Abstract:
Apparatus, and a method for its use, for automatically verifying the identity of a person seeking access to a protected property that is remotely located with respect to the apparatus, such as a remotely located computer file or building alarm system. The apparatus, which is disclosed in the form of a handheld device ( 14 ) or other portable device ( 14′ ), includes a sensor ( 16 ) for reading biometric data, such as a fingerprint image, from the person, and a correlator ( 28 ) for comparing the sensed data with a previously stored reference image ( 32 ) and for determining whether there is a match. If there is a match, the device ( 14 ) initiates an exchange of signals over a communication network, with the “door” ( 10 ) that protects the property. Specifically, the device ( 14 ) generates a numerical value, such as a cyclic redundancy code, from the stored reference image ( 32 ), encrypts the numerical value, and transmits it to the door ( 10 ) as confirmation of the person&#39;s identity. For further security, the person registers this numerical value at each door ( 10 ) to which access is desired. Upon receipt of identity confirmation from the device ( 14 ), the door ( 10 ) compares the received numerical value with the one stored during registration, before granting access to the protected property.

Description:
This application is a continuation of U.S. application Ser. No. 08/995,565, filed Dec. 22, 1997, now U.S. Pat. No. 6,038,666. 
     BACKGROUND OF THE INVENTION 
    
    
     The present invention relates generally to personal identification or verification systems and, more particularly, to systems that automatically verify a person&#39;s identity before granting access to valuable information or granting the ability to perform various transactions remotely. Traditionally, keys and locks, or combination locks, have been used to limit access to property, on the theory that only persons with a right to access the property will have the required key or combination. This traditional approach is, of course, still widely used to limit access to a variety of enclosed spaces, including rooms, buildings, automobiles and safe deposit boxes in banks. In recent years, mechanical locks have been supplanted by electronic ones actuated by encoded plastic cards, as used, for example, for access to hotel room doors, or to bank automatic teller machines (ATMs). In the latter case, the user of the plastic card as a “key” to a bank account must also supply a personal identification number (PIN) before access is granted. 
     A significantly different problem is presented when someone seeks access to information remotely, such as by telephone or through some other type of communication network. Telephone verification of identity is typically accomplished using passwords, personal identification numbers (PINs), or words of which only a limited number of people have knowledge. Banks frequently use the customer&#39;s mother&#39;s maiden name as an access code, sometimes coupled with other codes or numbers theoretically known only to the customer. There are many practical shortcomings to this approach, the most obvious of which is that any of these codes or secret words can be stolen, lost or fall into the wrong hands by other means. Security may be increased by encoding identity data into magnetic stripes on plastic identification cards, which are used in conjunction with telephones that have appropriate card readers. The use of “smart cards” containing even more information on an integrated-circuit TRW chip has also been proposed, but these approaches also have the drawback that the identity cards may be lost or stolen. 
     Accordingly, there is a widely felt need for a more reliable technique for providing secure access to information and assets, particularly for users who seek this access over a communication system of some kind. Ideally, the technique should positively verify the identity of the person seeking remote access, and should eliminate the need to carry multiple scannable cards, and the need to memorize combinations, passwords and PINs. The present invention satisfies this need. 
     SUMMARY OF THE INVENTION 
     The present invention resides in apparatus, and a method for its use, for automatically verifying the identity of a person seeking remote access to a protected property. The protected property may take a variety of forms, but typically includes a remotely located computer to which a user seeks access for reading or writing information. Alternatively, the protected property may be a building or other structure and the user wishes to activate or deactivate an alarm system in the building. 
     Briefly, and in general terms, the apparatus of the present invention comprises a personal identification device and means for securely communicating identity confirmation to a door that provides access to the protected property upon receipt of the identity confirmation. The personal identification device includes a sensor, for reading biometric data identifying a person seeking access to a protected property, storage means, for storing reference biometric data identifying a person authorized to have access to the protected property, and a correlator, for comparing the stored reference biometric data with the biometric data of the person seeking access and determining whether they match. The apparatus may further comprise a user interface having a first switch to initiate operation of the apparatus in a verification mode, and a second switch, actuation of which places the apparatus in an enroll mode of operation, wherein biometric data from the sensor are stored in the storage means for subsequent retrieval in the verification mode of operation. 
     In one of the disclosed embodiments of the invention, the sensor, the storage means and the correlator are all integrated into a portable communication device, such as a telephone, which may be a device carried by the person, or some other type of communication device remote from the protected property. In the disclosed embodiments, the means for securely communicating identity confirmation includes means for generating a numerical value from the stored reference biometric data; encryption logic, for encrypting the numerical value; and a communication interface for sending the encrypted numerical value to the door, together with identification data for the person. The door provides the desired access to the protected property upon confirming that the transmitted numerical value is the same as one previously provided by the person during a registration procedure. 
     The apparatus of the invention may further include a receiver, for receiving an encryption key generated by and transmitted from the door, and means for storing a private encryption key in the identification device. Further, the encryption logic in the device includes means for doubly encrypting the numerical value using the encryption key received from the door and the private encryption key. 
     The apparatus of the invention may also be defined as a separate device that includes a sensor, for reading fingerprint data identifying a user seeking access to a protected property; a memory for storing a reference fingerprint image of the user during an enrollment procedure and for holding the reference image for future use; an image correlator, for comparing the stored reference image with a fingerprint image of the user seeking access, as obtained from the sensor, and for determining whether the two images match; and means for securely communicating identity confirmation to a door that provides access to the protected property upon receipt of the identity confirmation. More specifically, the means for securely communicating identity confirmation includes means for generating a numerical value from the stored reference fingerprint image; encryption logic, for encrypting the numerical value; and a transmitter for sending the encrypted numerical value to the door, together with user identification data. The door provides the desired access to the protected property upon confirming that the transmitted numerical value is the same as one previously provided by the user during a registration procedure. 
     In the personal identification device as defined in the previous paragraph, the means for generating a numerical value includes means for generating a cyclic redundancy code from the stored reference fingerprint image. The device further includes a receiver, for receiving an encryption key generated by and transmitted from the door; and means for storing a private encryption key in the device. The encrypticn logic in the device includes means for doubly encrypting the numerical value using the encryption key received from the door and the private encryption key. 
     In terms of a novel method for automatically verifying the identity of user seeking access to a remotely located, protected computer, the invention comprises the steps of sensing biometric data of a user, through a sensor that is part of a personal identification device carried by the user; comparing the sensed biometric data with reference biometric data previously stored in the personal identification device; determining whether the sensed biometric data match the reference biometric data; if there is a match, securely communicating, through a communication network, an identity confirmation to a door that controls access to the protected computer; and upon confirmation of the identity of the user at the door, providing the desired access to this protected computer. The method further comprises the step of initiating normal operation of the personal identification device by means of a manual switch. 
     In one embodiment of the method, the step of securely communicating includes generating a numerical value from the stored reference biometric data; encrypting the numerical value; transmitting the encrypted numerical value to the door; transmitting user identification data to the door; receiving and decrypting the encrypted numerical value at the door; comparing the decrypted numerical value with one previously stored at the door by the user during a registration process, to confirm the identity of the user; and if the identity of the user is confirmed, activating a desired function to provide access to the protected property. 
     More specifically, the step of securely communicating further comprises the steps of generating at the door a random pair of door public and private encryption keys; transmitting the door public key to the personal identification device; selecting for the personal identification device a pair of public and private encryption keys for all subsequent uses of the device; providing the personal identification device public key to the door as part of the door registration process; and storing the personal identification device private key secretly in the device. The encrypting step includes doubly encrypting the numerical value with the door public key and the personal identification device private key. The method further includes the step, performed at the door, of decrypting the doubly encrypted numerical value using the personal identification device public key and the door private key. 
     The invention may also be defined as a method for a user to obtain access to a remotely located and protected computer, the method including the steps of placing a finer on a fingerprint sensor in a device; actuating the device to sense and record a fingerprint of the user; comparing the sensed fingerprint with reference fingerprint data previously stored in the device; transmitting, upon a successful comparison, an identity confirmation from the device and over a communication network to the protected computer; and providing requested access to the protected computer upon receipt of an identity confirmation. The step of transmitting an identity confirmation ideally includes encrypting the identity confirmation in the device and decrypting the identity confirmation in the protected computer. More specifically, encrypting in the device includes doubly encrypting using a public encryption key received from the protected computer and a private encryption key stored in the device, and decrypting includes doubly decrypting using a public key provided by the device user and a private encryption key generated in the computer. 
     It will be appreciated from the foregoing that the present invention represents a significant advance in providing secure access to remotely located computers or similar protected properties. More particularly, the invention allows multiple properties or assets to be accessed remotely using a security device, which reliably identifies its owner using biometric data, such as a fingerprint. Because identification is verified in a small portable device, communication with multiple “doors” to protected property can be limited to a simple identity confirmation message, appropriately encrypted to prevent eavesdropping or reverse engineering. Other aspects and advantages of the invention will become apparent from the following more detailed description, taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1A is a diagram illustrating an application of the invention, wherein a personal identification device integrated into a cellular telephone is used to open a door remotely, through a communication network; 
     FIG. 1B is a block diagram showing the use of a personal identification device in conjunction with a portable computer, to gain access to a remotely located computer; 
     FIG. 2 is a block diagram depicting the principal components of the present invention; 
     FIG. 3 is a more detailed block diagram showing the components of a processor module shown in FIG. 2; and 
     FIG. 4 is a block diagram showing a sequence of signals transmitted between the portable device and a door to protected property. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As shown in the drawings for purposes of illustration, the present invention pertains to a system for automatic verification of the identity of a person seeking remote access to protected property, over a communication network. Traditionally, remote access to protected property has been controlled with the use of passwords, codes and similar devices. 
     In accordance with the present invention, the person seeking access to protected property carries a portable identification device that includes a sensor capable of obtaining selected biometric measurements associated with the person, and communicating with a related device located near the “door” of the protected property. Preferably, the portable device also includes identity verification means, which compares the biometric measurements obtained from the sensor with corresponding measurements stored in a reference set of biometric measurements that were obtained from the same person during an enrollment procedure performed earlier. 
     FIG. 1A shows diagrammatically how the invention is used to open a “door,” indicated by reference numeral  10 , to protected property. A person seeking entry to the door  10  carries a small handheld device, which may be integrated into a cellular telephone  14 ′ or may take the form of a separate device  14  (FIG.  1 B). It will be understood, however, that the handheld device could be integrated into other types of communication terminals. The telephone  14 ′ communicates with a receiver  15  located near the door  10 . In the presently preferred embodiment of the invention, the telephone  14 ′ includes a biometric sensor, which, in the presently preferred embodiment of the invention, is a fingerprint sensor  16 . It will be understood, however, that the principles of the invention are also applicable to a device that employs other biometric properties to identify the user, such as print patterns from other parts of the anatomy, or iris patterns of the eye. 
     The telephone  14 ′ communicates with the receiver  15  through a communication network  17  and a communication interface  18  located near the door  10 . The interface  18  may be, for example, a telephone. FIG. 1B shows how the fingerprint sensor  16  may be connected to a laptop computer  19 . When the user wishes to access information in a remotely located computer, referred to as  10 ′ because it embodies another form of a “door,” the user connects the sensor  16  to the laptop computer  19 , effects a connection to the computer  10 ′ through the communication network  17  and communication interface  18 , and then is identified by means of the sensor. 
     When the user places a finger over the sensor  16  and actuates a switch, the person&#39;s fingerprint is scanned and is compared with a reference fingerprint image stored in the device  14  or  14 ′, which includes a fingerprint correlator (not shown in FIGS. 1A and 1B) for this purpose. If the comparison results in a match, the device  14 / 14 ′ transmits a confirming message to the door  10 , or the computer  10 ′. The door  10  is opened to allow access by the user  12 , or the computer  10 ′ is conditioned to permit data access by the user. 
     The nature of the confirming message sent to the door  10  or the computer  10 ′ is of considerable importance, because a simple “OK” or “open” signal in a standardized format would be easy to duplicate in a “cloning” process, and unauthorized access would be a relatively simple matter. The confirming message should ideally be in the same format for different access “doors,” but should be encoded or encrypted in a way that prevents its duplication and prevents reverse engineering of the device  14 . Details of one technique for accomplishing these goals are provided below. 
     FIG. 2 shows the principal components of the device  14 , including the fingerprint sensor  16 , a processor module  20 , a transceiver  22  and a battery power supply  24 . It will be understood that the same components may be integrated into another device, such as the cellular telephone  14 ′, and that the battery power supply  24  may be integrated with the telephone battery. The fingerprint sensor  16  may be of any available design, and may include a capacitive, optical or other sensor. The sensor  16  produces a binary or grayscale image of a portion of the user&#39;s fingerprint. For rapid processing, the entire image may not be used in the comparison process that follows, but what the sensor  16  provides is a detailed “map” of the fingerprint, including all of its ridges and valleys. The processor module  20  is shown in more detail in FIG.  3 . 
     The processor module  20  includes a processor  26 , which may be, for example a RISC (reduced instruction set computer) processor, a fingerprint matcher, which is a feature correlator  28  in the preferred embodiment of the invention, a cyclic redundancy code (CRC) generator  30 , storage  32  for a reference fingerprint image, encryption logic  34  and storage  36  for a private encryption key. The device  14  also includes a user interface  38  through which the user  12  initiates operation in various modes. Basically, the user interface  38  includes one main operating button, which may be incorporated into the fingerprint sensor  16 , and at least one additional button to initiate operation in the enrollment mode. The principal function of the processor  26  is to pre-process and enhance the fingerprint image provided by the sensor  16 . Pre-processing includes “cleaning” the image, cropping the image to eliminate background effects, enhancing contrast in the image, and converting the image to a more manageable binary form. In the enrollment mode, the pre-processed image is stored in the reference image storage area  32 , as indicated by the broken line  40 . Enrollment is performed when the user first acquires the device  14 , and is normally not repeated unless the device is lost or damaged. For additional security and convenience, the user may be asked to enroll two fingerprints, to allow for continued access if the user injures a finger, for example. In a verification mode of operation, the pre-processed fingerprint image is input to the correlator  28 , as indicated by line  43 , where it is compared with the reference image obtained from storage  32  over line  44 . The correlator  28  uses an appropriate technique to compare the images, depending on the level of security desired. Because speed of operation is an important factor, a bit-by-bit comparison of the entire images is usually not performed. Rather, significant features of the reference image are identified and the same features are looked for in the newly scanned image. The techniques disclosed in U.S. Pat. No. 5,067,162 may, for example, be incorporated into the correlator  28  for some applications of the device  14 . Preferably, the fingerprint correlator  28  should follow the teachings of a co-pending patent application entitled “Fingerprint Feature Correlator,” by inventors Bruce W. Evans et al., which is hereby incorporated by reference into this specification. As a result of the comparison of the images, the correlator  28  may generate a match signal on line  46 , which activates the CRC generator  30 . If a no-match signal is generated, as indicated on line  48 , no further processing is performed. Optionally, the no-match signal on line  48  may be used to actuate an indicator on the user interface  38 . 
     The cyclic redundancy code (CRC) generator  30 , when actuated by a match signal on line  46 , generates a relatively long (such as 128 bits) binary number derived from the reference image data. The CRC provides a single number that, for all practical purposes, uniquely identifies the stored reference fingerprint image. Even if two fingerprint images produced the same CRC, which is highly unlikely, the security of the system of the invention would not be compromised, as will shortly become clear. 
     The CRC itself is not stored in the device  14 , but is transmitted in encrypted form to the door receiver  15 . Before using the device  14  for access to a particular door  10  for the first time, the user  12  must first “register” at the door. The registration process is one in which an administrator of the door stores the user&#39;s name (or account number, or other identifying information), in association with a public encryption key to be used in the user&#39;s device  14 , and the user&#39;s CRC as derived from the user&#39;s reference fingerprint. If the door  10  provides access to a financial institution, for example, the user will register by bringing his or her device  14  to the institution, and transmitting the fingerprint CRC from the device to the door receiver  15 . In the registration mode, the door receiver  15  will store the user&#39;s CRC in association with the user&#39;s name or other identifying information. As part of the registration process, the user  12  will normally be required to present some form of identification other than the device  14 , to prove to the institution that the user is, in fact, the one whose name or other identifying information is presented and will be stored in the door  10 . 
     As will now be explained in more detail, in a subsequent use of the device  14  for access to a door  10  at which the user has registered, the device transmits a user name and the CRC corresponding to the stored reference image. Logic at the door  10  or computer  10 ′ then compares the received CRC with the one that was stored for the named user during registration. If there is a match, the door is opened for the user. 
     FIG. 4 shows the communications that pass between the personal identification device  14  and a door  10 , two different forms of which are shown, including a computer  10 . 1  and another type of “door”  10 . 2 , such as in a house or other property to which remote access is desired. Each door  10  has an actuator  50 , to perform some desired operation, such as opening the door, and each door also has a database  52  in which is stored the user name, the user device public encryption key and the user CRC, for each user registered to use the door. For file access to the computer  10 . 1 , the user may simply need to access personal data relating to a user account in bank or other institution, or may need to download information from a file in the computer. For access to the door  10 . 2 , the user may need, for example, to make sure that an alarm system has been activated in a residence or office. 
     When the user actuates the device  14 , the user name is transmitted to the door  10  in non-encrypted form, as indicated by line  54 . On receiving the user name, the door  10  generates a random pair of public and private encryption keys to be used in the ensuing exchange of messages. Since public key encryption is used in this illustrative embodiment of the invention, a few words of explanation are called for, but it will be understood that the principles of public key encryption are well understood in the field of secure communication. 
     In public key encryption, two separate encryption keys are used: a “public” key (potentially known to everyone and not kept secret), and a “private” key (known to only one party in a communication from one party to another). The pair of public-private keys has the property that, if either of them is used to encrypt a message, the other one of the pair will decrypt the message. For example, party A can send a secure message to party B by first encrypting with B&#39;s public key. Only B can decrypt the message, because only B has B&#39;s private key needed for decryption. Similarly, B could send an encrypted message to A using B&#39;s private key for encryption. A could decrypt the message with B&#39;s public key, but so could anyone else, because B&#39;s public key may be known to others. Therefore, the message transmitted using this “backward” form of public key encryption would not be secure. 
     The illustrative embodiment of the present invention uses a double encryption form of public key encryption. Both the device  14  and the door  10  have a public-private key pair. As presently contemplated, the device  14  of the invention will have a “fixed” public and private key pair, that is to say the public and private keys will not changed from one use of the device to the next. The device public key is registered with each door  10  and it would be impractical to change it for every use. The device private key is stored (at  36 , FIG. 3) in the device  14 , preferably in a form in which it cannot be discerned by inspection or reverse engineering. The key may, for example, be encoded into the silicon structure of the processor module  20  in such a way that it is practically indecipherable by any normal reverse engineering technique. Each door  10  generates a new public-private key pair on every new use of the door. Thus, these keys cannot be determined in advance of the actual message exchange with a device  14 . 
     Upon receipt of a user name from the device  14 , the door  10  to which access is sought generates a random pair of public-private keys, and transmits the public key to the device without encryption, as indicated by line  58 . Then, if the device  14  has validated the user&#39;s identification by successfully matching the sensed fingerprint image with the reference image, the device performs two levels of encryption on the CRC that is generated. First, the encryption logic  34  in the device  14  encrypts the CRC using the door&#39;s public key. Then the resulting encrypted CRC is doubly encrypted using the device&#39;s private key. The doubly encrypted CRC is transmitted to the door  10 , where it is decrypted using the device&#39;s public key and then using the door&#39;s private key to recover the CRC. The door  10  then compares this CRC with the CRC in its database  52  associated with the user name seeking access to the door. If there is a match, the door  10  signals its actuator  50  to open the door or to perform some other desired operation. 
     It will be appreciated frorm this description that the invention provides an extremely secure technique for accessing protected property. The device  14  is designed such that is cannot initiate a door opening operation without first matching the fingerprint of the user with the stored reference image. Even if a device thief successfully re-enrolls his own fingerprint into the device, the CRCs stored in each of the doors where the rightful user is registered would prevent operation of the doors by the thief. 
     Someone attempting to fabricate a “cloned” device would not have the device private key, so the door would be unable to decrypt messages from the cloned device. If someone were to eavesdrop on a device transmission and try to emulate this message in a subsequent attempt to open the same door, this approach would be foiled by the door&#39;s use of a different set of keys for each transaction. Therefore, the device&#39;s encrypted message to any door will be different on each occasion. 
     An additional level of security may be provided by storing the CRC at the door  10  in an internally encrypted form, to prevent theft of CRCs from doors. 
     If the door  10  is the computer  10 . 1 , and the user wishes to download information from the computer, this will usually require an additional exchange of messages between the device  14  and computer  10 . 1 , to establish an appropriate level of security for the transfer of from the computer. Techniques for effecting secure data transmission may include the exchange of messages to establish a session encryption key for the transmission, or an encryption key may have been previously established for this purpose. 
     It will be understood from the foregoing that the present invention represents a significant advance in the field of security devices for limiting access to remotely located property. In particular, the invention allows a person to obtain access to different properties remotely, using a handheld device that verifies its owner&#39;s identity very reliably, by means of unique biometric parameters, such as those found in a fingerprint. Moreover, the device of the invention is highly resistant to reverse engineering, “cloning” and other techniques for tampering to obtain access to the protected properties. It will also be appreciated that, although a specific embodiment of the invention has been described in detail for purposes of illustration, various modifications may be made without departing from the spirit and scope of the invention, which should not be limited except as by the appended claims.