40  and task computer  44  can output data to one or more output devices such as a video monitor  36  via a computer to monitor cable  38 . The system  14  with computers, input devices and output devices are supported on a surface  16 . 
   The authentication computer  40  and task computer  44  of the present invention can be a desktop computer, laptop computer, hand-held palm organizer or custom designed computer. The functions of the authentication computer  40  and task computer  44  can be incorporated into a single computer or functional modules can be distributed to many computers. Output devices other than those shown can be used. Input devices other than those shown can be used. 
   The authentication computer  40  and task computer  44  can output data to a data storage device, a printer, or a computer-network. Communication between computers in the system  14  can be via electric cords or wireless technology. 
   In the particular embodiment shown, in addition to the normal input functions of a mouse, the computer mouse  12  includes one or more input surfaces with pressure sensors to detect pressure signals when the user manipulates the computer mouse  12 . These signals from the pressure sensors, via the mouse to electronics cable  22  provide input to the sensor electronics module  28  that conditions and converts the analog signal to a digital signal. The digital signal via the electronics to computer cable  30  is sent to the authentication computer  40  for analysis. An example would be a computer mouse  12  with a pressure sensor structurally attached to the left mouse button  54  assembly to detect the pressure applied to a left push button  48  as it is depressed. This signal is conditioned and converted by the sensor electronics module  28  and sent to the authentication computer  40  via electronics to computer cable  30  for analysis. 
   In accordance with the present invention, the computer mouse  12  includes a plurality of pressure sensors to sense the pressure the user applies to the computer mouse  12  when the user manipulates the input surfaces of the computer mouse  12  such as the left button cover  26 , right button cover  18  upper mouse case  20  and lower mouse case  10 . As disclosed in greater detail below, the pressure sensors generate signals that represent respective physiological attributes of the user. It is to be understood that if desired, other input devices, such as the keyboard  34 , joystick, steering wheel and track ball can include the pressure sensors of the present invention. 
     FIG. 2  shows the preferred embodiment for detecting pressure on the lower mouse case  10 . A pressure sensor is positioned on the inside of the lower mouse case  10  where the thumb of a right-handed user would normally rest. In this embodiment, the lower mouse pressure sensor is a resistive strain gauge made by Measurements Groups Incorporated of North Carolina, mounted at a location in the lower mouse case  10 . Alternately, other types of sensors based on the following property changes can be used to measure pressure. These property changes include but are not limited to: capacitive, conductive, displacement, electromagnetic, electromechanical, electrochemical, inductive, magnetic, optical, and piezoelectric. When the user squeezes the lower mouse case  10 , the deflection of the material of the lower mouse case  10  measured by the strain gauge reflects the pressure applied by the user to the lower mouse case  10 . 
     FIG. 3  shows the preferred embodiment for detecting pressure applied by the user on the left mouse button  54 . The figure shows a cross sectional side view of a computer mouse  12  when the left mouse button  54  is not depressed, the left mouse button  54  assembly includes the left button cover  26 , left suspension structure  52 , left button pressure sensor, left post  50  and left push button  48 . The left suspension structure  52  holds the left button cover  26  such that the left post  50  is above the left push button  48 . A pressure sensor is mounted on the left suspension structure  52 .  FIG. 4  shows a cross sectional side view of a computer mouse  12  when the left mouse button  54  is depressed. When the left mouse button  54  is depressed, pressure on the left button cover  26  causes the left suspension structure  52  to deflect, the left button pressure sensor signal changes in correspondence to the amount of pressure the user is applying to the left mouse button  54 . 
   The pressure on the right mouse button is detected in the same way as the left mouse button  54 . The right mouse button assembly is constructed of a right suspension structure that holds the right button cover  18  such that the right post is above the right push button. A pressure sensor is mounted on the right suspension structure. When the right mouse button is depressed, pressure on the right button cover  18  causes the right suspension structure to deflect, the right button pressure sensor signal changes in correspondence with the amount of pressure the user is applying to the right mouse button. 
     FIG. 5  shows a diagram of the sensor electronics module  28  detailing the preferred embodiment of the device hardware. The diagram shows a plurality of pressure sensor inputs which are the left mouse pressure sensor  46 , right mouse pressure sensor  70 , upper case pressure sensor, and the lower mouse case pressure sensor  74 . When a user applies pressure to the computer mouse  12  a pressure wave is created. As an example,  FIG. 6  shows a graph of a pressure wave signal  68  from a single pressure sensor as it changes through the components of the sensor electronics module  28 . In  FIG. 6 , Graph A shows the pressure wave signal  68 , Graph B shows the minimum of the pressure wave signal offset  64  to zero by the Wheatstone bridge  66  and Graph C shows the pressure wave signal amplified  60  by the signal amplifier  62  to maximize the dynamic range before the signal is converted by the analog to digital converter  58 . The resulting digital signal from the analog to digital converter  58  is analyzed in the authentication computer  40 . 
   Continuous authentication of the user of the task computer  44  is performed by the authentication computer  40  using two modules. The first module is the registration module  76  and the second is the continuous authentication module  92  shown in  FIGS. 7 and 9  respectively. 
   In accordance with the present invention, the authentication computer  40  accesses the registration module  76  and continuous authentication module  92  that can be executed by the authentication computer  40  to undertake the inventive logic disclosed below in detail. It is to be understood that the control modules such as the registration module  76  and continuous authentication module  92  are executed by logic components such as are embodied in logic circuits or in software contained in an appropriate electronic data storage, e.g., computer memory, a hard disk drive and/or optical disk drive, that are conventionally coupled to the authentication computer  40 . 
   The flow charts herein illustrate the structure of the registration module  76  and continuous authentication module  92  of the present invention as embodied in computer program software. Those skilled in the art will appreciate that the flow charts illustrate the structures of logic elements, such as computer program code elements or electronic logic circuits that function according to this invention. Manifestly, the invention is practiced in its essential embodiment by a machine component that renders the logic elements in a form that instructs a digital processing apparatus (that is, a computer) to perform a sequence of function steps corresponding to those shown. In other words, the registration module  76  and continuous authentication module  92  may be a computer program that is executed by a processor within the authentication computer  40  as a series of computer-executable instructions. 
     FIG. 7  shows the logic of the preferred embodiment of the registration module  76 . The registration module  76  links the user identity  80  to the user&#39;s biometric characteristics  82 . Logic components shown in  FIG. 7  can be embodied as software, hardware or a combination of both. An authorized registrant uses the keyboard  34  to enter the user identity  80  to be linked to the biometric characteristics  82  of the user. The digitized signal  56  from the analog to digital converter  58  from the plurality of sensors provide input to a biometric characteristics extractor  84 . The biometric characteristics extractor  84  can use various methods to extract biometric characteristics  82  including, but is not limited to the following list: descriptive statistics, canonical correlation, Fourier analysis, wavelet analysis, fuzzy sets classification and neural networks classification. The biometric characteristics extractor  84  generates a set of biometric characteristics  82  from each of the sensors that are then linked to the user identity  80  in the identity database  78  to the user. As an example,  FIG. 8  shows the pressure wave signal  68  from a single pressure sensor of three different users before digitization of the pressure wave signal  68 . As the user applies pressure the signal increases, but each user&#39;s signal has different descriptive statistical characteristics. Characteristics of the first user  90  includes symmetry and narrowness of the pressure signal around the peak of the pressure wave. Characteristics of the second user  88  includes asymmetry and increased pressure signal duration. Characteristics of the third user  86  includes symmetry and an increased duration of high pressure. 
     FIG. 9  shows logic of the continuous authentication module  92  of the preferred embodiment of the device when used during the continuous authentication of the user. The continuous authentication module  92  verifies that the user&#39;s biometric characteristics  82  are in the identity database  78 , that the user is an authorized user and is allowed to have continued task computer  44  access. Logic components shown in  FIG. 9  can be embodied as software, hardware or a combination of both. The digitized signal  56  from the analog to digital converter  58  from the plurality of sensors provide input to a biometric characteristics extractor  84 . The biometric characteristics  82  extracted from the digitized signals are correlated to those biometric characteristics  82  in the identity database  78 . The biometric characteristics  82  correlation unit can use the following list of models to compare the biometric characteristics  82 , but is not limited to the following list: discriminant analysis, multidimensional scaling, factor analysis, neural networks, and support vector machine analysis. 
   Discriminant analysis has been shown to be on average 79% accurate with a single signal input when discriminating between six persons as shown in Ikehara, C. and Crosby, M. E., “User Identification Based on the Analysis of the Forces Applied by a User to a Computer Mouse 12,” Proceedings of the Hawaii International Conference on System 14 Sciences, Kona, Hi., 2003. Increased accuracy can be obtained from multiple sensors and sequential inputs (e.g., potentially greater than 95% accurate after 3 sequential signal inputs). 
   The output from the biometrics correlation unit  96  will indicate whether the user is or is not in the identity database  78  and if the user is in the identity database  78 , the biometrics correlation unit  96  will provide the user&#39;s identity. An authorized user will have continued access to the task computer  44  and the authorization procedure will repeat. When the biometrics correlation module cannot identify the user or when the user is not found on the authorized user list, the computer will perform an unauthorized user protocol  94 . The unauthorized user protocol  94  may include blocking access to the task computer  44  by sending a signal via the authentication to task computer cable  42 . 
   Computer systems protected by the invention would have a limited number of registered users (e.g., usually one to three users). Initial access would not be accomplished by comparing the user&#39;s biometrics to a large database of users (i.e., a one-to-many comparison), but by conventional high accuracy identification means such as a password. After initial access is obtained, continuous authentication of the user&#39;s identity would be performed by comparing the user&#39;s identity at initial access to the registered biometrics of that user (i.e., a one-to-one comparison). In many cases, a one-to-one comparison is faster and more accurate than a one-to-many comparison. A more detailed discussion of the differences and appropriateness of the one-to-one versus one-to-many comparison methods can be found in Nanavati, S., Thieme, M. and Navanati, R., “Biometrics: Identity Verification in a Networked World”, 2002, pp. 12-14. 
   While the particular INPUT DEVICE TO DETECT BIOMETRICS as herein shown and described in detail is fully capable of attaining the above-described objects of the invention, it is to be understood that it is the presently preferred embodiment of the present invention and is thus representative of the subject matter which is broadly contemplated by the present invention, that the scope of the present invention fully encompasses other embodiments which may become obvious to those skilled in the art. For example, continuous user authentication from a biometric characteristics  82  can be obtained from pressure sensors mounted within a joystick, steering wheel, trackball, or foot pedal. The scope of the present invention accordingly is to be limited by nothing other than the appended claims, in which reference to an element in the singular means “at least one” unless otherwise recited. 
   Since other modifications and changes varied to fit particular operating requirements and environments will be apparent to those skilled in the art, the invention is not considered limited to the example chosen for purposes of disclosure, and covers all changes and modifications which do not constitute departures from the true spirit and scope of this invention. 
   Having thus described the invention, what is desired to be protected by Letters Patent is presented in the subsequently appended claims.