KR20080007043A - Edi system and method of electronic document security in edi system - Google Patents

Abstract

An EDI(Electronic Data Interchange) system and a method for realizing a secure e-document service in the EDI system are provided to realize secure e-document interchange from a sender terminal to a receiver terminal by guaranteeing user authentication, and confidentiality, integrity, and non-repudiation of a message, and maximize efficiency of a user terminal by realizing an email-based EDI system. A sender MUA(Mail User Agent)(200) generates and transmits envelope data. An EDI device(220) transmits an electronically signed TID(Transaction ID) to the sender MUA when the envelope data is received, and transmits the encoded envelope data/TIP in response to a mail reception request. A receiver MUA(240) receives the encoded envelope data/TID by responding to a mail reception request transmitted to the EDI device. The sender MUA transmits the envelope data by using an SMTP(Simple Mail Transfer Protocol) and the EDI device transmits the electronically signed TID to the sender MUA by including the electronically signed TID to a response packet.

Description

Implementation method of electronic document security service in electronic document exchange system and electronic document exchange system {EDI system and method of electronic document security in EDI system}

Brief Description of the Drawings Fig. 1 is a diagram showing the configuration of a conventional electronic document exchange (EDI) system.

2 is a block diagram schematically showing an e-mail based electronic document exchange (EDI) system according to an embodiment of the present invention.

3 is a flowchart illustrating a process of transmitting an enveloped message by a calling terminal according to an exemplary embodiment of the present invention.

4 is a flowchart illustrating a process of receiving an enveloped message of a receiving terminal according to an exemplary embodiment of the present invention.

The present invention relates to an electronic document exchange, and more particularly, to an electronic document exchange system and a method for implementing an electronic document security service in the electronic document exchange system.

The EDI (Electronic Data Interchange) system refers to an electronic document exchange system that allows a computer to process standardized electronic documents agreed between the parties in a transaction.

Document exchange using the EDI system has many advantages in terms of efficiency, convenience and speed. However, since information is exchanged through an open communication network, there is a high risk of being infringed or lost by any third party during transmission.

In order to overcome this problem, in order to solve the security problem on the communication line between the user's computer and the relay system, a user agent (UA) system, which is an end terminal of the EDI security service, is provided in the user computer (see FIG. 1).

1 is a diagram schematically showing the configuration of a conventional electronic document exchange (EDI) system.

Referring to FIG. 1, an electronic document exchange (EDI) system according to the prior art includes a transmitting computer 100, a relay device 120, and a receiving computer 140.

The sending computer 100 includes a sending user agent 105 (UA). The sender UA 105 transmits an electronic document based on UN / EDIFACT, which is an international standard, or KEDIFACT, which is a domestic standard, using the International Telecommunication Union (ITU) X.400 standard protocol.

The relay device 120 includes a message transfer agent 125 and a message store 130. The message transfer agent 125 stores the message received from the sending UA 105 in the message store 130. Then, when the message transmission request is received from the receiving side UA 145 provided in the receiving side computer 140, the message transfer agent 125 receives the corresponding message among the messages stored in the message storage 130 (the receiving side UA ( 145). Through the above-described process, a message is transmitted and received between the sending side UA 105 and the called side UA 145.

As described above, the EDI system illustrated in FIG. 1 attempts to solve a security problem on a communication line between a user computer and a relay system by providing a user agent (UA) system in each user computer. That is, since information is exchanged through a private communication network such as a value added network (VAN), the risk of being infringed or lost by any third party during transmission can be eliminated.

However, if you have a UA system on your computer, you will need a large disk because your computer must have the ASN.1 notation and compiler required to create the UA system and Electronic Data Interchange (EDI) message protocol data unit (PDU). There was a problem requiring capacity.

In addition, when using the electronic document exchange system based on the e-mail to solve the problem that the user computer requires a large disk capacity as described above, the security problem of the transmitted and received messages still remains. This is because an e-mail based EDI system uses an open communication network such as the Internet. That is, the disclosure or alteration of the information, the reliability of the information exchanged between the trading parties may occur.

Therefore, for the Internet e-mail-based EDI system, four security problems must be solved: user authentication, message confidentiality, integrity, and non-repudiation.

The IETF Network Working Group is currently working on standardization of e-mail security services. The standardization work is RFC 3851 (Secure / Multipurpose Internet Mail Extensions (S / MIME) Version 3.1 Message Specification), RFC 2634 (Enhanced Security Services for S / MIME) is in Proposed Standard state.

The proposed standard proposes triple wrapped, which first signs a message, encrypts it, and then signs it again. For non repudiation of receipt, the internal signature allows you to request signed receipts. When the recipient receives a signed receipt, the recipient sends proof that the receipt has been received.

However, there is a problem in the security method in the standardization operation that even if the receiver receives and reads the message, the sender cannot confirm whether or not the message is received unless the receiver sends the information of the received message. In other words, in case of using the receiving user agent (UA) that does not comply with the standard, the receiver may not read the message even if the receiver receives and reads the message. In this case, there is a problem in that it cannot be confirmed.

Accordingly, the present invention has been made to solve the above-described problems, and in the e-mail-based EDI system, user authentication, message confidentiality, integrity, non-repudiation of transmission / reception, etc. The present invention provides a method for implementing an electronic document security service in an electronic document exchange system and an electronic document exchange system that can be guaranteed.

Another object of the present invention is to provide an electronic document exchange system and an electronic document security service implementation method for enabling secure electronic document exchange from a sender's terminal to a receiver's terminal.

It is still another object of the present invention to provide an electronic document exchange system and an electronic document security service implementation method for maximizing the efficiency of a user terminal by implementing an e-mail based EDI system.

Other objects of the present invention will become more apparent through the preferred embodiments described below.

According to an aspect of the present invention to achieve the above object, there is provided an electronic document exchange method using a communication network.

Non-repudiation method performed by the electronic document relay system according to an embodiment of the present invention generates a TID (Transaction ID) when the envelope data (enveloped data) is received from the sender MUA (Mail User Agent) step; And digitally signing the TID to the transmitting MUA. Here, when the normal verification of the digital signature of the TID is completed by the transmitting side MUA, the envelope data may be recognized as being normally transmitted to the electronic document relay system when the normal verification is performed.

The envelope data may be transmitted using the Simple Mail Transfer Protocol (SMTP).

The digitally signed TID may be attached to a response packet transmitted to the transmitting MUA.

Generating, by the transmitting MUA, the encrypted original text data using the transmission encryption key to generate the encrypted data to generate the envelope data; Generating an encrypted transmission encryption key by encrypting the transmission encryption key with a private key of a receiver; and generating the envelope data by using the encrypted data and the encrypted transmission encryption key.

The non-repudiation method may include: transmitting an envelope data encrypted using a relay encryption key and a TID encrypted using a recipient's public key to the receiving side MUA when a mail reception request is received from the receiving side MUA; Verifying the validity of the digital signature when the digitally signed TID is received from the receiving MUA; And if the digital signature is valid, transmitting the relay encryption key to the receiving MUA.

The non-repudiation method may further include storing transmission completion information of the encrypted envelope data in a reception history when the electronic signature is valid.

The receiving MUA may decrypt the encrypted TID using the recipient's private key.

Extracting a transmission encryption key by decrypting the encrypted envelope data using the relay encryption key to extract original text data from the encrypted envelope data; And extracting original data by decrypting the original data encrypted using the transmission encryption key. Here, the envelope data may include the encrypted original data and the encrypted transmission encryption key.

The relay encryption key may be generated using a random function.

The encrypted envelope data and the encrypted TID may be received by the receiving side MUA using POP3 (Post Office Protocol V3).

According to another aspect of the present invention for achieving the above object, there is provided an electronic document exchange system.

An electronic document exchange system according to a preferred embodiment includes a transmitting side MUA for generating and transmitting envelope data; When the envelope data is received, the electronic document exchange device transmits an electronically signed TID (Transaction ID) to the sender MUA, and transmits the encrypted envelope data and the encrypted TID corresponding to the mail receiving request. ; And a receiving side MUA that receives the encrypted envelope data and the encrypted TID in response to the mail receiving request sent to the electronic document exchange apparatus.

The transmitting side MUA may transmit the envelope data using the Simple Mail Transfer Protocol (SMTP).

The electronic document exchange device may transmit the digitally signed TID attached to a response packet transmitted to the transmitting side MUA.

Generating, by the transmitting MUA, the encrypted original text data using the transmission encryption key to generate the encrypted data to generate the envelope data; Generating an encrypted transmission encryption key by encrypting the transmission encryption key with a private key of a receiver; and generating the envelope data by using the encrypted data and the encrypted transmission encryption key.

The electronic document exchange apparatus transmits the envelope data encrypted using the relay encryption key and the TID encrypted with the recipient's public key to the receiving MUA to transmit the encrypted envelope data and the encrypted TID; Verifying the validity of the digital signature when the digitally signed TID is received from the receiving MUA; And if the digital signature is valid, transmitting the relay encryption key to the receiving MUA.

When the electronic signature is valid, the electronic document exchange device may store transmission completion information of the encrypted envelope data in a reception history.

The receiving MUA may decrypt the encrypted TID using the recipient's private key.

Extracting a transmission encryption key by decrypting the encrypted envelope data using the relay encryption key to extract original text data from the encrypted envelope data; And extracting original data by decrypting the original data encrypted using the transmission encryption key. Here, the envelope data may include the encrypted original data and the encrypted transmission encryption key.

The relay encryption key may be generated using a random function.

The encrypted envelope data and the encrypted TID may be received by the receiving side MUA using POP3 (Post Office Protocol V3).

As the invention allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the written description. However, this is not intended to limit the present invention to specific embodiments, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention. In describing the drawings, similar reference numerals are used for similar elements.

Terms such as first, second, A, and B may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as the second component, and similarly, the second component may also be referred to as the first component. The term and / or includes a combination of a plurality of related items or any item of a plurality of related items.

When a component is referred to as being "connected" or "connected" to another component, it may be directly connected to or connected to that other component, but it may be understood that other components may be present in between. Should be. On the other hand, when a component is said to be "directly connected" or "directly connected" to another component, it should be understood that there is no other component in between.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprise" or "have" are intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, components, or a combination thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art. Terms such as those defined in the commonly used dictionaries should be construed as having meanings consistent with the meanings in the context of the related art, and, unless expressly defined in this application, are construed in ideal or excessively formal meanings. It doesn't work.

Hereinafter, with reference to the accompanying drawings, it will be described in detail a preferred embodiment of the present invention. Hereinafter, the same reference numerals are used for the same components in the drawings, and duplicate descriptions of the same components are omitted. In addition, in describing the present invention, when it is determined that the detailed description of the related known technology may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted.

2 is a block diagram schematically illustrating an electronic mail based electronic document exchange (EDI) system according to an exemplary embodiment of the present invention.

As illustrated in FIG. 2, the EDI system according to the present invention includes a transmitting terminal 200, an electronic document relay system 220, a receiving terminal 240, and an authentication system 260.

The transmitting terminal 200 has a transmitting side MUA 210 including a transmitting security module 210, and the receiving terminal 240 includes a receiving side MUA 245 including a receiving security module 250. do.

The MUA (Mail User Agent) is a program (mail client) used when sending and receiving mail, and may be, for example, Outlook Express. Of course, the MUAs provided in the transmitting terminal 200 and the receiving terminal 240 are not limited to a specific program, but all MUAs that may include the security modules 210 and 250 according to the present invention may be applied. Is self explanatory. The security modules 210 and 250 may be installed together in each terminal when MUA is installed, or included in the MUA by a program update or installation method, or may be installed to operate in conjunction with the MUA. Operations and functions of the MUAs 205 and 245 and the security modules 210 and 250 can be easily understood through the following descriptions, and those skilled in the art can understand the security module 210 for performing the corresponding functions by a combination of program codes. 250) and the like will be possible to design and fabricate a detailed description thereof will be omitted. In addition, the transmitting terminal 200 and the receiving terminal 240 is a terminal device capable of transmitting and receiving mail through the electronic document relay system 220 using the MUA (205, 245) installed (for example, computer device, PDA) (Personal Digital Assistant) can be applied without any limitation.

Hereinafter, the operation of the EDI system according to the present invention will be briefly described with reference to FIG. 2.

The transmitting terminal 200 and the receiving terminal 240 have a corresponding certificate (for example, according to the sender's signature authentication and / or encryption authentication application) for use of the EDI system according to the present invention. Will be stored. The procedure for applying for and issuing a certificate is a general matter, so a description thereof will be omitted. The electronic document relay system 220 may also be provided from the authentication system 260 at the time or in advance if the sender or receiver's certificate is required and stored in a predetermined storage area.

When the sender terminal 200 receives a mail transmission command from the sender, the transmission security module 210 included in or linked to the sender MUA 205 performs an electronic signature on the original text data corresponding to the mail transmission command.

Subsequently, the transmission security module 210 (or the transmitting MUA 205 including the transmission security module 210) encrypts the digitally signed original data (signed data) using the transmission encryption key (CEK). Encrypt the sending encryption key with the recipient's public key.

Subsequently, the transmitting side MUA 205 transmits the encrypted data including the encrypted original text data and the encrypted transmission encryption key to the electronic document exchange system. Enveloped data transmitted by the sending MUA 205 may be transmitted using the Simple Mail Transfer Protocol (SMTP) which is a mail standard protocol.

It is apparent that the request for receiving the certificate (or public key) of the recipient and the authentication system 260 may be preceded by the authentication system 260 to encrypt the original data.

The mail transfer agent 225 of the electronic document relay system 220 that has received the enveloped data from the sender MUA 205 generates a transaction ID (TID) according to a predetermined rule, and then the electronic document relay system. The digital signature is performed with the private key of 220 and transmitted to the transmitting MUA 225. The generated TID may be stored in the message store 230 or a predetermined storage area. Obviously, the private key of the electronic document relay system 220 may be designated in advance. For example, the mail transfer agent 225 may be a mail server having a TID generation function or the like according to the present invention. Message store 230 may also be an external database. Of course, it is apparent that the electronic document relay system 220 may be an electronic document exchange device implemented as a single device to perform an operation according to the present invention.

In this case, the signed TID may be transmitted in response to a response packet (for example, code 250) transmitted from the electronic document relay system 220 to the transmitting MUA 205. The transmitting side MUA 205 may receive a signed TID and verify the digital signature to recognize or confirm that the electronic document relay system 220 has normally received the message. As a result, denial of reception of the electronic document relay system 220 can be prevented.

When the mail transmission request is received from the receiving MUA 245, the mail transmission agent 225 generates a relay encryption key (CEK) according to a predetermined rule to generate the enveloped data (that is, the received envelope received from the sending MUA 205). Data) and encrypts the TID with the public key of the recipient's public key infrastructure (PKI) certificate and transmits it to the receiving MUA 245. Post Office Protocol V3 (POP3), which is a standard protocol for receiving e-mail, may be used between the receiving side MUA 245 and the electronic document relay system 220.

At this time, the encrypted TID and the encrypted Enveloped data transmitted to the receiving side MUA 245 may be integrated into one data and transmitted. In other words, the two encrypted data can be transmitted in the form of new integrated data. Signed data and enveloped data are specifically defined in RFC3852 (Cryptographic Message Syntax (CMS)), and thus detailed description thereof will be omitted. However, in brief, each of the plain text messages and signatures may be referred to as a signed-data CMS format, and the encrypted data may be referred to as an enveloped-data CMS format. Enveloped data consists of a specific type of encrypted content and an encryption key of encrypted content for the recipient. In contrast, signed data is encoded by base64 encoding the digital signature content and the signature encrypted with the message digest (MD) of the content to be signed with the signer's private key.

The receiving side MUA 245 (or the receiving security module 250-hereinafter identical) receives the encrypted encrypted message and encrypted TID from the mail transfer agent 225, and then generates a private key ( Decrypt the encrypted TID using the Private Key). Subsequently, the receiving side MUA 245 requests the relay encryption key (CEK) by transmitting the decrypted TID to the mail transfer agent 225 to decrypt the encrypted enveloped message. In response to the relay encryption key request of the receiving MUA 245, the mail transmission agent 225 may recognize that the receiving MUA 245 normally receives the encrypted message.

When the receiving MUA 245 receives the relay encryption key CEK, the receiving MUA 245 decrypts the encrypted message encrypted by the mail transmission agent 225 using the receiving security module 250 to extract the encrypted message.

Subsequently, the reception security module 250 (or the reception MUA 245 including the reception security module 250) extracts a transmission encryption key (CEK) from the extracted envelope message, and decrypts the encrypted original text. Verify the sender's PKI certificate from 260 to verify the digital signature.

2, the EDI system according to the present invention has been briefly described.

In addition, although the security modules 210 and 250 may be included in or interlocked with each of the MUAs 205 and 245, the description has been given based on the case where each performs an independent operation. However, it is apparent that the MUAs 205 and 245 according to the present invention may be components (or software programs) including a conventional mail user agent (MUA) and the security modules 210 and 250 according to the present invention. The method of implementing the MUAs 205 and 245 according to the present invention as a Revised-MUA (that is, the integrated MUA of the conventional mail user agent (MUA) and the security modules 210 and 250) may be omitted. Only those skilled in the art will appreciate the description of the specification.

Therefore, the following description will focus on the case where the transmitting terminal 200 and the receiving terminal 240 are provided with the Revised-MUA 205 and 245 according to the present invention.

3 is a flowchart illustrating a process of transmitting an enveloped message by a calling terminal according to an exemplary embodiment of the present invention.

Referring to FIG. 3, in step 310, the transmitting side MUA 205 determines whether a mail transmission request is input from a user. The mail transmission request may be recognized as being input by the user at each time of the mail transmission time input by the user or predetermined (for example, set in a cycle).

If a mail transmission request is input, in step 315, the sending MUA 205 digitally signs the original text data (ie, the electronic document) to be transmitted to generate signed data. This is to prevent user authentication, data integrity and non repudiation of transmission. Subsequently, the transmitting side MUA 205 generates a transmission encryption key (CEK) using a predetermined rule, and then encrypts the signed data. The transmitting MUA 205 may use a random function, for example, to generate a transmission encryption key (CEK).

In step 320, the transmitting MUA 205 encrypts the generated transmission encryption key with the public key of the recipient's public key infrastructure (PKI) certificate.

In step 325, the transmitting side MUA 205 generates the encoded data by combining the signed data encrypted in step 315 and the transmission encryption key encrypted in step 320, and transmits the encrypted data to the electronic document relay system 220.

When the mail transmission agent 225 of the electronic document relay system 220 receives the enveloped data from the sending MUA 205, it generates a TID (Transaction ID) according to a predetermined rule (step 330). The TIDs may be generated sequentially with random values or randomly generated.

In step 335, the mail transmission agent 225 electronically signs the generated TID with a private key of the electronic document relay system 220 and transmits the generated TID to the sender MUA 205. The generated TID (or digitally signed TID) is stored in a predetermined storage area. Transmitting a TID by digital signature may be a value including a TID, a digital signature value, and a sender certificate (including a public key). Therefore, encryption or decryption thereof may be unnecessary.

When the sending MUA 205 receives a digitally signed TID from the mail transfer agent 225, the sending MUA 205 verifies the digital signature of the received TID. In general, for digital signature, a short document is created with a hash function and the short document is signed with a sender's private key. Then, the signed data including the original text, the digital signature value, and the sender's certificate is transmitted to the receiver. The receiver creates the abbreviated document from the original text, generates the digital signature value using the digital signature algorithm with the sender's public key, compares it with the digital signature value sent by the sender, and verifies the signature.

If the digital signature verification is normally performed, the electronic document relay system 220 may recognize that the received envelope data is normally received. Therefore, denial of reception of the electronic document relay system 220 can be prevented.

4 is a flowchart illustrating a process of receiving an enveloped message of a receiving terminal according to an exemplary embodiment of the present invention. By decrypting the received electronic document and verifying the digital signature, confidentiality, data integrity, user authentication and repudiation are possible.

Referring to FIG. 4, in step 410, the electronic document relay system 220 (or the mail transmission agent 225, which is the same below) determines whether a mail reception request is received from the receiving MUA 245.

When the mail reception request is received, the electronic document relay system 220 generates a relay encryption key (CEK) according to a predetermined rule, and then uses the generated relay encryption key to store the enveloped data (that is, the message storage 230). The encrypted data received from the transmitting MUA () is encrypted (step 415).

Subsequently, the electronic document relay system 220 encrypts a transaction ID (TID) corresponding to the enveloped data by using the public key of the recipient's PKI certificate (step 420).

In step 425, the electronic document relay system 220 transmits the encrypted encrypted data generated in step 415 and the encrypted TID generated in step 420 to the receiving side MUA (). In this case, the relay encryption key may be stored in a predetermined storage area.

The receiving side MUA 245 receives the encrypted enveloped data and the encrypted TID from the electronic document relay system 220 and decrypts the TID using the recipient's private key generated when issuing the PKI certificate (step). 430). That is, the present invention may be applied to an asymmetric key (public key) method in which a different key is used for encryption and decryption. Of course, it is obvious that the symmetric key scheme may be applied.

The receiving side MUA 245 electronically signs the decrypted TID in step 435 and transmits it to the electronic document relay system 220. This is to request a relay encryption key to the electronic document relay system 220 to read the original text sent from the sender.

In step 440, the electronic document relay system 220 verifies whether the digital signature of the TID received from the receiving MUA 245 is valid.

If the digital signature of the TID is not valid, the step may be terminated or an error message may be transmitted to the receiving side MUA 245.

However, if the digital signature of the TID is valid, the process proceeds to step 445, where the relay encryption key is encrypted with the public key of the receiver and transmitted to the receiving MUA 245. In addition, the information is stored as a reception history. The reception history is a record of the recipient reading the message (i.e., confirming that the message has been sent to the receiving MUA 245), thereby preventing the recipient from denying the reception.

In step 450, the receiving side MUA 245 receives the encrypted relay encryption key and decrypts it with the recipient's private key. In addition, the encrypted encrypted data received from the electronic document exchange device 1 is decrypted using the decrypted relay encryption key (that is, the extracted data is extracted).

Subsequently, the receiving side MUA 245 decrypts and extracts the encrypted transmission encryption key from the enveloped data using the recipient's private key (step 455).

Subsequently, the receiving side MUA 245 performs decryption using the extracted transmission encryption key to extract signed data (step 460).

Subsequently, the receiving MUA 245 extracts the original text data after verifying the digital signature from the extracted signed data (step 465).

As described above, the present invention has the effect of ensuring user authentication, confidentiality of messages, integrity, non-repudiation of transmission and reception in an EDI system based on e-mail. There is.

The present invention also has the effect of enabling secure exchange of electronic documents from the sender's terminal to the receiver's terminal.

In addition, the present invention has the effect of maximizing the efficiency of the user terminal by implementing an E-mail based EDI system.

Although the above has been described with reference to a preferred embodiment of the present invention, those skilled in the art to which the present invention pertains without departing from the spirit and scope of the invention as set forth in the claims below It will be appreciated that modifications and variations can be made.

Claims (20)

A non-repudiation method performed by an electronic document relay system, Generating envelope ID (TID) when envelope data is received from a sending MUA (Mail User Agent); And Electronically signing the TID and transmitting it to the transmitting side MUA, When the normal verification of the digital signature of the TID is completed by the transmitting side MUA, the envelope data is recognized as being normally transmitted to the electronic document relay system. Non repudiation method. The method of claim 1, The envelope data is non repudiation method by the electronic document relay system, characterized in that the transmission using the SMTP (Simple Mail Transfer Protocol). The method of claim 1, And the digitally signed TID is transmitted in response to a response packet transmitted to the transmitting side MUA. The method of claim 1, In order to generate the envelope data, the transmitting MUA generates Encrypting the electronically signed original data using the transmission encryption key to generate encrypted data; Generating an encrypted transmission encryption key by encrypting the transmission encryption key with a private key of a receiver; and And generating the envelope data by using the encrypted data and the encrypted transmission encryption key. The method of claim 1, When a mail reception request is received from a receiving MUA, transmitting envelope data encrypted using a relay encryption key and a TID encrypted using a recipient's public key to the receiving MUA; Verifying the validity of the digital signature when the digitally signed TID is received from the receiving MUA; And And if the electronic signature is valid, transmitting the relay encryption key to the receiving MUA. The method of claim 5, And if the electronic signature is valid, storing the transmission completion information of the encrypted envelope data in a reception history. The method of claim 5, And the receiving side MUA decrypts the encrypted TID using the recipient's private key. The method of claim 5, The receiving side MUA is to extract the original data from the encrypted envelope data, Extracting a transmission encryption key by decrypting the encrypted envelope data using the relay encryption key; And Decoding the original data encrypted by using the transmission encryption key to extract the original data, And the envelope data includes the encrypted original data and the encrypted transmission encryption key. The method of claim 5, The relay encryption key is a non-repudiation method by the electronic document relay system, characterized in that generated using a random function. The method of claim 5, And said encrypted envelope data and said encrypted TID are received by said receiving side MUA using POP3 (Post Office Protocol V3). In the electronic document exchange system, A transmitting side MUA for generating and transmitting envelope data; When the envelope data is received, the electronic document exchange device transmits an electronically signed TID (Transaction ID) to the sender MUA, and transmits the encrypted envelope data and the encrypted TID corresponding to the mail receiving request. ; And And a receiving side MUA that receives the encrypted envelope data and an encrypted TID in response to the mail receiving request sent to the electronic document exchange device. The method of claim 11, And the transmitting side MUA transmits the envelope data using the Simple Mail Transfer Protocol (SMTP). The method of claim 11, And the electronic document exchange system transmits the digitally signed TID attached to a response packet transmitted to the transmitting side MUA. The method of claim 11, In order to generate the envelope data, the transmitting MUA generates Encrypting the electronically signed original data using the transmission encryption key to generate encrypted data; Generating an encrypted transmission encryption key by encrypting the transmission encryption key with a private key of a receiver; and And generating the envelope data using the encrypted data and the encrypted transmission encryption key. The method of claim 11, The electronic document exchange apparatus transmits the encrypted envelope data and the encrypted TID, Transmitting envelope data encrypted using a relay encryption key and a TID encrypted with a recipient's public key to the receiving side MUA; Verifying the validity of the digital signature when the digitally signed TID is received from the receiving MUA; And And if the electronic signature is valid, transmitting the relay encryption key to the receiving side MUA. The method of claim 15, And when the electronic signature is valid, the electronic document exchange system stores transmission completion information of the encrypted envelope data in a reception history. The method of claim 15, The receiving side MUA decrypts the encrypted TID using the recipient's private key. The method of claim 15, The receiving side MUA is to extract the original data from the encrypted envelope data, Extracting a transmission encryption key by decrypting the encrypted envelope data using the relay encryption key; And Decoding the original data encrypted by using the transmission encryption key to extract the original data, And said envelope data comprises said encrypted original data and said encrypted transmit encryption key. The method of claim 15, And the relay encryption key is generated using a random function. The method of claim 15, And said encrypted envelope data and said encrypted TID are received by said receiving side MUA using POP3 (Post Office Protocol V3).

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