Abstract:
Smart card security is enhanced by making the smart card a two-piece device. Both parts of the smart card contain copies of user data and a processor, which executes program instructions stored in the smart card half so as to give each part of the two-part smart card security and intelligence. Both parts must be in communication with each other for the data in either card to be accessible and useable. By separating the two pieces, data compromise is virtually impossible.

Description:
FIELD OF THE INVENTION 
     This invention relates to data security devices. In particular, this invention relates to a method and apparatus for securely storing data in a personal data security device commonly known as a smart card. 
     BACKGROUND OF THE INVENTION 
     “Smart cards” as they are known, physically resemble the now ubiquitous credit cards but their similarities end there. These credit-card replacements are described in the literature. By way of example, they are described in an article appearing on page 47 of the February 1997 edition of the IEEE Spectrum magazine which is entitled “In Your Pocket Smartcards” by Carol Hovenga Fancher. 
     While smart cards physically resemble credit cards, smart cards are far more powerful in that they have one or more microcontrollers embedded in them which manage access to, and storage of, sensitive data that is actually stored in memory devices on the smart card. Data that might be stored in a smart card includes bank account numbers, personal data as well as a complete medical history, or the electronic equivalent of currency. Smart cards are widely used in Europe and are expected to eventually replace the library of cards most people carry and which include credit cards, phone cards, transit passes, frequent flyer cards, car rental cards and social security card. 
     Credit cards on the other hand, as well as debit cards and “ATM” (automatic teller machine) cards are mere sheets of plastic that are embossed with a series of numbers and letters that represent either the card number or an account number. A strip of magnetized material that is typically attached to one side of the card is programmed (magnetized) with a limited amount of data, typically the same number that is embossed on the card. When the card is “swiped” through a reader, information programmed into the magnetic strip is read. 
     While the security systems employed with smart cards is quite robust, losing a smart card might be considered to be roughly the equivalent of losing a wallet or purse—filled with money. Accordingly, for those who use a smart card and who want the highest possible security there will always exist the need for additional security measures. 
     SUMMARY OF THE INVENTION 
     The security of a personal data storage device (a smart card) is enhanced by providing to the smart card an additional layer of security in the form of an enabling key, which when coupled to the smart card enables the processor on the smart card to access and change storage information. If the enabling key is not accessible to the smart card, the smart card remains disabled. 
     In one embodiment the enabling key is physically connected to a terminal of the smart card. In another embodiment, a wireless radio link between the enabling key and smart card is used. 
     In every embodiment, the smart card is disabled if the enabling key and its own processor and data are not detected and accessed by the smart card. An additional level of security is realized by physically detaching (or geographically separating) the smart card and the enabling key in which event the smart card is disabled, preventing theft. If the key-fob enabling key is lost, intelligence on the smart card provides the smart card issuer sufficient data with which the key can be replicated. If the smart card is lost by the key fob is still available, data on the fob permits the card issuer to recreate the smart card data in its entirety. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  depicts a simplified representation of a two-part smart card, both parts of which are required to provide smart card functionality. 
         FIG. 2  depicts a simplified flow chart of the disclosed method. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 1  shows a simplified representation of a two-part personal data storage device, also known as a smart card  100  which provides increased security for sensitive user data such as credit card numbers, bank account numbers, medical history, electronic cash equivalency. Such data and data or information and records of similar import is referred to hereinafter as a set of user data. 
     A first part of the smart card  102  includes within it a processor  104  and at least one memory device, typically electrically erasable programmable read only memory  106  (EEPROM) but also possibly including read only memory (ROM) as well as random access memory (RAM), accessible via an address/data bus  108  that effectively couples together, devices that are operatively coupled to the bus  108 . 
     As those skilled in the art will recognize, semiconductor memory can readily be placed on the substrate for the processor  104  as well as on its own separate substrate. In addition to the processor  104  and memory, a bi-directional data interface  110 , which is also coupled to the bus  108 , provides a mechanism by which the first part of the smart card  102  can communicate with external devices, such as the second part  112  of the two-part smart card  100 . The bi-directional data interface  110  is also coupled to the processor  104  and memory  106  through the bus  108 . 
     The second part  112  of the two-part smart card  100  also incorporates within it a processor  116 , memory  118  and an I/O port  120 , all of which are coupled together via a separate bus  130 . The I/O port  120  can be considered to be a second interface circuit. The first and second interface circuits ( 110  and  120  respectively) grant communications access to the respective first and second smart card parts ( 102 ,  112  respectively). Electrical and mechanical coupling between the first and second ports  110 ,  120  so as to achieve an electrical connection between the two smart card parts is preferably accomplished using any appropriate mechanical electrical connector device (not shown but known to those skilled in the connector art) but selected depending upon the desired physical characteristics of the smart car when the two portions are together. Alternate embodiments would include using a RF data link, an optical link or an infrared link as well. 
     As shown in  FIG. 1 , a broken line  119  serves only to represent that all of the functionality of the second part  112  is embodied on a single piece of silicon, which in the preferred embodiment is also how the functional elements of the first part  102  are packaged. 
     The first part  102  of the smart card is considered hereinafter to be a first user data storage device in that it actually stores a first set of a users data (such as that listed above) within memory devices physically part of the device. The second part  112  of the smart card is considered to be a second user data storage device in that it too stores the first set of user data within it. 
     With respect to both of the smart card parts, the processors  104 ,  116  (within the corresponding smart card parts  102 ,  112 ) are coupled to the various circuits within each portion of the respective smart card parts by way of the busses  108 ,  130  which carry information between the various circuits that are coupled to it. By way of the busses, the processors are able to execute the instructions stored in various memory devices  106 ,  118  coupled to the busses  108 ,  130 . The programs stored in memory give the smart card portions intelligence. Various data can be written into the first smart card part  102  via the data interface circuit  110  such as a serial or parallel computer-to-computer data link (RS-232, IEEE 488, or other equivalent data pathway) or perhaps via a wireless RF data port  109 , (but also including an optical or infrared data port as well), coupled to the processor  104 . With respect to the second smart card port  112 , data can be written into the second smart card via its own similar data port  120  or perhaps its own wireless port  124 . Once data is written into the smart card parts, accessing the data or changing it is controlled by security measures designed into the smart card processor software. By appropriate program instructions and an appropriate reader, a smart card issuer can read data stored in memory of either smart card half, and reconstruct data in a missing half in that the respective halves of the smart card can be made to be substantially duplicate copies of each other. 
     Enhanced smart card security is achieved by denying access to the data stored in the first part of the smart card  102 , if the second part  112  is not accessible to the first part  102  (and vice versa), by either a wireless data exchange or a direct, electrical connection between the first and second parts. Software that controls the processor in the first part  104  denies access to stored data in the first part  104  if the second part of the card  112  is considered to be missing (or inaccessible to the first part). Similarly, access to data in the second part  112  is denied if the first part of the card  104  is missing from the second part (or inaccessible). By separating the two parts of the card, a card owner can effectively preclude anyone from using the card or accessing information stored in the respective parts. 
     Stored data security is enhanced even further if the data stored in the smart card parts is encrypted using data encryption techniques described in the prior art. Data security techniques for smart cards is disclosed in the literature. See for example “Locking the e-safe” by Robert W. Baldwin and C. Victor Chang of RSA Data Security, Inc. published in the February 1997 edition of the IEEE Spectrum, the teaching of which is incorporated herein by reference. 
     A transaction using the two-part smart card preferably proceeds according to the steps of the method  200  depicted in  FIG. 2 . In step  202 , the two-part smart card user initiates a desired transaction, which might include reading or writing a medical record or purchasing goods or services using data stored in the smart card that represents currency of the card user. Before any data within the smart card  100  can be accessed or changed, a data handshake between the processor  104  and a terminal of a vendor or merchant takes place via the wireless port  109  or the I/O port  110  either of which can be considered a first interface circuit. The first and second interface circuits grant conditional communications access to the data using an appropriate data exchange protocol. Various protocols as are known in the art can be used. 
     After the initial data handshake of a transaction is initiated, software within the first part of the smart card  102  and the second part of the smart card  112  exchange encryption keys which are required to access stored information. In a preferred, embodiment, the first and second encryption keys are the same. In step  204 , software programmed into the first part  102  of the smart card confirms that the second part  112  is the unique mate to the first part by way of the encryption key exchange. 
     In the preferred embodiment of the invention, a first set of user data (to be referred to as stored value) resides in both part  102  and part  112  of the two-part smart card. In step  206 , the first part of the smart card  102  reads stored value from the second part after the stored value is encrypted by the processor  116  of the second part  112  in order to prevent interception of the data as it crosses the boundary between the first and second parts  102 ,  112  respectively. 
     In step  208 , after receiving the encrypted stored value, which the first part  102  decrypts, the first part confirms that the value it received from the second part identically matches the value stored in the first part  102 . If as in step  210 , the value received into the first part  102  does not match the value stored in the second part, one or both parts sets an error condition flag  212  and re-attempts to confirm the identity of the second part by returning to step  204 . 
     If the value received (or perhaps other user data, such as the user&#39;s medical history) into the first part  102  matches the amount that was stored in the second part  112 , the processor  102  sets a transaction complete flag in step  216  and proceeds to conclude the transaction that was started in step  202 . If the smart card user is purchasing some goods or service or performing some other transaction (as indicated by the broken line from decision block  210 ), value is transferred from the first part via the I/O port  110  or the wireless connection or link  109  to compatible data equipment of the vendor. In step  214 , a financial transaction is performed (buying goods or services for example, or the stored value is incremented or decremented by a financial institution for instance), the processor in the first part  104  adjusts the stored value by the amount that was transferred, encrypts the new value and transfers the new value to the second part  112  for storage. By preventing transactions unless both parts are available throughout the entire transaction, the issuer of the smart card is guaranteed that the stored value is always the same in both parts. 
     Increased security is realized if the first and second smart card parts are separated. 
     By physically or electrically separating the two parts, it becomes impossible to access data stored in the second part  112  or in the first part  102 . In the event one piece is lost, by using data stored in the complementary piece, the smart card issuer or agent thereof, (having appropriate software and hardware, which is recognized by the software of the smart part parts  102 ,  112 ) can recreate the data stored in the other part because both card parts carry duplicate copies of data stored in each other. In applications like pre-paid phone cards and the like, economic loss caused by physical card loss can be reduced by keeping part of the card in the user&#39;s possession at all times. 
     By using a two-part smart card that is designed to require that both halves be in communication with each other, the likelihood of data loss or economic theft is reduced. Inasmuch as the halves can be physically separated, by keeping one half of the card secure, data in the other half is fully protected. If either half of the card is lost or destroyed, the remaining value or data can be recovered to the user by the card issuer.