Abstract:
A method for providing a secure communications channel for the transmission of large amounts of information between a RFID tag and a RFID reader. A laser beam is utilized to carry information and power from the RFID reader to the RFID tag. Thus, the laser beam has a dual use as an information carrier and a source of power for the RFID tag. Thus, only individuals and/or equipment that can both see the laser transmission and hear the RFID transmission can eavesdrop on the RFID tag RFID reader transmissions. This invention allows the use of complex algorithms to protect data being communicated because they can use the increased level of power available to the RDIF tag.

Description:
FIELD OF THE INVENTION  
       [0001]     This invention relates to electronic systems and, more particularly, to securely communicating with a radio frequency identification device that does not use batteries.  
       BACKGROUND OF THE INVENTION  
       [0002]     Radio frequency identification device (RFID) tags have been programmed to contain digital information either during the manufacturing of the read-only memory portion of the RFID integrated circuit, or in the field using electromagnetic radio frequency signals to store information in the nonvolatile memory portion of the RFID tag.  
         [0003]     A RFID tag does not require contact or line-of-sight to operate. RFID tags can function under a variety of environmental conditions and provide a high level of data integrity. RFID tags utilize radio frequency signals to transfer information from the RFID tag to a RFID reader and from the RFID reader to the RFID tag. Thus, radio waves are used to transfer information between the RFID tag and the RFID reader from the RFID reader to the RFID tag. A disadvantage of the foregoing is that the information transmitted by the RFID tag may be intercepted easily and read by an unintended party.  
         [0004]     One method utilized by the prior art to protect transmitted information between a RFID tag and a RFID reader was to encrypt the transmitted information.  
         [0005]     The packaging for RFID tags must be inexpensive, small and light. The least expensive RFID tags do not use batteries. Such RFID tags have electronic circuits that are powered by converting the energy of RF fields created by the RFID reader and captured by the RFID tag&#39;s antenna. As a result, the amount of electronic circuitry available in RFID tags powered only by the energy of RF fields is severely limited. Furthermore, the complexity of algorithms to process data and the amount of data stored in such circuits are also very limited. Currently, RFID tags use simple algorithms to protect the information exchanged with the RFID reader. The best RFID tags can do is to store a small amount of private information (e.g., their identity numbers or any secret information used to protect the communication with the RFID reader). Thus, one of the disadvantages of the prior art is that RDIF tag circuits do not protect private information against sophisticated attackers. Such attackers can obtain secret information stored in RFID tags using inexpensive equipment.  
         [0006]     Another disadvantage of the foregoing is that the amount of energy obtained by the RFID tags only from RF fields created by RFID readers is not sufficient to compute and analyze messages protected by strong cryptographic algorithms.  
         [0007]     RFID tags using batteries are more expensive, bigger and have a limited life. In addition to that, they may be less reliable as the battery may exhaust its energy during operation.  
       SUMMARY OF THE INVENTION  
       [0008]     This invention overcomes the disadvantages of the prior art by providing a secure communications channel for the transmission of a large amount of information between a RFID tag and a RFID reader. A laser beam is utilized to carry information and power from the RFID reader to the RFID tag. Thus, the laser beam has a dual use as an information carrier and a source of power for the RFID tag. Thus, only individuals and/or equipment that can both see the laser transmission and hear the RFID transmission can eavesdrop on the RFID tag RFID reader transmissions. This invention allows the use of complex algorithms to protect data being communicated, because they can use the increased level of power available to the RDIF tag. Additionally, more data can be stored in the tag. Additionally, using more sophisticated packaging can enhance the physical protection of stored data.  
         [0009]     This invention accomplishes the foregoing by generating a light beam that carries power and information to a radio frequency identification device, and receiving a radio frequency signal from the radio frequency identification device in response to the information carried by the light beam.  
         [0010]     An advantage of this invention is that the RFID tag does not require a battery since it receives power from a laser beam. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]      FIG. 1  is a block diagram showing communications between a RFID tag and a RFID reader;  
         [0012]      FIG. 2  is a drawing showing the elements of  FIG. 1  in greater detail; and  
         [0013]      FIG. 3  is a flow chart of the operation of digital signal processor  80  of  FIG. 2 . 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0014]     Referring now to the drawings in detail, and more particularly to  FIG. 1 , the reference character  9  represents a RFID tag. Tag  9  includes RFID circuit  10 , which has a RFID tag antenna  11  attached thereto. RFID circuit  10  is coupled to photocell and demodulator  12 . Demodulator and photocell  12  receives a light beam from laser beam generator  13 . Generator  13  is coupled to modulator  8  and modulator  8  is coupled to laser control computer  14 . Laser control computer  14  is coupled to data base  15  and computer  14  is also coupled to RFID reader  16 , which has a RFID reader antenna  17  attached thereto. Computer  14 , modulator  8  and generator  13  may be part of a bar code reader connected to the RFID reader  16 . Computer  14 , modulator  8 , generator  13 , reader  16  and antenna  17  comprise base station  7 . Communications between RFID circuit  10  and RFID reader  16  would be performed as follows.  
         [0015]     RFID reader  16  will cause RFID antenna  17  to transmit a radio frequency (RF) request signal via channel A that would be received by RFID tag antenna  11 . The aforementioned RF signal will request RFID circuit  10  to transmit its tag identification to RFID reader  16 . After antenna  11  receives the RF request signal, RFID circuit  10  will process the signal and transmit via antenna  11  and channel B a RF signal containing the tag identification of RFID circuit  10 . Antenna  17  will receive the signal containing the tag identification of RFID circuit  10 . RFID reader  16  will process and/or authenticate the signal containing the tag identification and transmit the tag identification of RFID circuit  10  to laser control computer  14 . Computer  14  will transmit the tag identification of RFID circuit  10  to database  15 . Database  15  will read its database to determine the cryptographic key for the tag identification of RFID circuit  10 . Database  15  will transmit the determined cryptographic key to computer  14 . Computer  14  will incorporate the cryptographic key into a message that becomes a signed message requesting tag  10  to transmit the protected information contained in circuit  10  to reader  16 . Computer  14  will transmit the signed message to modulator  8 . Modulator  8  will transmit the signed message to laser beam generator  13 . Generator  13  will process the signed message and produce a modulated laser light beam output that has the signed message and the power of the light beam. Photocell and demodulator  12  will receive the signed message and power. When photocell and demodulator  12  is illuminated by the laser power, the photocell will convert the laser power into electricity and the demodulator will demodulate the signed message. The electrical power will be transmitted to circuit  10  via a power channel and the signed message will be transmitted to circuit  10  via a data channel. Circuit  10  will transmit protected payload information stored in tag  10  via antenna  11 , channel C, and antenna  17  to RFID reader  16 . Protected payload information may be anything written into RFID tag  10 , i.e., the contents of a container; the identity of the owner of the container; instructions for transporting the goods contained in the container; the name of the owner of the goods in the container; the value of the goods contained in the container; information regarding previous processing steps for the goods contained in the container; biometric information contained in a passport; biometric information contained in a identification card; information contained in a smart card; a persons medical records; answers to questions contained in a mail piece; financial information contained in a mail piece, etc. The aforementioned payload information is transmitted from RFID reader  16  via channel D to other devices (not shown), i.e., a computer that uses the protected payload information the intended application.  
         [0016]      FIG. 2  is a drawing showing the elements of  FIG. 1  in greater detail. Antenna  11  includes feed terminals  22  and  24 , diodes  26 , and  30  and capacitors  28  and  32 . The low voltage or primary terminals of transformer  62  are connected across bypass capacitor  28 . Transformer  62  is tuned to resonate at the frequency of the power signal and is also matched to the load and operates to produce a higher voltage signal of this frequency at its output terminals. In other words, the carrier or radio frequency signals are bypassed by capacitor  28  whereas the envelope of the pulses, which occur at the modulation frequency, are applied to the tuned transformer. Effectively, therefore, the sidebands of the illuminating signal are used to obtain the power signal to energize information circuit  133  during the initial identity inquiry, i.e., to supply the power to a subset of the circuitry of circuit  10  sufficient to receive the request transmitted via channel A and to retrieve the tag ID from RFID circuit  10  and transmitted back via channel B to RFID reader  16 .  
         [0017]     A series chain comprising a power signal detector  64  and a filter capacitor  66  is connected across the secondary terminals of transformer  62 . The capacitance of this filter capacitor  66  must be sufficiently high as to store voltage throughout the clock and sync pulses included in the address code signal and to power the digital information circuit  133 . A second series chain comprising an address code detector  68  and a bypass capacitor  70  is connected across the output terminals of the transformer  62 . The capacitance of this bypass capacitor  70  must be sufficiently low as to transmit without significant distortion the clock and sync pulses included in the address code signal and must be sufficiently high as to store voltage throughout the period of the power signal.  
         [0018]     The digital information circuit  133  comprises a series chain comprising an address signal separator  72 , counter  38 , and response code storage and drive  40  and response code control  42 . Leads  34  are connected between filter capacitor  66  and the power input terminals of signal separator  72 , counter  38 , and response code storage and drive  40 . A lead  74  is connected from the junction of the address code detector  68  and the bypass capacitor  70  to the address signal separator  72 . Lead  74  applies the address code signal comprising clock and sync pulses to the address signal separator  72 . The address signal separator  72  is a pulse width discriminator that operates to separate the clock and sync pulses from the transmitted signal train. These separated signals are individually applied as pulses to the counter  38 . A response code control  42  may be connected to the response code storage and drive  40  to alter the number, duration, spacing, and modulation frequency of the pulses comprising the response code signal. The response code control  42  may be operated by manual switches or by a sensor. The response code signal produced by information circuit  133  is applied across the bypass capacitor  32  via leads  44 . Thus, information circuit  133  provides the identity of tag  9 .  
         [0019]     Power is transmitted from photocell and demodulator  12  to digital signal processor (DSP)  80  via lines  75  and data is transmitted from photocell and demodulator  12  to DSP  80  via lines  77 . Photocell and demodulator  12  is also coupled to leads  34  to supply power to response code storage and drive  40 . DSP  80  used the data carried by the light beam from generator  13  to authenticate the request for information, retrieve the information requested and send the information to response code storage and drive  40 . DSP  80  also transmits data and clock pulses to response code storage and drive  40  and antenna  11 . At this time antenna  11 , which is powered from photocell and demodulator  12  will communicate with RFID reader  16  using channel C.  
         [0020]     The request to transmit the tag ID from RFID circuit  10  is initiated by RFID reader  16 , which includes series chain comprising a clock-sync drive unit  54 , a power drive unit  56 , and a modulator  58  that is connected between the oscillator  74  and antenna  48 . Antenna  48  transmits a RF Request Signal via channel A that is received by feed  24  of antenna  11 . The aforementioned signal request RFID circuit  10  to transmit its tag identification to RFID reader  16 . Receiver  50  and receiver antenna  17  are components of reader  16 . Clock-synchronization drive unit  54  produces an address code signal comprising a synchronizing pulse followed by clock pulses. A lead  100  connects drive unit  54  to receiver  50 . This address code signal is employed to control the information received from digital information circuit  133  included in RFID circuit  10 . Power drive unit  56  produces a power signal that is higher in frequency than the frequency of the address code signal. The clock-sync drive unit  54  operates to turn off the power drive unit  56  during the time of occurrence of the clock and synchronizing pulses. Accordingly, an address coded power signal is applied to modulator  58 , which operates to modulate the frequency produced by oscillator  74  with this address coded power signal. Receiver  50  is coupled to RFID reader antenna  17  and drive unit  54 , receiver  50  produces a response code information signal or protected payload signal that is transmitted via channel D.  
         [0021]     The information containing the identity of RFID tag  10  is transmitted via channel B and is used by laser control unit  14  to retrieve the private information, i.e., cryptographic keys from database  15  to be subsequently used for the creation of the message to be transmitted via channel C. After the message to be transmitted on channel C was created in laser control computer  14 , it is used to modulate the laser beam produced by generator  13  under the control of modulator  8 .  
         [0022]     After RFID reader  16  processes the signal containing the tag identification, receiver  50  of reader  16  will transmit the tag identification of RFID circuit  10  to laser control computer  14 . Computer  14  will transmit the tag identification of RFID circuit  10  to database  15 . Database  15  will read its database to determine the cryptographic key for the tag identification of RFID circuit  10 . Database  15  will transmit the determined cryptographic key to computer  14 . Computer  14  will incorporate the cryptographic key into a message that becomes a signed message requesting tag  10  to transmit the protected information contained in circuit  10  to reader  16 . Computer  14  will transmit the signed message to laser control modulator  8 . Modulator  8  will transmit the signed message to laser beam generator  13 . Generator  13  will process the signed message and produce a modulated laser light beam output that has the signed message and the power of the light beam. Photocell and demodulator  12  will receive the signed message and power. When photocell and demodulator  12  is illuminated by the laser power, the photocell will convert the laser power into electricity and the demodulator will demodulate the continuous signed message. It would be obvious to one skilled in the art that other (less secure) methods of authenticating a message could be used instead of digital signatures (e.g., agreed upon algorithms, numeric transformations, etc.) The electrical power will be transmitted to DSP  80  via lines  75  and the signed message will be transmitted to DSP  80  via lines  77 . Circuit  10  will transmit payload information stored in information circuit  133  via feed  24  of antenna  11 , channel C, and antenna  17  to RFID reader  16 .  
         [0023]      FIG. 3  is a flow chart of the operation of digital signal processor  80  of  FIG. 2 . The program begins in block  200 , when power is supplied to DSP  80  ( FIG. 2 ). Then the program goes to block  201  where DSP  80  performs self-diagnostic tests. Now the program goes to block  202  where DSP  80  receives data from photocell demodulator  12 . Now the program goes to decision block  203 . Decision block  202  determines whether or not the data DSP  80  received from photocell demodulator  12  formed a complete message. If block  203  determines that DSP  80  did not receive a complete message the program goes back to the input of block  203 . If block  203  determines that DSP  80  received a complete message the program goes to block  204 . Block  204  verifies the authenticity of the message, by verifying the digital signature of the message. Then the program goes to block  205  to identify message type. At this point the program goes to decision block  206 . Decision block  206  determines whether or not the request in the message is allowed. If block  206  determines that the request is not allowed the program goes back to the input of block  202 . If block  206  determines that the request is allowed the program goes to the input of block  207 . Block  207  retrieves the requested information from the internal storage of the DSP  80 . Now the program goes to block  208  and sends the information to drive  40 . Then the program goes back to the input of block  202  to wait for incoming data.  
         [0024]     The above specification describes a new and improved method for securely communicating with a RFID device. It is realized that the above description may indicate to those skilled in the art additional ways in which the principles of this invention may be used without departing from the spirit. Therefore, it is intended that this invention be limited only by the scope of the appended claims.