Abstract:
Disclosed are various embodiments of techniques that may be used to improve the reliability of network authentication. A communication session is established between a server computing device and a client computing device. The communication session is established via a network using a credential for a network site. A verifier for the credential is generated, which may be used to confirm the authenticity of the credential. The verifier is provided to the client computing device via the network.

Description:
BACKGROUND 
     In an age of information, people may exchange data over communication sessions that may traverse various networks. Those participating in the communication session may wish to keep the data confidential as to the general public, while also exchanging data with the parties participating in the communication session. Traditional data security architectures suffer from vulnerabilities that may compromise the confidence of the data as it traverses networks such as the Internet. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Many aspects of the present disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the disclosure. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
         FIG. 1  is a drawing of a networked environment according to various embodiments of the present disclosure. 
         FIG. 2  is a flowchart illustrating one example of functionality implemented as portions of a marking service executed in a computing device in the networked environment of  FIG. 1  according to various embodiments of the present disclosure. 
         FIG. 3  is a flowchart illustrating one example of functionality implemented as portions of a validation service executed in a computing device in the networked environment of  FIG. 1  according to various embodiments of the present disclosure. 
         FIG. 4  is a schematic block diagram that provides one example illustration of a computing device employed in the networked environment of  FIG. 1  according to various embodiments of the present disclosure. 
         FIG. 5  is a schematic block diagram that provides one example illustration of a client device employed in the networked environment of  FIG. 1  according to various embodiments of the present disclosure 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure relates to techniques for detecting and/or deterring the inconspicuous interception of communication session data by network devices, commonly referred to as a “man-in-the-middle” (MitM) attack. During initiation of a communication session between a client and a server, the server may present a set of credentials that may be used to authenticate the particular server as the actual server expected by the client. During a man-in-the-middle attack, an intermediate network device may instead present an alternate set of credentials to the client, which for a variety of possible reasons, may be accepted by the client for authentication. 
     In some embodiments, a validation application executing in the client may be used to detect the presence of a man-in-the-middle by comparing the current presented credentials for a server to credentials or other identifiers presented previously during a prior communication session. In further embodiments, a marking service executing in a server may covertly provide credentials or other identifiers for verification by a client. In various embodiments, the server and/or client may initiate computationally intensive operations such as re-negotiation of communication sessions, multiple layers of encryption for a portion of the communication session, and/or other actions that may deter and/or detect man-in-the-middle activities. In the following discussion, a general description of the system and its components is provided, followed by a discussion of the operation of the same. 
     With reference to  FIG. 1 , shown is a networked environment  100  according to various embodiments. The networked environment  100  includes a computing device  103  in data communication with one or more client devices  106  by way of the network  109 . The network  109  includes, for example, the Internet, intranets, extranets, wide area networks (WANs), local area networks (LANs), wired networks, wireless networks, or other suitable networks, etc or any combination of two or more such networks. Data communication transiting the network  109  may be forwarded and/or examined by a network device  111 . 
     The computing device  103  may comprise, for example, a server computer or any other system providing computing capability. Alternatively, the computing device  103  may comprise a plurality of servers or other computing devices that are arranged, for example, in one or more server banks or computer banks or other arrangements. For example, the computing device  103  may comprise a cloud computing resource, a grid computing resource, and/or any other distributed computing arrangement. The computing device  103  may be located in a single installation or may be distributed among many different geographical locations. 
     Various applications and/or other functionality may be executed in the computing device  103  according to various embodiments. Also, various data is stored in a data store  112  that is accessible to the computing device  103 . The data store  112  may be representative of a plurality of data stores  112  as can be appreciated. The data stored in the data store  112 , for example, is associated with the operation of the various applications and/or functional entities described below. 
     The components executed on the computing device  103 , for example, include a network page server  121 , marking service  124 , and other applications, services, processes, systems, engines, or functionality not discussed in detail herein. The network page server  121  may encode for display network pages, data for mobile applications, or other network content embodied in some other form that facilitates access to one or more network sites. To that end, the network page server  121  may serve data such as network pages to client devices  106  over a communication session using a protocol such as hypertext transfer protocol (HTTP), HTTP Secure (HTTPS), simple object access protocol (SOAP), representational state transfer (REST), user datagram protocol (UDP), transmission control protocol (TCP), and/or other protocols. Such a network page server  121  may comprise a commercially available network page server  121  such as, for example, Apache® HTTP Server, Apache® Tomcat®, Microsoft® Internet Information Services (IIS), and/or other network page servers. 
     In some embodiments, the network page server  121  may secure a portion of the communication session with the client device  106  using secure sockets layer/transport layer security (SSL/TLS), such as may be used for the HTTPS protocol, and/or other protocols as can be appreciated. In order to facilitate establishing a secure communication session, the network page server  121  may use various credentials such as, for example, X.509 digital certificates, public keys, private keys, shared keys, and/or other types of credentials as can be appreciated. 
     The marking service  124  is executed in order to facilitate validation of credentials presented to a client device  106  on behalf of the computing device  103 . To this end, the marking service  124  may communicate with the network page server  121  in order to provide various possible types of credential identifiers and/or other data to the client device  106 . The marking service  124  may communicate with the network page server  121  using various protocols such as, for example, HTTP, HTTPS, SOAP, REST, UDP, TOP, and/or other protocols. The credential identifiers may include all or a portion of a credential, a cryptographic hash value for a credential, and/or other data that may be used to identify the particular credential  141 . 
     In some embodiments, the marking service  124  may include coding rules  131 , a transaction log  133 , and/or other possible data. The coding rules  131  comprise rules for providing network content including credential identifiers (“verifiers”) to client devices  106 . The coding rules  131  may specify types of credential identifiers to be used, the method of delivery for the credential identifiers, rules for particular client devices  106  or groups of client devices  106 , and/or other possible specifications as can be appreciated. 
     The transaction log  133  comprises data associated with historical use or non-use of the credential identifiers during a communication session between the network page server  121  and a client device  106 . For a given communication session, the transaction log  133  may include the credential identifiers delivered to a client device  106 , the network content or other data used to deliver the credential identifiers, the coding rule  131  used to initiate delivery or non-delivery of a credential identifier, and/or other potential activities. In other embodiments, the functionality of the marking service  124  may be integrated into the network page server  121  or may be a “plug-in” program module integrating with the network page server  121  using an application programming interface (API) or other programmatic interface of the network page server  121 . 
     The data stored in the data store  112  includes, for example, data relating to network sites  140  and potentially other data. Each of the network sites  140  comprises various data associated with the presence of a distinct network presence, such as a website, that may be accessible through the network page server  121 . The credentials  141  for each network site may include X.509 digital certificates, public keys, private keys, shared keys, and/or other types of credentials as can be appreciated. The network content  143  includes network pages, images, video, audio, and/or other types of content that may be delivered to a client device  106  by the network page server  121 . Furthermore, the network content  143  may include applications or other types of objects executable in a virtual machine such as, for example, Flash®, Java®, or JavaScript®. 
     The client device  106  is representative of a plurality of client devices  106  that may be coupled to the network  109 . The client device  106  may comprise, for example, a processor-based system such as a computer system. Such a computer system may be embodied in the form of a desktop computer, server, laptop computer, personal digital assistant, smartphone, set-top box, tablet computer system, game console, electronic book reader, or other devices with like capability. 
     The client device  106  may be configured to execute various applications such as a client application  161 , virtual machine  163 , validation application  165 , and/or other applications. The client application  161  may be executed in a client device  106 , for example, to access and render network content  143  served up by the network page server  121  and/or other servers, thereby rendering a user interface on the display. The client application  161  may, for example, correspond to a browser, a mobile application, etc., and the user interface may correspond to a network page, a mobile application screen, etc. The virtual machine  163  is a software implementation of a computer that is capable of executing the validation application  165  and potentially other applications and objects as would a physical computing device. Various virtual machines  163  may be available on the client device  106  including, for example, Flash®, Java®, JavaScript®, Python, and/or other virtual machines  163  as can be appreciated. 
     The validation application  165  is executed in order to validate credentials  141  presented to the client application  161  on behalf of the computing device  103  during the course of establishing a communication session. To this end, the validation application  165  may obtain one or more credential identifiers  167  (“verifiers”) for a given credential  141 . The credential identifiers  167  may be embedded within the validation application  165 , stored from prior communication sessions with the computing device  103 , obtained from the network content  143 , and/or from other possible sources. In some embodiments, signature data  169  may be used to specify locations from which credential identifiers  167  for a particular network site  140  may be obtained. 
     The network device  111  is representative of a plurality of network devices that may forward and/or examine communication data transiting the network  109 . The network device  111  may comprise, for example, a processor-based system such as a computer system. Such a computer system may be embodied in the form of a server, network router, a network switch, a network proxy, a firewall, or other devices with like capability. The network device  111  may comprise one or more credentials  141  that may be used to authenticate as one or more network sites  140  that may or may not be hosted in the network device  111 . 
     Next, a general description of the operation of the various components of the networked environment  100  is provided. To begin, an operator of the client device  106  uses the client application  161  to initiate a communication session with the network page server  121 . The network page server  121  may offer one or more credentials  141 , which may be used to authenticate the identity of the computing device  103  and/or the network page server  121  to the client device  106 . For example, the communication session may be carried out using the HTTPS protocol, which employs SSL/TLS to provide authentication, confidentiality, and potentially other services. Using the SSL/TLS protocol, the network page server  121  may provide the client device  106  with a credential  141 , such as a digital certificate, that may be used by the client application  161  to authenticate the computing device  103  and/or the network page server  121 . 
     The data exchanged during initiation and operation of the communication session traverses the network  109 , and may include a path transiting the network device  111 . As the data transits the network device  111 , the network device  111  may intercept and/or modify the data, including the credential  141  used during initiation of the communication session. As a result, a communication session that appears to terminate only on the client device  106  and the computing device  103 , may instead be two communication sessions—one session between the client device  106  and the network device  111 , and the second session between the network device  111  and the computing device  103 . This scenario may be possible due to ability of the network device  111  to successfully convince the client application  161  that a forged credential  141  of the network device  111  is the proper credential  141  for the computing device  103  and/or the network page server  121 . Although the various techniques described in this disclosure may operate with or without a network device  111  performing such a “man-in-the-middle” interception, the techniques may be used to reduce the likelihood that such interceptions are attempted. 
     In some embodiments, the validation application  165  executing in the client device  106  may obtain the credential  141  presented to the client application  161  during initiation of a present communication session. The credential  141  used in the present communication session may then be validated as the proper credentials for a given network site using one or more operations appropriate for the type of credential  141  and corresponding credential identifier(s)  169  available. 
     In some embodiments, for network sites  140  using a credential  141  that having been previously accessed by the client application  161 , the validation application  165  may store a credential identifier  167  for the network site  140 . Each of the credential identifiers  167  stored may be all or a portion of the credential  141 , derived from the credential  141  such as a cryptographic hash value or a digital signature, and/or other possible identifying data. 
     For example, a website for an electronic marketplace may use an X.509 digital certificate as a credential  141 . The digital certificate may contain various fields including a digital signature, an issuing certificate authority, and/or other possible data. In order to create a credential identifier  167  for the digital certificate, the validation application  165  may store the complete digital certificate, digital signature value of the digital certificate, the certificate authority used to issue the digital certificate, and/or other possible identifying data. 
     Using one or more credential identifiers  167  corresponding to one or more previous communication sessions with a particular network site  140 , the validation application  165  may validate that the credential  141  currently presented has been previously observed. Returning to the previous example, the credential identifiers  167  for an electronic marketplace may indicate a digital certificate issued by the certificate authority, “TrustCorp,” was previously presented for the electronic marketplace. In this example, the validation application  165  may generate a notice or initiate another action if the digital certificate now presented, perhaps by an intermediate network device  111 , is issued by the certificate authority, “RogueCorp.” Likewise, a digital signature or cryptographic hash may be used to determine if any portion of a credential  141  such as a digital certificate has been altered. 
     In some embodiments, one or more credential identifiers  167  may be delivered by the computing device  103  to present client devices  106 , thereby enabling validation of a credentials  141  without relying upon previously acquired credential identifiers  167 . To this end, the credential identifiers  167  may be inserted as a digital watermark into network content  143  for a network site  140  by the marking service  124 . The marking service  124  may identify an on-going communication session between the network page server  121  and the client application  161  which employs a credential  141  for a network site  140 . The marking service  124  may observe requests by the client application  161  for particular network content  143 , and may insert credential identifiers  167  into select network content  143  matching the coding rules  131 . 
     For example, the network site  140  may be a website with various network content  143 , including a background image. The coding rules  131  may specify insertion of a digital signature for a credential  141  into the background image of the website. In this example, the digital signature may be inserted into a metadata portion of the image, inserted into a visual portion of the image using steganography, and/or using various other techniques appropriate for the type of network content  143  and credential identifier to be inserted. The coding rules  131  may further specify actions to be undertaken on the basis of an identity of a client device  106 . For example, for a client device  106  having a network address from a particular geographic region, it may be desirable to insert (or not) a credential identifier  167  into network content  143  provided to the particular client device  106 . The geographic region may be determined based upon a geolocation sensor in the client device  106 , a location of the network address used by the client device  106 , and/or other possible techniques. 
     Actions associated with insertion and/or abstentions from inserting credential identifiers  167  into the network content  143  may be recorded by the marking service  124  in the transaction log  133 . The marking service  124  may further generate signature data  169  to be used by the validation application  165  to obtain the credential identifiers  167  that may be embedded within network content  143  for a given network site  140 . The signature data  169  may be based upon the coding rules  131  and/or the transaction log  133  and may be distributed to the client device  106 . The signature data  169  may be distributed to the client device  106  using the current or an auxiliary communication session with the computing device  103 , through a centralized update site accessible through the network  109 , and/or through other possible operations. 
     Once the validation application  165  obtains the credential identifiers  167  in the network content  143 , the validation application  165  may validate the credential  141  as previously described. In various embodiments, the validation application  165  itself may be network content  143  delivered to the client device  106 . For example, the validation application  165  may be a Flash® object or other code executable in a virtual machine  163  of the client device  106 . In this example, the credential identifiers  167  and/or signature data  169  may be embedded in the code delivered to the client device  106 . Once the validation application  165  obtains the credential identifiers  167 , the validation application  165  may validate the credential  141  as previously described. 
     Returning to the marking service  124 , in some embodiments, the coding rules  131  may direct the marking service  124  to re-negotiate an active communication session with the client application  161 , negotiate one or more additional communication sessions with the client application  161 , and/or other possible operations using the existing credential  141  of the network site  140 . Similarly, these operations may also or instead be carried out by the client application  161  under the direction of the validation application  165 . While negotiations and re-negotiations of communication sessions may not reveal the presence of a network device  111  as a “man-in-the-middle,” these may be regarded as computationally “expensive” operations. Thus, it may reduce the likelihood that such an attack may be carried out. 
     Similarly, in some embodiments, the coding rules  131  may direct the marking service  124  to apply an additional encryption operation to a portion of the network content  143 . Similarly, this operation may also or instead be carried out by the client application  161  under the direction of the validation application  165  configured with the signature data  169 . The appearance of such “double-encrypted” data that cannot be decrypted by receiving device may indicate the presence of a network device  111  as a “man-in-the-middle,”. 
     In this scenario, the network device  111  acting as an intermediary within the communication session may not be aware that portions of the network content have been double-encrypted. Therefore, the network device  111  may correctly translate ordinary data traversing the communication session, but may not be aware that the double-encrypted data should have an additional translation operation applied. Upon discovery of such a scenario, the network page server  121 , the client application  161 , and/or other service may generate a notice, end the communication session, and/or initiate another action. 
     Referring next to  FIG. 2 , shown is a flowchart that provides one example of the operation of a portion of the marking service  124  according to various embodiments. It is understood that the flowchart of  FIG. 2  provides merely an example of the many different types of functional arrangements that may be employed to implement the operation of the portion of the marking service  124  as described herein. As an alternative, the flowchart of  FIG. 2  may be viewed as depicting an example of steps of a method implemented in the computing device  103  ( FIG. 1 ) according to one or more embodiments. 
     This portion of the execution of the marking service  124  may be executed based on obtaining coding rules  131  ( FIG. 1 ) with which to identify and mark data exchanged during a communication session between a network page server  121  ( FIG. 1 ) and a client device  106  ( FIG. 1 ). Beginning with block  203 , the marking service  124  may communicate with the network page server  121  to identify one or more established communication sessions with a client device  106 . 
     Next, in block  206 , the marking service  124  determines if one of the communication sessions matches the criteria of the coding rules  131 . The marking service  124  may select a subset of the established communication sessions for marking based upon, for example, the location of the client device  106 , an operator of the client application  161  ( FIG. 1 ), the communication session activity, and/or other possible selection criteria as can be appreciated. 
     If the currently examined communication session does not match the criteria of the coding rules  131 , execution of the marking service  124  may proceed to block  215 . Alternatively, if the examined communication session does match the criteria, the marking service  124 , in block  209 , may initiate one or more actions, such as “watermarking,” prescribed in the coding rules  131 . As previously described, these actions may comprise embedding an identifier for a credential  141  ( FIG. 1 ) within network content  143  ( FIG. 1 ), delivering a validation application  165  ( FIG. 1 ) within the network content  143 , initiating a re-negotiation of the communication session, layering of encrypted data within the communication session, and/or other possible actions. 
     Then, in block  212 , the marking service  124  may store a transaction log  133  ( FIG. 1 ) of data associated with the various actions undertaken and/or foregone. Such data may include the criteria of the coding rules  131  used to identify the network content  143 , credential identifier data inserted into the network content  143  or provided to the client device  106 , any prior value of data modified in the communication session (e.g. layering of encryption), and/or other possible data. Subsequently, in block  215 , the marking service  124  determines if there are any further communication sessions remaining that have not been examined and/or marked. If no more communication sessions remain, this portion of the execution of the marking service  124  ends as shown. Alternatively, if other tables do remain, execution of the marking service  124  returns to block  203 . 
     Turning now to  FIG. 3 , shown is a flowchart that provides one example of the operation of a portion of the validation application  165  according to various embodiments. It is understood that the flowchart of  FIG. 3  provides merely an example of the many different types of functional arrangements that may be employed to implement the operation of the portion of the validation application  165  as described herein. As an alternative, the flowchart of  FIG. 3  may be viewed as depicting an example of steps of a method implemented in the computing device  103  ( FIG. 1 ) according to one or more embodiments. 
     This portion of the execution of the validation application  165  may be executed based on obtaining signature data  169  ( FIG. 1 ) with which to locate and obtain credential identifiers  167  ( FIG. 1 ) provided by the computing device  103  and/or other data stores accessible via the network  109  ( FIG. 1 ). Beginning with block  303 , the validation application  165  may communicate with the client application  161  ( FIG. 1 ) to identify one or more established communication sessions with a network page server  121  ( FIG. 1 ) of a computing device  103  ( FIG. 1 ). 
     Next, in block  306 , the validation application  165  determines if a communication session of the client application  161  with a network site  140  corresponds to the criteria specified in the signature data  169 . The signature data  169  may provide locations and techniques for obtaining credential identifiers, such as through the presence of digital watermarks, corresponding to various possible network sites  140  ( FIG. 1 ). However, if the currently examined communication session does not match the criteria, such as a network site  140 , of the signature data  169 , execution of the validation application  165  may proceed to block  321 . 
     Alternatively, if the examined communication session does match the criteria, the validation application  165 , in block  309 , may obtain a credential identifier  167  using the information provided in the signature data  169 . The signature data  169  may specify various locations and techniques to obtain credential identifiers  167  for a given network site  140 , including from within network content  143  having a digital watermark. For example, a network site  140 , such as a website for an electronic marketplace, may embed a Java® applet in page for user authentication. In this example, the Java® applet may be capable of providing credential identifiers  167  to the validation application  165 . Continuing the example, a masthead image for the electronic marketplace may also contain credential identifiers  167  within the metadata stored in the image file and/or credential identifiers  167  embedded using steganographic techniques. 
     Then, in block  312 , the validation application  165  may validate the credential  141  ( FIG. 1 ) presented to the client application  161  during establishment of the communication session. As previously described, each credential identifier  167  may be a copy of the proper credential  141  itself, a portion of the credential  141 , a cryptographic hash value of the identifier  141 , and/or other possible formats. The validation operation may determine the validity of the credential  141  using techniques appropriate for the credential  141  and the available credential identifiers  167 . 
     Next, in block  315 , the validation application  165  may determine if the credential presented to the client is the authentic credential  141  for a network site or a forged credential  141 . If the credential is the authentic credential  141 , execution of the validation application  165  may proceed to block  321 . Alternatively, if the validation application  165  determines the credential is not the authentic credential  141 , and thus may be a forged credential  141 , the validation service  165  may, in block  318 , generate a notice for the validation failure, as well as potentially initiate other actions. 
     Moving on, in block  321 , the validation application  165  may determine if execution should continue on the basis of a user request, a lack of further unvalidated communication sessions, and/or other possible reasons. If execution of the validation application is to continue, the execution of the validation application  165  returns to block  303 . Alternatively, this portion of the execution of the validation application  165  ends as shown. 
     With reference to  FIG. 4 , shown is a schematic block diagram of the computing device  103  according to an embodiment of the present disclosure. The computing device  103  includes at least one processor circuit, for example, having a processor  403  and a memory  406 , both of which are coupled to a local interface  409 . To this end, the computing device  103  may comprise, for example, at least one server computer or like device. The local interface  409  may comprise, for example, a data bus with an accompanying address/control bus or other bus structure as can be appreciated. 
     Stored in the memory  406  are both data and several components that are executable by the processor  403 . In particular, stored in the memory  406  and executable by the processor  403  are the network page server  121 , marking service  124 , and potentially other applications. Also stored in the memory  406  may be a data store  112  and other data. In addition, an operating system may be stored in the memory  406  and executable by the processor  403 . 
     It is understood that there may be other applications that are stored in the memory  406  and are executable by the processors  403  as can be appreciated. Where any component discussed herein is implemented in the form of software, any one of a number of programming languages may be employed such as, for example, C, C++, C#, Objective C, Java®, JavaScript®, Perl PHP, Visual Basic, Python, Ruby, Delphi, Flash, or other programming languages. 
     A number of software components are stored in the memory  406  and are executable by the processor  403 . In this respect, the term “executable” means a program file that is in a form that can ultimately be run by the processor  403 . Examples of executable programs may be, for example, a compiled program that can be translated into machine code in a format that can be loaded into a random access portion of the memory  406  and run by the processor  403 , source code that may be expressed in proper format such as object code that is capable of being loaded into a random access portion of the memory  406  and executed by the processor  403 , or source code that may be interpreted by another executable program to generate instructions in a random access portion of the memory  406  to be executed by the processor  403 , etc. An executable program may be stored in any portion or component of the memory  406  including, for example, random access memory (RAM), read-only memory (ROM), hard drive, solid-state drive, USB flash drive, memory card, optical disc such as compact disc (CD) or digital versatile disc (DVD), magnetic tape, or other memory components. 
     The memory  406  is defined herein as including both volatile and nonvolatile memory and data storage components. Volatile components are those that do not retain data values upon loss of power. Nonvolatile components are those that retain data upon a loss of power. Thus, the memory  406  may comprise, for example, random access memory (RAM), read-only memory (ROM), hard disk drives, solid-state drives, USB flash drives, memory cards accessed via a memory card reader, optical discs accessed via an optical disc drive, magnetic tapes accessed via an appropriate tape drive, and/or other memory components, or a combination of any two or more of these memory components. In addition, the RAM may comprise, for example, static random access memory (SRAM), dynamic random access memory (DRAM), or magnetic random access memory (MRAM) and other such devices. The ROM may comprise, for example, a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), or other like memory device. 
     Also, the processor  403  may represent multiple processors  403  and the memory  406  may represent multiple memories  406  that operate in parallel processing circuits, respectively. In such a case, the local interface  409  may be an appropriate network  109  ( FIG. 1 ) that facilitates communication between any two of the multiple processors  403 , between any processor  403  and any of the memories  406 , or between any two of the memories  406 , etc. The local interface  409  may comprise additional systems designed to coordinate this communication, including, for example, performing load balancing. The processor  403  may be of electrical or of some other available construction. 
     With reference to  FIG. 5 , shown is a schematic block diagram of the client device  106  according to an embodiment of the present disclosure. The client device  106  includes at least one processor circuit, for example, having a processor  503  and a memory  506 , both of which are coupled to a local interface  509 . To this end, the client device  106  may comprise, for example, at least one client computer or like device. The local interface  509  may comprise, for example, a data bus with an accompanying address/control bus or other bus structure as can be appreciated. 
     Stored in the memory  506  are both data and several components that are executable by the processor  503 . In particular, stored in the memory  506  and executable by the processor  503  are the client application  161 , virtual machine  163 , validation application  165 , and potentially other applications. Also stored in the memory  506  may be a data store and other data. In addition, an operating system may be stored in the memory  506  and executable by the processor  503 . 
     It is understood that there may be other applications that are stored in the memory  506  and are executable by the processors  503  as can be appreciated. Where any component discussed herein is implemented in the form of software, any one of a number of programming languages may be employed such as, for example, C, C++, C#, Objective C, Java®, JavaScript®, Perl, PHP, Visual Basic, Python, Ruby, Delphi, Flash, or other programming languages. 
     A number of software components are stored in the memory  506  and are executable by the processor  503 . In this respect, the term “executable” means a program file that is in a form that can ultimately be run by the processor  503 . Examples of executable programs may be, for example, a compiled program that can be translated into machine code in a format that can be loaded into a random access portion of the memory  506  and run by the processor  503 , source code that may be expressed in proper format such as object code that is capable of being loaded into a random access portion of the memory  506  and executed by the processor  503 , or source code that may be interpreted by another executable program to generate instructions in a random access portion of the memory  506  to be executed by the processor  503 , etc. An executable program may be stored in any portion or component of the memory  506  including, for example, random access memory (RAM), read-only memory (ROM), hard drive, solid-state drive, USB flash drive, memory card, optical disc such as compact disc (CD) or digital versatile disc (DVD), magnetic tape, or other memory components. 
     The memory  506  is defined herein as including both volatile and nonvolatile memory and data storage components. Volatile components are those that do not retain data values upon loss of power. Nonvolatile component are those that retain data upon a loss of power. Thus, the memory  506  may comprise, for example, random access memory (RAM), read-only memory (ROM), hard disk drives, solid-state drives, USB flash drives, memory cards accessed via a memory card reader, optical discs accessed via an optical disc drive, magnetic tapes accessed via an appropriate tape drive, and/or other memory components, or a combination of any two or more of these memory components. In addition, the RAM may comprise, for example, static random access memory (SRAM), dynamic random access memory (DRAM), or magnetic random access memory (MRAM) and other such devices. The ROM may comprise, for example, a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), or other like memory device. 
     Also, the processor  503  may represent multiple processors  503  and the memory  506  may represent multiple memories  506  that operate in parallel processing circuits, respectively. In such a case, the local interface  509  may be an appropriate network  109  ( FIG. 1 ) that facilitates communication between any two of the multiple processors  503 , between any processor  503  and any of the memories  506 , or between any two of the memories  506 , etc. The local interface  509  may comprise additional systems designed to coordinate this communication, including, for example, performing load balancing. The processor  503  may be of electrical or of some other available construction. 
     Although the network page server  121 , marking service  124 , client application  161 , virtual machine  163 , validation application  165 , and other various systems described herein may be embodied in software or code executed by general purpose hardware as discussed above, as an alternative the same may also be embodied in dedicated hardware or a combination of software/general purpose hardware and dedicated hardware. If embodied in dedicated hardware, each can be implemented as a circuit or state machine that employs any one of or a combination of a number of technologies. These technologies may include, but are not limited to, discrete logic circuits having logic gates for implementing various logic functions upon an application of one or more data signals, application specific integrated circuits having appropriate logic gates, or other components, etc. Such technologies are generally well known by those skilled in the art and, consequently, are not described in detail herein. 
     The flowcharts of  FIGS. 2 and 3  show the functionality and operation of an implementation of portions of the marking service  124  and the validation application  165 , respectively. If embodied in software, each block may represent a module, segment, or portion of code that comprises program instructions to implement the specified logical function(s). The program instructions may be embodied in the form of source code that comprises human-readable statements written in a programming language or machine code that comprises numerical instructions recognizable by a suitable execution system such as a processor  403 / 503  in a computer system or other system. The machine code may be converted from the source code, etc. If embodied in hardware, each block may represent a circuit or a number of interconnected circuits to implement the specified logical function(s). 
     Although the flowcharts of  FIGS. 2 and 3  show a specific order of execution, it is understood that the order of execution may differ from that which is depicted. For example, the order of execution of two or more blocks may be scrambled relative to the order shown. Also, two or more blocks shown in succession in  FIGS. 2 and 3  may be executed concurrently or with partial concurrence. Further, in some embodiments, one or more of the blocks shown in  FIGS. 2 and 3  may be skipped or omitted. In addition, any number of counters, state variables, warning semaphores, or messages might be added to the logical flow described herein, for purposes of enhanced utility, accounting, performance measurement, or providing troubleshooting aids, etc. It is understood that all such variations are within the scope of the present disclosure. 
     Also, any logic or application described herein, including the marking service  124  and validation application  165 , that comprises software or code can be embodied in any non-transitory computer-readable medium for use by or in connection with an instruction execution system such as, for example, a processor  403 / 503  in a computer system or other system. In this sense, the logic may comprise, for example, statements including instructions and declarations that can be fetched from the computer-readable medium and executed by the instruction execution system. In the context of the present disclosure, a “computer-readable medium” can be any medium that can contain, store, or maintain the logic or application described herein for use by or in connection with the instruction execution system. The computer-readable medium can comprise any one of many physical media such as, for example, magnetic, optical, or semiconductor media. More specific examples of a suitable computer-readable medium would include, but are not limited to, magnetic tapes, magnetic floppy diskettes, magnetic hard drives, memory cards, solid-state drives, USB flash drives, or optical discs. Also, the computer-readable medium may be a random access memory (RAM) including, for example, static random access memory (SRAM) and dynamic random access memory (DRAM), or magnetic random access memory (MRAM). In addition, the computer-readable medium may be a read-only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), or other type of memory device. 
     It should be emphasized that the above-described embodiments of the present disclosure are merely possible examples of implementations set forth for a clear understanding of the principles of the disclosure. Many variations and modifications may be made to the above-described embodiment(s) without departing substantially from the spirit and principles of the disclosure. All such modifications and variations are intended to be included herein within the scope of this disclosure and protected by the following claims.