Abstract:
A method receives authentication credentials for a user from a client device and receives a request from the user for content stored on a remote storage system. A portion of the content is encrypted and a corresponding decryption key is available only at the computer system. The remaining portion of the content is unencrypted. The method retrieves the content from the remote storage system and uses the received credentials to determine whether the user is authorized to view the encrypted portion. When the user is not authorized, the method forms alternative content by replacing the encrypted portion with a substitute element and transmits the alternative content to the client device. When the user is authorized, the method decrypts the encrypted portion of the content using the decryption key, and combines the decrypted portion with the unencrypted portion to form updated content. The updated content is transmitted to the client device.

Description:
RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 14/326,151, filed Jul. 8, 2014, now U.S. Pat. No. 9,298,939, entitled “Privacy-Protective Data Transfer,” which is a continuation of U.S. patent application Ser. No. 13/403,836, filed Feb. 23, 2012, now U.S. Pat. No. 8,776,249, entitled “Privacy-Protective Data Transfer,” which claims priority to U.S. Provisional Patent Application No. 61/474,226, entitled “Privacy-Protective Data Transfer and Storage,” filed Apr. 11, 2011, all of which are incorporated by reference herein in their entirety. 
     This application is related to U.S. patent application Ser. No. 13/403,833, now U.S. Pat. No. 8,782,392, entitled “Privacy-Protective Data Transfer and Storage,” filed Feb. 23, 2012, which is incorporated by reference herein in its entirety. 
    
    
     TECHNICAL FIELD 
     The disclosed embodiments relate generally to data management. More particularly, the disclosed embodiments relate to data transfer and storage that protects privacy interests in the data. 
     BACKGROUND 
     Data files can be stored remotely at remote third-party sites (or company servers) rather than locally. Benefits of remote storage include data backup and redundancy, and remote access to the particular data files by one or more users. A data file to be stored remotely may contain private or confidential content, and the private content needs to be protected from attacks on the third-party site from without or within. To protect the private content, the data file may be transmitted in secure data transmissions between local systems and the third-party site, and the data file may be encrypted and stored in the encrypted form. However, in such an environment the encryption of the data file is typically handled by the third-party site, and the decryption keys are held by the third-party site. Thus, the privacy of the data file is still vulnerable to compromise by malicious operators of the third-party site or an external attack on the third-party site. Alternatively, each user of a data file with private content can encrypt the file prior to transmitting it to the third party site, but this requires each user to have the appropriate key or keys for encrypting the document each time it is transmitted to others and for decrypting the data file when it is accessed. This arrangement is inconvenient due to the need of multiple users to manage keys and also insecure due to the sharing of keys. 
     SUMMARY 
     According to some embodiments, a method is performed at a computer system having one or more processors and memory storing one or more programs executed by the one or more processors. The method includes generating a document, including marking one or more portions of the document as private, and sending the document to an intermediary system for transmission to a destination system, where prior to the document being transmitted to the destination system, the marked portions of the document are encrypted by the intermediary system using a key that is unavailable to the destination system. 
     According to some embodiments, a client system includes one or more processing units, and memory storing one or more programs be executed by the one or more processing units. The one or more programs include instructions for generating a document, including marking one or more portions of the document as private, and sending the document to an intermediary system for transmission to a destination system, where prior to the document being transmitted to the destination system, the marked portions of the document are encrypted by the intermediary system using a key that is unavailable to the destination system. 
     According to some embodiments, a non-transitory computer readable storage medium stores one or more programs configured for execution by a computer. The one or more programs include instructions for generating a document, including marking one or more portions of the document as private, and sending the document to an intermediary system for transmission to a destination system, where prior to the document being transmitted to the destination system, the marked portions of the document are encrypted by the intermediary system using a key that is unavailable to the destination system. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram illustrating a privacy-protective data transfer and storage system, according to some embodiments. 
         FIG. 2  is a block diagram illustrating a distributed computer system, according to some embodiments. 
         FIG. 3  is a block diagram illustrating a client system, according to some embodiments. 
         FIG. 4  is block diagram illustrating a server system, according to some embodiments. 
         FIG. 5  is a block diagram illustrating a privacy proxy system, according to some embodiments. 
         FIGS. 6A-6B  are screenshot diagrams illustrating a displayed document with private content, according to some embodiments. 
         FIGS. 7A-7B  are flow diagrams illustrating a process for transmitting a document to a destination system for storage, according to some embodiments. 
         FIGS. 8A-8B  are flow diagrams illustrating a process for transmitting a document, according to some embodiments. 
         FIG. 9  is a flow diagram illustrating a process for indexing a document for searching, according to some embodiments. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to one of ordinary skill in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, components, circuits, and networks have not been described in detail so as not to unnecessarily obscure aspects of the embodiments. 
     It will also be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first contact could be termed a second contact, and, similarly, a second contact could be termed a first contact, without departing from the scope of the present invention. The first contact and the second contact are both contacts, but they are not the same contact. 
     The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the description of the invention and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will also be understood that the term “and/or” as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
     As used herein, the term “if” may be construed to mean “when” or “upon” or “in response to determining” or “in response to detecting,” depending on the context. Similarly, the phrase “if it is determined” or “if (a stated condition or event) is detected” may be construed to mean “upon determining” or “in response to determining” or “upon detecting (the stated condition or event)” or “in response to detecting (the stated condition or event),” depending on the context. 
       FIG. 1  is a block diagram illustrating a privacy-protective data transfer and storage system  100 , according to some embodiments. A data file  111  is located at a client system  102 . In some embodiments, the data file  111  is an electronic document of any suitable type, such as a plain text document, MICROSOFT WORD document, Portable Document Format (PDF) document, MICROSOFT EXCEL spreadsheet, MICROSOFT POWERPOINT presentation, email message, and so forth. In some other embodiments, the data file  111  is an electronic document or an image or graphics file, video file, or audio file. The contents of the data file  111  may include text, graphics, images, audio, video, or any combination thereof. For convenience and ease of understanding, hereinafter a data file may also be referred to as a document. 
     The client system  102  (sometimes called a “client computer,” or “client device” or “client”) may be any computer or device able to process a data file or document (e.g., document  111 ) and transmit (or “send”) and receive data files or documents to other systems. Examples of client systems  102  include, without limitation, desktop computers, laptop computers, tablet computers, mobile devices such as mobile phones, personal digital assistants, set-top boxes, or any combination of the above. 
     Among the contents of a document  111  are one or more portions (or the entirety) of the contents that are demarcated or otherwise marked or designated as private or confidential, or more generally, demarcated or otherwise marked or designated as requiring a more restrictive level of security and/or privacy (hereinafter collectively referred to as “marked as private”). For example, a document  111  may have one or more portions of its contents (e.g., certain text portions, certain graphics or images, etc.) that includes sensitive information or for which viewing and/or editing is restricted to a more limited set of users than the remainder of the contents of the document  111 . The portions for which more restrictive viewing or editing rights are required may be marked as private. 
     A document  111  is generated at a client system  102  by an application  104 . A user of client system  102  may use the application  104  to create a new document and to demarcate or otherwise mark or designate one or more discrete portions of the contents of the created document as private (hereinafter collectively referred to as “mark as private”). A user may also use the application  104  to mark discrete portions of the contents of a document created outside of the application  104  as private, and the application  104  generates a version of the document that has the private portions marked. Whether a document  111  was initially created within the application  104  or without, a document  111  that is modified from within the application  104  may include one or more portions that are marked as private. In some embodiments, the portions that are marked as private are marked as such in accordance with user input (e.g., a user selecting particular text, images, and/or other content in a document and then activating a command in the application  104  to mark the selected portion(s) as private). 
     The document  111  is sent to a privacy proxy system  106  in a data transmission  110 . In some embodiments, the data transmission  110  is an encrypted or secure transmission. For example, data transmission  110  may be sent in accordance with the Secure Sockets Layer (SSL) or the Transport Layer Security (TLS) protocol. At the privacy proxy system  104 , when the encrypted data transmission  110  is decrypted to access the document  111 , the marked portions in the document  111  are unencrypted. In some other embodiments, the data transmission  110  is an unencrypted transmission; the marked portions in the document  111  are unencrypted during the transmission and at receipt by the privacy proxy system  106 . 
     The privacy proxy system  106  may be any computer or device (or a system of multiple computers/devices, e.g., multiple servers) able to process a data file or document and transmit (or “send”) and receive data files or documents to and from other systems. Examples of a privacy proxy system  106  include, without limitation, a server computer system. In some embodiments, the privacy proxy system  106  is implemented as a web proxy server system, with additional functionality related to the processing of documents with portions marked as private (e.g., document content encryption and decryption, encryption key and decryption key management, etc.). 
     After receiving the data transmission  110  and extracting the document  111  from the data transmission  110 , the privacy proxy system  106  encrypts the marked portions of the document  111 . The unmarked portions of the document  111  remain unencrypted. Thus, the result of the encryption is a data file or document  113  that includes the marked portions, which are encrypted, and the unmarked portions, which remain unencrypted, of the document  111 . For ease of understanding, data file or document  113  may be referred to as a partially encrypted data file or document  113 . In some embodiments, the privacy proxy system  106  encrypts the marked portions of the document  111  using an appropriate key from one or more encryption and/or decryption keys  108  in accordance with any suitable key-based encryption algorithm. 
     The partially encrypted document  113  is sent, through network(s)  112 , in a data transmission  116  to a server system  114 . In some embodiments, the data transmission  116  is an encrypted or otherwise secure transmission. For example, data transmission  116  may be sent using the Secure Sockets Layer (SSL) or the Transport Layer Security (TLS) protocol. 
     In some embodiments, a user may be notified or choose to send documents to the server system  114  through the privacy proxy system  106 . In some embodiments, when the privacy proxy system  106  is bypassed, the sent documents are not encrypted by the privacy proxy system  106  as described above, and alternative security and privacy measures may be used in place of the privacy proxy system  106  (e.g., encryption of the document at the client). 
     Server system  114  may be any computer or device (or a system of multiple computers/devices) able to process a data file or document and transmit (or “send”) and receive data files or documents to other systems. Examples of server system  116  include, without limitation, a server computer system. 
     The server system  114  receives the data transmission  116  and extracts the partially encrypted document  113  from the data transmission  116 . The server system  114  is not provided the appropriate key(s)  108  for decrypting the encrypted marked portions of the partially encrypted document  113 . Thus, the server system  114  does not decrypt the encrypted marked portions of the partially encrypted document  113 . Whatever processing server system  114  performs on the partially encrypted document  113 , the processing is performed while the marked portions remain encrypted. The server system  114  stores the encrypted document  113  in memory or some storage medium (e.g., non-volatile storage, such as a hard disk drive). 
     In some embodiments, the server system  114  indexes the encrypted document  113  (e.g., for searching). The partially encrypted document  113  is indexed based on the unencrypted unmarked portions, as the marked portions remain encrypted. 
     The server system  114  may send the partially encrypted document  113  to a client system  102  (e.g., in response to a request from the client system  102  for the partially encrypted document  113 , with the request from the client system  102  corresponding to a request made by a user for the original document  111  corresponding to the partially encrypted document  113 ) through the privacy proxy system  106 . The server system  114  sends the partially encrypted document  113 , through network(s)  112 , in a data transmission  118 . The data transmission  118  is sent to the privacy proxy system  106 . In some embodiments, the data transmission  118  is an encrypted or otherwise secure transmission. For example, data transmission  118  may be sent using the Secure Sockets Layer (SSL) or the Transport Layer Security (TLS) protocol. 
     The privacy proxy system  106  receives the data transmission  118  and extracts the partially encrypted document  113  from the data transmission  118 . Using the encryption/decryption key(s)  108 , the privacy proxy system  106  decrypts the encrypted marked portions of encrypted document  113  to reconstitute the document  111 . The document  111  is sent in a data transmission  120  to the client system  102 . In some embodiments, the data transmission  120  is an encrypted or otherwise secure transmission. For example, data transmission  120  may be sent using the Secure Sockets Layer (SSL) or the Transport Layer Security (TLS) protocol. 
     The client system  102  receives the data transmission  120  and extracts the document  111  from the data transmission  120 . The document  111  may be displayed in the application  104 . 
       FIG. 2  is a block diagram illustrating a distributed computer system  200 , according to some embodiments. In some embodiments, the distributed computer system  200  is an implementation of the privacy-protective data transfer and storage system  100  shown in  FIG. 1 . The distributed system  200  includes multiple client systems  102 - 1 ,  102 - 2 , thru  102 -M, and privacy proxy system  106 . In some embodiments, the clients  102  and the privacy proxy system  106  are components of a private (e.g., a corporate or enterprise) network environment  201 . The client systems  102  and the privacy proxy system  106  may be interconnected by one or more communication networks  204  (e.g., local area networks (LAN), virtual private networking (VPN), etc.) within the private network environment  201 . 
     The private network environment  201  may transmit data to server system  114 , which includes servers  114 - 1 ,  114 - 2 , thru  114 -N. The network environment  201  may be interconnected with the servers  114  through one or more network(s)  112 . 
     In some embodiments, a client system  102  (e.g., client  102 - 1 ) includes an application  104  configured to enable the user to mark portions of a document as private. For some applications  104 , the capability to enable the user to mark portions of a document as private is provided through the addition of a plug-in  202  to the application  104 . Alternatively, the application  104  may have native support for marking of portions of a document as private (e.g., the application was designed and programmed to support the feature from the start). 
     The privacy proxy system  106  includes the encryption/decryption key(s)  108  and a document encryption/decryption module or application  206 . The encryption/decryption module  206  uses the key(s)  108  to encrypt or decrypt marked portions in documents. In some embodiments, the privacy proxy system  106  is a web proxy server system in the network environment  201  (e.g., a content filtering web proxy for a corporate network). In some embodiments, the key(s)  108  are kept within the private network environment  201  and not provided to entities outside of the private network environment  201 , such as server system  114 . By keeping the key(s)  108  within the private network environment  201 , the privacy of the marked portions of a document stored at the server system  114  is less likely to be compromised by operators of the server system  114  or by attacks on the server system  114 . In some embodiments, the privacy proxy system  106  also includes a key management module (not shown) for automatically, and/or with administrator intervention, managing encryption and decryption keys. 
     In some embodiments, a document  111  and the corresponding partially encrypted document  113  stored at the server system  114  may be accessible to multiple users in the private network environment  201  but only a subset of those multiple users have rights to read and/or edit the marked portions. When the partially encrypted document  113  is transmitted from the server system  114  to the network environment  201 , how the partially encrypted document  113  is processed by the privacy proxy system  106  and presented to a user varies with which user is requesting the corresponding original document  111 . 
     For example, in some embodiments, if a user with full rights to the entire document makes a request for the document  111  at a client  102 , the privacy proxy system  106 , after receiving the partially encrypted document  113 , decrypts the marked portions of the partially encrypted document  113  (i.e., reconstituting the document  111 ) and sends the document  111  to the client  102 . The application  104 , recognizing that the user has full rights to the document (e.g., by comparing the user&#39;s login credentials at the client  102  or other authentication credentials to the document&#39;s rights metadata), displays the entire document in the clear to the user and enables editing by the user. If the user does not have reading rights to the marked portions, the privacy proxy system  106  may omit the decryption of the partially encrypted document  113  and send the partially encrypted document  113  to the client  102 . The application  104  displays the unmarked portions of the partially encrypted document  113  in the clear but the encrypted marked portions are replaced with other displayed content, such as a message or symbol indicating that the marked portions of the document are encrypted. Alternatively, the privacy proxy system  106  decrypts the partially encrypted document  113  but the application  104  displays the unmarked portions in the clear and displays other content in place of the decrypted marked portions, such as a message or symbol indicating that the marked portions of the document are private. 
     In some embodiments, the privacy proxy system  106  decrypts the partially encrypted document  113  regardless of whether the requesting user has rights to the marked portions, and the application  104  is responsible for presenting the reconstituted document  111  in accordance with the rights that the requesting user has. In some embodiments, the privacy proxy system  106  decrypts the partially encrypted document  113  in accordance with the requesting user&#39;s rights level; the partially encrypted document is not decrypted for a user who does not have the rights to read the marked portions. Examples of how a marked portion of a document is presented to a user at a client  102  are further described below with reference to  FIGS. 6A and 6B . 
     In some other embodiments, the privacy proxy system  106  decrypts the partially encrypted document  113  if the proper decryption key is available at the privacy proxy system  106 , and does not decrypt the partially encrypted document  113  if the proper decryption key is not available, and the reconstituted document  111  may be presented to the user at the client  102  in a manner described below with reference to  FIGS. 6A-6B . Whether the proper decryption key is available at the privacy proxy system  106  or not is based on management of decryption keys by key management systems implemented for the private network environment  201  (e.g., at the privacy proxy system  106 ). 
     In some further embodiments, the decryption of the partially encrypted document  113  corresponding to the original document  111 , or not, based on availability of the proper decryption key described above is irrespective of rights or permissions associated with the original document  111  and is transparent to the user. In other words, management of document rights or permissions (e.g., read rights, edit rights, full rights, and the like) and encryption/decryption of documents are handled separately. For example, a user who has no read (or higher) rights to the document  111  cannot request it (e.g., attempts by the user to request the document  111  are denied), and the partially encrypted document  113  corresponding to the document  111  is not sent from the server  114  to the privacy proxy system  116 , whether or not the proper key is available. If the user does have read or higher rights to the document  111  and makes a request for it, the partially encrypted document  113  corresponding to the document  111  is sent from the server  114  to the privacy proxy system  116 , but whether the privacy proxy system  116  decrypts the partially encrypted document  113  depends on the availability of the proper key; the user&#39;s rights level is irrelevant to the decision to decrypt or not. 
       FIG. 3  is a block diagram illustrating a client system  102 , according to some embodiments. The client system  102  typically includes one or more processing units (CPU&#39;s)  302 , one or more network or other communications interfaces  308 , memory  304 , and one or more communication buses  310  for interconnecting these components. The client system  102  includes a user interface  306 . The user interface  306  includes a display device  303  and optionally includes an input means such as a keyboard, mouse, or other input buttons  305 . Alternatively or in addition the display device  303  includes a touch sensitive surface (not shown), in which case the display device  303  is a touch sensitive display. In client systems that have a touch sensitive display, a physical keyboard is optional (e.g., a soft keyboard may be displayed when keyboard entry is needed). Furthermore, some client systems use a microphone and voice recognition to supplement or replace the keyboard. 
     Memory  304  includes high-speed random access memory, such as DRAM, SRAM, DDR RAM or other random access solid state memory devices; and may include non-volatile memory, such as one or more magnetic disk storage devices, optical disk storage devices, flash memory devices, or other non-volatile solid state storage devices. Memory  304  may optionally include one or more storage devices remotely located from the CPU(s)  302 . Memory  304 , or alternately the non-volatile memory device(s) within memory  304 , comprises a non-transitory computer readable storage medium. In some embodiments, memory  304  or the computer readable storage medium of memory  304  stores the following programs, modules and data structures, or a subset thereof:
         an operating system  312  that includes procedures for handling various basic system services and for performing hardware dependent tasks;   a network communication module  314  that is used for connecting the client system  102  to other computers via the one or more communication network interfaces  308  (wired or wireless) and one or more communication networks, such as the Internet, other wide area networks, local area networks, metropolitan area networks, and so on;   an online security module  316  for implementing, in conjunction with network communication module  314 , secure data transmission and receipt (e.g., data transmission and receipt in accordance with the SSL or TLS protocol);   one or more client application modules  104  for creating, modifying, and presenting content (e.g., documents); for marking one or more portions, or the whole, of documents as private in accordance with user input; and presenting documents with marked portions differently in accordance with the requesting user&#39;s rights to the document and to the marked portions;   optionally, a privacy module  318 , within a client application  104 , for implementing functionality related to marking one or more portions, or the whole, of documents as private in accordance with user input; and presenting documents with marked portions differently in accordance with the requesting user&#39;s rights to the document and to the marked portions; and   content  320 , such as a document  320 - 1 , which includes one or more marked portions  322 , optionally one or more unmarked portions  324 , and rights metadata  326  that defines who has what rights (e.g., reading rights, editing rights) to the marked portions  322  and the unmarked portions  324 .       

     The client application modules  104  may be standalone applications stored in the memory  304  or online applications (e.g., web application  418 ,  FIG. 4 ) whose instructions are downloaded from a server system (e.g., server system  114 ) and executed in a web browser application at the client system  102 . 
     The rights metadata  326  for a document  320 - 1  may be set by the creator of the document  320 - 1  or another user with full rights to the document  320 - 1 . In some embodiments, the rights metadata  326  may be set or modified from within the application  104 . 
       FIG. 4  is a block diagram illustrating a server system  114 , according to some embodiments. The server system  114  typically includes one or more processing units (CPU&#39;s)  402 , one or more network or other communications interfaces  408 , memory  404 , and one or more communication buses  410  for interconnecting these components. 
     Memory  404  includes high-speed random access memory, such as DRAM, SRAM, DDR RAM or other random access solid state memory devices; and may include non-volatile memory, such as one or more magnetic disk storage devices, optical disk storage devices, flash memory devices, or other non-volatile solid state storage devices. Memory  404  may optionally include one or more storage devices remotely located from the CPU(s)  402 . Memory  404 , or alternately the non-volatile memory device(s) within memory  404 , comprises a non-transitory computer readable storage medium. In some embodiments, memory  404  or the computer readable storage medium of memory  404  stores the following programs, modules and data structures, or a subset thereof:
         an operating system  412  that includes procedures for handling various basic system services and for performing hardware dependent tasks;   a network communication module  414  that is used for connecting the server system  114  to other computers via the one or more communication network interfaces  408  (wired or wireless) and one or more communication networks, such as the Internet, other wide area networks, local area networks, metropolitan area networks, and so on;   an online security module  416  for implementing, in conjunction with network communication module  414 , secure data transmission and receipt (e.g., data transmission and receipt in accordance with the SSL or TLS protocol);   one or more web applications  418 , which may be sent to a client system (e.g., client system  102 ) for execution as an application  104  at the client system, for creating, modifying, and presenting content (e.g., documents); for marking one or more portions, or the whole, of documents as private in accordance with user input; and presenting documents with marked portions differently in accordance with the requesting user&#39;s rights to the document and to the marked portions;   optionally, a privacy module  420 , within a web application  418 , which may be sent to the client system (e.g., client system  102 ) for execution as privacy module  318  in conjunction with the execution of a web application  418 , for implementing functionality related to marking one or more portions, or the whole, of documents as private in accordance with user input; and presenting documents with marked portions differently in accordance with the requesting user&#39;s rights to the document and to the marked portions;   a search module  422  for indexing content  424  for searching and performing searches on content  424 ;   content  424  stored at the server system  114 , such as an encrypted document  424 - 1 , corresponding to document  320 - 1 , which includes one or more encrypted marked portions  426 , optionally one or more unmarked portions  324 , and rights metadata  326  that defines who has what rights (e.g., reading rights, editing rights) to the marked portions  322  and the unmarked portions  324 ; and   search index  428  that includes an index of content  424  for searching.       

       FIG. 5  is a block diagram illustrating a privacy proxy system  106 , according to some embodiments. The privacy proxy system  106  typically includes one or more processing units (CPU&#39;s)  502 , one or more network or other communications interfaces  508 , memory  504 , and one or more communication buses  410  for interconnecting these components. 
     Memory  504  includes high-speed random access memory, such as DRAM, SRAM, DDR RAM or other random access solid state memory devices; and may include non-volatile memory, such as one or more magnetic disk storage devices, optical disk storage devices, flash memory devices, or other non-volatile solid state storage devices. Memory  504  may optionally include one or more storage devices remotely located from the CPU(s)  502 . Memory  504 , or alternately the non-volatile memory device(s) within memory  504 , comprises a non-transitory computer readable storage medium. In some embodiments, memory  504  or the computer readable storage medium of memory  504  stores the following programs, modules and data structures, or a subset thereof:
         an operating system  512  that includes procedures for handling various basic system services and for performing hardware dependent tasks;   a network communication module  514  that is used for connecting the privacy proxy system  106  to other computers via the one or more communication network interfaces  508  (wired or wireless) and one or more communication networks, such as the Internet, other wide area networks, local area networks, metropolitan area networks, and so on;   an online security module  516  for implementing, in conjunction with network communication module  514 , secure data transmission and receipt (e.g., data transmission and receipt in accordance with the SSL or TLS protocol);   one or more encryption/decryption key(s)  108  used in the encryption or decryption of content, such as documents;   document encryption/decryption module  206  for, in conjunction with key(s)  108 , encrypting or decrypting documents; and   key management module  518  for management of key(s)  108  (e.g., creation or deletion of key(s)  108 , defining rights to access the key(s)  108 , etc.).       

     In some embodiments, the management of the key(s)  108  takes place at the privacy proxy system  106 . When the privacy proxy system  106  and the clients  102  are within a private network environment  201 , an administrator within the private network environment  201  may use the key management module  518  to manage the key(s)  108 . This keeps the key management within the private network environment, and the responsibility for managing the key(s)  108  remain with the owners of the documents to be encrypted. 
       FIGS. 3-5  are intended more as functional descriptions of the various features which may be present in a set of computer systems than as a structural schematic of the embodiments described herein. In practice, and as recognized by those of ordinary skill in the art, items shown separately could be combined and some items could be separated. For example, some items shown separately in these figures could be implemented on single servers and single items could be implemented by one or more servers. The actual number of systems used to implement a privacy proxy and how features are allocated among them will vary from one implementation to another. 
     Each of the methods described herein with respect to  FIGS. 7-10  may be governed by instructions that are stored in a non-transitory computer readable storage medium and that are executed by one or more processors of one or more servers or clients. The above identified modules or programs (i.e., sets of instructions) need not be implemented as separate software programs, procedures or modules, and thus various subsets of these modules may be combined or otherwise re-arranged in various embodiments. Each of the operations shown in  FIGS. 7-10 , described below, may correspond to instructions stored in a computer memory or non-transitory computer readable storage medium. 
       FIGS. 6A and 6B  are diagrams illustrating a displayed document  600  with private content, according to some embodiments. As described above, a document (e.g., document  111 ) may be accessible to multiple users, but only a subset of those users may have rights (e.g., to read and/or edit) portions of the document that are marked as private. Alternatively, a proper key for decrypting a partially encrypted document corresponding to an original document may be or may not be available. When a document is presented to a user at a client device  102 , the marked private portions may be presented differently based on the rights of the user or on key availability. 
     The document  600  includes unmarked content portions  602 ,  606  and a marked content portion  604 . The document  600  may be created or generated, modified, and viewed in an application  104  in a client device  102  and sent, through the privacy proxy system  106 , to the server system  114  for storage. The privacy proxy system  106  encrypts the marked portion  604  before sending the document  600  to the server system  114 . While stored at the server system  114 , the encrypted marked portion  604  remains encrypted (e.g., because the key needed to decrypt the marked portion  604  is not available to the server system  114 ). A user at a client device  102  may make a request for the document  600 , and in response the document  600  is sent by the server system  114  to the privacy proxy system  106 . 
     In some embodiments, in response to the request for the document  600 , the privacy proxy system  106  decrypts the marked portion  604  regardless of whether the requesting user has the rights to read the marked portion  604 . The application  104  controls how the marked portions are displayed in accordance with the user&#39;s rights. In some other embodiments, in response to the request for the document  600 , the privacy proxy system  106  decrypts the marked portion  604  if the requesting user has the rights to read the marked portion  604  and omits the decrypting if the requesting user does not have the right to read the marked portion  604 . The application  104  replaces the still-encrypted marked portion  604  with other content. In some further embodiments, the privacy proxy system  106  decrypts the marked portion  604  if the proper decryption key is available at the privacy proxy system  106 , and does not decrypt the marked portion  604  if the proper decryption key is not available at the privacy proxy system  106 . 
     The privacy proxy system  106  sends the document  600  to the client system  102 . At the client system  102 , the document  600  is displayed to the requesting user in an application  104 . The unmarked portions  602 ,  606  are displayed in the clear, as shown in  FIGS. 6A and 6B . That is, the contents of the unmarked portions  602 ,  606  are displayed in their original forms. In some embodiments, the marked portion  604  is presented differently in accordance with the rights of the requesting user. If the user has the right to read the marked portion  604 , the marked portion  604  is decrypted by the privacy proxy system  106  and presented at the client system  102  in the clear as user-readable marked portion  604 -A, as shown in  FIG. 6A . If the user does not have the right to read the marked portion  604 , alternative content  604 -B is displayed in place of the content of the marked portion  604 . 
     In some other embodiments, the marked portion  604  is decrypted if the proper decryption key is available and the decrypted marked portion  604  is displayed in the clear as user-readable marked portion  604 -A. If the proper decryption key is not available, the marked portion  604  is not decrypted and alternative content  604 -B is displayed in place of the content of the marked portion  604 . 
     In some embodiments, the alternative content  604 -B is any of: black bars obscuring the marked portion (e.g., as in a redacted document), a graphic (e.g., a mosaic blur over the content of the marked portion), alternative text (e.g., a message warning that the content in the marked portion is private, as shown in  FIG. 6B ), or a blank area. 
       FIGS. 7A-7B  are flow diagrams illustrating a process  700  for transmitting a document to a destination system for storage, according to some embodiments. Each of the operations shown in  FIGS. 7A-7B  may correspond to instructions stored in a computer memory or computer readable storage medium. In some embodiments, process  700  may be implemented at a privacy proxy system  106 . 
     The privacy proxy system receives a first data transmission from a first client system ( 702 ). The first data transmission includes a first document, which has one or more portions marked as private. A first document may be sent from a client system (e.g., client system  102 ), with the eventual destination of the document being a destination system (e.g., server system  114 ). The first document (the “original document” has one or more content portions (or the entirety of the document) marked as requiring more restrictive security or privacy (e.g., may be read by only certain users). The privacy proxy system, as an intermediary between the client system and the destination system, receives the document in a data transmission from the client system. 
     The privacy proxy system encrypts the marked portions of the first document using a key ( 704 ). The document encryption/decryption module  206  encrypts the portions of the first document that are marked as private using any suitable key-based encryption algorithm or cipher and a key  108  appropriate for the encryption algorithm/cipher. The result of the encryption operation is a partially encrypted version of the first document (which may be called the “partially encrypted” first document), where the marked portions of the first document are encrypted and the remainder of the first document that is not marked as private (the “unmarked remainder”) is not encrypted. 
     In some embodiments, the first data transmission is encrypted ( 706 ), and prior to encrypting the marked portions, the privacy proxy system decrypts the first data transmission to access the first document ( 708 ). The first data transmission may be an encrypted transmission in accordance with a secure communication protocol (e.g., SSL, TLS). After receiving the first data transmission but prior to encrypting the marked portions, the privacy proxy system extracts the first document from the first data transmission by decrypting the first data transmission in accordance with the secure communication protocol, in order to access the first document for the operation of encrypting the marked portions. 
     The privacy proxy system sends a second data transmission to a destination system ( 710 ). The second data transmission includes a second document, which includes the encrypted marked portions of the first document and the unencrypted unmarked remainder of the first document. In some embodiments, the second document is the partially encrypted first document; the second document is the first document, with the marked portions encrypted. In some other embodiments, the second document is a new document generated anew from the encrypted marked portions of the first document and the unencrypted, unmarked remainder of the first document. The unmarked remainder is not encrypted beyond any encryption applied to the second data transmission as a whole (e.g., encryption applied to secure the second data transmission in accordance with a secure communication protocol, such as SSL or TLS). 
     The key needed to decrypt the encrypted marked portions is unavailable to the destination system ( 712 ). In some embodiments, the key used to encrypt the marked portions is also not made available, nor provided, to the destination system. Without the decryption key, the destination system cannot easily decrypt the encrypted marked portions of the second document. The destination system may process the second document based on the unencrypted portions (i.e., the unmarked remainder), such as indexing the second document for searching based on the contents of the unmarked remainder or matching a search query to content in the unmarked remainder. An advantage of restricting the availability, to the destination system, of the key needed to decrypt the encrypted marked portions is that security and/or privacy of the marked portions are less likely to be compromised by attacks on the destination system. 
     The second document is stored at the destination system ( 714 ). At the destination system, the second document may be stored in non-volatile memory (e.g., hard disk drive, solid state memory, non-volatile memory associated with a database connected to the destination system). 
     In some embodiments, the privacy proxy system sends the second data transmission to the destination system as an encrypted data transmission ( 716 ). The second data transmission is sent as an encrypted transmission in accordance with a secure communication protocol (e.g., SSL, TLS). The destination system extracts the second document from the second data transmission by decrypting the second data transmission in accordance with the secure communication protocol, in order to access the second document for processing. 
     In some embodiments, the privacy proxy system receives a third data transmission from the destination system ( 718 ). The third data transmission includes a third document, which includes the encrypted marked portions and the remainder of the first document that is not marked as private. In some embodiments, the third document is the second document or a copy of the second document, which, as described above, includes the encrypted marked portions and the unencrypted, unmarked remainder. In some embodiments, the third document is the partially encrypted first document or a copy of the partially encrypted first document. 
     The privacy proxy system decrypts the encrypted marked portions using the key ( 724 ). The privacy proxy system uses an appropriate decryption key and the decryption counterpart of the encryption algorithm/cipher to decrypt the encrypted marked portions in the third document. The result of the decryption operation is the original document, with the marked portions and the unmarked portions unencrypted. 
     In some embodiments, the third data transmission is encrypted ( 720 ), and prior to decrypting the encrypting the marked portions, the privacy proxy system decrypts the third data transmission to access the third document ( 722 ). The third data transmission may be an encrypted transmission in accordance with a secure communication protocol (e.g., SSL, TLS). After receiving the third data transmission but prior to decrypting the encrypted marked portions, the privacy proxy system extracts the third document from the third data transmission by decrypting the third data transmission in accordance with the secure communication protocol, in order to access the third document for the operation of decrypting the encrypted marked portions. 
     In some embodiments, the privacy proxy system sends a fourth data transmission to a second client system, the fourth data transmission including a fourth document, which includes the decrypted marked portions and the remainder of the first document that is not marked as private ( 726 ). The fourth document is displayed at the second client system ( 728 ). In some embodiments, the fourth document is the first document or a copy of the first document, reconstituted from the third document. For example, the first document may be reconstituted from the third document by decrypting the encrypted marked portions in the third document (which, in some embodiments, is the partially encrypted first document). The privacy proxy system sends the fourth document to the second client system for displaying at the second client system. Depending on the rights of the user who requested the document, the fourth document may be displayed entirely in the clear or with the marked portions obscured or replaced with other content, examples of which are described above with reference to  FIGS. 6A-6B   
     In some embodiments, the privacy proxy system sends the fourth data transmission to the second client system as an encrypted data transmission ( 730 ). The fourth data transmission may be sent as an encrypted transmission in accordance with a secure communication protocol (e.g., SSL, TLS). The second client system extracts the fourth document from the fourth data transmission by decrypting the fourth data transmission in accordance with the secure communication protocol, in order to access the fourth document for displaying. By sending the fourth data transmission as an encrypted data transmission, the fourth document is protected from compromise by an attack on the fourth data transmission. 
     In some embodiments, the privacy proxy system sends a request to the destination system for the second document in response to a request from a client system for the first document (i.e., the original document). The client system (e.g., the second client system) sending the request for the original document may be the same client system as, or different client system from, the client system that sent the first data transmission (e.g., the first client system). In response to the request from the privacy proxy system, the destination system sends the third data transmission, with the third document, to the privacy proxy system. 
     In some embodiments, step  724  (decrypting the encrypted marked portions) is skipped if the appropriate decryption key is not available for the third document, and the fourth data transmission includes the third document instead of the fourth document. At step  728 , the third document, which includes the encrypted marked portions and the remainder of the first document that is not marked as private, is displayed at the client system instead of the fourth document. 
       FIGS. 8A-8B  are flow diagrams illustrating a process  800  for transmitting a document, according to some embodiments. Each of the operations shown in  FIGS. 8A-8B  may correspond to instructions stored in a computer memory or computer readable storage medium. In some embodiments, process  800  may be implemented at a client system  102 . 
     The client system generates a document, including marking one or more portions of the document as private ( 802 ). In some embodiments, the client system marks the one or more portions of the document as private in accordance with user input ( 804 ). At the client system, a user may input content into an application (e.g., application  104 ) or open an existing document in the application, and mark one or more portions of the input content or of the existing document content as private. The application generates a document that includes the input content or the content of the existing document, with the portions marked by the user marked as private. 
     The client system sends the document to an intermediary system for transmission to a destination system ( 806 ), where, prior to the document being transmitted to the destination system, the marked portions of the document are encrypted by the intermediary system using a key that is unavailable to the destination system ( 808 ). For example, the client system sends the document to a privacy proxy system  106 , and the privacy proxy system  106  sends the document to a server system  114 . The marked portions of the document is encrypted by the intermediary system using a key  108  that is not made available to the server system  114  prior to being sent to the server system  114 . 
     In some embodiments, the client system receives a copy of the document from the intermediary system ( 810 ), where the copy of the document is transmitted from the destination system to the intermediary system prior to the receiving, the copy of the document transmitted from the destination system include the encrypted marked portions ( 812 ). In response to a request from the client system for the document, the privacy proxy system retrieves a partially encrypted document corresponding to the requested document from the server system. 
     In some embodiments, the encrypted marked portions in the copy of the document are decrypted by the intermediary system prior to the receiving ( 814 ). The privacy proxy system decrypts the partially encrypted document to reconstitute a copy of the requested document. The copy of the requested document is sent by the privacy proxy system and received by the client system. 
     In some embodiments, the client system displays the copy of the document ( 816 ). The copy of the document, including the marked portions, may be displayed in the clear (as in  FIG. 6A , for example) by the client system to the requesting user, if the user is one that has the requisite rights to read the marked portions. If the user does not have rights to read the marked portions, when displaying the marked portions, the application  104  may obscure or replace the marked portions on the display with one or replacement elements or other content (as in  FIG. 6B , for example). 
     In some embodiments, the client system receives a copy of the document from the intermediary system ( 818 ), where the copy of the document is transmitted from the destination system to the intermediary system prior to the receiving, the copy of the document transmitted from the destination system include the encrypted marked portions ( 820 ). In response to a request from the client system for the document, the privacy proxy system retrieves a partially encrypted document corresponding to the requested document from the server system. 
     In some embodiments, the encrypted marked portions remain encrypted ( 822 ). The privacy proxy system maintains the encryption on the partially encrypted document. The partially encrypted document is sent by the privacy proxy system and received by the client system. 
     In some embodiments, the client system displays the copy of the document, including displaying one or more replacement elements in place of the encrypted marked portions ( 824 ). The marked portions, as they remain encrypted, are not displayed in the clear. The application  104  may obscure or replace the marked portions on the display with one or more replacement elements or other content (e.g., alternative content  604 -B,  FIG. 6B ). 
     In some embodiments, the replacement element or other content is alternative text, obscured text, a graphic, or a blank area ( 826 ). The marked portions, when they are not displayed in the clear, may be replaced with one or more replacement elements, on the display, for display purposes. The replacement may be alternative text (e.g., a message informing the user that the content in the marked portions is private), obscured text (the text in the marked portions blacked out or obscured by a mosaic effect, to resemble redacted text), a blank area, or a graphic (e.g., an icon giving visual indication that the marked portions are restricted). 
       FIG. 9  is a flow diagram illustrating a process  900  for indexing a document for searching, according to some embodiments. Each of the operations shown in  FIG. 9  may correspond to instructions stored in a computer memory or computer readable storage medium. In some embodiments, process  900  may be implemented at a server system  114 . 
     A document is received by the server system ( 902 ). The received document includes one or more encrypted portions and an unencrypted remainder. Thus, portions of the document are encrypted (and thus those portions appear to be, before decryption, random data) and the remainder of the document is in the clear. In some embodiments, the received document is a partially encrypted document that originated from a client system  102  through an intermediary system (e.g., a privacy proxy system  106 ) and is partially encrypted by the intermediary system (e.g., the partially encrypted document described above with reference to  FIGS. 7A-7B, 8A, 8B ). The original document that yielded the partially encrypted document has one or more portions marked as private and an unmarked remainder. The portions marked as private correspond to the encrypted portions in the received document, and the unmarked remainder corresponds to the unencrypted remainder in the received document. 
     The document is indexed based only on the unencrypted remainder of the document ( 904 ). The received document is indexed for searching, but the indexing for the document is based on the unencrypted portions and not at all on the encrypted portions; the encrypted portions appear as random data and thus are not a useful basis for indexing. Further, a key for decrypting the received document is not available to nor provided to the server system  114 . Thus, the server system cannot easily decrypt the encrypted portions of the received document to access the contents. Thus, the indexing of the document is based on the unencrypted remainder, and the server system  114  attempt to match received search queries to the unencrypted remainder. 
     In some embodiments, the privacy proxy system  106 , when encrypting a document  111 , may add additional metadata to the document. For example, the privacy proxy system  106  may add metadata indicating the version of the key used to encrypt the document. As another example, the privacy proxy system  106  may add additional rights metadata (e.g., corporate-wide special rights policies) to the document. 
     As described above, the application  104  is configured to enable a user to mark discrete portions of a document as private. In some embodiments, a marked document includes metadata indicating the portions that are marked, where the metadata follows a protocol. The application  104  and/or the plug-in  202  are configured to understand and follow the protocol with respect to generating the data indicating the marked portions and determining whether a document has marked portions and the locations of those marked portions within the document. The privacy proxy system  106  is configured to understand and follow the protocol, so that the encryption and decryption can be limited to the marked portions. In some embodiments, the server system  106  is also configured to understand and follow the protocol, so that the server system  106  knows that a document includes marked portions and avoid those marked portions when processing the document (e.g., when indexing the document). 
     In some embodiments, the privacy proxy system  106  has a list or database of server systems  106  that are configured to understand and follow the protocol described above. The privacy proxy system  106  may send partially encrypted documents only to the server systems  106  in the list/database. Additionally, even if a partially encrypted document is sent to a server system  106  that does not follow the protocol described above, the privacy of the partially encrypted document is still protected because the destination server system  106  does not have the key needed to decrypt the document. 
     It should be appreciated that the encryption and/or decryption keys (e.g., key(s)  108 ) described above may refer to one or more keys. For example, in some embodiments, a key is used for both encryption and decryption. In some other embodiments, one key is used for encryption and another for decryption. Further, multiple keys, including different versions, may be used for encryption and/or decryption using one algorithm or multiple different algorithms (e.g., a set of keys for encryption/decryption using one algorithm and another set of keys for encryption/decryption using another algorithm). The appropriate key that is used in the operations described above should be, to one of ordinary skill in the art, apparent from the context. 
     Although some of various drawings illustrate a number of logical stages in a particular order, stages which are not order dependent may be reordered and other stages may be combined or broken out. While some reordering or other groupings are specifically mentioned, others will be obvious to those of ordinary skill in the art and so do not present an exhaustive list of alternatives. Moreover, it should be recognized that the stages could be implemented in hardware, firmware, software or any combination thereof. 
     The foregoing description, for purpose of explanation, has been described with reference to specific embodiments. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular uses contemplated. However, the illustrative discussions above are not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations are possible in view of the above teachings.