Method and system for providing document retention using cryptography

Techniques for utilizing security criteria to implement document retention for electronic documents are disclosed. The security criteria can also limit when, how and where access to the electronic documents is permitted. The security criteria can pertain to keys (or ciphers) used to secure (e.g., encrypt) electronic files (namely, electronic documents), or to unsecure (e.g., decrypt) electronic files already secured. At least a portion of the security criteria can be used to implement document retention, namely, a document retention policy. After a secured electronic document has been retained for the duration of the document retention policy, the associated security criteria becomes no longer available, thus preventing subsequent access to the secured electronic document. In other words, access restrictions on electronic documents can be used to prevent access to electronic documents which are no longer to be retained.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to: (i) U.S. patent application Ser. No. 10/815,229, filed concurrently herewith, and entitled “METHOD AND SYSTEM FOR PROVIDING CRYPTOGRAPIC DOCUMENT RETENTION WITH OFF-LINE ACCESS,” which is hereby incorporated herein by reference; (ii) U.S. patent application Ser. No. 10/206,737, filed Jul. 26, 2002, and entitled “METHOD AND SYSTEM FOR UPDATING KEYS IN A DISTRIBUTED SECURITY SYSTEM,” which is hereby incorporated herein by reference; (iii) U.S. patent application Ser. No. 10/676,850, filed Sep. 30, 2003, and entitled “METHOD AND SYSTEM FOR SECURING DIGITAL ASSETS USING TIME-BASED SECURITY CRITERIA,” which is hereby incorporated herein by reference; (iv) U.S. patent application Ser. No. 10/405,587, filed Apr. 1, 2003, and entitled “METHOD AND SYSTEM FOR SECURING DIGITAL ASSETS USING CONTENT TYPE DESIGNATIONS,” which is hereby incorporated herein by reference; (v) U.S. patent application Ser. No.: 10/246,079, filed Sep. 17, 2002, and entitled “METHOD AND APPARATUS FOR GENERATING KEYS FROM ACCESS RULES IN A DECENTRALIZED MANNER AND METHODS THEREFOR,” which is hereby incorporated herein by reference; (vi) U.S. patent application Ser. No.: 10/186,203, filed Jun. 26, 2002, and entitled “METHOD AND SYSTEM FOR IMPLEMENTING CHANGES TO SECURITY POLICIES IN A DISTRIBUTED SECURITY SYSTEM,” which is hereby incorporated herein by reference; (vii) U.S. patent application Ser. No.: 10/159,537, filed May 5, 2002, and entitled “METHOD AND APPARATUS FOR SECURING DIGITAL ASSETS,” which is hereby incorporated herein by reference; and (viii) U.S. patent application Ser. No.: 10/127,109, filed Apr. 22, 2002, and entitled “EVALUATION OF ACCESS RIGHTS TO SECURED DIGITAL ASSETS,” which is hereby incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to security systems for data and, more particularly, to security systems that protect electronic files in an inter/intra enterprise environment.

2. Description of Related Art

The Internet is the fastest growing telecommunications medium in history. This growth and the easy access it affords have significantly enhanced the opportunity to use advanced information technology for both the public and private sectors. It provides unprecedented opportunities for interaction and data sharing among businesses and individuals. However, the advantages provided by the Internet come with a significantly greater element of risk to the confidentiality and integrity of information. The Internet is an open, public and international network of interconnected computers and electronic devices. Without proper security means, an unauthorized person or machine may intercept information traveling across the Internet and even gain access to proprietary information stored in computers that interconnect to the Internet.

There are many efforts in progress aimed at protecting proprietary information traveling across the Internet and controlling access to computers carrying the proprietary information. Cryptography allows people to carry over the confidence found in the physical world to the electronic world, thus allowing people to do business electronically without worries of deceit and deception. Every day millions of people interact electronically, whether it is through e-mail, e-commerce (business conducted over the Internet), ATM machines, or cellular phones. The perpetual increase of information transmitted electronically has led to an increased reliance on cryptography.

One of the ongoing efforts in protecting the proprietary information traveling across the Internet is to use one or more cryptographic techniques to secure a private communication session between two communicating computers on the Internet. The cryptographic techniques provide a way to transmit information across an unsecure communication channel without disclosing the contents of the information to anyone eavesdropping on the communication channel. Using an encryption process in a cryptographic technique, one party can protect the contents of the data in transit from access by an unauthorized third party, yet the intended party can read the encrypted data after using a corresponding decryption process.

A firewall is another security measure that protects the resources of a private network from users of other networks. However, it has been reported that many unauthorized accesses to proprietary information occur from the inside, as opposed to from the outside. An example of someone gaining unauthorized access from the inside is when restricted or proprietary information is accessed by someone within an organization who is not supposed to do so. Due to the open nature of networks, contractual information, customer data, executive communications, product specifications, and a host of other confidential and proprietary intellectual property remain available and vulnerable to improper access and usage by unauthorized users within or outside a supposedly protected perimeter.

Many businesses and organizations have been looking for effective ways to protect their proprietary information. Typically, businesses and organizations have deployed firewalls, Virtual Private Networks (VPNs) and Intrusion Detection Systems (IDS) to provide protection. Unfortunately, these various security means have been proven insufficient to reliably protect proprietary information residing on private networks. For example, depending on passwords to access sensitive documents from within often causes security breaches when the password of a few characters long is leaked or detected. Consequently, various cryptographic means are deployed to provide restricted access to electronic data (namely, electronic documents) in security systems.

Besides restricting access to electronic documents, businesses and organizations also face the difficulty of implementing document retention for electronic documents. In today's heavily regulated business environment, various electronic documents need to be retained for a certain period of time and thereafter may be disposed of. Although conventional approaches are able to retain documents for a period of time and then dispose of them, these conventional approaches require that the retention duration be known and specified. With file security systems that oversee the creation and securing of electronic documents, often the electronic documents have retention periods that depend on future events that are unscheduled. Unfortunately, however, conventional approaches are unable to adequately handle document retention when unscheduled future events are involved.

Therefore, there is a need to provide more effective ways to impose document retention restrictions on electronic resources even when unscheduled future events are involved.

SUMMARY OF THE INVENTION

The invention relates to techniques for utilizing security criteria to implement document retention for electronic documents. The security criteria can also limit when, how and where access to the electronic documents is permitted. The security criteria can pertain to keys (or ciphers) used to secure (e.g., encrypt) electronic files (namely, electronic documents), or to unsecure (e.g., decrypt) electronic files already secured. At least a portion of the security criteria can be used to implement document retention, namely, a document retention policy. After a secured electronic document has been retained for the duration of the document retention policy, the associated security criteria becomes no longer available, thus preventing subsequent access to the secured electronic document. In other words, access restrictions on electronic documents can be used to prevent access to electronic documents which are no longer to be retained.

In one embodiment, the security criteria can be managed by a document retention system. In another embodiment, the security criteria can be managed more generally by a file security system.

The invention can be implemented in numerous ways, including as a method, system, device, and computer readable medium. Several embodiments of the invention are discussed below.

As a method of providing automated document retention for electronic documents, one embodiment of the invention includes the acts of: obtaining an electronic document; assigning a document retention policy to the electronic document, the document retention policy being based on a future event that is unscheduled; and cryptographically imposing the document retention policy on the electronic document.

As a method for restricting access to an electronic document, one embodiment of the invention includes the acts of: identifying an electronic document to be secured, the electronic document having at least a data portion that contains data; obtaining a document key; encrypting the data portion of the electronic document using the document key to produce an encrypted data portion; obtaining a retention access key, the retention access key being used to enforce a document retention policy on the electronic document; encrypting the document key using the retention access key to produce an encrypted document key; forming a secured electronic document from at least the encrypted data portion and the encrypted document key; and storing the secured electronic document.

As a method for accessing a secured electronic document by a requester, the secured electronic document having at least a header portion and a data portion, one embodiment of the invention includes the acts of: obtaining a retention access key, the retention access key being used to enforce a document retention policy on the electronic document; obtaining an encrypted document key from the header portion of the secured electronic document; decrypting the encrypted document key using the retention access key to produce a document key; decrypting an encrypted data portion of the secured electronic document using the document key to produce a data portion; and supplying the data portion to the requestor.

As a method for distributing cryptographic keys used in a file security system, one embodiment of the invention includes the acts of: receiving a request for a document retention key that is necessary to gain access to a cryptographically secured electronic document; identifying a document retention period associated with the document retention key, the document retention period being dependent on a future event that was unscheduled when the document retention period was associated with the electronic document; determining whether the document retention period associated with the document retention key has been exceeded; and refusing to distribute the document retention key in response to the request when it is determined that the document retention period for the electronic document has been exceeded.

As a file security system for restricting access to electronic files, one embodiment of the invention includes at least a key store and an access manager operatively connected to the key store. The key store stores a plurality of cryptographic key pairs. Each of the cryptographic key pairs includes a public key and a private key, and at least one of the cryptographic key pairs pertains to a retention policy that is dependent on a future event. The access manager determines whether the private key of the at least one of the cryptographic key pairs pertaining to the retention policy is permitted to be provided to a requester based on whether the future event has occurred. The requester requires the private key of the at least one of the cryptographic key pairs pertaining to the retention policy to access a secured electronic file. The secured electronic file was previously secured using the public key of the at least one of the cryptographic key pairs pertaining to the retention policy, and the future event was unscheduled at the time the electronic file was so secured.

As a computer readable medium including at least computer program code for providing automated data retention for electronic data, one embodiment of the invention includes at least: computer program code for obtaining electronic data; computer program code for assigning a data retention policy to the electronic data, the data retention policy being based on a future event that is unscheduled; and computer program code for cryptographically imposing the data retention policy to the electronic data.

DETAILED DESCRIPTION OF THE INVENTION

The invention relates to techniques for utilizing security criteria to implement document retention for electronic documents. The security criteria can also limit when, how and where access to the electronic documents is permitted. The security criteria can pertain to keys (or ciphers) used to secure (e.g., encrypt) electronic files (namely, electronic documents), or to unsecure (e.g., decrypt) electronic files already secured. At least a portion of the security criteria can be used to implement document retention, namely, a document retention policy. After a secured electronic document has been retained for the duration of the document retention policy, the associated security criteria becomes no longer available, thus preventing subsequent access to the secured electronic document. In other words, access restrictions on electronic documents can be used to prevent access to electronic documents which are no longer to be retained.

In one embodiment, the security criteria can be managed by a document retention system. In another embodiment, the security criteria can be managed more generally by a file security system.

Secured files are files that require one or more keys, passwords, access privileges, etc. to gain access to their content. The security is often provided through encryption and access rules. The files, for example, can pertain to documents, multimedia files, data, executable code, images and text. In general, a secured file can only be accessed by authenticated users with appropriate access rights or privileges. In one embodiment, each secured file is provided with a header portion and a data portion, where the header portion contains, or points to, security information. The security information is used to determine whether access to associated data portions of secured files is permitted.

As used herein, a user may mean a human user, a software agent, a group of users, a member of the group, a device and/or application. Besides a human user who needs to access a secured document, a software application or agent sometimes needs to access secured files in order to proceed. Accordingly, unless specifically stated, the “user” as used herein does not necessarily pertain to a human being.

The invention is related to processes, systems, architectures and software products for providing automated retention of digital assets (e.g., electronic documents). The invention is particularly suitable in an enterprise environment. The invention can also be implemented by a security system that additionally secures digital assets (i.e., secured data) so that only authenticated users with appropriate access rights or privileges can gain access thereto. Digital assets may include, but not be limited to, various types of documents, multimedia files, data, executable code, images and text.

FIG. 1is a block diagram of a file security system100according to one embodiment of the invention. The file security system100includes an access server102that provides central management for the file security system100. The access server102can store or retrieve files from a server file store104. The access server102can control the distribution of cryptographic keys from a key store106. In addition, the access server102can generate cryptographic keys that are stored to the key store106. Alternatively, the access server102can store cryptographic keys in the key store106that have been received by the access server102.

The file security system100also includes user machines108and user file stores112. The user machines108couple to the access server102via a network110. The network110can be a private network or a public network. The user machine108also has a user file store112coupled thereto. The user file store112can store electronic files locally for the user of the corresponding user machine108. On the other hand, the server file store104can provide centralized, remote storage of electronic files for any of the users of the user machines108.

According to the invention, the file security system100enables a user at the user machine108to secure an electronic file (document) such that access to the secured electronic file is restricted. In one embodiment of the invention, the access restriction is or includes a document retention restriction. As an example, the document retention restriction could permit subsequent access to the secured electronic file only during the retention period. After the retention period, the secured electronic file would be unable to be unsecured and thus subsequent access would be cryptographically prevented. In one embodiment, the retention period is initially based on a future event that is unscheduled. Here, the file security system100can interact with an event evaluator114to determine (e.g., periodically) whether the future event has now been scheduled. Once the future event is scheduled, the retention period is determinable. The event evaluator114can be referred to as a remote resource that is used to evaluate future events. The event evaluator114can be a web server or a document management system (e.g., a contract management system).

Once an electronic file has been secured, a user at a user machine can attempt to access the secured electronic file. In doing so, the user machine for the user would need to access the access server102and retrieve the appropriate one or more cryptographic keys from the key store106that are needed to unsecure the secured electronic file. However, after expiration of the retention period for the secured electronic document, the access server102does not permit the delivery of at least certain cryptographic keys from the key store106(private keys) that are needed to unsecure secured electronic files. The access server102normally also requires the user to be authorized to access the electronic file prior to delivery of at least certain cryptographic keys from the key store106. Typically, the cryptographic keys needed to unsecure a secured electronic file are private keys.

Nevertheless, once the restrictions and/or authorizations have been satisfied and the private keys have been supplied, the private keys are usable to unsecure the secured electronic files. Typically, the private keys will expire after a relatively short period of time (e.g., 1-30 days) so that users are forced to again retrieve the necessary cryptographic keys.

FIG. 2is a flow diagram of a retention policy assignment process200according to one embodiment of the invention. The retention policy assignment process200operates to cryptographically secure an electronic document to implement document retention. The retention policy assignment process200is, for example, performed by a computing device, such as the access server102or the user machines108illustrated inFIG. 1.

The retention policy assignment process200initially opens or creates200an electronic document. A user of a computing device may assist with the opening or creation of the electronic document. Next, a decision202determines whether document retention is requested. Here, according to the invention, document retention policies can be imposed on the electronic document. Hence, the decision202determines whether document retention is to be imposed on the electronic document. When the decision202determines that document retention is not to be imposed, then the retention policy assignment process200is complete and ends with no document retention policy being imposed.

On the other hand, when the decision202determines that document retention is requested, then a document retention policy is specified204based on a future event that is presently unscheduled. Typically, the document retention policy specifies that the electronic document is to be maintained until some future point in time. However, when the document retention policy is based on a future event which is presently unscheduled, the future point in time is not known and cannot be determined. Once the future event becomes scheduled, then the period of time for document retention can be determined. In other words, the document retention policy becomes determinable because the future event is no longer unscheduled. Next, the document retention policy is cryptographically imposed206on the electronic document. Recall, however, that the document retention policy at this point is based on a future event which is presently unscheduled. In one implementation, a cryptographic key is utilized to encrypt the electronic document so that access to the electronic document can be restricted after the document retention policy has been exceeded. In other words, after the period of time for document retention specified by the document retention policy has been exceeded, the cryptographic key that is needed to gain access to the electronic document is no longer made available to users. As a result, because the electronic document was previously cryptographically secured using a cryptographic key, if the corresponding or counterpart cryptographic key is no longer available, then the electronic document remains encrypted and thus unusable. In any case, following the operation206, the retention policy assignment process200is complete and ends.

Once a document retention policy has been assigned to an electronic document, the document retention system or file security system100as shown inFIG. 1needs to periodically evaluate whether future events associated with the document retention policies are now scheduled. In one embodiment, the access server102shown inFIG. 1can be utilized to periodically evaluate whether future events have become scheduled.

FIG. 3is a flow diagram of a future event evaluation process300according to one embodiment of the invention. The future event evaluation process300can, for example, be performed by the access server102illustrated inFIG. 1.

The future event evaluation process300initially identifies302a future event. Here, the future event is a future event that is being monitored by a document retention system (or file security system) because it is utilized by one or more document retention policies assigned to one or more electronic documents managed by the system. After the future event has been identified302, a remote resource can be queried304for status of the future event. The remote resource can, for example, be a file, a web server or an external system. An example of an external system would be a document management system or a contract management system. In any case, the event evaluator114shown inFIG. 1can represent the remote resource that is being queried304.

Next, a decision306determines whether a status response has been received from the remote resource. When the decision306determines that a status response has not been received, then the future event evaluation process300awaits a status response. However, after a period of time in which no response is received, the status response can be deemed or default to indicate that the future event remains unscheduled. On the other hand, when the decision306determines that the status response has been received, a decision308determines whether the future event is now scheduled by examination of the status response. When the decision308determines that the future event is now scheduled, then schedule information pertaining to the future event can be stored310. For example, the access server102shown inFIG. 1can store schedule information for the future event. At a minimum, the schedule information can contain an indication that the future event is now scheduled. Typically, the schedule information would specify a date representing the occurrence (past or future) of the future event. Alternatively, when the decision308determines that the future event still remains unscheduled, then the operation310is bypassed.

Following the operation310or its being bypassed, a decision312determines whether there are other future events to be evaluated. When the decision312determines that there are other future events to be evaluated, the future event evaluation process300returns to repeat the operation302and subsequent operations, thereby allowing other future events to be similarly evaluated. On the other hand, when the decision312determines that there are no other future events to be evaluated, then the future event evaluation process300is complete and ends. Typically, the future event evaluation process300would be periodically invoked to evaluate whether any future events have become scheduled.

In one embodiment, when the remote resource can be addressed for requests (queries) by a Universal Resource Locator (URL). The URL could point to a file, a web-server or some other web-based application. In case where the URL points to a file, the file stores and can provide the status response as to whether the associated future event is unscheduled or not. The URL specifies the correct file and can do so by identifying the descriptions of future events, an event type and an event identifier.

In another embodiment, when the remote resource is a web server or an external system, the request (query) to the web server or external system can use a URL to access the web server. The URL can specify the web server or external system and describe the future event of interest. Alternatively, the query or request to the web server or external system can be a markup language (e.g., XML) document. Such a status request would also at least describe the future event of interest. The status response from the web server or external system can return an indication as to whether the associated future event is unscheduled or not. As an example, the status response can be a markup language (e.g., XML) document. It should be noted that the status response can also be signed with an electronic signature that can be used to authenticate its origin.

In still another embodiment, the remote resource is network accessible (e.g., web server or external system). Here, the remote resource can be accessed using networking techniques, such as TCP/IP networks, to get future event information from the remote resource.

FIG. 4is a flow diagram of an expiration process400according to one embodiment of the invention. The expiration process400represents other processing that determines whether document retention periods associated with electronic documents have been exceeded, and if so, renders the associated electronic documents inaccessible. The expiration process400would typically be periodically invoked. The expiration process400can, for example, be performed by the access server102illustrated inFIG. 1.

The expiration process400initially identifies402a future event. Here, the future event is a future event associated with a document retention policy that is being utilized to retain one or more electronic documents by a document retention system (or file security system).

Next, a decision404determines whether the future event has been scheduled. As an example, the decision404can examine schedule information that is stored by the future event evaluation process300illustrated inFIG. 3. In any case, the decision404determines whether the future event has now been scheduled. When the decision404determines that the future event has been scheduled, then a decision406determines whether a document retention period associated with the now scheduled future event has expired. For example, a document retention period might typically be represented as a predetermined period of time following a future event. Hence, once the future event is scheduled and thus has a date certain, the document retention period is determinable.

When the decision406determines that the document retention period has expired, then the cryptographic key associated with the document retention policy is identified408. The document retention policy may be associated with one or a plurality of cryptographic keys that are utilized to secure one or a plurality of different electronic documents. In any event, once the cryptographic key is identified408, the cryptographic key is deactivated410. In other words, the cryptographic key utilized to implement the document retention policy for the electronic document is destroyed, deleted or disabled. Consequently, the cryptographic key is no longer useable to gain access to the electronic document that has been encrypted therewith, thereby implementing the document retention policy. In other words, the associated electronic document is thereafter inaccessible by those persons or machines that were previously able to access the electronic document. In effect, the electronic document has been effectively destroyed. The operations408and410are bypassed when the decision404determines that the future event has not yet been scheduled or when the decision406determines that the document retention period has not yet expired.

In any case, following the operation410or its being bypassed, a decision412determines whether there are other future events to be similarly processed so as to determine whether the associated document retention period or periods have expired. Hence, when the decision412determines that other future events are to be processed, the expiration process400returns to repeat the operation402and subsequent operations to process another future event.

FIG. 5is a flow diagram of an access request process500according to one embodiment of the invention. The access request process500is, for example, performed by a computing device, such as the user machines108illustrated inFIG. 1.

The access request process500begins with a decision502that determines whether an electronic document access request has been received. A user of a computing device can initiate an electronic document access request. When the decision502determines that an electronic document access request has not been received, then the access request process500awaits such as request. Once the decision502determines that a document access request has been received, then a decision504can determine whether document retention is imposed on the electronic document that is to be accessed. When the decision504determines that document retention is not imposed on the electronic document to be accessed, access to the electronic document is permitted506.

On the other hand, when the decision504determines that document retention is imposed on the electronic document to be accessed, a cryptographic key associated with the document retention policy that is imposed on the electronic document is requested508. A decision510then determines whether the requested key has been received. Here, the requested key is the cryptographic key that has been requested508. In one implementation, such as shown inFIG. 1, the user machine108requests the key from the access server102, and the key is provided (if at all) to the user machine108via the network110.

When the decision510determines that the requested key has not been received, then access to the electronic document is denied512. In this case, the document retention policy causes the cryptographic key to be no longer available to the requestor. In such case, although the requestor may have access to the electronic document, since the cryptographic key is not available, the requestor is not able to gain access to the electronic document. In other words, the electronic document remains in its encrypted format and thus unusable by the requestor. In such case, the document retention policy imposed on the electronic document caused the electronic document to expire.

On the other hand, when the decision510determines that the requested key has been received, then access to the electronic document is permitted514through use of the cryptographic key. In other words, the cryptographic key can be used to decrypt the encrypted electronic document, thereby allowing the requestor to gain access to the electronic document.

Following the operations506,512and514, the access request process500is complete and ends. However, it should be noted that additional layers of encryption could be imposed on the electronic document besides the level of encryption utilized to implement a document retention policy. Hence, other keys or requirements can be imposed by a file security system in order to further restrict access to the electronic documents. For example, co-pending U.S. patent application Ser. No. 10/405,587, filed Apr. 1, 2003 and entitled “METHOD AND SYSTEM FOR SECURING DIGITAL ASSETS USING CONTENT TYPE DESIGNATIONS,” describes representative other document security measures and is hereby incorporated herein by reference.

As previously noted, document retention can be provided by a file security system. In which case, an electronic file can be cryptographically secured using a key that is associated with file retention. The key can then automatically be made unavailable after the retention period for the electronic document has been exceeded. Accordingly, the electronic file is no longer accessible after the retention period is exceeded. Typically, such inaccessibility is permanent and irreversible. However, in special situations, the automatic nature of the non-retention can be suspended so as to permit extended access. For example, a system administrator can cause the retention period to be extended so that the electronic file remains accessible even after the original extension period has been scheduled. This override capability can be important when, for example, legal issues arise concerning the electronic file. In such cases, the electronic file should be retained and not automatically expired. In one embodiment, the system administrator can either override an assigned retention period or set a new retention period (which may also be based on a future event).

FIG. 6is a flow diagram of a file securing process600according to one embodiment of the invention. The file securing process600is, for example, performed by a computing device, such as the access server102or the user machines108illustrated inFIG. 1.

The file securing process600initially identifies602an electronic file to be secured. Here, the electronic file is identified to the computing device carrying out the file securing process600. A user of the computing device may assist in the identification of the electronic file. After the electronic file to be secured has been identified602, a document retention access key is obtained604. Typically, the document retention access key is obtained604from an access server. For example, if the file securing process600is performed by the user machine108, the document retention access key can be retrieved remotely from the access server102, which can retrieve the document retention access key from the key store106. Here, the document retention access key is a public key and is normally readily available.

Next, after the time-based access key has been obtained604, the electronic file is secured606through use of the document retention access key. The result of the securing of the electronic file is to produce a secured electronic file. Typically, the electronic file is cryptographically secured through encryption (directly or indirectly) using the document retention access key. In one embodiment, one or more other keys are used to further control access to the electronic file. Thereafter, the secured electronic file is stored608. After the secured electronic file is stored608, the file securing process600ends. Following the securing process600, the secured electronic file can be distributed to one or more user machines108having interested users.

FIGS. 7A and 7Bare flow diagrams of a document securing process700according to one embodiment of the invention. The document securing process700is, for example, performed by a computing device, such as the access server102or the user machines108illustrated inFIG. 1.

The document securing process700opens or creates702an electronic document. At this point, the electronic document is unsecure, which is often referred to as being in the “clear.” Next, a decision704determines whether the electronic document is to be secured. Here, the user or creator of the electronic document has the option of securing the document, if so desired. When the decision704determines that the electronic document is not to be secured, then the electronic document is saved706. Here, the electronic document being saved is not secured. Following the block706, the document securing process700ends with the electronic document being saved in an unsecured fashion.

On the other hand, when the decision704determines that the electronic document is to be secured, then a data portion of the electronic document is encrypted708using a document key. The document key can be a cryptographic key that is generated or obtained. Typically, each document managed and secured by the file (document) security system would be encrypted708using a different document key. After the data portion of the electronic document has been encrypted708, a decision710determines whether a document retention restriction should be imposed on the electronic document. The user or creator of the electronic document can have the option of securing the document with a document retention access restriction, if so desired.

When the decision710determines that a document retention restriction should be imposed on the electronic document, a public document retention access key is requested712. In one embodiment, the public document retention access key can be requested from the access server102by the user machine108. The access server102can then retrieve or generate the public document retention access key and supply it to the user machine108. In an alternative implementation, the user machine may have already received the public document retention access key (e.g., such as in a key cache) and thus would not need to request such.

Next, a decision714determines whether the public document retention access key has been received. Once the decision714determines that the public document retention access key has been received (or already available), the document key is encrypted716using the public document retention access key. Here, the document key is being encrypted using the public document retention access key. In other words, the public document retention access key is indirectly used to encrypt the electronic document by encryption of the document key. Next, a secured electronic document is formed718from the encrypted data portion and the encrypted document key. Thereafter, the secured electronic document is saved720. In this case, following the block720, the document securing process700ends with the electronic document being saved in a secured fashion with at least a document retention access restriction.

Alternatively, when the decision710determines that a document retention access restriction is not to be imposed on the electronic document, then the blocks712-716are bypassed. In such case, the secured electronic document is formed718from the encrypted data portion and the document key. Here, the document key is not encrypted using a public document retention access key. The resulting secured electronic document is then saved720. In this case, following the block720, the document securing process700ends with the electronic document being saved in a secured fashion without any time-based access restrictions.

FIG. 8is a flow diagram of a document unsecuring process800according to one embodiment of the invention. The document unsecuring process800can be performed at a client machine or a server machine, such as the user machine108or the access server102illustrated inFIG. 1.

The document unsecuring process800begins with a decision802that determines whether a request to access a secured electronic document has been received. When the decision802determines that a request to access a secured electronic document has not yet been received, the document unsecuring process800awaits such a request. In other words, the document unsecuring process800can be considered to be invoked once access to a secured electronic document is requested.

Once the decision802determines that a request to access a secured electronic document has been received, a decision804determines whether a document retention restriction is present. In one implementation, the decision804can evaluate a header portion of the secured electronic document to determine whether a document retention restriction is present. In another implementation, the decision804can evaluate a system policy to determine whether a document retention restriction is present. As an example, the header can include an indicator of a document retention restriction.

When the decision804determines that a document retention restriction is present, then a private document retention access key is requested806. In one embodiment, the private document retention access key is requested806from a file security system, such as a server machine thereof (e.g., access server102). Then, a decision808determines whether the requested key has been received. When the decision808determines that the requested key has not yet been received, a decision810determines whether access to the requested key has been denied. Typically, the private document retention access key is only available so long as a retention period for the secured electronic document has not been exceeded. In one embodiment, the access server102controls access to the private document retention access key which is stored in the key store106. Hence, in such an embodiment, the access server102would deny any request for the document retention access key after the retention period has been exceeded. In any case, when the decision810determines that access to the requested key has been denied, then access to the secured electronic document is denied and notice that access has been denied is returned812. In one embodiment, the notice can more specifically indicate that access is denied because the document has expired. Following the block812, the document unsecuring process800ends with access to the secured electronic document being denied.

On the other hand, when the decision810determines that access to the requested key has not been denied, then the document unsecuring process800returns to repeat the decision808so as to wait for the requested key to be received. Once the decision808determines that the requested key (the private document retention access key) has been received, the encrypted document key from the secured electronic document is decrypted814using the private document retention access key to yield the document key (unencrypted). Here, in one embodiment, a header portion of the secured electronic document includes at least the encrypted document key (as well as the indicator for the private document retention access key). Next, an encrypted data portion of the secured electronic document is decrypted816using the document key. Finally, the data portion of the electronic document is then returned818to the requester. Additionally, it should be noted that when the decision804determines that a document retention access restriction is not present, then the document unsecuring process800skips blocks806-814and proceeds to block816. Following block818, the document unsecuring process800ends with access to the secured electronic document being successful.

In one embodiment, the document retention access keys (e.g., the public and private key pair) can be unique (i.e., different) for each electronic document. Alternatively, to manage the number of key pairs, the document retention access keys can be shared by electronic documents being retained for a like duration.

FIG. 9is a flow diagram of an access key retrieval process900according to one embodiment of the invention. The access key retrieval process900is, for example, performed by a server machine, such as the access server102illustrated inFIG. 1.

The access key retrieval process900begins with a decision902that determines whether a request for a document retention access key has been received. When the decision902determines that a request for a document retention access key has not yet been received, the access key retrieval process900awaits such a request. Once the decision902determines that a document retention access key has been received, the access key retrieval process900continues. In other words, the access key retrieval process900can be deemed invoked when a request for a document retention access key is received.

In any case, once the access key retrieval process900continues, a decision904determines whether the requested access key is a private key. When the decision904determines that the requested key is not a private key (i.e., is a public key), then a public document retention access key (which was requested) is sent906. Typically, the public document retention access key would be sent to a requestor (such as a user machine). In one embodiment, the public document retention access key is retrieved from a remote key store by a server and sent by the server to the requestor.

On the other hand, when the decision904determines that the requested key is a private key (i.e., a private document retention access key), a decision912determines whether the private document retention access key is available. When the decision912determines that the private document retention access key is not available, then the key request is denied914. In such case, the requestor would not be able to utilize the electronic documents that have been secured with the associated document retention policy. In effect, the electronic documents would be deemed expired (i.e., no longer retained).

Alternatively, when the decision912determines that the private document retention access key is available, then the private document retention access key is sent916to the requester. In this case, the requestor is able to use the requested key to gain access to the electronic documents. Following the blocks906,914and916, the access key retrieval process900ends.

FIG. 10shows a basic security system1000in which the invention may be practiced in accordance with one embodiment thereof. The security system1000may be employed in an enterprise or inter-enterprise environment. It includes a first server1006(also referred to as a central server) providing centralized access management for the enterprise. The first server1006can control restrictive access to files secured by the security system1000as well as file (e.g., document) retention. To provide dependability, reliability and scalability of the system, one or more second servers1004(also referred to as local servers, of which one is shown) may be employed to provide backup or distributed access management for users or client machines serviced locally. The server1004is coupled to a network1008and a network1010. For illustration purposes, there are two client machines1001and1002being serviced by the local server1004. Alternatively, one of the client machines1001and1002may be considered as a networked storage device.

Secured files may be stored in any one of the devices1001,1002,1004and1006. When a user of the client machine1001attempts to exchange a secured file with a remote destination1012being used by an external user, the processes discussed above can be utilized to ensure that the requested secure file is delivered without compromising the security imposed on the secured file.

According to one embodiment, a created document is caused to go through an encryption process that is preferably transparent to a user. In other words, the created document is encrypted or decrypted under the authoring application so that the user is not aware of the process. One or more keys, such as a user key and a document retention access key, can be used to retrieve a file key to decrypt an encrypted document. Typically, the user key is associated with an access privilege for the user or a group of users, and the document retention access key is associated with a retention period imposed on the created document. For a given secured document, only a user with proper access privileges can access the secured document and then only after a time restriction, if present, is satisfied.

In one setting, a secured document may be uploaded via the network1010from the client computer1001to a computing or storage device1002that may serve as a central repository. Although not necessary, the network1010can provide a private link between the computer1001and the computing or storage device1002. Such link may be provided by an internal network in an enterprise or a secured communication protocol (e.g., VPN and HTTPS) over a public network (e.g., the Internet). Alternatively, such link may simply be provided by a TCP/IP link. As such, secured documents on the computing or storage device1002may be remotely accessed.

In another setting, the computer1001and the computing or storage device1002are inseparable, in which case the computing or storage device1002may be a local store to retain secured documents or receive secured network resources (e.g., dynamic Web contents, results of a database query, or a live multimedia feed). Regardless of where the secured documents or secured resources are actually located, a user, with proper access privileges and within retention periods, can access the secured documents or resources from the client computer1001or the computing or storage device1002using an application (e.g., Microsoft Internet Explorer, Microsoft Word or Adobe Acrobat Reader).

Accordingly, respective local modules in local servers, in coordination with the central server, form a distributed mechanism to provide not only distributed access control enforcement but also file (e.g., document) retention. Such distributed access control enforcement ensures the dependability, reliability and scalability of centralized access control management undertaken by the central server for an entire enterprise or a business location.

FIG. 11shows an exemplary data structure1120of a secured file that may be used in one embodiment of the invention. The data structure1120includes two portions: a header (or header portion)1122and encrypted data (or an encrypted data portion)1124. The header1122can be generated in accordance with a security template associated with a data store and thus provides restrictive access to the data portion1124which, for example, is an encrypted version of a plain file. Optionally, the data structure1120may also include an error-checking portion1125that stores one or more error-checking codes, for example, a separate error-checking code for each block of encrypted data1124. These error-checking codes may also be associated with a Cyclical Redundancy Check (CRC) for the header1122and/or the encrypted data1124. The header1122includes a flag bit or signature1127and security information1126that is in accordance with the security template for the data store. According to one embodiment, the security information1126is encrypted and can be decrypted with a user key associated with an authenticated user (or requestor).

The security information1126can vary depending upon implementation. However, as shown inFIG. 11, the security information1126includes a user identifier (ID)1128, access policy (access rules)1129, keys (cryptographic keys)1130, and other information1131. Although multiple user identifiers may be used, a user identifier1128is used to identify a user or a group that is permitted to access the secured file. The access rules1129provide restrictive access to the encrypted data portion1124. The keys1130are cipher keys (and/or pointers or indentifiers therefor) that, once obtained, can be used to decrypt the encrypted data portion1124and thus, in general, are protected. In one implementation of the data structure1120, at least one of the keys1130is encrypted in conjunction with the access rules1129. In another implementation of the data structure1120, at least one of the keys1130is a file retention access key or is a key encrypted with a file retention access key, either of which can possibly be further protected by the access rules1129. The other information1131is an additional space for other information to be stored within the security information1126. For example, the other information1131may be used to include other information facilitating secure access to the secured file, such as version number or author identifier.

The various embodiments, implementations and features of the invention noted above can be combined in various ways or used separately. Those skilled in the art will understand from the description that the invention can be equally applied to or used in various other settings with respect to different combinations, embodiments, implementations or features as provided in the description herein.

The advantages of the invention are numerous. Different embodiments or implementations may yield one or more of the following advantages. One advantage of the invention is that retention of electronic data (e.g., electronic documents) is provided in a robust, cryptographically secure manner. Another advantage of the invention is that retention policies can be based on future events that are unscheduled when assigned to electronic data. Still another advantage of the invention is that the needed cryptographic keys to unsecure secured electronic data are no longer released by a server to a client once a retention policy has expired, thereby effectively and properly disposing of the electronic data.

The foregoing description of embodiments is illustrative of various aspects/embodiments of the present invention. Various modifications to the invention can be made to the preferred embodiments by those skilled in the art without departing from the true spirit and scope of the invention as defined by the appended claims. Accordingly, the scope of the present invention is defined by the appended claims rather than the foregoing description of embodiments.