Patent Publication Number: US-2005127172-A1

Title: Access system

Description:
RELATED APPLICATIONS  
      This application claims priority to U.S. Provisional Application No. 60/512,461 filed Oct.  16 ,  2003 , entitled “Access System” and U.S. application Ser. No. 10/870,475 filed Jun. 16, 2004, entitled “Access System,” which claims priority to Germany Application DE 20309254.6, filed on Jun. 16, 2003 in Germany, all of which are herein incorporated by reference in their entirety. 
    
    
     FIELD OF THE INVENTION  
      The present invention is related to access devices to provide physical access to a secured area and, in particular, to access devices compatible with current access control systems while providing higher levels of security.  
     BACKGROUND OF THE INVENTION  
      Secured access to sensitive areas has become an important issue, especially after the events of Sep. 11, 2001. As such, there is a current focus on technological systems for controlling access to security areas in both the private and public arenas. Such systems must be made highly impervious to attack by those wishing to gain unauthorized access to the secured area.  
      Security systems using, for example, Wiegand readers and control panels adapted to evaluate the data read from a Wiegand card are well known and widely employed in various applications like systems for unlocking doors or parking garage gates, etc. Usually, the Wiegand reader is located to be accessible to the user (Wiegand card holder) while the control panel, which after a positive evaluation of the data, performs a security relevant operation (e.g. unlocking a door) is located in an area which is not accessible to the user, e.g. in a secure room, to guarantee a certain level of security.  
      U.S. Pat. No. 5,679,945 discloses an access system that provides an “intelligent” card reader in order to replace existing magnetic stripe readers, bar code readers and Wiegand readers without the need for retrofitting of existing computer systems, which are coupled to the existing readers. However, readers that utilize a standard signal for communication into a secured area are easily attacked by those seeking unauthorized access to the secured area. Therefore, access systems utilizing readers that provide standard signals (e.g., Wiegand, Mag Stripe, or bar-code standard signals) do not provide a high level of security because those signals are more susceptible to, for example, replay attacks. Replay attacks in a conventional access control system can be accomplished by an intruder gaining access to the communication wires. By capturing the data sent on a valid data transfer, the attacker can later replay the same data and gain unauthorized entrance.  
      Therefore, there is a strong need, especially in a highly security conscious environment, to provide access systems with high levels of security against unauthorized access.  
     SUMMARY  
      In accordance with the present invention, an access system is provided that includes an input device accessible to a user and capable of reading authentication and/or identification information provided by the user, and a standard control panel coupled to the input device for evaluation of the information provided by the user. The standard control panel can be located in a secure area remote from the input device and can accept input signals compatible with those from standard signal readers that read traditional access cards, such as, for example, magnetic strip (Mag Stripe) cards, Wiegand cards, bar-code cards, etc. The input device can, for example, be a device that reads smart cards or memory cards, either contact or contactless. In some embodiments, the input device can also read inputted information from the user (user information) or data regarding the user (e.g., biometric data such as fingerprints).  
      An access system according to the present invention can include an input device that is accessible to a user and capable of reading authentication and/or identification information provided by the user; a standard signal control panel coupled to the input device for evaluation of the information provided by the user, the control panel being located in a secure area remote from the input device; and a signal processor coupled between the input device and the standard signal control panel, the signal processor being located in the secure area, wherein the input device provides data in a secured communication channel to the signal processor; and the signal processor, in response to the data provided by the input device, provides the data to the standard signal control panel utilizing a standard signal.  
      These and other embodiments are further discussed below with respect to the following figures. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  shows a block diagram illustrating an access system according to the prior art.  
       FIG. 2  shows a block diagram of an embodiment of an access system according to the present invention.  
       FIG. 3  is shows a block diagram of embodiment of an access system according to the present invention.  
       FIG. 4  shows a block diagram of an embodiment of an access system according to the present invention.  
       FIG. 5  shows a block diagram of an embodiment of an access system according to the present invention that utilizes encrypted or signed, self-clocked data transmission.  
       FIGS. 6A and 6B  illustrate uni-directional and bi-directional data transmission, respectively.  
       FIG. 7  illustrates sample wave shapes for Wiegand signals, Mag-Stripe signals, and self-clocked di-phase signals.  
       FIG. 8  illustrates sample timing diagrams for self-clocked di-phase communication on Transmit and Receive data.  
       FIG. 9  shows a block diagram of a signal processor according to the present invention.  
       FIG. 10  shows a security system according to the present invention.  
       FIG. 11  illustrates relative security level based on combinations of various inputs requested of a user attempting to gain access.  
       FIG. 12  illustrates a three-factor card reader.  
       FIG. 13  illustrates other card readers. 
    
    
      In the figures, elements having the same designation have the same or similar functions.  
     DESCRIPTION OF THE EMBODIMENTS  
      Embodiments of the present invention provide an access system with an extremely high level of security. Embodiments of the invention include a signal processor coupled between the input device and the control device. The input devices in some embodiments can include encryption to encrypt information obtained from the user (i.e., from a memory or smart card, from input to a keypad, and/or from user data—for example fingerprints). The signal processor, which can be placed in a secured location, can convert the encrypted information into a standard signal that can be sent to the standard control device, for example a standard Wiegand signal, magnetic strip signal, or strip-chart signal. Embodiments of the present invention, then, can be highly versatile because they can, for example, be utilized with Wiegand control panels without being restricted to Wiegand readers as input devices and without transmitting insecure Wiegand signals from the reader to a secured area.  
      With the signal processor located in a secured location, for example at or near the control panel, the risk of interference with the data by those attempting to gain unauthorized access can be significantly reduced. A higher level of security can be guaranteed with regard to the data transfer from the input device to the control panel because it is not possible to intercept and abuse the authentication/identification information provided by the user if it is encrypted until it reaches the signal processor, especially if the signal processor and the control panel are located in a secure area which is not accessible from an unsecured area, and if a dynamic element is used in the data transfer. A second communication channel between the input device and the securely located signal processor can be provided. The input device can include a smart card reader into which a secure output can be implemented, for example an RS422, an RS485 or a TCP/IP output protocol can be implemented in some embodiments.  
      An access system according to some embodiments of the present invention may further include a host computer coupled to the input device and located remotely from the input device. The host computer may also be coupled to the control panel and the signal processor. Data may be transmitted between the input device and the host computer utilizing, for example, an RS485 or a TCP/IP protocol  
       FIG. 1  shows a block diagram of a prior art access system that includes a standard Wiegand reader  10  and a Wiegand control panel  12  adapted to retrieve data from standard Wiegand reader  10 . The Control panel  12  is located in a secure area  14  remote from Wiegand reader  10 , which is accessible to a user attempting to obtain access to a secure area. In order to gain access, the user inserts his Wiegand card (not shown), which contains authentication and, if required, identification information, into the Wiegand reader  10 . The information is transmitted from the reader  10  to the control panel  12  where the information is evaluated. Depending on the result of the evaluation, the control panel  12  either performs a security relevant operation, e.g. unlocking a door or the like, to grant the user the requested access, or it denies access.  
      The weak point in an access system such as that illustrated in  FIG. 1  is the link between Wiegand reader  10  and control panel  12 . The Wiegand data lines are susceptible to replay attacks, i.e. data can be intercepted at the wiring going into secured area  14  and replayed to gain unauthorized entrance.  
       FIG. 2  shows an embodiment of an access system according to the present invention. A reader  16  is coupled to a signal processor  18 . Signal processor  18  receives signals from reader  18  and converts these signals to standard signals that can be transmitted to control panel  12 . In some embodiments, signal processor  18  and control panel  12  are physically located in a secured area  14 . In some embodiments, control panel  12  can be a Wiegand control panel. It should be understood that the term “Wiegand control panel” is not restricted to a particular hardware configuration but rather includes any suitable control panel, which is capable of processing data signals in a Wiegand format by using corresponding signal processing or software. Additionally, although an embodiment utilizing a Wiegand control signal is described here, other control signal formats can also be utilized, for example magnetic strip (Mag Stripe) formats or bar-code formats.  
      In the embodiment shown in  FIG. 2 , the standard Wiegand reader  10  shown in  FIG. 1  is replaced by another input device, for example a smart card reader  16  into which a smart card (not shown) containing authentication/identification information can be inserted (for contact reading) or otherwise interfaced with (for example for contactless reading). Reader  16  can include an encryption circuit that encrypts the information read from the smart card and an output port, for example an RS422, an RS485 or a TCP/IP output port, for outputting data to signal processor  18 . The embodiment of the access system shown in  FIG. 2  includes a signal processor  18  coupled between reader  16  and control panel  12 . Signal processor  18  and control panel  12  can be co-located in secure area  14 , which is remote from card reader  16 .  
      In some embodiments, card reader  16  can include a contactless reader for reading a contactless smart card. In general, embodiments of card reader  16  can include contactless smart card readers, contact smart card readers, memory card readers, a user input device such as a keypad on which a user can input authentication/identification data, biometric devices such as a fingerprint or retinal scan reader for directly evaluating the identity of the user, and other signaling devices for communicating with the user.  
      To begin operation of the embodiment of the access system shown in  FIG. 2 , the user inserts a smart card into smart card reader  16 , or in the case of a contactless smart card brings the smart card in close proximity to reader  16 . The information on the smart card is read by reader  16 . In some embodiments, the information from the smart card can be encrypted in reader  16 . The information can then be transmitted to signal processor  18  using a secured, for example RS422, RS485 or TCP/IP protocol, output port. Data transfer between smart card reader  16  and signal processor  18 , then, can be regarded as a “secure channel.” Signal processor  18  converts the information received from reader  16  into a standard signal (e.g., a Wiegand signal, a bar code signal, or a magnetic stripe signal) that can be received by control panel  12 . Control panel  12  is able to evaluate the standard signal and, based on access protocols, decides whether to allow or to deny access to the user.  
       FIG. 3  shows another embodiment of access system according to the present invention. The embodiment shown in  FIG. 3  includes reader  16 , signal processor  18  and control panel  12  as was previously discussed with  FIG. 2 . Further, a host computer  20  can be coupled to one or more of control panel  12 , signal processor  18 , and reader  16 . Remote host computer  20  can be located outside secure area  14  and is coupled to reader  16  and to control panel  12 . Communication between host computer  20  and reader  16  can be provided by a further secure channel, for example data can be transferred using an RS485 or a TCP/IP protocol.  
      The operation of the embodiment of the access system of  FIG. 3  to gain access is similar to that described above with respect to  FIG. 2 . However, the embodiment of access system shown in  FIG. 3  can easily be adapted to various requirements. For example, the secure channel between remote host computer  20  and reader  16  can be used to change the configuration of reader  16  on command from host computer  20  in a comfortable and secure manner. For example, differing levels of security can be implemented by sending commands to reader  16  and control panel  12  from host computer  20 . Additionally, host computer  20  can be used to define the type of input devices from which correct identification data is obtained that are required to gain access. Suitable input devices that can be included in reader  16  include a contactless smart card reader, a contact smart card reader, PIN pads (or keypads), biometric devices (for example fingerprint or retinal readers), and combinations thereof. The input devices from which data is required in order to gain access can be changed as a function of security threat level, day of week, time of day, or other conditions. The coupling between host computer  20  and control panel  12  allows checking as to whether a control panel operation has been successfully executed. Further, host computer  20  can be used to identify a possible malfunction of control panel  12  by utilizing test signals.  
      Additionally, reader  16  may include user-interface (for example a data screen or set of LED displays) for communicating information to a user. The LED signals may originate from control panel  12  and be transmitted through the secured channel between signal processor  18  and reader  16  as is indicated in  FIG. 3 . Further, the secured channel between signal processor  18  and reader  16  may be bi-directional as is shown in  FIG. 3 . In that case, control panel  12  may transmit data and instructions to reader  16 , for example regarding security levels and such, over a bi-directional secured line. Additionally, LED display data may be transmitted between control panel  12  and reader  16  over separate lines or through the bi-direction secured line. Control panel  12  may also communicate system status to reader  16  for display to a user directly without communicating through signal processor  18 .  
       FIG. 4  illustrates an access system similar to that illustrated in  FIG. 3 , except that the secured channel between reader  16  and signal processor  18  is a unidirectional line. Reader  16 , then, cannot receive data from control panel  12  through the secured channel. In some embodiments, status information can be communicated between control panel  12  and reader  16  using a separate line. Status information can be displayed in reader  16  through LCD displays, LED lights, or audible tones, for example. As further shown in  FIG. 4 , setup information can be transmitted to reader  16  separately. Setup information can include for example, which of the various input devices of reader  16  are activated in order to collect the appropriate information from the user to meet the current level of security.  
       FIG. 5  illustrates another embodiment of an access system according to the present invention. As has been discussed above, reader  16  is typically located in a non-secure area on the outside of a locked entranceway. Reader  16  can include interfaces for smart cards, contactless smart cards, biometric readers (e.g. fingerprint readers), PIN pads, and/or other user interface devices. Reader  16  transmits data which may be encrypted and/or digitally signed, extracted from a smart card or other input device to signal processor  18 , which is located in secure area  14 . In some embodiments, signal processor  18  can be located near or possibly in standard signal control panel  12 .  
      Digital signatures may be used to authenticate the information being sent to the control panel to ensure that it originated with the card or device that actually sent the information, and to ensure that the transmitted information was not altered after the information being transmitted was digitally signed.  
      There exist many well-known processes for creating and validating digital signatures. One example is the Digital Signature Algorithm, which may be used by a signatory to generate a digital signature on data and by a verifier to verify the authenticity of the signature. Each signatory has a public and private key. The private key is used in the signature generation process and the public key is used in the signature verification process.  
      To generate the correct digital signature for a signatory, knowledge of the private key of the signatory is needed. In other words, signatures cannot be forged, without knowledge of a signatory&#39;s private key. However, by using the signatory&#39;s public key, anyone can verify a correctly signed message.  
      The Digital Signature Algorithm uses parameters denoted by p, q, g, and x, which are defined below:  
      p is an L-bit prime p, where 512≦L≧1024, and L is divisible by 64;  
      q is a 160-bit prime q, such that q is a factor of p−1, i.e. (p−1)=qz, where z is any natural number;  
      h is chosen such that, 1&lt;h&lt;p−1 and g=h z  mod&gt;1;  
      x is chosen randomly such that 0&lt;x&lt;q and y=g x  mod p.  
      The Public Key is y and the Private Key is x.  
      To generate a digital signature, the algorithm also makes use of a one-way hash function, SHA(m), such as, for example, the Secure Hash Algorithm, and a randomly generated number k, where 0&lt;k&lt;q. Parameter k is regenerated for each time a signature is generated. Parameters x and k are used for signature generation and are kept secret.  
      The Digital Signature (r,s) of a message M is the pair of numbers r and s computed according to the equations below: 
 
 r =( g   k  mod  p ) mod  q  and 
 
 s =( k   −1    SHA ( M )+ xr )) mod  q.  
 
      Prior to verifying the signature in a signed message, p, q, g and the sender&#39;s public key y and identity are made available to verifiers. These parameters may be publicly distributed. Additionally, the Digital Signature (r, s) is also made available along with its associated message M to potential verifiers.  
      To verify the signature, the verifier first checks to see that 0&lt;r&lt;q and 0&lt;s&lt;q; if either condition is violated, the signature is invalid.  
      If these two conditions are satisfied, the verifier computes: 
 
w=s −1  mod q; 
 
 u   1 =(( SHA ( M ))* w )mod  q ; 
 
 u   2 =( rw ) mod  q;  and 
 
 v =(( g   u1   *y   u2 ) mod  p ) mod  q.  
 
      If v=r, then the signature is verified. On the other hand, if v≠r, then the message may have been modified and the signature should be considered invalid.  
      In some embodiments, data sent from reader  16  to signal processor  18  can be clocked data or self-clocked data. As has been described above, signal processor  18  converts the data received from reader  16  into a standard format signal, such as, for example, Wiegand, Mag Stripe, or bar code that is recognizable by standard signal control panel  12 .  
      In some embodiments, a host computer  20  can communicate with signal processor  18  and with reader  16  through signal processor  18 . As discussed above, host computer  20  can, for example, vary the level of security or alter the action or display setup of reader  16 .  
      In some embodiments, a security module or processor is located in each of reader  16  and signal processor  18  to allow for the secure transfer of data between reader  16  and signal processor  18 , either through encryption or digitally signing the data. In some embodiments, a dynamic element can be used in the data transmission process to ensure that a replay attack cannot be used to gain unauthorized access to an entrance portal through reader  16 . Replay attacks in a conventional access control system can be accomplished by an intruder gaining access to the communication wires, between the output terminal of reader  10  ( FIG. 1 ) and the control panel  12 . By capturing the data sent on a valid data transfer, the attacker can later replay the same data and gain unauthorized entrance. In some embodiments consistent with the present invention, the dynamic element could include date and time information corresponding to the date and time when the reader was accessed. The date and time information can be sent to the signal processor, which can then check the received information with the current date and time to ensure that the information sent is not a replay attack.  
      In some embodiments, the secured communication channel between reader  16  and signal processor  18  can utilize the wiring that may be in place when replacing a conventional access system, for example the Wiegand wiring. The existing two wires can be used for data and clock for one-way communication between reader  16  and signal processor  18  or bi-directional communication can be established using self-clocked data, for example non-return to zero (NRZ) or Di-phase communications. There are many advantages to using a bi-directional communication path between reader  16  and signal processor  18 . Some of these include error retransmission capability, the ability to transmit status level information between control panel  12  to reader  16  via data signal processor  18 , and general two-way communications for various other functions.  
      Utilizing self-clocked NRZ or Di-phase communication between reader  16  and signal processor  18  allows for improved data detection and immunity to sporadic ‘noise’ signals generated by external sources on the data lines between reader  16  and signal processor  18 . The technique employs the use of a sampling clock that is at a frequency of 8, 16, 32 or higher times that of the data transmission frequency. Multiple samples can be taken of the data line in each bit transmission in order to ascertain the data bit&#39;s true state. A plurality of clock signals indicating the same data status during the given bit time can be used to ascertain the state of the data bit. In some embodiments, both reader  16  and signal processor  18  can have independent sampling clocks running at the same higher frequency as that of the data bit frequency. In some embodiments, the data between reader  16  and signal processor  18  may be out of synchronization by only a few, for example one, clock cycle of the higher frequency clock.  
      Di-phase communication can be used to further improve communication between reader  16  and signal processor  18 . The state of the data is changed on every data bit time period. If the data were in a high state it would be changed to a low state, and vice versa. A data ‘one’ is in the same state for the entire bit period. A data ‘zero’ changes state at the half-bit time. The value of the data bit is determined by comparing the state of the data bit during the first half of the data bit period and the second half of the data bit period. If the data state is the same in both half-bit times, the value of the data bit is a ‘one’; if the data state is different in both halves of the bit time the data bit is a ‘zero’.  
      In some embodiments, reader  16  can change configuration on request from a host computer via a communications channel or from control panel  12  through status lines. In some embodiments, data signal processor  18  can receive configuration information from host computer  20  or from standard signal control panel  12  and can transmit the configuration data to reader  16  via the bi-directional data lines between signal processor  18  and reader  16 . An example of configuration information being sent to reader  16  is a requirement for additional user inputs, such as card and PIN pad data; card, PIN pad and biometric data; or other combinations. Such security level changes may be sent as required based on time of day, day of the month, or National Security levels.  
       FIGS. 6A and 6B  illustrate uni-directional and self-clocked bi-directional data lines, respectively.  FIG. 6A  shows how the Data out- 0  line from the reader, such as from exemplary reader  16 , is sent to the Signal Processor across the data channel interface. A signal arriving on the Data out- 0  or D 0  lines, at the Signal Processor is always interpreted as a “0”.  FIG. 6B  shows transmission of data using a self-clocked bi-directional line for the Data in- 1  signal, across the data channel interface. Data transmitted by the Reader is buffered and sent to the Signal Processor. Similarly, data transmitted by the Signal Processor is buffered and sent to the Reader. A signal arriving on the Data out- 1 , Data in- 1  or D 1  line at the Signal Processor is always interpreted as a “1”.  
       FIG. 7  illustrates sample wave shapes for Wiegand (D 0 , D 1 ), Mag Stripe (Clock and Data), and self-clocked Di-phase. The data being transmitted, shown in the Data row of  FIG. 7  is the 9-bit binary stream “110100101”. As shown in  FIG. 7 , transmission of this data using Wiegand (D 0 , D 1 ) depicted as W-D 0  and W-D 1  uses 9 clock cycles. Whenever a “0” is being transmitted during a clock cycle, the W-D 0  line is asserted. If a “1” is being transmitted during a clock cycle, the W-D 1  line is asserted. Thus, the W-D 1  line is asserted during the first two clock cycles corresponding to the first two binary digits “11” of the 9-bit stream being transmitted. On the third clock cycle, the W-D 0  line is asserted corresponding to the third digit (“0”) of the binary stream. In the Mag Stripe (Clock and Data), as shown in  FIG. 7 , the Data line is asserted for “1&#39;s” and negated for “0&#39;s”. Thus, the Data line is asserted for the first two clock cycles and then negated during the third clock cycle corresponding to the initial “110” data sequence of the 9-bit stream.  
      In the Self-Clocked Di-phase scheme, if the line is held to a constant value over the entire clock period, then the data being transmitted is a “1”. On the other hand, if the line value changes in the middle of the clock period the data being transmitted is a “0”. Thus, the line is high for the entire first clock period, low for all of the second clock period, and changes in the middle of third clock period corresponding to the “110” data sequence.  FIG. 8  illustrates an example of self-clocked Di-phase communication, on transmit and receive data.  FIG. 8  shows changes in the “Data Out” and “Data In” signals over 16 cycles of the base input clock, which corresponds to the Bit Time or Bit Period. Changes in Data Out or Data In during the bit period indicate that a “0” is being transmitted whereas a constant value (0 or 1) for the entire period indicates that the data on the line is a “1”.  
       FIG. 9  shows an embodiment of signal processor  18 . The embodiment of signal processor  18  shown in  FIG. 9  includes a microprocessor  21  coupled to a reader communications switch  20  and a control panel data line switch  22 . Further, microprocessor  21  may be coupled to a communications channel interface  23  for communications with host computer  20  and to a security access module (SAM)  24 .  
      Reader communications switch  20  can be coupled to one or more readers  16  of differing types through, for example, a bidirectional data communications channel. Further, data regarding each of the readers can be communicated to control panel  12  through control panel line switch  22 . In some embodiments, data regarding the readers could include data regarding the status of the readers, such as whether they are active, inactive or malfunctioning.  
      Conversion of data from reader  16  to a standard signal for standard signal control panel  12  can be accomplished in software operating on microprocessor  21  and stored in memory. In some embodiments, software operating on microprocessor  21  and stored in memory could implement portions of a digital signature verification and authentication algorithm. SAM  24  stores and implements encryption codes and, in some embodiments, can be removable using a “SAM lock”.  
       FIG. 10  shows an example of a security system according to the present invention. A security system according to the present invention includes one or more access systems according to the present invention. Further, host computer  20  may include one or more workstations, such as an access control station, badging station, and guard workstation. As shown, control panel  12  communicates, through signal processor  18 , with reader  16  and can open an appropriate door  30  once access is approved.  
      In some embodiments of the invention, various levels of security may be programmed into control panel  12  and reader  16 . For example, security levels may be classified with regard to threat level, for example low, guarded, significant, high, and severe. The level of authentication/identification required for each threat level may be different. For example, in a low threat security environment access may be gained with a contactless card. With a guarded level, the access system may be set to require both a contactless card and that the user input a personal identification number (PIN) into a keypad. With a significant threat, a contact card and a PIN may be required. In a high threat security level, a contact card and some biometric input (e.g., fingerprint) may be required to gain access. In a severe threat security level, three inputs—a contact card, a PIN, and a biometric input—may be requested of a user attempting to gain access.  FIG. 11  illustrates the relative security level with respect to various inputs and combinations of inputs requested of the user in a security system. In some embodiments, a single smart card may be configured to provide both contactless and contact connection with reader  16 .  
       FIG. 12  illustrates a card reader that can be utilized in embodiments of the present invention. The embodiment of card reader shown in  FIG. 12  includes an LCD display, a keypad for accepting PIN information, a smart card reader, a contactless reader, and a fingerprint sensor. A series of LEDs can indicate security level. Further, an acoustic alarm may be included.  
       FIG. 13  illustrates other types of card readers that may be utilized with embodiments of the present invention.  
      Although any standard formats may be utilized in embodiments of the present invention, in some embodiments, the contact card readers may be ISO 7816 card readers and the contactless cards may be ISO 14443, parts 1-4 with a FIPS 140-2 approved algorithm. Further, the card reader can be programmable, for example in order to extract SEIWG-12 data strings or other ID strings from a smart card.  
      Several standards and working groups have been established in the area of access control. For example, the Security Equipment Integration Working Group has issued a specification on Sep. 30, 2002: “Development of a specification for SEIWG-compliant Access Control Components; a study by the Security Equipment Integration Working Group,” Sep. 30, 2002, which is herein incorporated by reference in its entirety and made a part of this disclosure. Further, the Physical Access Interoperability Working Group has implemented a “Technical Implementation Guidance: Smart Card Enabled Physical Access Control Systems, Version 1.0,” Jul. 2, 2003, which is herein incorporated by reference in its entirety and made a part of this disclosure. Additionally, the Security Industry Association has issued an “Access Control Standard Protocol for the 26-Bit Wiegand Reader Interfaces,” Oct. 17, 1996, which is herein incorporated by reference in its entirety and made a part of this disclosure. The later document provides information regarding the Wiegand standard.  
      Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. For example, embodiments utilizing standards other than the Wiegand standard for signaling between signal processor  18  and control panel  12  can be utilized. Additionally, other protocols may be utilized for secure transmission channels other than the RS422, RS485 or TCP/IP protocols described as examples here. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.