Abstract:
The restriction of particular resources includes providing a digital signature for unauthorized resources based on a structure-related parameter of the resource. Thus, attempts at circumventing recognition of such resource will likely result in altering the overall functionality of the resource. Further, such digital signatures are encoded in a critical file required for loading of a resource, thus ensuring that the identity of the resource is considered before execution thereof. Enforcement of the resource restriction includes generating a verification signature for a resource that requests loading. The verification signature is compared to the signature coded into the critical file, and a positive match results in the resource being blocked from loading.

Description:
FIELD 
   The present invention relates to regulating the use of resources loading on processing devices. 
   BACKGROUND 
   The misuse of computer software is costly. For the provider and/or user of unauthorized software, the cost of misusing software can be measured, in part, in terms of legal costs and fines if found to violate any copyrights and/or licensing agreements associated with the misused software. Additional dangers lie in the fact that unauthorized software applications often contain viruses with the potential to damage individual computers or even an entire network. Further still, unlicensed software may cause incompatibility between programs that would normally function together seamlessly. Yet another cost associated with the misuse of computer software is to a developer, server, or provider of licensed software products for whom the cost of misused software can be measured primarily in terms of lost licensing revenue. 
   Accordingly, developers, servers, and providers of licensed or otherwise authorized software products are highly motivated to regulate the execution of software on authorized operating systems for client devices and server devices. Crucial considerations for succeeding in such endeavor include quickly and accurately identifying and then restricting unauthorized software applications from loading without hindering the concurrent execution of licensed software applications. 
   Previous attempts at identifying software products for the purpose of restricting those that are not licensed or otherwise authorized include performing a bit-by-bit comparison of the entire code of a file against a known version thereof, comparing the size of a file to previously known parameters, and comparing a predetermined number of bits at the beginning of the file to those of previous versions of the file. However, such efforts are easily thwarted because the binary code associated with unauthorized software products may be changed, even slightly, to avoid detection. For instance, changing a file name or file location can change the appearance and/or size of a file, thus frustrating efforts to regulate the usage thereof. Even minor code fixes, not intended to circumvent file recognition, can render a file unrecognizable relative to known versions. Furthermore, such efforts consume valuable processing resources and/or overhead, which impede the usage of licensed or otherwise authorized software products. 
   SUMMARY 
   Application identification and license enforcement are described herein. 
   According to one aspect, restricting the use of particular resources includes providing a cryptographic signature for a particular resource predicated on a static feature of the resource. Thus, attempts at circumventing recognition of such resource will likely result in altering the overall functionality of the resource. The signatures are encoded in a critical file required for loading and/or running of the resource, thus ensuring that the identity of the resource is verified before the resource is executed. Enforcement of the resource restriction includes generating a verification cryptographic signature for a resource that requests loading. The verification signature is compared to the signature coded into the critical file, and a determination is made as to whether to block the resource from loading and/or running based on whether the comparison results in a positive match. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The following detailed description, while indicating example embodiments, is only illustrative since various changes and modifications will become apparent to those skilled in the art from the following detailed description, in which: 
       FIG. 1  shows a client/network system in accordance with example embodiments; 
       FIG. 2  illustrates the processing for a feature according to an example embodiment; 
       FIG. 3  illustrates an example of processing further to the embodiment of  FIG. 2 ; 
       FIG. 4  illustrates the processing according to another example embodiment; 
       FIG. 5  illustrates an example of processing further to the embodiment of  FIG. 4 ; and 
       FIG. 6  illustrates a general computer environment which can be used to implement the techniques described herein. 
   

   DETAILED DESCRIPTION 
   In the example network environment of  FIG. 1 , multiple client computing devices  105 ,  110 ,  115 , and  120 , also referred to as clients, are coupled to server devices  125  and  130  via network  100 . Network  100  is intended to represent any of a variety of conventional network topologies and types, which may include wired and/or wireless networks. Network  100  may further utilize any of a variety of conventional network protocols, including public and/or proprietary protocols. Network  100  may include, for example, the Internet as well as possibly at least portions of one or more local area networks (LANs). 
   Computing device  105  may include any of a variety of conventional computing devices, including a desktop personal computer (PC), workstations, mainframe computers, Internet appliances, and gaming consoles. Further computing devices associated with network  100  may include a personal digital assistant (PDA)  110 , a laptop computer  115 , and a cellular telephone  120 , etc., which may be in communication with network  100  by a wired and/or wireless link. Further still, one or more of computing devices  105 ,  110 ,  115 , and  120  may include the same types of devices, or alternatively different types of devices. 
   Server devices  125  and  130  may provide any of a variety of data and/or functionality to computing devices  105 ,  110 ,  115 , and  120 . The data may be publicly available or alternatively restricted (e.g., restricted to only certain users, available only if the appropriate fee is paid, etc.), as will be discussed in greater detail below. 
   The discussions herein refer to server devices and client devices, with all features described above included in the scope of a corresponding description. A server device may include any device that is the source of content, and a client device may include any device that receives such content (e.g., for presentation to a user at the client device). For example, in a peer-to-peer network, the device that is the source of the content may be referred to as the server device while the device that receives the content may be referred to as the client device. 
   Server devices  125  and  130  may include at least one of a network server and an application server. A network server is a server device that delivers content to any of client devices  105 ,  110 ,  115 , and  120  by way of network  100 . Such content may include a text file coded in HTML, which may also contain JavaScript code or other commands. Although frequently referred to herein as a “web server”, it is to be appreciated that network server device  125  can be used in other networks that are not part of the World Wide Web. 
   A web server  125  or  130  may provide comprehensive Internet services to client devices  105 ,  110 ,  115 , and  120 . Web server  125  or  130  may incorporate any or all of an HTTP (hypertext transport protocol) server for delivering web pages and files, an FTP server (file transport protocol) for delivering file downloads, an NTTP server (network news transport protocol) for delivering newsgroup files, and an SMTP server (simple mail transfer protocol) for delivering e-mail. 
   The term “web server” may be used to refer to the combined hardware and operating system of server devices  125  and  130 , the operating system organizing and controlling the hardware and other software resources of server devices  125  and  130 . Resources including operating systems and other applications or programs may be provided to server devices  125  and  130  by at least one of data source  135 , which is off-line, and data source  140 , which is on-line. Similarly, the software resources existing on server devices  125  and  130  may similarly be upgraded or replaced using off-line and on-line means and methodologies, which are well known in the art. 
   Application server  125  or  130 , which is typically web-based, is a server device in a client/server environment that performs business logic, provides a user interface, and performs data processing. An application server runs software in an intranet/Internet environment that hosts a variety of language systems used to program database queries and/or general business processing. Application servers may provide organizational support for groupware, directory services, and databases. Groupware includes software for supporting multiple users working on related tasks, often linking non-web-based applications such as those for managing calendars, schedules, contacts, and tasks. Directory services utilize specialized databases, typically hierarchical in design, to manage user accounts and network authorizations. Databases include sets of related files created and managed by a database management system (DBMS). 
   Web servers and application servers may be separate devices or they may reside in a same server device, often depending on the size and needs of the entity or organization that they service. Further, overlap may exist between a web server and an application server servicing a common entity or organization. For instance, a web server may invoke scripts and services to query databases and perform business processing, and an application server may include an HTTP server to deliver web pages to client devices. 
   For a variety of reasons, mostly financial, “blade servers” are being made available to provide entities and organizations with a server dedicated solely to web serving and hosting purposes. More particularly, blade servers are intended to provide high performance web-based services, including web page serving and ASP (active server page) execution, at a low entry price. As a restricted-use server device, a blade server is to prevent the loading of applications or programs that lack an appropriate web server license. Non-limiting examples of such restricted applications pertain to groupware, database and directory services. 
   Example embodiments related to such a restricted-use server device include, both singularly and in combination together: the generation of a unique identifier for a software application or program, the identifier also being referred to as a digital ID, signature, or fingerprint; and the enforcement of an application or program restriction, often the result of the lack of a web server licensing agreement. In particular, embodiments of a restricted-use server device identify a restricted application or program, and further restrict the loading of such a software application or program based on the identification of the application or program. Even more specifically, an embodiment of a license enforcement scheme for a restricted-use server device assigns a unique identification to a restricted application, “bakes” or codes the identification and a restriction/authorization status of the restricted application into an operating system to run on a server device, identifies all applications sought to be loaded on the server device, and appropriately restricts the applications based on a positive comparison between the identification and restriction/authorization status coded into the operating system and the identification made at the server device. 
   The process of  FIG. 2  and data flow of  FIG. 3  pertain to a data source  135  or  140  (see  FIG. 1 ) that may include, either singularly or in combination thereof, licensing manager component  137  or  142  and software developer component  138  or  143 . At data source  135  or  140 , a licensing structure is implemented to render particular files, which are software applications or programs to be executed on a server device, eligible or ineligible for execution. Implementation of the licensing structure results in a command  205  to generate a unique identifier for the particular applications or programs in accordance with a corresponding licensing status. 
   Applications and programs are formatted in an executable code (hereafter “executable”) in order to be executed by server device  125  or  130 . Executables have an import table, which lists one or more dynamic link libraries (DLL) associated with the executable. A DLL is a module that can be used to perform one or more functions at runtime for the executable. Import tables may also be regarded as a set of data identifying an application or program, or as a linker table describing specific linkages to other applications or programs. For the sake of consistency, the description that follows will make reference to an import table though the corresponding discussion set forth above is to be included in the scope thereof. 
   According to the example embodiment of  FIG. 2 , the names of the functions included in each of the DLLs are retrieved  215  from the import table. These retrieved names, which may include the names of the DLLs, are used to generate  220  a unique identification for the application or program. These names can be combined in any of a variety of manners to generate the unique identification. 
     FIG. 3 , which shows a signature generator, illustrates an example of uniquely identifying each application or program, e.g.,  220  of  FIG. 2 . As discussed above, a unique identification for each application or program may alternatively be referred to as a digital signature or fingerprint. For the sake of consistency, the description that follows will reference a signature though the above discussion of the terms identification and fingerprint are to be included in the scope thereof. 
   In  FIG. 3 , a sorted list  305  of the retrieved function names is culled from the import table in a case-insensitive manner, based on a predetermined criterion, e.g., alphabetically, by name size in ascending or descending order, etc. The sorted list  305  of function names, which may include the corresponding DLL name, are then concatenated, or strung together consecutively. 
   The function names from an import table are generally unique, and typically cannot be changed without affecting the very functionality of the corresponding executable. Although major version releases of an application or program may include changes in an import table, import tables typically vary little from one version of an application or program to another, and generally not at all in localized versions of the application or program, i.e., they are static in nature and are considered to be integral to the structure of the application or program. Further, the function names are resistant to minute differences in executables including minor code tweaks to fix bugs, re-ordering binaries, filename changes, and filename location changes. Regardless of an underlying motivation, the aforementioned minute differences have previously succeeded in efforts to circumvent detection and/or recognition of particular applications or programs without changing the functionality thereof. Conversely, any change to a function name affects the functionality of the application or program. More specifically, since the function names are references to functions in an external DLL file, changing a function name means that the corresponding function will not be found in the DLL resulting in a runtime error, and thus the program or application will be inoperable. Therefore function names are presently utilized for generating the signature for an application or program, thus preserving the reliable and robust nature of the example embodiments described herein. 
   The sorted and concatenated elements  305  of the import table are hashed  315  resulting in a unique signature  320  for the application or program. The hash is a cryptographic manipulation, and according to an example embodiment, includes a one-way MD5 (Message Digest 5) hash function. The result of an MD5 hash is a unique 16-byte signature for the executable of the application or program. Alternative one-way hash functions may be used, including SHA1 (Secure Hash Algorithm 1). The generated signature may be alternatively referred to as a “hash.” 
   As mentioned above, this process is reliable and robust due to the utilization of at least the unique function names from the import table. In particular, sorting the function names from an import table in a predetermined manner and hashing a concatenation or string thereof result in a miniscule rate of collisions, i.e., the chance of identical signatures for multiple executables is very small. Further still, the hashing of only elements from the import table occupies a limited portion of processing resources, thus reducing the associated overhead. For instance, it is not necessary to load the entire binary code to memory for the hash computation. In addition, since only import table elements are hashed, very little of the actual binary code comprising the application or program are utilized in the signature generating effort. Also, considering the small size of an import table relative to the remainder of the application or program, the hash computation may be performed rapidly thereby reducing any hindrance to reliable execution of any authorized applications or programs running concurrently. 
   Continuing with regards to  FIG. 2 , data source  135  or  140  adds  225  the generated signature  335  to an operating system to be executed by server device  125  or  130 . In view of the critical role an operating system plays for implementing a restricted-use server device, a list of prohibited applications or programs may be coded into a DLL for an operating system, which resides in the server device memory at all times while the server device is running and provides basic services. That is, the hashes are preferably coded into a critical file of the operating system. The kernel is the part of the operating system that is closest to the hardware of the server device and may activate the hardware directly or interface to another software layer that drives the hardware. In a Microsoft® Windows® operating system environment, an appropriate DLL for containing a list of prohibited applications or programs would be the kernel32.dll. Such example is non-limiting. For a restricted-use server device such as a blade server, the hash list includes the signatures for unlicensed applications or programs. However, it is further contemplated that the hash list may include the signatures of licensed applications or programs, or applications or programs that are at least one of ineligible and eligible for execution, with the respective hashes being appropriately categorized according to eligibility or accessibility. 
   Having been coded to include at least a hash and perhaps a restriction/authorization classification for respective applications or programs, the operating system may be loaded onto a server device  125  or  130 . For example, the operating system may be loaded onto server device  125  from off-line data source  135 , or onto server device  125  or  130  from on-line data source  140 . Further, operating system service packs with updated hashes may be loaded onto the server devices  125  and  130  in a similar manner. Appropriate means and methodologies are well known in the art. 
     FIGS. 4 and 5  are examples of the enforcement implemented by a restricted-use server device in accordance with the application or program identification described above. In particular, the data flow of  FIG. 5  may be incorporated within the processing described in reference to  FIG. 4  below. 
   When a startup configuration of server device  125  or  130  or a direct invocation at a local system calls for an application or program to be opened or loaded at restricted-use server device  125  or  130 , the application or program on the operating system at server device  125  or  130  requests  405  a running state, i.e., requests execution by the server device. The operating system loads the code of the executable of the application or program through an application programming interface (API). That is, an executable must be processed by an API in order to achieve a running state. An example of an API in a Microsoft® Windows® operating system environment is called CreateProcess. Such example is non-limiting. 
   When the API receives the request  405  for a running state for an application or program, a determination  415  may be made as to whether particular applications or programs are being blocked at the particular server device  125  or  130 , i.e., whether the server device is a restricted-use server device. However, since blade servers may be designed, manufactured, and/or sold as restricted-use server devices, this decision step may be circumvented in favor of the assumption that unlicensed applications or programs are to be blocked from loading, i.e., restricted. 
   The API of an operating system generates  435  a verification signature of the application or program requesting a running state. Generation  425  of the verification signature for the application or program requesting a running state can be performed following the same procedure described above with respect to  FIG. 3 , relating to the generation of a signature for an application or program to be coded into an operating system. However, the discussion further below regarding  FIG. 5  will provide additional details regarding the generation and processing of the verification signature. 
   The generated verification signature is compared to the signatures of the applications or programs that are coded into a DLL for an operating system kernel, and thus a determination  445  is made as to whether or not the application or program requesting a running state is restricted. A negative determination allows  425  the respective application or program to be loaded by the operating system at the restricted-use server, though a positive determination denies  455  access to the application or program. 
     FIG. 5  refers back to the generation  435  of the verification signature of the application or program requesting a running state at the restricted-use server device  125  or  130 . When application or program  505  requests a running state, the import table  510  of the executable of the application or program is put  515  in a canonical form, e.g., alphabetically. For example, import table  510  includes hypothetical functions names, which may include the DLL name, as listed in the import table, “CFUNCTION,” “EFUNCTION,” “BFUNCTION,” “BDLL,” “AFUNCTION,” and “DFUNCTION.” The function names are sorted alphabetically as “AFUNCTION,” “BDLL,” “BFUNCTION,” “CFUNCTION,” “DFUNCTION,” and “EFUNCTION.” Alternate criteria by which the function names may be sorted include, for example, name size in ascending or descending order, etc. 
   The sorted function names  515  are then summed or concatenated, resulting in a single string including all of the function names from the sorted list  515  of import table elements. The sorted elements of the function table, having been strung together, are then hashed  525  using a cryptographic algorithm. A one-way hashing algorithm is utilized to generate a fixed string of numbers from a string of function names, which may include the DLL name. Example embodiments include hashing the import table elements using an MD5 hashing algorithm. However, the example embodiments described herein are not limited to such hash function. Any of a variety of hashing algorithms can be used; however, the hashing algorithm used should be the same as was used to generate the signature in  220  of  FIG. 2 . 
   The result of the one-way hashing function is a digital signature  535  of the application or program requesting a running state. An MD5 hashing of the sorted and concatenated import table elements  515  results in a 16-byte hash. 
   Generating verification signature  535  is quick and reliable due to the utilization of at least the unique function names from the import table. As discussed above regarding the unique and static nature of the function names from an import table, hashing the sorted and concatenated function names results in a low rate of collisions, i.e., the chance of identical signatures for multiple executables is very small. 
   According to an example embodiment of a restricted-use server device, the API compares the hash, or verification signature  535 , of the application or program requesting a running state to the list of signatures  555  of restricted applications or programs that has already been coded, or “baked,” into the operating system. A negative result, with no matches between verification signature  535  and any of the signatures coded into the operating system, results in the application or program being loaded. A positive result, with verification signature  535  matching one of the signatures in the DLL of the operating system, results in the application or program being blocked from loading. Thus, usage of the server device is restricted in accordance with web server licenses for respective applications or programs. 
   The list of restricted applications or programs is formulated based on many considerations, including those of a business and/or financial nature. Thus, revisions to the list of signatures for restricted applications or programs can be continually updated as licenses are expired, revoked, purchased, renewed, etc. Accordingly, server devices  125  and  130  of  FIG. 1  may periodically receive updated lists of restricted applications or programs in the forms of upgraded operating systems, service packs, etc. 
   The embodiments described above may be modified to reference not only restricted applications or programs but also authorized applications or programs. Such decisions may be made in accordance with evaluations of available resources and overhead. Regardless, such modifications do not in any way limit the scope of the embodiments described herein. 
   Further, the example embodiments described above are directed to blade web servers, although one of ordinary skill in the art should be able to appropriately modify such embodiment, as appropriate, for implementation of restricted-use application servers as well. Further, the embodiments may be modified, for example, to be implemented by both web servers and applications servers to prohibit the loading of applications suspected of containing bugs or viruses that may damage individual computers or even an entire network. Further, the embodiments may be modified to be implemented by a client operating system, for example to prohibit the loading of executables known to contain faulty or malicious code. The Microsoft® Windows® XP operating system is a non-limiting example of such an operating system. Further still, it may be desired to use such verification process to check for allowable, or eligible, applications or programs. For example, for a business kiosk intending to run only particular applications or programs server processing may be expedited if a corresponding server device checks for only authorized applications or programs. 
     FIG. 6  illustrates a general computer environment  600 , which can be used to implement the techniques described herein. The computer environment  600  is only one example of a computing environment and is not intended to suggest any limitation as to the scope of use or functionality of the computer and network architectures. Neither should the computer environment  600  be interpreted as having any dependency or requirement relating to any one or combination of components illustrated in the example computer environment  600 . 
   Computer environment  600  includes a general-purpose computing device in the form of a computer  602 . Computer  602  can be, for example, client device  105 ,  110 ,  115 , or  120  or server device  125  or  130  of  FIG. 1 . The components of computer  602  can include, but are not limited to, one or more processors or processing units  604 , a system memory  606 , and a system bus  608  that couples various system components including the processor  604  to the system memory  606 . 
   The system bus  608  represents one or more of any of several types of bus structures, including a memory bus or memory controller, a peripheral bus, an accelerated graphics port, and a processor or local bus using any of a variety of bus architectures. By way of example, such architectures can include an Industry Standard Architecture (ISA) bus, a Micro Channel Architecture (MCA) bus, an Enhanced ISA (EISA) bus, a Video Electronics Standards Association (VESA) local bus, a Peripheral Component Interconnects (PCI) bus also known as a Mezzanine bus, a PCI Express bus, a Universal Serial Bus (USB), a Secure Digital (SD) bus, or an IEEE 1394, i.e., FireWire, bus. 
   Computer  602  may include a variety of computer readable media. Such media can be any available media that is accessible by computer  602  and includes both volatile and non-volatile media, removable and non-removable media. 
   The system memory  606  includes computer readable media in the form of volatile memory, such as random access memory (RAM)  610 ; and/or non-volatile memory, such as read only memory (ROM)  612  or flash RAM. A basic input/output system (BIOS)  614 , containing the basic routines that help to transfer information between elements within computer  602 , such as during start-up, is stored in ROM  612  or flash RAM. RAM  610  typically contains data and/or program modules that are immediately accessible to and/or presently operated on by the processing unit  604 . 
   Computer  602  may also include other removable/non-removable, volatile/non-volatile computer storage media. By way of example,  FIG. 6  illustrates a hard disk drive  616  for reading from and writing to a non-removable, non-volatile magnetic media (not shown), a magnetic disk drive  618  for reading from and writing to a removable, non-volatile magnetic disk  620  (e.g., a “floppy disk”), and an optical disk drive  622  for reading from and/or writing to a removable, non-volatile optical disk  624  such as a CD-ROM, DVD-ROM, or other optical media. The hard disk drive  616 , magnetic disk drive  618 , and optical disk drive  622  are each connected to the system bus  608  by one or more data media interfaces  626 . Alternatively, the hard disk drive  616 , magnetic disk drive  618 , and optical disk drive  622  can be connected to the system bus  608  by one or more interfaces (not shown). 
   The disk drives and their associated computer-readable media provide non-volatile storage of computer readable instructions, data structures, program modules, and other data for computer  602 . Although the example illustrates a hard disk  616 , a removable magnetic disk  620 , and a removable optical disk  624 , it is to be appreciated that other types of computer readable media which can store data that is accessible by a computer, such as magnetic cassettes or other magnetic storage devices, flash memory cards, CD-ROM, digital versatile disks (DVD) or other optical storage, random access memories (RAM), read only memories (ROM), electrically erasable programmable read-only memory (EEPROM), and the like, can also be utilized to implement the example computing system and environment. 
   Any number of program modules can be stored on the hard disk  616 , magnetic disk  620 , optical disk  624 , ROM  612 , and/or RAM  610 , including by way of example, an operating system  626 , one or more application programs  628 , other program modules  630 , and program data  632 . Each of such operating system  626 , one or more application programs  628 , other program modules  630 , and program data  632  (or some combination thereof) may implement all or part of the resident components that support the distributed file system. 
   A user can enter commands and information into computer  602  via input devices such as a keyboard  634  and a pointing device  636  (e.g., a “mouse”). Other input devices  638  (not shown specifically) may include a microphone, joystick, game pad, satellite dish, serial port, scanner, and/or the like. These and other input devices are connected to the processing unit  604  via input/output interfaces  640  that are coupled to the system bus  608 , but may be connected by other interface and bus structures, such as a parallel port, game port, or a universal serial bus (USB). 
   A monitor  642  or other type of display device can also be connected to the system bus  608  via an interface, such as a video adapter  644 . In addition to the monitor  642 , other output peripheral devices can include components such as speakers (not shown) and a printer  646  which can be connected to computer  602  via the input/output interfaces  640 . 
   Computer  602  can operate in a networked environment using logical connections to one or more remote computers, such as a remote computing device  648 . By way of example, the remote computing device  648  can be a PC, portable computer, a server, a router, a network computer, a peer device or other common network node, and the like. The remote computing device  648  is illustrated as a portable computer that can include many or all of the elements and features described herein relative to computer  602 . Alternatively, computer  602  can operate in a non-networked environment as well. 
   Logical connections between computer  602  and the remote computer  648  are depicted as a local area network (LAN)  650  and a general wide area network (WAN)  652 . Such networking environments are commonplace in offices, enterprise-wide computer networks, intranets, and the Internet. 
   When implemented in a LAN networking environment, the computer  602  is connected to a local network  650  via a network interface or adapter  654 . When implemented in a WAN networking environment, the computer  602  typically includes a modem  656  or other means for establishing communications over the wide network  652 . The modem  656 , which can be internal or external to computer  602 , can be connected to the system bus  608  via the input/output interfaces  640  or other appropriate mechanisms. It is to be appreciated that the illustrated network connections are examples and that other means of establishing at least one communication link between the computers  602  and  648  can be employed. 
   In a networked environment, such as that illustrated with computing environment  600 , program modules depicted relative to the computer  602 , or portions thereof, may be stored in a remote memory storage device. By way of example, remote application programs  658  reside on a memory device of remote computer  648 . For purposes of illustration, applications or programs and other executable program components such as the operating system are illustrated herein as discrete blocks, although it is recognized that such programs and components reside at various times in different storage components of the computing device  602 , and are executed by at least one data processor of the computer. 
   Various modules and techniques may be described herein in the general context of computer-executable instructions, such as program modules, executed by one or more computers or other devices. Generally, program modules include routines, programs, objects, components, data structures, etc. for performing particular tasks or implement particular abstract data types. Typically, the functionality of the program modules may be combined or distributed as desired in various embodiments. 
   An implementation of these modules and techniques may be stored on or transmitted across some form of computer readable media. Computer readable media can be any available media that can be accessed by a computer. By way of example, and not limitation, computer readable media may comprise “computer storage media” and “communications media.” 
   “Computer storage media” includes volatile and non-volatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules, or other data. Computer storage media includes, but is not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to store the desired information and which can be accessed by a computer. 
   “Communication media” typically embodies computer readable instructions, data structures, program modules, or other data in a modulated data signal, such as carrier wave or other transport mechanism. Communication media also includes any information delivery media. The term “modulated data signal” means a signal that has one or more of its characteristics set or changed in such a manner as to encode information in the signal. As a non-limiting example only, communication media includes wired media such as a wired network or direct-wired connection, and wireless media such as acoustic, RF, infrared, and other wireless media. Combinations of any of the above are also included within the scope of computer readable media. 
   Reference has been made throughout this specification to “one embodiment,” “an embodiment,” or “an example embodiment” meaning that a particular described feature, structure, or characteristic is included in at least one embodiment of the present invention. Thus, usage of such phrases may refer to more than just one embodiment. Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. 
   One skilled in the relevant art may recognize, however, that the invention may be practiced without one or more of the specific details, or with other methods, resources, materials, etc. In other instances, well known structures, resources, or operations have not been shown or described in detail merely to avoid obscuring aspects of the invention. 
   While example embodiments and applications of the present invention have been illustrated and described, it is to be understood that the invention is not limited to the precise configuration and resources described above. Various modifications, changes, and variations apparent to those skilled in the art may be made in the arrangement, operation, and details of the methods and systems of the present invention disclosed herein without departing from the scope of the claimed invention.