Abstract:
A document authentication system and method combine digital and non-electronic (or visual) authentication methodologies in an integrated, unified manner. As well as providing indicia of digital authentication, the invention generates a physical artifact that can be validated by unaided human visual perception. The present invention thus provides an opportunity to improve the level of trust in authentication of documents, while preserving the advantages of both traditional and digital authentication mechanisms.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to authenticating documents, and more particularly to methods, systems, and computer program products for generating document authentication indicia that can be verified both digitally and by non-electronic means. 
     BACKGROUND OF THE INVENTION 
     Systems and methods exist for generating document authentication indicia that can be verified by conventional, non-electronic means. Such mechanisms have been used for centuries, so as to reassure a reader of a document that the document is authentic, that its source or author is as stated, and that the document has not been tampered with. Such authentication mechanisms can also provide a document recipient with a mechanism for ensuring that the author or signer of a document cannot later repudiate his or her authorship or assent to the document. Examples of mechanisms for performing these functions are handwritten signatures, seals (such as wax, embossed, or ink seals), non-erasable ink, and the like. 
     More recently, digital means for authenticating documents have emerged. Digital signatures, implemented by a combination of hash operations and asymmetric encryption, provide assurances as to document authenticity and integrity. Digital signatures are generally applied, transmitted, and verified by computers, in a manner that is usually invisible to users. Authors and signers generate digital signatures by activating commands in a software package or operating system, while document recipients and other users can verify signature authenticity by activating validation commands. In many cases, validation takes place automatically upon receipt of a document that requires it. 
     Each of these two methodologies has its strengths and weaknesses. Digital mechanisms are often more reliable and accurate and may be more convenient as long as the appropriate software and computer equipment are readily available. However, such techniques require complete trust in the computer system and software. Older visual-based methodologies appeal to some users by providing more tangible indicia that can be visually perceived, readily understood, and directly verified; many users consider such visual indicia to be more trustworthy than the mysterious processes that take place in digital mechanisms. Visual methodologies can also be used in situations where a computer is not available or is not convenient. 
     Since each mechanism has its advantages and disadvantages, it is not uncommon for some users to apply both traditional and digital authentication methods to the same document. However, such approaches do not generally integrate the two types of authentication. Rather, they are often even more cumbersome and inconvenient to apply, and often emphasize the disadvantages of the two methodologies rather than their strengths. 
     What is needed, then, is a technique that brings together the advantages of both authentication methodologies in a unified approach that streamlines and improves the processes of generating authentication indicia and verifying such indicia. What is further needed is a technique that provides users with the intuitive assurance of a visual authentication methodology, combined with the reliability and convenience of digital authentication methods. 
     SUMMARY OF THE INVENTION 
     The present invention provides a new model for document authentication that combines digital and physical (or visual) authentication methodologies in an integrated, unified manner. As well as providing indicia of digital authentication, the system of the present invention generates a physical artifact that can be validated by unaided human visual perception. The present invention thus provides an opportunity to improve the level of trust in authentication of documents, while preserving the advantages of both traditional and digital authentication mechanisms. 
     In one aspect, the invention operates to generate a document to be authenticated as follows: 
     1. A device receives a source document  102 A to be authenticated. The device includes some sort of scanning or reading mechanism, such as a scanner or multifunction peripheral, for accepting input of this kind. 
     2. A public key and a reference to a storage location (such as a URL) are provided, either as part of source document  102 A or by some other means. 
     3. The device reads document  102 A, optionally encrypts it using the public key, and uploads content from document  102 A to the storage location specified by the URL. 
     4. The device generates a digital signature, for example by computing a hash H 1  of the content and then encrypting H 1  with a private key. 
     5. The device prints a new version  102 S of the document, including some or all of the content from the source document, along with indicia of authentication such as the generated digital signature and a public key corresponding to the signature. The new version  102 S of the document can also contain a URL pointing to the specific storage location that contains the uploaded content. Any or all of these items on the new version can be provided in machine-readable format, such as a barcode. 
     In one aspect, the invention operates to authenticate document  102 S that has been so generated, as follows: 
     1. A document  102 S to be authenticated is provided at a device. The device (which may or may not be the same device that was used to generate the document) includes some sort of scanning or reading mechanism, such as a scanner or multifunction peripheral. Document  102 S contains: a) a visually readable representation of content, such as printed words, images, and the like; b) a reference (such as a URL) that points to a stored digital representation of content, where the visually readable representation purports to be equivalent to the stored digital representation; c) a digital signature; and d) the public key of a person who has signed the document, or a reference that points to such a public key. In one aspect of the invention, items b), c), and d) are provided in machine-readable format such as a bar code. 
     2. The device reads document  102 S, and extracts items b), c), and d). 
     3. The device retrieves the stored digital representation from the URL. 
     4. The device verifies the digital signature, by for example: applying a hash algorithm to the digital representation retrieved from the URL to derive a hash result H 2 ; and applying the public key of the document signer to decrypt the digital signature to derive result H 1 . Hash result H 2  is compared with hash result H 1 . 
     5. If H 1 =H 2 , the device then generates a new digital signature for the document by encrypting H 1  using a private key associated with the device. 
     6. The device renders the retrieved digital content into an image suitable for printing. 
     7. The device (or a connected printer) then prints a new version  102 C of the document (printed on a sheet of paper, or generated in some other tangible physical medium, PDF file, or the like) that contains: a) the digital content that was retrieved from the URL and rendered; b) a digital representation (such as a barcode) of the new digital signature generated by the device; and c) a representation of (or reference to) a public key associated with the device. The new digital signature and the other digital content can be printed, for example, as part of a “footer” on document  102 C. The footer may also include a barcode or other representation of a URL or other location where the document has been stored. The footer may also include the previous digital signature and public key (items c) and d) from the document provided in step #1), so that the new version  102 C of the document constitutes an assertion that the previous digital signature was valid. 
     A person can then visually compare the output document  102 C with previous version  102 S (or with a representation of previous version  102 S) to ensure that the rendered digital content in document  102 C is identical to the visually readable content from the document  102 S. If the images match, there is some assurance that the document  102 S provided in step 1 is authentic. Thus, authenticity is verified by the combination of: a) visual comparison of the documents  102 C and  102 S; and b) signature verification of step 4. 
     In an alternative embodiment, documents  102 C and  102 S can be compared by electronic means, for example using well-known image comparison and image matching techniques. This can be done in addition to or instead of the visual comparison being performed by a human being. 
     Furthermore, the new document  102 C can be used as additional authenticating indicia, since it includes a new digital signature signifying that document  102 C has been “witnessed” by the device. 
     In addition, multiple checks on the document  102 S, or on document  102 C, or on any copy or reprint or version of the document, can be performed by scanning the document in any other device that embodies the above-described invention. The resulting printed documents can be visually checked against one another and/or against the original, to provide further assurance of authenticity. Each device that authenticates a document asserts that the digital data retrieved from the indicated URL renders into an image and applies a signature to provide evidence of such assertion. 
     An example of the application of the present invention is as follows: Two parties sign a paper contract. The device of the present invention scans the contract, uploads the scanned image data to a server identified by a server URL  105 R (for example, http://upload.ricoh.com), and generates a digital signature from the scanned image data. The server responds to the upload request with a specific content URL  105 S indicating the storage location where the content image is being stored, and the server stores the content image at that location. In one embodiment, the specific filename or directory for content URL  105 S is generated based on a hash result on the content image (for example, http://upload.ricoh.com/HASH — 1234). Server  100  may generate this content URL  105 S, or MFP  101 S may do so. The device prints out a new version of the document that includes an authenticity indicator, for example in the document footer. This authenticity indicator includes a reference to the content URL  105 S, the digital signature, and the public key of the device. In other examples, server URL  105 R and content URL  105 S can be identical to one another. 
     This new version of the document can then be used as verifiable indicia of the authenticity of the document. Any third party can use a device as provided by the present invention to scan the new version of the document and perform the steps outlined above. Comparison of the printed document and the device output yields an indicator that the document is authentic; furthermore, the device&#39;s verification of the digital signature (step 4 above) provides digital verification of authenticity. In addition, when the third party scans the document in this manner, the device generates yet another version of the document, this time with the additional indicator that the document has been “witnessed” by the third party&#39;s device. This additional indicator may be, for example, a new digital signature as described in step 6 above. Any number of third parties can perform this authentication operation, and the document can therefore be witnessed any number of times. 
     An advantage of the present invention is that any device operating according to the principles described herein can be used to authenticate any of the digitally signed copies of the document. 
     In addition, when providing the original document to the device for initial generation of authentication indicia, any number of auxiliary items, such as supplementary pages, documents, photographs, or other media items, can also be provided. These items are also scanned and uploaded to the server. In one aspect of the present invention, thumbnails or other representations of the auxiliary items are included in the printed output generated by the device, so as to provide visual indications of the entirety of the content to which the authentication indicia applies. 
     By providing physical representations of the content for visual comparison by a user, along with digital verification of signatures, the present invention effectively combines the advantages of both traditional and digital authentication schemes in a unified manner. Such a system is difficult to defeat, as it would detect forgeries of authentication stamps. Simple attempts at forgery, such as physically cutting and pasting authenticity stamps, would be easily detected by a user. More sophisticated attempts, such as scanning a signature and printing it onto another sheet, would be detected when the doctored page were submitted for authentication, since the output version of the document would not match the original. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings illustrate several embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
         FIG. 1  is a block diagram depicting an overall architecture for one embodiment of the present invention. 
         FIG. 2  is an event diagram depicting a method for authenticating a document according to one embodiment of the present invention. 
         FIG. 3  is an example of a template form for generating documents, according to one embodiment. 
         FIG. 4  is an example of a document generated using the template form of  FIG. 3 . 
         FIG. 5  is an example of the document of  FIG. 4  after a device has added a digital signature, URL, and public key according to the techniques of the present invention. 
         FIG. 6  is an example of the document of  FIG. 5  after it has been authenticated according to the techniques of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     The present invention is now described more fully with reference to the accompanying Figures, in which several embodiments of the invention are shown. The present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather these embodiments are provided so that this disclosure will be complete and will fully convey the invention to those skilled in the art. 
     Referring now to  FIG. 1 , there is shown an overall architecture for one embodiment of the present invention. Referring also to  FIG. 2 , there is shown an event diagram depicting a method for authenticating a document according to one embodiment of the present invention. For illustrative purposes,  FIGS. 1 and 2  depict an arrangement where two multi-function peripherals (MFPs)  101 S and  101 C are used to practice the present invention. However, one skilled in the art will recognize that the invention can be implemented using a single MFP, or any number of MFPs. 
     In the example shown, one MFP  101 S is used to generate a verifiable document  102 S from an original document  102 A, while another MFP  101 C is used to authenticate document  102 S and to generate evidence of such authentication in the form of document  102 C. It is assumed, for illustrative purposes, that MFPs  101 S and MFP  101 C are under the control of two different individuals (called Sally and Charlie, respectively), that they operate independently, and that they may be located remotely from one another. 
     One skilled in the art will further recognize that the present invention can be implemented using devices other than MFPs. For example, the invention can be implemented using one or more conventional scanners coupled to one or more computers that runs software for executing the steps of the invention. The invention can also be implemented using one or more printers, fax machines, scanners, or the like, either instead of or in addition to the MFPs shown in  FIGS. 1 and 2 . 
     In one embodiment, MFPs  101 S and  101 C of the present invention each include input and output capabilities, such as for example a scanner, keypad, screen, printing mechanism, and the like, as well as network connectivity that allows each MFP  101 S,  101 C to communicate with other components such as server  100  using well known network protocols such as TCP/IP and HTTP. In one embodiment, the various components of  FIG. 1  are located remotely with respect to one another; the present invention can function equally effectively regardless of the actual physical locations of the various components. 
     Thus, as will be apparent to one skilled in the art, the arrangement of  FIG. 1  is intended to be illustrative of one example of an architecture for implementing the present invention, and is not intended to limit the scope of the invention claimed herein to the particular features and components depicted. Similarly, the sequence of steps depicted in  FIG. 2  is intended to be illustrative of one example of operation of the present invention, and is not intended to limit the scope of the invention claimed herein to the particular steps or order of steps depicted. 
     Document  102 A is an original document that a first user (referred to herein as Alice) has created or generated  201 , or has in her possession. Alice wishes to generate some indicia of authenticity for document  102 A. In one embodiment, in addition to including content  103 , document  102 A also includes public key  104 A associated with Alice, and/or uniform resource locator (URL)  105 R pointing to server  100  that includes storage location  107  where document content  103  is to be stored. In one embodiment, public key  104 A and server URL  105 R are provided in machine-readable format, such as a barcode. 
     For example, Alice may have generated document  102 A by writing content  103  on template form  300  such as a piece of standard letterhead that has been pre-printed with public key  104 A and server URL  105 R. An example of such template form  300  for generating documents is shown in  FIG. 3 , including public key  104 A and server URL  105 R, both shown in machine-readable format. Blank area  301  is provided for content  103 . One skilled in the art will recognize that the particular form  300  as shown in  FIG. 3  is merely an example, and that any other arrangement for such form  300  can be used without departing from the essential characteristics of the invention. 
     In one embodiment, template form  300  is provided to Alice by an individual (referred to herein as Roger) who has some pre-existing relationship with Alice (for example, her superior or co-worker), and server URL  105 R represents a storage location associated with that individual. In one embodiment, Roger retains the private key corresponding to public key  104 A on a secure server, which may be server  100  or may be some other machine. 
     Roger may have pre-existing relationships with other co-workers as well, and may have a different type of template form  300  (with different preprinted public key  104 ) for each such co-worker. 
     Additional, auxiliary media items may also be associated with document  102 A; for example, Alice may have some photographs or other items in her possession that somehow relate to document  102 A. In one embodiment, where document  102 A is a multi-page document, public key  104 A and server URL  105 R are only printed on one page of document  102 A (such as the first page); the remaining pages are considered to be auxiliary media items within the context of the following discussion. In other words, only the first page of document  102 A is generated on letterhead, and the remaining pages are generated on ordinary paper and are associated with the first page when scanned in. In another embodiment, each page of multi-page document  102 A has public key  104 A and server URL  105 R (in other words; each page is generated on a sheet resembling template form  300 ). 
     Referring now also to  FIG. 4 , there is shown an example of document  102 A generated using template form  300  depicted in  FIG. 3 . Alice has written content  103  on area  301  of template form  300 . Digital photograph  400  is an auxiliary media item associated with document  102 A. 
     Once Alice has generated document  102 A, she presents document  102 A to MFP  101 S, which in this example is associated with or belongs to another individual (referred to herein as Sally) who is responsible for attesting to the authenticity of documents. MFP  101 S scans  202  document  102 A, for example in response to Alice inserting document  102 A in a scanner coupled to or integral to MFP  101 S. In one embodiment, Sally need not have any pre-existing relationship with Alice, but is simply associated with MFP  101 S where Alice has chosen to generate an verifiable document. If auxiliary media items associated with document  102 A exist, MFP  101 S scans those as well, for example by reading digital media. 
     MFP  101 S obtains public key  104 A and server URL  105 R, for example by reading these from document  102 A. In embodiments where document  102 A does not include server URL  105 R, MFP  101 S selects or identifies a storage location  107  and/or server  100  by other means, for example in response to Alice or Sally typing in a location at a keypad on MFP  101 S or selecting from any number of choices presented on a screen at MFP  101 S. Alternatively, a default storage location  107  can be associated with MFP  101 S, so that MFP  101 S uses that storage location  107  if it does not receive any explicit indication of a server URL  105 R at the time document  102 A is being scanned. 
     Similarly, in embodiments where document  102 A does not include public key  104 A, MFP  101 S obtains public key  104 A by other means, for example in response to Alice or Sally typing in the key  104 A at a keypad on MFP  101 S or presenting a key fob, identification card, or other item that contains the public key  104 A. Alternatively, a default public key  104 A can be associated with MFP  101 S, so that MFP  101 S uses that public key  104 A if it does not receive any explicit indication of a public key  104 A at the time document  102 A is being scanned. 
     In yet another embodiment, document  102 A provides a reference to (such as a pointer to a storage location for) public key  104 A, rather than containing public key  104 A itself. In yet other embodiments, as will be recognized by one skilled in the art, the invention is practiced without using a public key  104 A. 
     MFP  101 S uploads  203  data representing a scanned image  103 I of document content  103  to server  100 . As described in more detail below, MFP  101 S can encrypt content image  103 I using public key  104 A before uploading  203  content image  103 I. The location of server  100  is specified by server URL  105 R, which may also specify the particular storage location  107  within server  100  where document content image  103 I is to be stored. In one embodiment, server  100  responds to the upload request with a specific content URL  105 S indicating storage location  107  where content image  103 I is being stored, and server  100  stores content image  103 I at that location  107 . In one embodiment, the specific filename or directory for content URL  105 S is generated based on a hash result on content image  103 I (for example, http://upload.ricoh.com/HASH — 1234). Server  100  may generate this content URL  105 S, or MFP  101 S may do so, or some other component of the system may do so. 
     If auxiliary media items were scanned, those are uploaded to server  100  as well and stored there together as part of document content image  103 I. 
     Uploaded document content image  103 I may be stored in any format such as for example PDF, JPEG, SVG, or the like. It may be compressed or uncompressed, encrypted or non-encrypted. 
     MFP  101 S generates  204  digital signature  106 S by conventional digital signature generation methods. As is known in the art, a digital signature may be generated by hashing content image  103 I (or an encrypted version of content image  103 I) to generate a message digest, and then encrypting the message digest using a private key, so that the message digest can later be decrypted using a public key and compared with an independently-derived message digest. The hash algorithm can be any well-known algorithm, such as Secure Hash Algorithm 1 (SHA1), or the like. In the present invention, MFP  101 S generates  204  digital signature  106 S by applying a private key such as one associated with MFP  101 S or associated with Sally. In other embodiments, uploaded content image  103 I can be encrypted; therefore, server  100  or MFP  101 C applies decryption to generate hash results and verify signatures. In yet another embodiment, the hash result (or message digest) is left unencrypted; later verification of the hash result then involves independently generating a hash results and comparing it with the previously generated one. For purposes of the following discussion, the term “digital fingerprint” is used to refer to the message digest, whether it is unencrypted or whether it is encrypted to form a digital signature. 
     MFP  101 S then prints  205  a new version of document  102 A, referred to herein as document  102 S. This new version  102 S includes a representation of content  103 , and can also include representations (such as thumbnails) of the auxiliary media items, if any, associated with document  102 A. For example, if document  102 A is a multi-page document, thumbnails of the various pages can be included on a single-page document  102 S. 
     Document  102 S also includes, in one embodiment, representations of digital signature  106 S and public key  104 S, where public key  104 S corresponds to the private key that was used in generating digital signature  106 S. In one embodiment, document  102 S also includes content URL  105 S, which may be a more specific URL than server  105 R in that it identifies the specific location  107  within server  100  where document content image  103 I is stored. In another embodiment, content URL  105 S is identical to server URL  105 R. In one embodiment, any or all of  103 ,  106 S,  104 S, and  105 S are included on the face of document  102 S as one or more machine-readable codes such as barcodes. One skilled in the art will recognize, however, that these items can be presented in any format, whether machine-readable, human-readable, or both. 
     Referring also to  FIG. 5 , there is shown an example of document  102 S as generated by MFP  101 S, including content  103  and thumbnail  500  of digital photograph  400 . Also included is footer  501  including digital signature  106 S, content URL  105 S, and public key  104 S. Digital signature  106 S, content URL  105 S, and public key  104 S are provided in machine-readable format. 
     Printed document  102 S contains indicia of authenticity in the form of signature  106 S. Any MFP can verify the authenticity of signature  106 S by applying public key  104 S. Document  102 A also contains a representation of content  103  originally created by Alice on document  102 A, as well as thumbnails  500  or other representations of auxiliary items, if any. Alice (or anyone else) can distribute document  102 S to whomever she wishes, and the recipient of document  102 S can verify the authenticity of document  102 S at any MFP  101  that operates according to the principles described herein. 
     For example, Alice may decide to give  206  document  102 S to an individual referred to herein as Charlie. Charlie can then verify the authenticity of  102 S by presenting document  102 S to MFP  101 C, which can be any MFP such as one associated with Charlie or with some other individual. MFP  101 C scans  207  document  102 S, and then retrieves  208  document content image  103 I from storage location  107  specified by content URL  105 S. 
     MFP  101 C then verifies  209  the authenticity of digital signature  106 S with respect to the retrieved content image  103 I. For example, MFP  101 C applies public key  104 S to digital signature  106 S to obtain a first message digest, and also applies a hash algorithm (such as SHA1) to retrieved content image  103 I to independently derive a second message digest. In an embodiment where an unencrypted hash result (message digest) is encoded on document  102 S, MFP  101 C simply applies a hash algorithm to retrieved content image  103 I to independently derive a second message digest; no application of public key  104 S is required. 
     The two message digests are compared electronically; if they match, MFP  101 C indicates that digital signature  106 S is authentic and that content  103  has not been tampered with. In one embodiment, more than one hash algorithm may be available, so that digital signature  106 S is prefixed with or appended with an indication of which hash algorithm is to be used in verifying, authenticity. 
     MFP  101 C then renders  210  document content image  103 I retrieved from storage location  107 . Rendering  210  can be performed according to a standard well-known mechanism, and usually depends on the format of the retrieved document content image  103 I. As described above, content image  103 I may be stored in any format such as for example PDF, JPEG, SVG, or the like; a rendering algorithm corresponding to the format is used for rendering  210  document content image  103 I. 
     If desired, MFP  101 C can also generate a new version of the document, referred to as document  102 C, that contains additional verification indicia which signifies that the document has been authenticated by MFP  101 C. To generate this new version  102 C, MFP  101 C first generates  211  digital signature  106 C using conventional digital signature generation methods. For example, MFP  101 C may hash content  103  to generate a message digest, and then encrypt the message digest using a private key such as one associated with MFP  101 C or associated with Charlie. 
     MFP  101 C then prints  212  new version of document  102 C. This new version  102 C includes a representation of content  103 , and can also include representations (such as thumbnails) of any auxiliary media items retrieved from server  100  that are associated with document  102 C. In one embodiment, all auxiliary media items are included with content image  103 I in a digital packet stored at location  107 . 
     Document  102 C also includes, in one embodiment, representations of digital signature  106 C and public key  104 C, where public key  104 C corresponds to the private key that was used in generating digital signature  106 C. In one embodiment, document  102 C also includes representations of digital signature  106 S and public key  104 S as evidence that document  102 C has been authenticated by MFP  101 S as well as MFP  101 C. In one embodiment, document  102 C also includes content URL  105 S, which identifies the specific location  107  within server  100  where document content image  103 I is stored. In one embodiment, any or all of  103 ,  106 S,  104 S,  106 C,  104 C, and  105 S are included on the face of document  102 C as one or more machine-readable codes such as barcodes. One skilled in the art will recognize, however, that these items can be presented in any format, whether machine-readable, human-readable, or both. 
     Referring also to  FIG. 6 , there is shown an example of document  102 C as generated by MFP  101 C, including the same elements as document  102 S of  FIG. 5  (content  103 , thumbnail  500 , and footer  501  including digital signature  106 S, content URL  105 S, and public key  104 S). Document  102 C also contains footer  601  including digital signature  106 C and public key  106 S, both added by MFP  101 C. In the example, digital signatures  106 S and  106 C, content URL  105 S, and public keys  104 S and  104 C are all provided in machine-readable format. 
     The fact that MFP  101 C has successfully verified signature  106 S on document  102 S provides Charlie with a measure of assurance as to the authenticity of document  102 S. Furthermore, Charlie (or anyone) can use the printed new version  102 C as evidence of such authentication. Version  102 C provides evidence that MFP  101 C has verified the authenticity of document  102 S, and further attests that both Charlie&#39;s and Sally&#39;s digital signatures  106 C and  106 S have been properly applied to document  102 S. 
     Furthermore, Charlie can compare the printed new version  102 C with document  102 S that he received from Alice, in order to visually ascertain whether content  103  on the two documents is identical. Since content  103  on document  102 C was retrieved from server  100 , any tampering that has been done to content  103  on document  102 S would cause documents  102 S and  102 C to fail to match one another. This visual check provides a further measure of confidence in the authenticity of document  102 S. Thus, the present invention provides a useful technique whereby authenticity of a document (such as document  102 S) can be checked by visual means as well as electronically. 
     In one embodiment, in steps  203  through  205  above, further verification of the authenticity of the content  103  of document  102 S can be provided. This further verification can be generated and provided as follows: 
     After document  102 A has been scanned  202  by MFP  101 S, content image  103 I is encrypted using public key  104 A that is associated with Alice. Only the encrypted version of content image  103 I is uploaded  203  to server  100 ; any unencrypted copy of content image  103 I is destroyed. Then, only a holder of a private key associated with public key  104 A can decrypt the version of content image  103 I that is uploaded  203  to server. 
     Another person having access to the private key associated with public key  104 A, such as Roger, decrypts content image  103 I and verifies that it is bona fide content  103  associated with its author Alice. Roger makes this determination based on his pre-existing relationship with Alice, which may dictate certain parameters that Roger checks for when reviewing documents purporting to authored by Alice. For example, if Roger is Alice&#39;s co-worker or superior, he knows what kind of content Alice might be providing or is authorized to produce, and can vouch for its integrity or authenticity. Once Roger has determined that content  103  is bona fide, Roger makes content image  103 I available in decrypted form at server  100 , so that it can later be downloaded, rendered, and output by MFP  101 C (or other devices or entities). If no such verification of authenticity is available, content image  103 I is not made available in decrypted form at server  100 . In this embodiment, then, the availability of content image  103 I in decrypted form at server  100  signifies that some entity (Roger) has attested to the authorship and/or authenticity of content image  103 I. Roger can indicate whether or not he attests to the authenticity of content image  103 I by the use, for example, of a user interface on a client computer connected to server  100 . 
     Alternatively, Roger applies his own digital signature to content image  103 I as attestation of authorship and/or authenticity of content image  103 I. In this variation, the decrypted version of content image  103 I can be made available whether or not Roger&#39;s attestation has been applied. However, if no attestation of authorship and/or authenticity has been made, the stored content image  103 I at server  100  will not include Roger&#39;s signature. Then, Charlie (or anyone else) can check for Roger&#39;s signature on content image  103 I retrieved in step  208  to determine whether or not there is attestation of authorship and/or authenticity. Then, even if no such attestation is available, Charlie (or anyone else) can still choose to print and/or use content  103  and can perform the other forms of authentication described above as long as the decrypted version of content image  103 I is available. 
     In the above description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the invention. It will be apparent, however, to one skilled in the art that the invention can be practiced without these specific details. In other instances, structures and devices are shown in block diagram form in order to avoid obscuring the invention. 
     Reference in the specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment. 
     Some portions of the detailed description are presented in terms of algorithms and symbolic representations of operations on data bits within a computer memory. These algorithmic descriptions and representations are the means used by those skilled in the data processing arts to most effectively convey the substance of their work to others skilled in the art. An algorithm is here, and generally, conceived to be a self-consistent sequence of steps leading to a desired result. The steps are those requiring physical manipulations of physical quantities. Usually, though not necessarily, these quantities take the form of electrical or magnetic signals capable of being stored, transferred, combined, compared, and otherwise manipulated. It has proven convenient at times, principally for reasons of common usage, to refer to these signals as bits, values, elements, symbols, characters, terms, numbers, or the like. 
     It should be borne in mind, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. Unless specifically stated otherwise as apparent from the discussion, it is appreciated that throughout the description, discussions utilizing terms such as “processing” or “computing” or “calculating” or “determining” or “displaying” or the like, refer to the action and processes of a computer system, or similar electronic computing device, that manipulates and transforms data represented as physical (electronic) quantities within the computer system&#39;s registers and memories into other data similarly represented as physical quantities within the computer system memories or registers or other such information storage, transmission or display devices. 
     The present invention also relates to an apparatus for performing the operations herein. This apparatus may be specially constructed for the required purposes, or it may comprise a general-purpose computer selectively activated or reconfigured by a computer program stored in the computer. Such a computer program may be stored in a computer readable storage medium, such as, but is not limited to, any type of disk including floppy disks, optical disks, CD-ROMs, and magnetic-optical disks, read-only memories (ROMs), random access memories (RAMs), EPROMs, EEPROMs, magnetic or optical cards, or any type of media suitable for storing electronic instructions, and each coupled to a computer system bus. 
     The algorithms and modules presented herein are not inherently related to any particular computer or other apparatus. Various general-purpose systems may be used with programs in accordance with the teachings herein, or it may prove convenient to construct more specialized apparatuses to perform the method steps. The required structure for a variety of these systems will appear from the description below. In addition, the present invention is not described with reference to any particular programming language. It will be appreciated that a variety of programming languages may be used to implement the teachings of the invention as described herein. Furthermore, as will be apparent to one of ordinary skill in the relevant art, the modules, features, attributes, methodologies, and other aspects of the invention can be implemented as software, hardware, firmware or any combination of the three. Of course, wherever a component of the present invention is implemented as software, the component can be implemented as a standalone program, as part of a larger program, as a plurality of separate programs, as a statically or dynamically linked library, as a kernel loadable module, as a device driver, and/or in every and any other way known now or in the future to those of skill in the art of computer programming. Additionally, the present invention is in no way limited to implementation in any specific operating system or environment. 
     It will be understood by those skilled in the relevant art that the above-described implementations are merely exemplary, and many changes can be made without departing from the true spirit and scope of the present invention. Therefore, it is intended by the appended claims to cover all such changes and modifications that come within the true spirit and scope of this invention.