Abstract:
The present invention provides a method and apparatus for protecting an Encrypting PIN Pad (EPP) against tampering. The apparatus provides an EPP comprising a first layer comprising at least two spaced apart electrode elements, and a second layer comprising at least one bridge element for electrically bridging a space between the at least two electrode elements when the first layer and the second layer are urged together.

Description:
FIELD OF THE INVENTION 
     The present invention relates to an Encrypting PIN (personal identification number) pad (EPP). In particular, but not exclusively, the present invention relates to an EPP including protection against malicious tampering, such as front side attacks. 
     BACKGROUND OF THE INVENTION 
     It is known for a variety of unattended PIN entry devices (PEDs) to include an encryption keyboard/keypad for a customer to enter a PIN code in a secure manner. Such a keypad is known in the art as an Encrypting PIN pad (or EPP) and may include only a secure PIN entry device and rely upon external displays and card readers of the PED. Alternatively, an EPP may include a secure PIN entry device and a built-in display and/or card reader. 
     Known PEDs include Self-Service Terminal (SSTs), such as Automated Teller Machines (ATMs), automated fuel dispensers, kiosks and vending machines, or the like. An ATM typically requires a customer to enter a secure PIN code via an EPP in the ATM for authorising a customer transaction at the ATM. Working cryptographic keys and master keys of the financial institution owning the ATM, for example, are also typically stored in core processing components of an EPP. People with malicious intent have been known to probe into an EPP in an attempt to capture customer PIN codes when they are entered, or even read working cryptographic keys and master keys of the financial institution, thereby placing customers&#39; money (and the financial institution&#39;s money) at risk. Accordingly, the physical and logical design and manufacture of EPPs must adhere to increasingly strict requirements, regulations and certifications. 
     EPPs have a clearly defined physical and logical boundary and a tamper-resistant or tamper-evident shell. An EPP conventionally includes a keyboard panel, a lining plate, keys, a water-resistant sealing layer, a main control board and a base plate. The EPP is assembled by stacking up these components in sequence. 
     EPPs are also tamper responsive in that they will destroy critical information if the EPP is tampered with, thereby preventing the critical information, such as encryption keys, being disclosed to an attacker. 
     EPPs include different mechanisms to detect tampering. One type of tamper detection mechanism is for an EPP to include a probing detection and protection circuit which, in the event of a front side attack on the EPP (that is, an attempt to tamper with the EPP from the keypad side of the overall unit), outputs a self-destruct signal enabling a self-destruct function of the EPP to prevent the attacker from accessing confidential information stored in the EPP. However, such conventional systems can be bypassed or damaged to gain access to the main control board. 
     Another type of tamper detection mechanism is for an EPP to include a number of separation switches to indicate a tamper should the keypad, and other internals of the EPP, become separated from the EPP body. However, such switches are not perfectly protected from a front side attack on the EPP. Such attacks can be made to remove the EPP keys and either glue down the separation switches or inject electrically conductive ink under each switch to maintain contact when the EPP keypad and internals are separated from the EPP body. 
     SUMMARY OF THE INVENTION 
     It is an aim of certain embodiments of the present invention to at least partly mitigate the above-mentioned problems. 
     It is an aim of certain embodiments of the present invention to protect an EPP against a front side attack. 
     It is an aim of certain embodiments of the present invention to protect an EPP against malicious probing, prying, or injecting of electrically conductive ink and/or adhesive, or the like. 
     It is an aim of certain embodiments of the present invention to detect tampering of an EPP at an SST. 
     According to a first aspect of the present invention there is provided an Encrypting PIN Pad (EPP) comprising:
         a first layer comprising at least two spaced apart electrode elements; and   a second layer comprising at least one bridge element for electrically bridging a space between the at least two electrode elements when the first layer and the second layer are urged together.       

     Aptly, the second layer comprises a composite layer, comprising electrically conductive particles combined with an elastomeric binder, to provide the at least one bridge element. 
     Aptly, the composite layer comprises Quantum Tunnelling Composite (QTC) (trade mark) material. 
     Aptly, the second layer further comprises an elastomeric layer for supporting the composite layer. 
     Aptly, the at least two spaced apart electrode elements comprise a first electrode surrounding a second electrode. 
     Aptly, the first electrode is ring-shaped and the second electrode is a central region within and spaced apart from the first electrode. 
     Aptly, the first layer comprises a plurality of electrical tracks printed on a flexible support, wherein a first and further track of the plurality of tracks each comprising a respective one of the two electrode elements. 
     Aptly, the first layer further comprises at least one protective mesh layer. 
     Aptly, the EPP further comprises at least one actuator member for urging the first layer and the second layer together. 
     Aptly, the EPP further comprises a keyboard body for supporting a plurality of keys, wherein the at least one actuator member extends inwardly from the keyboard body towards the first layer. 
     Aptly, the at least one actuator member is an elongate pin. 
     Aptly, the at least one actuator member comprises a circular or polygonal cross section having a size substantially matching at least a size of the bridge element. 
     Aptly, the EPP further comprises an intermediate layer located between the at least one actuator member and the first layer. 
     Aptly, the intermediate layer comprises at least one layer of rubber material. 
     Aptly, the EPP further comprises a controller for detecting unauthorised separation of the first layer and the second layer. 
     Aptly, the EPP further comprises a support layer for supporting the controller, wherein the support layer is located on a distal side of the first layer relative to the keyboard body. 
     Aptly, the EPP further comprises a spacer layer located between the first layer and the support layer. 
     Aptly, the spacer layer comprises at least one aperture for locating at least one electrical connection extending between the controller and the first layer and/or the second layer. 
     Aptly, the at least one aperture is sized to accommodate at least the controller supported on the support layer. 
     Aptly, the EPP further comprises an alarm device responsive to the controller for indicating unauthorised separation of the first layer and the second layer. 
     Aptly, the first and second layers are urged together when the first layer is urged towards the second layer, or the second layer is urged towards the first layer, or the first layer and the second layer are both urged towards each other. 
     According to a second aspect of the present invention there is provided a Self-Service Terminal (SST) comprising an EPP, the EPP comprising:
         a first layer comprising at least two spaced apart electrode elements; and   a second layer comprising at least one bridge element for electrically bridging a space between the at least two electrode elements when the first layer and the second layer are urged together.       

     According to a third aspect of the present invention there is provided a method of detecting tampering at an Encrypting PIN Pad (EPP), comprising the steps of:
         in a normal mode of operation, providing an electrically conductive bridge via a layer in an EPP between at least two spaced apart electrode elements on a further layer of the EPP; and   in a tamper mode of operation, removing the bridge between the electrode elements.       

     Aptly, the method further comprises:
         monitoring an electrical resistance across the at least two spaced apart electrodes.       

     Aptly, the method further comprises:
         determining a change in the electrical resistance across the at least two spaced apart electrodes relative to a predetermined threshold resistance.       

     Aptly, the method further comprises:
         activating an alarm device in response to the sensed separation of the first layer and the second layer.       

     Aptly, the method further comprises:
         activating a self-destruct function of the EPP in response to the sensed separation of the first layer and the second layer.       

     According to a fourth aspect of the present invention there is provided a method of manufacturing an Encrypting PIN Pad (EPP), comprising:
         urging together a first layer and a second layer within a secure housing, wherein the first layer comprises at least two spaced apart electrode elements and the second layer comprises at least one bridge element, wherein, when the first layer and the second layer are urged together in a normal state of the EPP, an electrically conductive bridge is provided across a space between the at least two electrode elements said bridge being removed when the first layer and second layer are separated.       

     Aptly, the method further comprises:
         applying a pressure to the second layer to urge the second layer towards the first layer via at least one actuator member that extends from a keyboard body at a front region of the secure housing towards the first layer.       

     According to a fifth aspect of the present invention there is provided an Encrypting PIN Pad (EPP) comprising:
         at least one contact switch mounted on a support layer in a secure housing of the EPP; and   a protection layer, comprising at least one through hole, in the secure housing and located between the at least one contact switch and a front region of the secure housing;   wherein at least one biasing pin extends from the front region through the through hole to bias the at least one contact switch in a normal state of operation.       

     Aptly, in a tamper state, when a front region of the secure housing supporting the at least one biasing pin is at least partially separated from the secure housing, the pin is located to no longer bias the contact switch. 
     Aptly, in a tamper state, the front region of the secure housing is moved away from the at least one contact switch such that the at least one biasing pin no longer biases the at least one contact switch. 
     Aptly, the at least one contact switch comprises a plurality of contact switches disposed in a spaced apart relationship across an internal space in the secure housing, and the at least one biasing pin comprises a plurality of biasing pins each associated with a respective one of the plurality of contact switches and a respective one of a plurality of through holes in the protection layer. 
     Aptly, the front region of the secure housing comprises a keyboard body for supporting a plurality of keys. 
     Aptly, the EPP further comprises a sealing layer disposed between the front region of the secure housing and the support layer. 
     Aptly, the sealing layer comprises at least one through hole for the at least one biasing pin to extend through to bias the at least one contact switch in a normal state of operation. 
     Aptly, the sealing layer comprises a layer of elastomeric material. 
     Aptly, the EPP further comprises a spacer layer located between the sealing layer and the support layer. 
     Aptly, the spacer layer comprises at least one recess for receiving the at least one contact switch to thereby accommodate the at least one contact switch device between the spacer layer and the support layer. 
     Aptly, the spacer layer comprises at least one opening communicating with the recess to allow the at least one biasing pin to extend through the spacer layer to bias the at least one contact switch. 
     Aptly, the at least one opening is axially aligned with the at least one through holes of the sealing layer and protection layer. 
     Aptly, the spacer layer comprises a metal plate. 
     Aptly, the at least one contact switch comprises a silicon switch body. 
     According to a sixth aspect of the present invention there is provided an Encrypting PIN Pad (EPP) comprising: a housing defining (i) a plurality of key apertures and (ii) a plurality of pins extending from a lower surface; a plurality of keys, each key being located within a respective one of the plurality of key apertures; a support plate mounted to the lower surface of the housing and defining (i) a plurality of key apertures, each key aperture being disposed in registration with a respective one of the plurality of keys and (ii) a plurality of pin apertures, each aperture being disposed in registration with a respective one of the plurality of pins; an elastomeric mat mounted to the support plate; a multi-layer keyboard printed circuit board comprising a plurality of key domes, each key dome being disposed in registration with a respective key, and a plurality of separation switches, each separation switch being disposed in registration with a respective one of the plurality of pins; a backplate mounted on the multi-layer keyboard printed circuit board and secured to the housing; a cryptographic printed circuit board coupled to the keyboard printed circuit board via an elongate connector; and a cover mounted on the cryptographic printed circuit board and secured to the housing to maintain the keys, the support plate, the elastomeric mat, the keyboard printed circuit board, the backplate, and the cryptographic printed circuit board in position as an integrated unit. 
     Certain embodiments of the present invention provide a method and apparatus for protecting an EPP against a front side attack. 
     Certain embodiments of the present invention provide a method and apparatus for protecting an EPP against malicious probing, prying, or injecting of electrically conductive ink and/or adhesive, or the like. 
     Certain embodiments of the present invention provide a method and apparatus for detecting tampering of an EPP of an SST. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       Embodiments of the present invention will now be described hereinafter, by way of example only, with reference to the accompanying drawings in which: 
         FIGS. 1 a  to 1 c    illustrate an encrypting PIN pad (EPP) according to a first embodiment of the present invention; 
         FIG. 2 a    illustrates an exploded schematic of the EPP of  FIGS. 1 a    to  1   c;    
         FIG. 2 b    illustrates a part of the EPP shown in  FIG. 2   a;    
         FIG. 3 a    illustrates an exploded schematic of an EPP according to a second embodiment of the present invention; 
         FIG. 3 b    illustrates a part of the EPP shown in  FIG. 3   a;    
         FIG. 4  illustrates an exploded schematic of an EPP according to a third embodiment of the present invention; 
         FIG. 5  illustrates an exploded schematic of an EPP according to a fourth embodiment of the present invention; and 
         FIG. 6  illustrates part of a user interface of an Automated Teller Machine (ATM) including an EPP according to any of the described embodiments of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     In the drawings like reference numerals refer to like parts. 
       FIG. 1  illustrates an Encrypting PIN Pad (EPP)  100  according to a first embodiment of the present invention. The EPP  100  comprises a keyboard body  102  which supports a keypad  104  including sixteen individual keys  105  for a customer to use when entering his/her PIN and when making transaction selections, each key having either a digit (with one of the numbers from  0  to  9 ) etched or printed thereon, words such as “Cancel,” “Clear”, and “Enter,” or such like, etched or printed thereon, or left blank. The keypad  104  protrudes from an upper surface of the EPP  100 .  FIG. 1 b    is a pictorial side view of the EPP  100  in the direction of arrows  1   b - 1   b  on  FIG. 1   a.    
       FIG. 1 c    is a schematic diagram of the components within the EPP  100 . These components include an encryption unit  182 . The encryption unit  182  includes a cryptographic processor  190 , volatile memory  192  in the form of random access memory (RAM), and non-volatile memory  194  in the form of FLASH memory. The RAM  192  stores a cryptographic key  196 . The FLASH memory  194  stores at least one algorithm  198   a  (PIN encryption algorithm  198   a ) for encrypting information entered via keypad  104  using the cryptographic key  196 , and one algorithm  198   b  (key deriving algorithm  198   b ) for deriving a new cryptographic key. The processor  190 , the RAM  192 , and the flash memory  194  communicate via an internal bus  191 . 
     Suitable cryptographic processors  190  include one of the range of secure microcontrollers supplied by Maxim Integrated Products, Inc. of 160 Rio Robles, San Jose, Calif. 95134, U.S.A. 
     Data from the keypad  104  is transmitted to the cryptographic processor  190 , which processes the keypad entries using a keyboard control algorithm (not shown) executing within the cryptographic processor  190 . The cryptographic processor  190  also includes internal RAM (not shown) and internal non-volatile memory (not shown) for use in performing cryptographic functions. The cryptographic processor  190  includes an erase function that operates automatically to delete stored encryption keys within the cryptographic processor  190  in the event that any sensors in the EPP  100  detect tampering. 
     In normal operation the EPP  100  outputs encrypted data to an ATM controller module (not shown) via an output port  120  in the form of a USB port. 
     Parts of the EPP  100  are shown in more detail in  FIGS. 2 a  and 2 b   . The EPP  100  includes the keyboard body  102  supporting the plurality of keys (not shown), a base layer  204 , and an intermediate layer  206 . The base layer  204  supports a primary printed circuit board (PCB) (not shown) of the encryption unit  182  including the processor  190  for performing encryption functions of the EPP  100 . The intermediate layer  206  supports a secondary PCB (not shown) including the keypad matrix circuit responsive to the keys supported by the keyboard body  102 . The primary and secondary PCBs are connected by a suitable electrical connection, such as a ‘zebra strip’  212 . A metal spacer plate  214  is located between the base layer  304  and the intermediate layer  206 . The spacer layer  214  includes a through aperture  216  for accommodating one or more electronic components  208  of the primary PCB and the zebra strip  212  when the EPP  100  is securely assembled and in a ‘normal’ state. 
     The intermediate layer  206  also supports pairs of spaced apart electrodes  218 . The pairs of electrodes  218  are spaced apart from each other across the intermediate layer  206 . Three pairs of spaced apart electrodes  218  are shown in  FIG. 2 a    for ease of reference, but any desired number of pairs of spaced apart electrodes may be chosen. As shown in  FIG. 2 b   , the electrodes  217  of a respective pair of spaced apart electrodes  218  are separated from each other by a space  219 . 
     A layer of Quantum Tunnelling Composite (QTC™) material  220  is disposed between the pairs of spaced apart electrodes  218  and the keyboard body  102 . The QTC™ material layer  220  may be a single sheet of QTC™ material or may be a composite layer of QTC™ material supported on the underside of a sheet of rubber (or other elastomeric) material. QTC™ material is a composite material made from conductive filler particles combined with an elastomeric binder, typically silicon rubber. QTC™ material has the ability to smoothly change from an electrical insulator to a metal-like conductor when placed under pressure. 
     An actuator  222  in the form of a block extends inwardly from the keyboard body  102  towards a respective pair of spaced apart electrodes  218 . Three actuators  222  are shown in  FIG. 2 a    for ease of reference, each actuator being appropriately located in relation to a respective pair of spaced apart electrodes  218 . Each actuator  222  is shown as a rectangular block but may be any suitable size or shape relative to the size and shape of a respective pair of electrodes  218  and the distance a respective pair of electrodes is spaced apart from each other. The actuator  222  may be any suitable material, such as metal or plastic, for example and may be attached as a separate part to the keyboard body  102  or integral with the keyboard body  102 . The actuator  222  is rigid enough to be able to transfer a force from the keyboard body  102  and apply a pressure on the QTC™ sheet  220 . 
     In an assembled and ‘normal’ state, each actuator  222  applies a pressure to a respective region of the QTC™ layer  220  to thereby change its state from an insulator to an electrical conductor. In the assembled and normal state of the EPP  100 , the QTC™ layer  220  contacts the pairs of spaced apart electrodes  218  and when the state of respective regions of the QTC™ layer  220  is changed to an electrically conductive state by the pressure being applied thereto by the respective actuators  222 , an electrical bridge is formed across the space  219  between a respective pair of spaced apart electrodes  218 . 
     An electrical resistance across each of the bridges is monitored by the encryption unit  182  and a threshold resistance is determined when the EPP  100  is in a ‘normal’ state. The resistance across each of the bridges relative to the threshold resistance will not change when the EPP is in a ‘normal’ state. However, if the keyboard body  102  is moved away from the intermediate layer  206 , as would be the case when a front attack on the EPP is made, the pressure being applied on the QTC™ layer by the actuators  222  would decrease, the electrical conductivity of the respective regions of the QTC™ layer would decrease accordingly, and the electrical resistance being monitored across each of the bridges would increase. This change in resistance relative to the threshold resistance is detected by the encryption unit  182  to indicate a tamper of the EPP  100 . Similarly, if conductive ink is maliciously injected into the EPP  100  via the keyboard body  102  to come between the QTC™ layer  220  and a respective pair of spaced apart electrodes  218 , the electrical resistance being monitored across a respective bridge decreases. This change in resistance relative to the threshold resistance is detected by the encryption unit  182  to indicate a tamper of the EPP  100 . In the event of a tamper being detected, an alarm device (not shown) is activated in an attempt to warn off a criminal and/or a self-destruct function of the EPP  100  is activated accordingly. 
     An EPP  300  according to a second embodiment of the present invention is illustrated in  FIGS. 3 a  and 3 b   . In this embodiment, as best shown in  FIG. 3 b   , each pair of spaced apart electrodes  318  comprises a ring-shaped electrode  319  and a central electrode  317  located within and spaced apart from the ring-shaped electrode  319  to provide a space  321  therebetween. Each of the actuators  322  is a cylindrical metal post which is shaped and sized to match the shape and size of a respective pair of electrodes  318 . It will be understood that other suitable shapes and sizes of electrode pairs and respective actuators can be provided according to certain other embodiments of the present invention. 
     An EPP  400  according to a third embodiment of the present invention is illustrated in  FIG. 4 . In this embodiment, the QTC™ layer shown in the previous embodiments is replaced with a flexible support layer  450  having a plurality of spaced apart electrical tracks  419  printed on it. A pair of adjacent electrical tracks of the plurality of electrical tracks provides a pair of spaced apart electrodes  418 . The intermediate layer  206  supports an electrical bridge element  420  which is located relative to a respective pair of electrodes  418 . Of course, the plurality of electrical tracks  419  can be shaped and designed to provide a number of spaced apart pairs of electrodes  418 . For ease of reference, three bridge elements  420  are shown in  FIG. 4  which are each located relative to three respective pairs of spaced apart electrodes  418 . In a ‘normal’ assembled state of the EPP, each bridge element  420  contacts a respective pair of electrodes  418  to form an electrical bridge across a space provided between the electrodes  418 . A sealing layer  460  of rubber material is disposed between the flexible support layer  450  and the keyboard body  102  to seal the EPP  400  to prevent ingress of water and/or dirt. This sealing layer  460  also provides tactile feedback to the keys and helps prevent over-travel of the keys otherwise caused by manufacturing tolerances. The actuators  422  as shown in  FIG. 4  are metal posts extending inwardly from the keyboard body  102  towards the back of the EPP  400  to urge the sealing layer  460  towards the intermediate layer  206  to ensure the spaced apart electrodes  418  contact their respective bridge elements  420  in a ‘normal’ assembled state of the EPP  400 . 
     An electrical resistance across each of the bridges is monitored by the encryption unit  182  and a threshold resistance determined for when the EPP  400  is in a ‘normal’ assembled state can be compared to the monitored resistance. The resistance across each of the bridges relative to the threshold resistance will not change when the EPP  400  is in a ‘normal’ assembled state. However, if the keyboard body  102  and flexible support layer  450  is wholly or at least partially moved away from the intermediate layer  206  in an attempt to gain access to the primary PCB supported on the base layer  204 , the respective bridges are entirely or partly broken and in turn the open circuit condition causes the electrical resistance being monitored across each of the bridges to increase. This change in resistance relative to the threshold resistance is detected by the encryption unit  182  to indicate a tamper event at the EPP  400 . Similarly, if conductive ink is maliciously injected into the EPP  400  via the keyboard body  102  to come between the electrical tracks  419  of the flexible support layer  450  and the respective bridge elements  420 , the electrical resistance being monitored across a respective bridge decreases. This change in resistance relative to the threshold resistance is detected by the encryption unit  182  to indicate a tamper event of a different type at the EPP  400 . In the event of a tamper being detected, an alarm device (not shown) is activated in an attempt to warn off a criminal and/or a self-destruct function of the EPP  400  is activated accordingly. 
     An EPP  500  according to a fourth embodiment of the present invention is illustrated in  FIG. 5 . In this embodiment, the metal spacer plate  214  located between the base layer  204  and the intermediate layer  206  has a plurality of recesses  570  provided in the underside of the spacer plate  214 , wherein the underside is proximal to the base layer  204 . Each recess  570  is sized and shaped to receive and accommodate a respective contact switch  580 . A suitable contact switch may be a silicon switch, for example. The spacer layer  214  includes a through aperture  516  for accommodating one or more electronic components  208  of the primary PCB and the zebra strip  212  for connecting the primary and secondary PCBs when the EPP  500  is securely assembled and in a ‘normal’ state. 
     A through aperture  572  is centrally disposed in each recess of the spacer plate  214 . The actuators  522  of this embodiment are elongate metal posts each sized to engage a respective contact switch  580  when the EPP  500  is in a ‘normal’ assembled state. When the EPP  500  is in a ‘normal’ state, each contact switch  580  is held in a closed state by its respective actuator  522 . To allow each actuator  522  to engage a respective contact switch  580 , respective through apertures  582 ,  592  are provided in the sealing layer  460  of rubber material and the intermediate layer  206  respectively. 
     Malicious separation of the keyboard body  102  away from the remainder of the EPP  500 , and thus away from the contact switches  580 , causes the switches  580  to change from the closed state to an open state. This change is detected by the encryption unit  182  to indicate a tamper of the EPP  500 . In the event of a tamper being detected, an alarm device (not shown) is activated in an attempt to warn off a criminal and/or a self-destruct function of the EPP  500  is activated accordingly. 
     An ATM typically includes a user interface for a customer to initiate a transaction at the ATM. Certain parts of an ATM user interface  600  according to an embodiment of the present invention are shown in  FIG. 6 . The user interface  600  includes a card reader/writer slot  610 , a display  602 , and an EPP  100  according to an embodiment of the present invention. The user interface  600  can optionally include other access ports/slots, such as a private audio port  220 . The keypad  104  of the EPP  100  provides an interface between a customer and the EPP  100 . A keypad aperture  615  of the ATM aligns with the keypad perimeter  106  of the EPP  100  so that only the keypad  104  of the EPP  100  is visible to an ATM customer through the keypad aperture  615  of the ATM. It will be understood however that an EPP according to any embodiment of the present invention as described herein may be utilised with other types of SST, such as automated fuel dispensers, kiosks and vending machines, or the like. 
     Throughout the description and claims of this specification, the words “comprise” and “contain” and variations of them mean “including but not limited to” and they are not intended to (and do not) exclude other moieties, additives, components, integers or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise. 
     Features, integers, characteristics or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of the features and/or steps are mutually exclusive. The invention is not restricted to any details of any foregoing embodiments. The invention extends to any novel one, or novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed. 
     The reader&#39;s attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.