Patent Publication Number: US-11651099-B2

Title: Persisting encrypted remote browser data at a local browser for use in a remote browser

Description:
FIELD 
     The present disclosure relates to the field of remote browsing; and more specifically to persisting encrypted remote browser data at a local browser for use in a remote browser. 
     BACKGROUND 
     Bad actors and cyber-attackers create malicious websites that install malware onto or otherwise attack a user&#39;s machine (whether that machine is a PC, Mac, tablet, phone, virtual-reality headset, augmented/mixed reality headset, or other computing device). These attackers can infect a user&#39;s machine at many levels, including taking advantage of security holes in operating systems and applications interfaces to system resources and drivers. One manner of securing an application is to execute the application remotely on a server instead of locally on a client device where the hosted remoted application can be protected inside of a sandbox, such as a virtual machine. When the application is a web browser, this is sometimes referred to as “browser isolation.” 
     Several attempted solutions have been employed to allow web browsers to be isolated by running them as remote processes. One such solution is to employ “pixel pushing” or “pixel mirroring” which allows a web page to be rendered remotely utilizing a web browser running on an external server to execute any active code associated with the web page and to produce a series of images which are sent back to a client web browser as compressed pixels or video (using for example H264 video format) to be eventually rendered by the web browser on the client device. Another solution is to employ “Document Object Model” (DOM) remoting/mirroring. With this solution, the DOM corresponding to a page is sanitized before it is sent to the client to remove potentially malicious code and reconstructed on the client before rendering. Using DOM mirroring, a sanitizing process on the isolated browser computing system (e.g., a server) identifies bad HTML and active content and cleans up the DOM tree and reformats it without the active content or with content that has been transcoded into a safe format. 
     When a user browses the internet using a conventional browser, some amount of data is stored locally. For instance, session information may be stored so that a user is not required to log into a service each time it is visited. As another example, theme preferences for a website (e.g., dark or light) may be stored. The data is typically stored in cookies. 
     SUMMARY 
     A remote browsing session is initiated between a remote browser client executing on a client device and a remote browser host executing on a remote browser server. The remote browser host receives, from the client device, encrypted remote browser data of remote browser data that affects the remote browsing session. For instance, the remote browser data may include cookies, browser extension data, data to be stored in a local database of the client, browser history, autofill history, theme preferences, bookmarks, passwords, a listing of open tabs, payment information, addresses, and/or phone numbers. The client does not have access to a decryption key for the encrypted remote browser data. The encrypted remote browser data is decrypted to reveal the remote browser data, and the remote browser host is configured with the remote browser data. The remote browser host manages updates to the remote browser host during the remote browsing session. Periodically, the remote browser data is encrypted and transmitted to the remote browser client for storage. The remote browser client may store the encrypted remote browser data in local storage, IndexedDB, or other client storage. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention may best be understood by referring to the following description and accompanying drawings that are used to illustrate embodiments. In the drawings: 
         FIG.  1    illustrates an exemplary remote browsing environment for persisting encrypted remote browser data at a local client device that can be used in a remote browser, according to an embodiment. 
         FIG.  2    is a flow diagram that illustrates exemplary operations for managing remote browser data in a remote browser host according to an embodiment. 
         FIG.  3    illustrates a block diagram for an exemplary data processing system  300  that may be used in some embodiments. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     A remote browsing session is established between a local browser executing on a client device and a remote browser executing on a server. During a remote browsing session, remote browser data is generated and managed by the remote browser. The remote browser data may include cookie data, browser extension data (e.g., the login state of the extension, setting(s) of the extension, what extension(s) are installed, etc.), data to be stored in a local database of the client device (e.g., local storage, session storage, synched storage, IndexedDB), settings (e.g., appearance settings, default search engine, startup page, etc.), browser history, autofill history, theme preferences for a website (e.g., dark or light)), bookmarks, passwords, a listing of open tabs, payment information, addresses, and/or phone numbers. Periodically, the remote browser data is encrypted and transmitted from the remote browser to the local browser executing on the client device. The local browser does not have access to a key for decrypting the remote browser data. The local browser persists the data on the client device (e.g., in local storage, through IndexedDB, etc.). The remote browser may remove the remote browser data for the local browser (both encrypted and decrypted) when the remote browsing session ends. When a new remote browsing session is established or shortly thereafter, the local browser causes the stored encrypted remote browser data to be transmitted to the remote browser. The remote browser decrypts the encrypted remote browser data and configures the remote browser with the decrypted data (e.g., installs the cookies, sets the bookmarks, etc.). 
     Even though the remote browsing session is temporary, and the remote browser may not store any data about previous remote browsing sessions, browser data that is conventionally stored at a local client device for a conventional browser can be used by remote browsers in subsequent remote browsing sessions. Also, the browser data is encrypted thereby protecting the browser data from unintentional or malicious leaks. 
       FIG.  1    illustrates an exemplary remote browsing environment where remote browser data is stored in an encrypted format at a client device that can be decrypted by a server running a remote browser host. The system includes the client device  110  that executes a local browser  115 . The client device  110  is a computing device (e.g., laptop, desktop, smartphone, mobile phone, tablet, gaming system, wearable device, Internet-of-Things (IoT) device, set-top box, etc.) that can access network resources through the local browser  115  (e.g., a browser, a mobile application, or other network application). Although the term “browser” is used, the local browser  115  may be any application that can access network resources. 
     The local browser  115  may be a dedicated application for remote browsing. Alternatively, the local browser  115  may be a standard application with the capability of executing a remote browsing session. In either case, the local browser  115  establishes a remote browsing session  130  with the remote browser server  120 . For instance, a remote browser host  125  is generated (e.g., a containerized instanced) for the remote browsing session  130  and a remote browser client is created within the local browser  115 . During the remote browsing session  130 , input received by the remote browser client  117  such as browsing to websites, keystrokes, mouse commands, scroll commands, and other cursor and input events are sent to the remote browser host  125  for further processing. In effect, the remote browser client  117  on the local browser  115  controls the remote browser host  125 . The remote browser host  125  receives and transmits internet traffic to web applications  140  (e.g., websites or other web applications) on behalf of the remote browser client  117 . The remote browser host  125  can perform actions like a normal browser such as downloading web pages, uploading data, applying style sheet definitions, executing client-side scripts (e.g., JavaScript), etc. The remote browser host  125  can transmit the changes to the remote browser client  117  for display. Thus, the execution actions of the web applications are performed at the remote browser host  125  thereby minimizing vulnerabilities caused by downloading web pages with malicious content, execution of client-side scripts with malicious content, or applying stylesheet definitions. Any malicious tinkering with the executable code in the remote browser host is restricted to the particular isolation environment. Further, when the remote browser client  117  exits, the isolation environment (e.g., the container) is removed so that any malware is not perpetuated by the remote browser host  125 . 
     Remote browser data is generated and/or updated during the remote browsing session  130 . Thus, the remote browser data is related to the remote browsing session. For example, remote browser data may include cookies that are set during the remote browsing session  130  (e.g., by the web applications  140 ). As another example, remote browser data related to browser extensions may be generated and/or updated during the remote browsing session (e.g., whether a session is logged in, setting(s) of a browser extension, what extension(s) are installed). As other examples, remote browser data may include data to be stored in a local database of the client device  110  (e.g., local storage, session storage, synched storage, IndexedDB); settings (e.g., appearance settings, default search engine, startup page, etc.); browser history; autofill history; theme preferences for a website (e.g., dark or light)); bookmarks; passwords; a listing of open tabs; payment information; addresses; and phone numbers. 
     While the remote browsing session  130  is active, the remote browser host  125  manages the remote browser data using the remote browser data manager  127 . For instance, the remote browser data manager  127  may configure the remote browser host  125  with the settings and/or preferences defined in the remote browser data. As another example, the remote browser data manager  127  may manage encrypting the remote browser data and communicating the encrypted remote browser data to the remote browser client  117 . In an embodiment, the remote browser data is removed from the remote browser host  125  when the remote browser host  125  exits (e.g., when the remote browsing session  130  ends). 
     The remote browser data is encrypted and sent to the remote browser client  117  during the remote browsing session  130 . For instance, the remote browser data manager  127  of the remote browser host  125  may encrypt the remote browser data and periodically transmit at least portions of the remote browser data to the remote browser client  117 . The remote browser data may be encrypted with a key that is not available to the client device  110 , the local browser  115 , or to the remote browser client  117 . That is, the encrypted remote browser data cannot be decrypted locally by the remote browser client  117 , the local browser  115 , or the client device  110 . Instead, the remote browser data is encrypted such that the remote browser host  125  can decrypt the encrypted remote browser data or otherwise have access to the decrypted remote browser data. In an embodiment, the remote browser client  117  does not receive unencrypted remote browser data from the remote browser host  125 . 
     The remote browser client  117  stores the encrypted remote browser data  150  in local client storage  145 . The local client storage  145  may be local storage, IndexedDB, or other client storage available to the remote browser client  117 . The encrypted remote browser data  150  may be an opaque binary blob, which may be serialized and possibly compressed. In an embodiment, the remote browser client  117  transmits the encrypted remote browser data  150  to the remote browser host  125  as part of the establishment of the remote browsing session  130  or shortly thereafter. For instance, the remote browser client  117  may transmit the encrypted remote browser data  150  to the remote browser server  120  using an HTTP/S POST request. As another example, the remote browser client  117  may transmit the encrypted remote browser using an WebRTC connection between the remote browser client  117  and the remote browser server  120  or other secure connection. 
     The remote browser data manager  127  decrypts the encrypted remote browser data  150  or otherwise receives the decrypted remote browser data. The remote browser data manager  127  may use the decrypted remote browser data to configure the browsing session for the client as appropriate. 
     In an embodiment, the remote browser server  120  is one of multiple remote browser servers to which the client device  110  can connect and establish a remote browsing session with. For instance, there may be multiple remote browser servers that are part of multiple data centers to which the client device  110  can connect. The remote browser servers may be geographically distributed (e.g., throughout the world). The remote browser servers may be anycasted to the same IP address. The client device  110  may connect to a particular remote browser server due to the client device being closest to that remote browser server (out of the remote browser servers) in terms of routing protocol configuration (e.g., Border Gateway Protocol (BGP) configuration) according to an anycast implementation as determined by the network infrastructure (e.g., router(s), switch(es), and/or other network equipment). In such an embodiment, even though the client device can establish different remote browsing sessions with different remote browser servers (which may be geographically separate), the remote browser data may be communicated from the client device to the remote browser host dynamically thereby providing a consistent experience. 
     Although embodiments have described sending encrypted remote browser data to the remote browser client, in other embodiments the remote browser data (or at least a portion of the remote browser data) is sent unencrypted to the remote browser client. In such other embodiments, when a new remote browsing session is established or shortly thereafter, the remote browser client causes the stored remote browser data to be transmitted to the remote browser in a like way as described with reference to the stored encrypted remote browser data. The remote browser would decrypt any encrypted remote browser data (if any) and configure the remote browser with the data like previously described (e.g., installs the cookies, sets the bookmarks, etc.). 
       FIG.  2    is a flow diagram that illustrates exemplary operations for managing remote browser data in a remote browser host according to an embodiment. The operations of  FIG.  2    will be described with reference to  FIG.  1   . The operations of  FIG.  2   , however, can be performed by embodiments different than that of  FIG.  1   , and the embodiments shown in  FIG.  1    can perform different operations than that of  FIG.  2   . 
     At operation  210 , the remote browser server  120  begins initiating a remote browsing session with the local browser  115 . For instance, the remote browser server  120  may receive a request (e.g., an HTTP/HTTPS request) that originated from the local browser  115  that triggers a remote browsing session. For instance, although not illustrated in  FIG.  1   , the local browser  115  may be configured such that all internet traffic is received by a gateway device that may be capable of examining the traffic. If the received traffic meets a policy, the traffic may be directed to the remote browser server  120  for establishing a remote browsing session with the local browser  115 . There may be one or more policies. The one or more policies may include one or more the following; a policy that defines domain(s) and/or IP address(es) for which a remote browsing session is to apply; a policy that defines domain(s) and/or IP address(es) for which a remote browsing session is not to apply (and therefore all other domain(s) and/or IP address(es) the remote browsing session will not apply); a policy that indicates one or more categories of destinations for which the remote browsing session is to apply and/or not apply (e.g., malware, security threats, games, adult themes, social networks, video streaming, etc.). Alternatively, any received traffic may initiate a remote browsing session. 
     In an embodiment, as part of establishing a remote browsing session with the local browser  115 , the remote browser client  117  is served to the local browser  115 . For example, the remote browser client  117  may be a web-based remoting client that connects to the remote browser host  125 . The remote browser host  125  handles the internet traffic including downloading and executing all foreign webpage code (e.g., HTML, CSS, JavaScript, etc.). The remote browser host  125  may intercept draw commands and transmit the vector draw commands to the remote browser client  117  for rendering. The remote browser client  117  may be implemented using a client-side script (e.g., a JavaScript file), a WebAssembly library or other binary-code format library for handling draw commands, and an HTML file. The client-side script may interface with an application programming interface (API) of the local browser  115  to cause the local browser  115  to load and hook the rendering file into the event loop, to intercept events from an event loop to listen for events associated with the local browser and invoke the draw handling code in the rendering file (for example, using callbacks from the browser&#39;s internal event loop), and is configured to initiate a secure connection (e.g., via WebRTC or other secure connection) from the remote browser client  117  to the remote browser host  125 . The binary-code format library (e.g., the WebAssembly file) includes the draw handling code in a compiled instance of a graphics library that is typically configured to cause draw commands to be rendered in the same manner on the remote browser client  117  as on the remote browser host  125  to ensure consistent rendering. The HTML file is typically configured to cause the remote browser client  117  to generate a drawing canvas, which if it incorporates HTMLS, may interface to one or more GPUs. The cookie typically includes connection information to facilitate persistent remote browsing sessions with intermittent terminations of the connection (for example, shutting down the client device or closing the local browser  115  and reconnecting to the same remote browsing session). 
     As part of establishing the remote browsing session, the remote browser server  120  may receive encrypted remote browser data from the remote browser client  117 . When decrypted, the remote browser data can be used to customize the remote browser host  125  for the particular remote browser client  117 . The remote browser server  120  may also receive an identifier of a key that can be used for decrypting the encrypted remote browser data (e.g., a thumbprint for the decryption key). At operation  215 , the remote browser server  120  determines whether encrypted remote browser data has been received from the local browser  115 . The encrypted remote browser data may be received as an HTTP/S POST request or through a secure connection such as a WebRTC connection between the local browser  115  and the remote browser server  120 . If no encrypted remote browser data is received, then flow moves to operation  220  where the remote browser server  120  initiates the remote browsing session  130  with no remote browser data. If encrypted remote browser data is received, then flow moves to operation  225 . 
     At operation  225 , the remote browser server  120  attempts to decrypt the received encrypted remote browser data. For instance, the remote browser data manager  127  attempts to decrypt the received encrypted remote browser data. In an embodiment, the remote browser server  120  receives from the local browser  115  an identifier for the decryption key that can decrypt the encrypted remote browser data. In such an embodiment, the remote browser server  120  uses the identifier to access the decryption key and attempts to decrypt the data. Next at operation  230 , a determination is made whether the decryption is successful. If it is not successful, then operation  220  is performed where the remote browser server  120  initiates the remote browsing session  130  with no remote browser data. If the decryption is successful, then operation  235  is performed. 
     At operation  235 , the remote browser data manager  127  configures the remote browser host  125  with the decrypted remote browser data  129 . If the remote browser data includes cookies, the remote browser data manager  127  installs the cookies into a cookie store for the remote browser host  125 . The remote browser host  125  then uses the cookies for the session as if it is a regular local browser (e.g., transmits cookies to web servers as appropriate). 
     If the remote browser data includes extension data (e.g., whether an account corresponding to the extension is logged in, whether an extension is to be installed), the remote browser data manager  127  may configure that extension accordingly. As another example, if the remote browser data includes data that identifies the extensions that are installed, the remote browser data manager  127  may install those extensions and/or enable those extensions for the remote browser host  125 . For instance, the remote browser host  125  may allow the user to interact with that extension (via the remote browser client  117 ) if that extension is configured for interaction. If the extension modifies pages (e.g., is an ad-blocker), the extension modifies the pages at the remote browser host  125  on behalf of the remote browser client  117 . The modified page would then be subject to be transmitted to the remote browser client  117  through the remote browsing session  130 . 
     If the remote browser data includes settings for the remote browser host such as appearance settings, default search engine, startup page, etc., the remote browser data manager  127  configures the remote browser host  125  with those settings. As another example, if the remote browser data includes browser history data, the remote browser data manager  127  may configure the remote browser host  125  with the browser history data. Likewise, if the remote browser data includes autofill history, the remote browser data manager  127  may configure the remote browser host  125  with the autofill history. If the remote browser data includes passwords, the remote browser data manager  127  may configure the remote browser host  125  with the saved password information. If the remote browser data includes a listing of open or saved tabs, the remote browser data manager  127  may cause the remote browser host  125  to download the content of the saved tabs. 
     After the remote browser host  125  is configured, the remote browsing session  130  is initiated. During the remote browsing session  130 , input received by the remote browser client  117  such as browsing to websites, keystrokes, mouse commands, scroll commands, and other cursor and input events are sent to the remote browser host  125  for further processing. In effect, the remote browser client  117  on the local browser  115  controls the remote browser host  125 . The remote browser host  125  receives and transmits internet traffic to web applications  140  (e.g., websites or other web applications) on behalf of the remote browser client  117 . The remote browser host  125  can perform actions like a normal browser such as downloading web pages, uploading data, applying style sheet definitions, executing client-side scripts (e.g., JavaScript), etc. The remote browser host  125  can transmit the changes to the remote browser client  117  for display. 
     Remote browser data is generated and/or updated during the remote browsing session  130 . For example, remote browser data may include cookies that are set during the remote browsing session  130  (e.g., by the web applications  140 ). As another example, remote browser data related to browser extensions may be generated and/or updated during the remote browsing session (e.g., whether a session is logged in, setting(s) of a browser extension, what extension(s) are installed, etc). As a specific example, an extension store may be associated with the remote browsing session that allows users to select and install certain extensions for remote browsing. As other examples, the user may add or modify a bookmark, may add or modify a saved password, generate browser history, generate autofill history, etc. 
     With reference back to  FIG.  2   , at operation  240 , the remote browser host  125  receives remote browser data during the remote browsing session  130 . The remote browser data manager  127  manages the remote browser data while the remote browsing session  130  exists. For instance, the remote browser data manager  127  is authoritative for the remote browser data during the remote browsing session  130 . As an example, the remote browser client  117  does not transmit stored cookies to the remote browser host  125  during the remote browsing session  130 . 
     Next, at operation  245 , periodically the remote browser host  125  encrypts and transmits updates to the remote browser data to the remote browser client  117 . The transmission may be over a WebRTC connection between the remote browser client  117  and the remote browser host  125 . The encrypted remote browser data may be an opaque binary blob, which may be serialized and possibly compressed. In an embodiment, a separate encryption key is generated for each separate local browser. An X509 certificate may be used for public/private key generation, revocation of expired or compromised keys, a way to fingerprint or identify each key, and allows for a chain of trust to revoke pools of certificate at once. As an example, if a cookie is set during the remote browsing session  130 , the remote browser data manager  127  may encrypt the cookie and send the update to the remote browser client  117 . In an embodiment, regardless of the site being accessed, the remote browser client  117  includes the iframe  142  of the same domain (e.g., a domain of the remote browsing service) and the encrypted remote browser data is sent to the iframe  142 . In an embodiment, the remote browser data manager  127  encrypts and transmits an update to the remote browser data on each update. For instance, if a cookie is updated or set, the remote browser data manager  127  may encrypt the cookie data and transmit the encrypted remote browser data to the remote browser client  117 . In another embodiment, the remote browser data manager  127  batches updates to the remote browser data on a regular interval (e.g., 100 ms) and transmits the data only if there are changes. For instance, if there are  10  cookies that are updated or set within the interval, the remote browser data manager  127  may encrypt the remote browser data for those  10  cookies and transmit the update to the remote browser client  117  at the end of the interval. In a batch embodiment, the remote browser data manager  127  may encrypt each update separately or encrypt the entire remote browser data update. 
     The remote browser client  117  receives the encrypted remote browser data from the remote browser host  125  and stores the encrypted remote browser data  150  in the local client storage  145 . The local client storage  145  may be local storage, IndexedDB, or other client storage available to the remote browser client  117 . The remote browser client  117  does not have access to a key to decrypt the encrypted remote browser data  150 . 
     In an embodiment, the remote browser data manager  127  periodically collapses updates to the remote browser data and sends the entire encrypted remote browser data to the remote browser client  117 . The collapsing of the updates removes redundant data (e.g., outdated values of a cookie). The trigger to collapse the updates may be based on the size of the redundant data. For instance, if the size of the redundant data meets a threshold (e.g., 50%) of the total data, the remote browser data manager  127  may collapse the updates. Thus, at operation  250 , the remote browser data manager  127  periodically collapses updates to the remote browser data and sends all the encrypted remote browser data to the remote browser client  117 . The remote browser client  117  receives the entire encrypted remote browser data and removes any previous update from the local client storage  145 . 
     When the remote browsing session  130  ends, (e.g., the remote browser client  117  is closed), the decrypted remote browser data  129  is removed in an embodiment. 
     In an embodiment, the remote browser session is implemented by the remote browser host transmitting draw commands to the remote browser client to execute as previously described. In another embodiment, the remote browser session is implemented through pixel pushing as previously described. In such an embodiment, the remote browser host transmits a series of images to the local browser as possibly compressed pixels or videos and also transmits the encrypted remote browser data. The page that is to include the rendered pixels or video may also include an iframe for receiving the encrypted remote browser data. In another embodiment, the remote browser session is implemented using DOM mirroring. In such an embodiment, the remote browser host transmits the cleaned up web page to the local browser and also transmits the encrypted remote browser data. 
       FIG.  3    illustrates a block diagram for an exemplary data processing system  300  that may be used in some embodiments. One or more such data processing systems  300  may be used to implement the embodiments and operations described with respect to the remote browser server, client device, or other electronic devices. The data processing system  300  is an electronic device that stores and transmits (internally and/or with other electronic devices over a network) code (which is composed of software instructions and which is sometimes referred to as computer program code or a computer program) and/or data using machine-readable media (also called computer-readable media), such as machine-readable storage media  310  (e.g., magnetic disks, optical disks, read only memory (ROM), flash memory devices, phase change memory) and machine-readable transmission media (also called a carrier) (e.g., electrical, optical, radio, acoustical or other form of propagated signals—such as carrier waves, infrared signals), which is coupled to the processing system  320  (e.g., one or more processors and connected system components such as multiple connected chips). For example, the depicted machine-readable storage media  310  may store program code  330  that, when executed by the processor(s)  320 , causes the data processing system  300  to perform any of the operations described herein. 
     The data processing system  300  also includes one or more network interfaces  340  (e.g., a wired and/or wireless interfaces) that allows the data processing system  300  to transmit data and receive data from other computing devices, typically across one or more networks (e.g., Local Area Networks (LANs), the Internet, etc.). The data processing system  300  may also include one or more input or output (“I/O”) components  350  such as a mouse, keypad, keyboard, a touch panel or a multi-touch input panel, camera, frame grabber, optical scanner, an audio input/output subsystem (which may include a microphone and/or a speaker), other known I/O devices or a combination of such I/O devices. Additional components, not shown, may also be part of the system  300 , and, in certain embodiments, fewer components than that shown in One or more buses may be used to interconnect the various components shown in  FIG.  3   . 
     The techniques shown in the figures can be implemented using code and data stored and executed on one or more electronic devices (e.g., a remote browser server, a client device, an origin server). Such electronic devices store and communicate (internally and/or with other electronic devices over a network) code and data using computer-readable media, such as non-transitory computer-readable storage media (e.g., magnetic disks; optical disks; random access memory; read only memory; flash memory devices; phase-change memory) and transitory computer-readable communication media (e.g., electrical, optical, acoustical or other form of propagated signals—such as carrier waves, infrared signals, digital signals). In addition, such electronic devices typically include a set of one or more processors coupled to one or more other components, such as one or more storage devices (non-transitory machine-readable storage media), user input/output devices (e.g., a keyboard, a touchscreen, and/or a display), and network connections. The coupling of the set of processors and other components is typically through one or more busses and bridges (also termed as bus controllers). Thus, the storage device of a given electronic device typically stores code and/or data for execution on the set of one or more processors of that electronic device. Of course, one or more parts of an embodiment of the invention may be implemented using different combinations of software, firmware, and/or hardware. 
     In the preceding description, numerous specific details are set forth in order to provide a more thorough understanding of the present embodiments. It will be appreciated, however, by one skilled in the art that the invention may be practiced without such specific details. In other instances, control structures, gate level circuits and full software instruction sequences have not been shown in detail in order not to obscure understanding of the embodiments. Those of ordinary skill in the art, with the included descriptions, will be able to implement appropriate functionality without undue experimentation. 
     References in the specification to “one embodiment,” “an embodiment,” “an example embodiment,” etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described. 
     Bracketed text and blocks with dashed borders (e.g., large dashes, small dashes, dot-dash, and dots) may be used herein to illustrate optional operations that add additional features to embodiments of the invention. However, such notation should not be taken to mean that these are the only options or optional operations, and/or that blocks with solid borders are not optional in certain embodiments of the invention. 
     While the flow diagrams in the figures show a particular order of operations performed by certain embodiments of the invention, it should be understood that such order is exemplary (e.g., alternative embodiments may perform the operations in a different order, combine certain operations, overlap certain operations, etc.). 
     While the invention has been described in terms of several embodiments, those skilled in the art will recognize that the invention is not limited to the embodiments described, can be practiced with modification and alteration within the spirit and scope of the appended claims. The description is thus to be regarded as illustrative instead of limiting.