Abstract:
A secure method for sending register, authenticated electronic documents is disclosed. The sender sends a first set of data, not including the plaintext message, encrypted with the public key of the recipient, and a second set of data, including the plaintext message, encrypted with a session key which was included in the encrypted first set of data. The recipient is first asked if he wants to receive the message, and then, upon seeing an abstract, asked if he wants to receive the full message. Confirmatory data regarding the decryption of the message and the presentation of the data to the recipient is recorded and sent to an authentication agent.

Description:
This application is a continuation-in-part of application Ser. No. 09/465,246, filed on Dec. 18, 1999, now U.S. Pat. No. 6,963,971 the contents of which are hereby incorporated by reference. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention relates to methods for authenticating electronic documents, and in particular to a method that registers proof of the exact content of electronic documents and provides for the establishment of an evidence trail. 
   2. Description of the Prior Art 
   Electronic documents such as E-mail have changed the face of commerce. The wide-spread use of electronic documents has increased the pace of commerce and is itself a product of the need to respond quickly to the demands of the marketplace. Electronic communication has replaced paper documents in many transactions. However, the move away from paper documentation to the fast-moving world of electronic documents has come at a price. 
   As presently configured, electronic documents lack the accountability provided by paper documents. For example, a paper contract bearing signatures provides a vastly greater level of accountability than an E-mail document. Signatures can be verified, providing for a level of non-repudiation which is not available with electronic documents. If one&#39;s signature is on a contract, it is difficult to say one was not involved in an agreement. 
   With E-mail, there are no signatures. Additionally, neither party has proof that the other individual received the E-mail in question, nor does either party have proof of the contents of the E-mail message. For these reasons, electronic documents cannot be trusted for evidentiary purposes. 
   There have been attempts to provide accountability for electronic documents. U.S. Pat. No. 5,608,800, Hoffmann et al., concerns a process intended to establish whether data transmitted to a recipient has been altered or illicitly introduced. This invention only provides a small part of the goal of making electronic documents as secure and accountable as paper documents. The method provides no means for providing the sender with proof that the intended recipient received the document, nor does the method provide for an evidence trail in the event of a dispute between sender and recipient over message content and timing. 
   U.S. Pat. No. 5,587,809, Le Corre et al., is a method that provides non-repudiation for fax senders and recipients. While this invention does provide a measure of non-repudiation, it is limited to faxes, requires special equipment, i.e., a secure fax machine, and provides proof only that a neutral third party sent a fax upon the request of the recipient. The recipient can still deny receipt of the fax or dispute the contents of the fax. 
   U.S. Pat. No. 5,615,268, Bisbee, goes further in the process of providing authentication and accountability for electronic documents. However, it requires users to have special equipment, PCM/CIA cards, and does little to protect the privacy of sender and recipient. 
   None of the above methods takes into account the interests of all parties concerned with authenticated electronic document transmission. With the present invention, there are four possible participants in an authenticated electronic document transmission, namely the sender, the recipient, a neutral third party, and the government. Each party must have its requirements taken into account for an authentication method to be accepted for wide-spread use. 
   OBJECTS AND SUMMARY OF THE INVENTION 
   An examination of each party&#39;s requirements shows that the participants have both similar and differing needs. A sender wants to know that only the intended recipient can have access to an authenticated message, and that eavesdroppers will be denied access. The sender wants proof that the recipient received and opened the message, and that the message sent was the message received. Finally, the sender wants an evidence trail and record that can be used in court if a dispute occurs regarding the contents and/or the time of delivery of the message. 
   The recipient wants to be certain of the validity of the sender&#39;s identity. The recipient wants to know that the authenticated document cannot be altered in transmission without detection. Like the sender, the recipient wants the message to be secure from eavesdropping and wants a record and evidence trail available in the event of a future dispute. Finally, the recipient wants the ability to refuse acceptance of an authenticated message if he so chooses. 
   The third party is concerned with liability, costs, and legal responsibility. The third party wants to be sure that the authenticated document was received as sent and is error free. The third party wants minimal records for each authenticated document. The third party wants to be able to provide absolute security and anonymity for clients except in those cases where court order requires that it allow government access. When government does require access, the third party wants to be able to provide real-time access as efficiently and inexpensively as possible. 
   The government wants real-time access to electronic documents in those cases where court-ordered access is granted. Governments want key escrow for all internationally transmitted, encrypted documents. The inventors believe that any method for authenticated electronic document transmission must take into account the needs cited above. Additionally, given that commerce is global, electronic document authentication methods must be adaptable to the access requirements of any government. 
   Besides the considerations cited above, an authentication method must be acceptable to the marketplace for pragmatic purposes. Users should not have to purchase special equipment. Any user with a computer and a modem should be able to use the system, no matter what the platform. As with the mail or commercial document delivery systems, users should be able to transmit authenticated electronic documents to strangers and to both willing and hostile recipients. Additionally, an authentication method should be user friendly, no more difficult to operate than an Automated Teller Machine. 
   Encryption is central to the invention because it ensures that only the intended recipient can receive the plaintext of an authenticated document, it validates sender identity and it provides privacy and security. As envisioned, the invention uses a neutral third party for key distribution, record keeping, and authenticated message distribution. 
   The Authentication Agent is a neutral witness to the transmission and receipt of authenticated electronic documents. Additionally, the Authentication Agent serves as a registry that keeps indisputable proof of document contents and a log of document transfers. 
   All users must be registered with the Authentication Agent, and must obtain authentication method software, along with a packet of session keys from the agent. 
   The sender composes the document and derives a plaintext document abstract which is entered in the document header by the sender&#39;s software program. The sender encrypts the document header in the public key of the authentication agent and sends the header to the authentication agent. This encrypted document header contains the name and address of the recipient, the name and address of the sender, the plaintext document abstract of the document (including the header), the session key and the public key of the recipient. 
   The authentication agent establishes a transaction file, containing the information in the document header and the time and date of the opening of the file. The authentication agent informs the sender that the document can be sent. 
   The sender encrypts the document (including the header) in the session key and a separate copy of the header in the public key of the recipient and transmits them to the recipient. The software encrypts only the header and document plaintext document abstracts registered in the transaction file of the authentication agent. In this way only the document identified by the sender to the authentication agent can be encrypted and sent to the recipient. 
   The recipient is informed that he has a message from the sender and asked if he wishes to read it. If he agrees, he is presented with the header of the document encrypted in his Public key. 
   The recipient decrypts the header, and is asked if he wishes to read the document. If he agrees, the software uses the session key to decrypt the document, derives a plaintext document abstract, and checks to see that this document abstract is identical with the one in the header. If the two document abstracts match, the recipient is presented with the validated plaintext version of the document and the authentication agent is informed of the time and date of the successful completion of the process. The authentication agent records the time and date of the successful completion of the process in the Document Transaction File. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further objects and advantages of the invention will become apparent from the following description and claims, and from the accompanying drawings, wherein: 
       FIG. 1  is a flowchart of the process of the present invention. 
       FIG. 2  is a block diagram of the interaction between the sender, the recipient and the authentication agent in the present invention. 
       FIG. 3  is a diagram of the data strings used in the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring now to the drawings in detail wherein like numerals refer to like elements throughout the several drawings, one sees that  FIG. 1  is a flowchart of the authentication process of the present invention. 
   At the outset, the authentication process of the present invention is highly automated. As such, the authentication agent is a computerized database. As envisioned, all interaction between the authentication agent and a sender and recipient are totally automated with no human interaction on the part of the third parties. The communication between the various parties can be any electronic communication method, such as the Internet, direct modem connections or other dedicated or non-dedicated data lines. It is further envisioned that all parties are separate entities. 
   It is further envisioned that the actions required of the sender and recipient in the authentication process are minimal. The sender typically defines the electronic document to be authenticated, provides the name and address of the recipient, and then indicates a commitment to send the authenticated document. All other actions taken as the sender&#39;s part of the authentication process originate from, and are governed by, the sender&#39;s authentication software. 
   Likewise, the recipient&#39;s actions are typically limited to indicating that he or she wishes to receive the document. All other parts of the authentication process originate from, and are governed by, the recipient&#39;s authentication software. It should be noted that sender and recipient elements are part of a single software package because all participants in the method of the invention will typically be both sender and recipient. 
   In  FIG. 1 , the sender  10  begins the authentication process by composing a plaintext document  210  and plaintext document abstract  204  as shown in block  102 . The sender  10  further enters the sender&#39;s name and address  202 . The sender software then creates a header (see String  1  of  FIG. 3 ) which includes the recipient&#39;s name and electronic address  200 , the sender&#39;s name and electronic address  202 , the plaintext document abstract  204 , the session key  206  (as previously provided in a packet from authentication agent  14 ), and the recipient&#39;s public key  208 . This header (including data  200 - 208 ) is then encrypted in the public key of the authentication agent  14  and sent as string  1  (Step A of  FIG. 2 ) to authentication agent  14  as shown in block  102  of  FIG. 1  and as shown in  FIG. 2 . 
   As shown in block  106 , authentication agent  14  decrypts string  1  and creates a transaction file, including the data from string  1  (i.e., the header data  200 - 208 ), along with the time and date. The transaction file is likewise described in the parent application Ser. No. 09/465,246, the contents of which are incorporated by reference. 
   As shown in block  108  of  FIG. 1 , as well as Step B of  FIG. 2 , authentication agent  14  informs sender  12  that a message can be sent. 
   As shown in block  110 , the sender then encrypts the plaintext document  210  and the header (data  200 - 208 ) with the session key  206 . Likewise, as shown in block  112 , the sender encrypts the header (data  200 - 208 ) in the public key of the recipient. As shown in block  114  of  FIG. 1  and in string  2  of  FIG. 3 , the results of block  110  and  112  are used to create string  2  which is sent to recipient  12 , as shown in  FIG. 2  as Step C. In an alternative embodiment, the plaintext document  210  (which includes the abstract) may be free of encryption in string  2 , the header data does not include a session key and the data from the header is encrypted only in the public key of the recipient (that is, string  2  includes only one copy of the data from the header, and this one copy is encrypted in the public key of the recipient). 
   As shown in block  116 , the recipient is notified that a message is available and asked to confirm if delivery is requested. 
   As shown in block  118 , if the recipient  12  answers affirmatively to block  116 , the header (data  200 - 208 ), which was encrypted with the public key of the recipient and transmitted as part of string  2 , is decrypted and the plaintext document abstract  204  is presented to the recipient  12 . 
   As shown in block  120 , the recipient  12  is then asked if he wants to read the plaintext document  210 . 
   As shown in block  122 , if the recipient  12  answers affirmatively to block  118 , the data in string  2  which was encrypted with the session key  206  is decrypted and the two decrypted plaintext document abstracts  204  (one from the header which was encrypted in the public key of the recipient and the other from the header which was encrypted with the session key  206 , see string  2  in  FIG. 3 ) are compared. In the alternative embodiment, plaintext document  210  is not encrypted and therefore requires no decryption at this step. 
   As shown in block  124 , the two decrypted plaintext document abstracts  204  are compared. If the abstracts match each other, then the recipient  12  is presented with the validated plaintext document  210  (in the alternative embodiment, there is a comparison between the abstract from the unencrypted plaintext document and the abstract which is derived from the decrypted header information). Thereafter, the authentication agent is informed of the successful communication by step D of  FIG. 2 , string  3  of  FIG. 2 , including at least the message ID information  212  and the time and date of successful delivery. The authentication agent  14  can then update the transaction file appropriately to confirm receipt. 
   Ramifications of the Invention 
   The present invention provides a method by which E-mail and other modes of digital data communication can be given evidentiary qualities. No longer will companies have to depend on expensive document carriers to transport critical documents. With the present invention, a contract may be sent from New York to Tokyo via E-mail with both sender and recipient able to have complete confidence in the security and accuracy of the data transfer process. The sender will be able to prove that the recipient accessed and successfully opened the document. 
   Additionally, both sender and recipient can be assured that any attempt by the other party to alter the electronic document after the fact will be detected immediately. Finally, both sender and recipient will know that the Authentication Agent has a log documenting the history of the authentication process. A sender will be able to state with complete confidence that he made an electronic document available to the recipient at an exact time and date, and that the recipient accessed and successfully opened the document at an exact time and date. 
   Potential Enrollees to the System 
   Moreover, all users of internet services are identified by their Internet Service Providers and have e-mail addresses which are interoperable. This provides a database of pre-identified users which accompanying e-mail address which can easily, quickly and economically provide a vast pool of potential customers who already have the equivalent of Individual Digital Signature Certificates. Moreover, individuals identified by state license numbers (lawyers, doctors, architects, etc.) who have e-mail addresses could be enrolled in this system. 
   Thus the several aforementioned objects and advantages are most effectively attained. Although preferred embodiments of the invention have been disclosed and described in detail herein, it should be understood that this invention is in no sense limited thereby and its scope is to be determined by that of the appended claims.