Background Art The recent proliferation of Internet web sites has put a tremendous amount of information at the fingertips of anyone with a web browser. Many web sites are made up of a number of pages, each of which includes several links to other web pages, both within the web site and in other web sites, where more information can be found, or another topic can be investigated. These links, or hyperlinks. simplify navigation through the Internet and allow information to be managed in discrete chunks.

However, the fluidity with which the Internet adapts by adding, removing, or modifying web pages makes the maintenance of hyperlinks difficult. For example, a web page may include a hyperlink to a page that is subsequently deleted, making the hyperlink defective. Alternatively, the content of the referenced page may be altered, possibly in a way that affects the interpretation of the referencing page. Such an alteration may be confusing for the reader or embarrassing for the creator of the web site. Although the creator may regularly check the hyperlinks to verify that the referenced sites are still suitable, such a task can become quite time-consuming for large web sites, and is furthermore prone to overlook small changes, which may in fact have large consequences. Currently, it is difficult, if not impossible, to adequately assure the integrity of hyperlinks in a document. For example, as stated in Proposed Technical Standards and Guidelines for Electronic Filing in the United States Courts at http: www. cohasset. com/elec_filing/printable. html, current protocol specifically prohibits hyperlinks in electronic filings because of these problems.

Disclosure of Invention The systems and methods described herein are useful for creating hyperlinks capable of verifying that the content of the referenced document has not been altered, e. g., is the same as the content of the document at the time the hyperlink was

created. Thus, in one aspect, disclosed herein is a hyperlink including an address of an electronic document, and a value representative of the contents of said electronic document at a predetermined time. The electronic document may be a web-based document or any other document containing a hyperlink. In certain embodiments, the value is a digitally signed value.

In another embodiment, the systems and methods described herein provide a hyperlink including means for retrieving an electronic document, and means for comparing the contents of the retrieved document to the contents of the document at a predetermined time.

In another aspect, disclosed herein is a method for creating a self-verifying hyperlink by providing an electronic document accessible at an address. determining a value representative of the contents of the electronic document, and creating a hyperlink which includes the address and the value. In certain embodiment, the method also includes digitally signing the value. In certain embodiments, creating a hyperlink includes coupling a URL address with the value.

In yet another aspect, disclosed herein is a system for monitoring the contents of electronic documents, including an address for retrieving an electronic document coupled to a value representative of the contents of a predetermined version of the electronic document, a retrieval system for obtaining a current version of the electronic document at the address, a processor for calculating a value representative of the current version of the electronic document, and a comparator for comparing the value representative of the predetermined version with the value representative of the current version to determine if the electronic document has been modified. In certain embodiments, the value representative of the predetermined version is a digitally signed value. In certain embodiments, the address is a URL address.

In another embodiment, disclosed herein is a system for verifying the contents of an electronic document, including means for locating an electronic document coupled to a value representative of the contents of the document at a predetermined time, means for retrieving the electronic document, means for generating a value representative of the contents of the retrieved document, and means for comparing the value representative of contents of the retrieved document

with the value representative of the contents of the document at a predetermined time to determine if the document has been altered since the predetermined time.

In still another aspect, disclosed herein is a method for verifying the contents of an electronic document by providing an address for retrieving an electronic document coupled to a value representative of the contents of the electronic document at a predetermined time, retrieving the electronic document from the address, determining a value for the retrieved document, and comparing the determined value with the value representative of the contents of the electronic document at the predetermined time to determine if the document has been modified since the predetermined time. In certain embodiments, providing an address includes providing a URL address, or providing an address for retrieving an electronic document coupled to a digitally signed value representative of the contents of the electronic document at a predetermined time.

In yet another aspect, disclosed herein is a web page including a hyperlink as described herein.

In another aspect, disclosed herein is system for verifying the contents of an electronic document having a retrieval system for obtaining an electronic document stored at an address, a processor for calculating a value representative of a retrieved document using a predetermined formula, and a comparator for comparing the value representative of the retrieved document with a value representative of a document previously retrieved from the address to verify that the values are identical.

In still another aspect, disclosed herein is a self-verifying hyperlink, comprising an address of an electronic document, a value representative of the contents of said electronic document at a predetermined time, and instructions for determining a value representative of the contents of the electronic document. In certain embodiments, the instructions are capable of being executed by a processor.

Brief Description of Drawings Figure 1 illustrates a document containing hyperlinks which reference other electronic documents.

Figure 2 presents one possible structure of a self-verifying hyperlink according to the present invention.

Figure 3 depicts a computer network for verification of retrieved documents according to the present invention.

Figure 4 shows a system useful for verifying the content of retrieved documents according to the present invention.

Figure 5 illustrates a method for verifying the contents of a document retrieved using a self-verifying hyperlink according to the present invention.

Best Mode for Carrying Out the Inveniton The description below pertains to several possible embodiments of the invention. It is understood that many variations of the systems and methods described herein may be envisioned by one skilled in the art. and such variations and improvements are intended to fall within the scope of the invention. Accordingly, the invention is not to be limited in any way by the following disclosure of certain illustrative embodiments.

Described herein are self-verifying hyperlink references and methods of using such references for ensuring that the content of a referenced document is identical to the content of the referenced document when the reference was made in the originating document containing the hyperlink reference. As illustrated in Figure 1, an electronic document 1, such as a web page, may include reference 2 to other electronic documents 3,4, and 5, which may contain information such as text, images, charts, etc., e. g.. which may supplement the content of the originating document 1. The activation of these references may retrieve the referenced documents and display them to the user, initiate downloading of the referenced document, etc. Referenced documents 3,4, and 5 may be stored on the same server as the originating document 1, or on different servers, e. g., servers located across a network, such as the Internet. Described herein are hyperlinks, such as is schematically depicted in Figure 2, designed to permit the verification and/or validation of the content of the retrieved document, e. g., to protect against undesirable alterations in the content. As shown for the network 10 of Figure 3, such hyperlink references may be used to verify the contents of documents obtained by a client 20 from a local server 40, or from a foreign server 41 coupled to the local server 40 via the Internet 30.

As shown in Figure 2, the self-verifying hyperlink 2 may include an address portion 7 representative of the location of the referenced document, such as a URL address, and a verification portion 8 which may include a portion of the referenced document or a value representative of all or a portion of the content of the referenced document. For example, in HTML, a hyperlink may be: <A HREF http ://www. refdoc. com/refdoc VERIFY= (verification portion) >, wherein VERIFY is indicative of the function used to determine the verification portion and is represented in a manner suitable for execution by a web browser or other suitable interface. Similar hyperlinks may be constructed using XML, ASN. 1, or any other suitable language or encoding scheme. Changes in the content may prevent the content from being displayed or send a warning or error message to the viewer, to an administrator of the originating document, or to another appropriate person or system. In this way, changes in the content of referenced documents can be monitored to prevent a hyperlink reference from retrieving an inappropriate or undesirable document.

In one embodiment, the verification portion includes a predetermined portion of the referenced document, such as the first twenty words, characters #212-245, every sixteenth character, or any other portion as desired. When the document is retrieved, for example, by a user operating a web browser with a computer, the predetermined portion of the retrieved document is compared to the verification portion of the hyperlink.

If the two portions are identical, the retrieved document may be displayed to the user. If the two portions differ, a message may be sent to the user, for example, indicating that the content of the document has been altered, or that the document cannot be displayed. In certain embodiments, the retrieved document, although altered, may be presented to the user. Furthermore, a message may be sent to the administrator, author, or maintainer of the originating document indicating that the content of the referenced document should be verified to determine whether significant changes have been made in the content of the referenced document. Such a message may include the address of the referenced document and/or the address of the originating document.

In certain embodiments, a self-verifying hyperlink may include a value representative of all or a portion of the referenced document instead of, or in addition to, the predetermined portion. Such a value may be the result of applying a predetermined formula to the contents of all or a portion of the referenced document.

Exemplary formulas that may be applied in this fashion include hashing functions, such as MD2, SHA, SHA1 and MD5, although other suitable formulas and functions will be known to those of skill in the art. Because the calculated value for a given document is difficult to predict, the use of such formulas confers the additional avantage that manipulating a document to have a different content yet identical value is rendered difficult. Thus, intentional falsification of referenced documents is severely hampered by the use of such formulas and values.

In certain embodiments, the formula used to calculate the value may be capable of distinguishing a content of a document from its format. For example, the formula may calculate a single value for a span of text whether it is stored as an Adobe Acrobat file, an HTML file, a text file, or in any other format. In this way, the value calculated by the formula better represents the content of the document, and will not indicate a change of content merely because the format of the document has been altered. Similarly, the formula may consider substantive changes, such as changes in the text, while ignoring formatting changes, such as punctuation, margins, fonts, italics, etc., which do not substantially alter the meaning of the text.

In embodiments wherein the verification portion or value is representative of a predetermined portion of a referenced document, the verification portion may be associated with or include terms indicative of the representative portion. so that the hyperlink may identify, review, and compare the predetermined portion of the referenced document. For example, in one embodiment, the verification portion may include information representative of the beginning of the representative portion and information representative of the length of the representative portion. In a different embodiment, the verification portion may be associated with information representative of the beginning of the representative portion and information representative of the end of the representative portion. Such information may be represented, for example, as XML, SGML, or HTML metatags.

In some embodiments, the verification portion may be digitally signed by the author, administrator, or other official or system associated with the originating document to ensure the accuracy and source of the verification portion of the hyperlink, e. g., by using a high assurance digital signature scheme, as is known in the art. Additionally or alternatively, the verification portion may be digitally signed by a recognized authority, such as a certifying authority to further protect the verification portion from unauthorized alteration or tampering. Either or both digital signatures may include a time stamp. A digitally signed verification portion may then be represented in a digital form and included in a hyperlink as discussed above.

In certain embodiments, it may further be advantageous to digitally sign the originating document (or at least a portion thereof which contains the hyperlink), or to include a digitally signed verification portion for the content of the originating document in the hyperlink, to provide additional security for the hyperlink.

A self-verifying hyperlink may be created by providing an electronic document, such as a web page, accessible at an address and linking the address of the document to a verification portion representative of the contents of the document. The verification portion may include a portion of the electronic document or a value representative of all or a part of the electronic document as discussed above. The format and technique used to create the self-verifying hyperlink will vary with the language or encoding scheme used to create the hyperlink, but will be readily understood by one of skill in the art. In certain embodiments, the verification portion may be digitally signed or encrypted to protect against tampering or accidental alteration. In certain embodiments, the address is a URL address. The self-verifying hyperlink may be included in a web page.

A self-verifying hyperlink may be verified by an application, such as a web browser, word processor, electronic mail client, or a COTS application, including. for example, Netscape Navigator, Microsoft Internet Explorer. Adobe Acrobat.

Microsoft Word, etc., by any technique which performs a verification function as described herein. For example, the application may be configured, e. g., by including suitable code, supplementing the code, providing a plug-in or helper application, applying a patch, etc., to implement the verification function as described herein. In

one embodiment, a web browser can be configured with a verification plug-in which, upon activation of a self-verifying hyperlink, e. g., by right-clicking on the hyperlink, permits the user to deploy the verification function in addition to retrieving the referenced document.

Upon deploying the verification function, the application or associated software portion may authenticate the referenced document by unwrapping the verification portion within the hyperlink, validating the digital signature and notary (if appropriate), then retrieving the content of the referenced document or predetermined portion thereof. The retrieved content is compared to the verification portion, e. g. by applying a hashing algorithm such as SHA to the retrieved content and comparing the result with the verification portion embedded within the hyperlink. The user may then be notified of the authenticity or invalidity of the referenced document.

In yet another embodiment, a self-verifying hyperlink may include instructions, e. g., computer code, such as a Java applet or other application, for performing all or part of the verification process. Thus, the self-verifying hyperlink may thus include instructions for applying a formula, such as a hash function, to all or a predetermined portion of a referenced document. The hyperlink may further include instructions for comparing the result of applying the formula to the verification portion included in the hyperlink, to thereby determine whether the content of the referenced document has been altered. Thus, in certain embodiments, the calculations related to verification may be performed by the server or system which stores the originating document, or by the user's system, e. g., the client running a web browser, etc., depending on the instructions associated with or included in the self-verifying hyperlink.

A system 100 for monitoring the content of an electronic document referenced by a hyperlink, as shown in Figure 4, may thus include a retrieval system 110 for accessing an electronic document located at an address, such as a URL address, and a comparator 130 for comparing the content of the retrieved document with a verification portion representative of the contents of the referenced document

associated with the address, e. g., a verification portion of a self-verifying hyperlink as described above. In certain embodiments, the system 100 may also include a processor 120 for performing calculations or computations on the retrieved document, for example, in embodiments wherein the verification portion includes a code such as a hash value. The various components described above may be implemented as software modules, and any or all of the above components may be merged into a single component capable of performing one or more of the above functions. Alternatively, any or all of the above components may be implemented as hardware devices. One of skill in the art will understand that such modifications and alternative systems are encompassed by the present disclosure.

A method 200 for verifying the content of a retrieved document is illustrated in Figure 5. In the method, a user, for example, operating a web browser may view an originating page and activate a hyperlink as described above, for example, by clicking on it, to provide an address of an electronic document 210. The system may retrieve the document from the address 220 and compare the contents of the retrieved document to the verification portion 230. The method for performing the comparison will vary, depending on the method used to derive the verification value.

For example, if the verification portion was derived by selecting a portion of the referenced document, an analogous portion of the retrieved document may be selected for comparison. If the verification portion is a value resulting from applying a formula or function to all or a portion of the contents of the referenced document, the same formula or function may be applied to the retrieved document or a portion thereof, as will be apparent to one of skill in the art. Suitable instructions for performing the comparison may be included in the self-verifying hyperlink.

If comparison of the retrieved document to the verification value indicates that the contents of the referenced document have not been changed, the document may be displayed to the user. If comparison indicates that changes have taken place, the system may provide a warning to the user and/or to a person associated with the originating page to indicate that the referenced document has been altered. In certain embodiments, the system may not display an altered document to the user.