JP2008299561A - Device for transmitting electronic mail - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an device for transmitting electronic mail, capable of being easily incorporated to a conventional device and improving security, without having to depend on manual operations. <P>SOLUTION: The device comprises a mail transmitting and receiving part 11 which receives an e-mail M from a client 20 via a network and transmits at least transmittable e-mails; a receiving processing part 12 which detects whether the e-mail M includes an attached file or not; an attached file encryption part 13, which encrypts the attached file of the e-mail M with a cipher key specified, based on mail source and mail address for each destination to form an encrypted attached file; a cipher key acquisition part 14 which acquires a cipher key from a cipher key storage part 2, in response to a request from the attached file encryption part 13; an attached file storage part 15 which stores the attached file, in association with the mail source and mail address thereof; and a transmission processing part 16, which acquires the encrypted attached file based on this mail source and mail address and replaces the attached file of the e-mail M to this mail address by the acquired file to form the transmittable e-mail. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electronic mail transmitting apparatus that receives an electronic mail and encrypts and transmits an unencrypted attached file.

  With the spread of electronic mail in recent years, it is a common practice to send business data obtained by digitizing business documents such as contracts and design documents attached to the electronic mail. Here, when a server having a conventional configuration is used as an e-mail server having business data as an attached file, the e-mail is stored on a local disk such as a hard disk.

  Here, when the e-mail is stored on the local disk, it may be transmitted unintentionally by a so-called virus or the like. As a result, it may be disclosed to an unspecified number of people, or sent to a destination without taking security measures, leading to an unexpected situation. Such a situation can also occur due to errors.

As a countermeasure against such a virus, a technique for encrypting an electronic mail not only in an electronic mail communication path but also in a mail box is known (see, for example, Patent Document 1). There is also a management method in which when sending an e-mail, the attached file must be encrypted before being sent.
JP 2006-039740 A

  However, in the conventional electronic mail communication device described in Patent Document 1, only specific electronic mail (for example, so-called encrypted mail) is encrypted, and other general electronic mail is transmitted without being encrypted. For this reason, there is still a problem that sufficient security cannot be secured for general electronic mail. Also, the e-mail encryption technique encrypts not only the attached file but also the entire e-mail, and it is difficult to incorporate it into a commonly used e-mail system. In addition, a dedicated mail server is required for referring to the e-mail, leading to the introduction of new equipment and increasing the economic burden. On the other hand, depending on the management method, sharing of the encryption key, encryption processing, etc. are left to the sender, and it is still difficult to eliminate errors.

  In view of the above situation, an object of the present invention is to provide an electronic mail transmitting apparatus that can be easily incorporated into a conventional apparatus and can improve security for attached files without relying on human hands.

In order to solve the above problems, the present invention provides the following configurations.
The invention according to claim 1 is an email transmission / reception unit that receives an e-mail and transmits a predetermined e-mail; a reception processing unit that determines whether an attached file is attached to the received e-mail; An attached file encryption unit that creates an encrypted attached file by encrypting the attached file of the received e-mail for each destination with an encryption key specified based on the transmission source and the destination, and an encryption key storage for storing the encryption key An encryption key acquisition unit that acquires an encryption key from the encryption key storage unit in response to a request from the attached file encryption unit, and a transmission source and destination of the e-mail that has received the encrypted attachment file And acquiring the encrypted attachment file specified based on the transmission source and destination of the received e-mail from the attachment file storage unit. A transmission processing unit that creates an e-mail that can be transmitted by replacing the attached file of the destination e-mail, and the e-mail transmission / reception unit is created by the transmission processing unit for an e-mail with an attached file The sendable e-mail is transmitted, and the received e-mail is transmitted for an e-mail without an attached file.

  According to a second aspect of the present invention, in the electronic mail transmitting device according to the first aspect, when the attached file encryption unit cannot encrypt the attached file, the transmission processing unit transmits to the corresponding destination. An e-mail from which the attached file is deleted is created as an e-mail, and the e-mail transmitting / receiving unit transmits the e-mail from which the attached file has been deleted by the transmission processing unit.

  According to a third aspect of the present invention, in the electronic mail transmitting device according to the first aspect, when an e-mail in which an attached file is deleted is created as an e-mail to be transmitted to a corresponding destination by the transmission processing unit, the e-mail It is added that the attached file is deleted, and the mail transmitting / receiving unit transmits the electronic file to which the attached file is deleted.

  According to a fourth aspect of the present invention, in the electronic mail transmitting device according to the first aspect, when the transmission processing unit creates an electronic mail from which an attached file is deleted as an electronic mail to be transmitted to a corresponding destination, the mail transmission / reception is performed. Is notified to the transmission source that the attached file has been deleted from the destination electronic mail.

  According to a fifth aspect of the present invention, in the electronic mail transmitting device according to the first aspect, the encryption key storage unit is configured as an external server that is communicably connected via the network. .

  According to the first aspect of the present invention, a mail transmission / reception unit that receives an e-mail and transmits a predetermined e-mail, and a reception processing unit that determines whether or not an attached file is attached to the received e-mail. An attached file encryption unit that creates an encrypted attached file by encrypting the attached file of the received e-mail for each destination with an encryption key specified based on the source and destination, and an encryption key storage for storing the encryption key And an encryption key acquisition unit that acquires an encryption key from the encryption key storage unit in response to a request from the attached file encryption unit, and stores the encrypted attachment file in correspondence with the transmission source and destination of the received email The attachment storage unit and the encrypted attachment specified based on the source and destination of the received e-mail are acquired from the attachment storage unit, and the attachment file of the e-mail of this destination is acquired. A transmission processing unit that creates a sendable e-mail by replacing it with a file, and the e-mail transmission / reception unit sends a sendable e-mail created by the transmission processing unit to an e-mail with an attached file, and attaches it An e-mail transmission device that can easily be incorporated into a conventional device and can improve security for attached files without relying on human hands, because the received e-mail is transmitted in response to an e-mail without a file. Can be realized.

  According to the second aspect of the invention, in addition to the effect of the first aspect, when the attached file encryption unit cannot encrypt the attached file, the transmission processing unit sends an e-mail to the corresponding destination. Since the e-mail from which the attached file is deleted is created and the e-mail transmitting / receiving unit transmits the e-mail from which the attached file has been deleted by the transmission processing unit, at least an e-mail without an attached file can be transmitted to the destination.

  According to the invention of claim 3, in addition to the effect of claim 1, when an e-mail in which an attached file is deleted is created as an e-mail to be transmitted to a corresponding destination by the transmission processing unit, Append that the attached file has been deleted, and send / receive the email transmission / reception unit to notify the recipient that the attached file has been deleted for security reasons to send the added electronic file that the attached file has been deleted be able to.

  According to the invention of claim 4, in addition to the effect of claim 1, when the e-mail transmission / reception unit creates an e-mail with the attached file deleted as an e-mail to be transmitted to the corresponding destination by the transmission processing unit, Since the sender is notified that the attached file has been deleted from the destination electronic mail, the sender can be notified that the attached file has been deleted for security reasons.

  According to the invention of claim 5, in addition to the effect of claim 1, the encryption key storage unit is configured as an external server that is communicably connected via a network. Resources can be brought into the outside where they can be used.

Hereinafter, embodiments of the present invention will be described with reference to the drawings showing examples.
FIG. 1 is a block diagram schematically showing an embodiment of an electronic mail transmitting apparatus according to the present invention. As shown in FIG. 1, the e-mail transmission device 1 receives an e-mail M from a client 20 that is communicably connected via a network 30 and transmits a predetermined e-mail, A reception processing unit 12 that determines whether or not an attached file is attached to the received electronic mail M, and encrypts the attached file of the received electronic mail M for each destination with an encryption key that is specified based on the transmission source and the destination. An attached file encryption unit 13 for creating an encrypted attached file, an encryption key obtaining unit 14 for obtaining an encryption key from the encryption key storage unit 2 in response to a request from the attached file encryption unit 13, and an encrypted attachment An attached file storage unit 15 that stores a file in correspondence with the transmission source and destination of the email M, and an encrypted attachment file specified based on the transmission source and destination of the email M A transmission processing unit 16 that obtains a file from the attached file storage unit 15 and replaces it with the attached file of the destination email M to create a sendable email. A sendable e-mail created by the transmission processing unit 16 is sent to the e-mail, and a received e-mail is sent to an e-mail without an attached file.

  Here, the encryption key storage unit 2 is configured to store an encryption key for each transmission source and destination of an email, and is configured to be accessible even if included in the email transmission device 1. Server 3 or both of them. When configured as an external server, the encryption key can be managed in an environment in which security measures are taken in response to, for example, LDAP (Lightweight Directory Access Protocol).

  FIG. 2 is a flowchart for describing processing performed by the reception processing unit. When the mail transmission / reception unit 11 receives an e-mail, the reception processing unit 12 examines a predetermined part of the received e-mail (S101) and determines whether there is an attached file (S102). When it is determined that there is an encrypted attached file, an electronic mail that can be transmitted is created and transmitted, and an encrypted attached file electronic mail is created and transmitted (S103).

  Here, the determination of whether or not there is an attached file depends on the configuration of the e-mail. This can be realized by determining whether “mixed” is set.

  When it is determined in step S102 that there is no attached file, the mail transmitting / receiving unit 11 transmits the received electronic mail as it is (S104), and the process ends.

  The encrypted attached file e-mail creation / transmission process will be described below. First, a process for acquiring an encryption key will be described. FIG. 3 is a flowchart illustrating an example of processing for acquiring an encryption key from an encryption key storage unit based on an e-mail address. First, the encryption key acquisition unit 14 performs an encryption key reading process from the encryption key storage unit 2 in response to a request from the attached file encryption unit 13 (S211).

  FIG. 4 is an explanatory diagram illustrating a configuration of a record in which the encryption key storage unit stores the encryption key. As shown in FIG. 4, the encryption key 402 is stored in the transmission source record of the encryption key storage unit 2 in association with the destination mail address 401. In step S211, for example, a process of reading the encryption key corresponding to the sender and destination email addresses from the encryption key storage unit 2 is performed.

  Next, the encryption key acquisition unit 14 determines whether or not the encryption key can be read by the reading process in step S211 (S212), and if it is determined that the encryption key can be read, the read encryption key Is output to the attachment encryption unit 13 of the request source (S213), and if it is determined that the file cannot be read, a notification that the request has not been properly read is output to the attachment file encryption unit 13 of the request source (S213).

  FIG. 5 is a flowchart corresponding to FIG. 3 in a configuration in which the encryption key can be stored in the external server in addition to the encryption key storage unit. In this configuration, the encryption key acquisition unit 14 reads an encryption key from the external server 3 via the mail transmission / reception unit 11 as indicated by a broken line in FIG. Hereinafter, the same steps as those described with reference to FIG. 3 are denoted by the same reference numerals, and the description thereof is omitted.

  When it is determined that the encryption key cannot be read in the process in step S212 after the encryption key reading process from the encryption key storage unit in step S211, the encryption key acquisition unit 14, for example, as described above Then, the encryption key is read into an external server via the mail transmission / reception unit 11 (S224).

  Next, the encryption key acquisition unit 14 determines whether or not the encryption key can be read by the reading process in step S224 (S225), and if it is determined that the encryption key can be read, the read encryption key Is output to the attachment encryption unit 13 of the request source (S213), and if it is determined that the file cannot be read, a notification that the request has not been properly read is output to the attachment file encryption unit 13 of the request source (S226).

  In this embodiment, when the encryption key cannot be read from the encryption key storage unit, the external server is configured to perform the read process. A configuration in which reading processing is performed only on the server may be used.

  FIG. 6 is a flowchart for explaining a processing example performed by the attached file encryption unit in the encrypted attached file e-mail creation and transmission process. First, the attached file encryption unit 13 acquires the total number N of destination mail addresses in the received electronic mail (S301), and sets the address counter cnt to 1 (S302).

  Next, the attached file encryption unit 13 acquires a destination mail address in the order specified by the address counter cnt (S303), and further acquires an attached file from the electronic mail (S304). Here, the method of acquiring the attached file differs depending on the configuration of the e-mail. For example, in the case of MIME (Multipurpose Internet Mail Extensions), the method is performed as follows.

  In the case of MIME, since the following string in Content-Type is information that can identify an attached file (hereinafter, attached file information), this portion in which the attached file information is described is cut out and cut out. Get the file type and file name from the header of the part. Next, the data of the attached file is acquired, information on the encoding method of the attached file is acquired from the header, and the attached file is restored and acquired by performing decoding according to the encoding method.

  Next, the attached file encryption unit 13 stores predetermined information including the destination mail address in the attached file storage unit 15 (S305). FIG. 7 is an explanatory diagram of a record configuration in which the attached file storage unit stores a destination mail address. In FIG. 7, this record includes a transmission source mail address 701, a time stamp 702, a destination mail address 703, an attached file 704, and the like.

  Here, the sender mail address 701 stores the sender mail address described in the FROM in the header of the email, and the time stamp 702 indicates the arrival time of the email up to a digit of, for example, 1/100 second. The destination e-mail address 703 stores the e-mail address of the destination described in TO, CC, and BCC in the header of the e-mail, and the attached file 704 stores an attached file to be attached according to the destination e-mail address 703. It is a field. In step S305, in addition to the destination mail address 703, the source mail address 701 and the time stamp 702 are also stored in correspondence.

  Next, the attached file encryption unit 13 performs the encryption key reading process according to the destination mail address as described above via the encryption key acquisition unit 14 (S306), and whether or not the encryption key can be read. Is determined (S307).

  When it is determined in step S307 that the encryption key has been read, the attached file encryption unit 13 creates an encrypted attached file by encrypting the attached file using the read encryption key (S308). The file is stored in the field of the corresponding attached file 704 in the record specified by the source mail address 701, the time stamp 702, and the destination mail address 703 (S309).

  Here, the encryption method performed in step S308 is not particularly limited. For example, an encryption method using a public key such as a DES (Data Encryption Standard) encryption method or an RSA public key method may be used for encryption. it can. In addition, for decryption performed on the destination side of the encrypted attachment file, for example, double-clicking the icon of the encrypted attachment file to launch the encryption input dialog, for example, from the viewpoint of operability Is preferable. Alternatively, another self-expanding configuration may be used to input a cipher.

  When it is determined in step S307 that the encryption key cannot be read, or when the encrypted attached file is stored in step S309, the attached file encryption unit 13 sets the address counter cnt to the total number N of destination mail addresses. It is determined whether or not they are equal (S310). When it is determined that they are equal, the processing ends. When it is determined that they are not equal, the address counter cnt is incremented by 1 (S311), and the above processing is repeated from step S303.

  FIG. 8 is a flowchart for explaining the transmission process of the encrypted attached file e-mail creation / transmission process. First, the transmission processing unit 16 acquires the total number N of destination mail addresses in the received e-mail (S401), and sets the address counter cnt to 1 and the error counter err to 0 (S402).

  Next, the transmission processing unit 16 deletes the attached file from the received e-mail to make an e-mail main body (S403). The method of deleting the attached file differs depending on the configuration of the e-mail. For example, in the case of the above-mentioned MIME, since the character string below boundary = in the Content-Type is attached file information, it is deleted.

  Next, the transmission processing unit 16 acquires a destination mail address in the order specified by the address counter cnt from the e-mail (S404), and a corresponding attached file based on the source mail address and the destination mail address. Is read from the attached file storage unit 15 (S405), and it is determined whether or not the corresponding attached file has been read (S406).

  When it is determined in step S406 that the attached file has been read, the transmission processing unit 16 copies the main body of the e-mail and attaches the read attached file to create a sendable e-mail and sets it as an e-mail to this destination. (S407), when it is determined in step S406 that the attached file cannot be read, as error processing, the fact that the attached file has been deleted and the reason thereof are added to the main body of the e-mail so that it can be read as an e-mail. The record that could not be stored is stored (S408), and the error counter err is incremented by 1 (S409).

  FIG. 9 is a diagram showing an example of contents to be added to the electronic mail main body in error processing. As the contents of the additional writing, as shown in FIG. 9, for example, at least the deletion of the attached file, the reason for the deletion, and the contact information are described. Here, the above-mentioned contact address refers to a contact address of an administrator of a system to which the electronic mail transmitting apparatus according to the present invention is applied.

  When a sendable e-mail attached with an attached file is created in step S407, or when the error counter err is incremented by 1 in step S409, the reception processing unit 12 sends the attached file attached in step S407. The possible e-mail or the e-mail obtained by performing error processing in step S408 is transmitted to the corresponding destination (S410).

  Next, when the e-mail is transmitted to the corresponding destination in step S410, the transmission processing unit 16 determines whether or not the address counter cnt is equal to the total number N of the destination e-mail addresses (S411), and determines that they are not equal. When this happens, the address counter cnt is incremented by 1 (S412), and the above-described processing from step S404 is repeated.

  When it is determined in step S411 that the address counter cnt is equal to the total number N of destination mail addresses, the transmission processing unit 16 determines whether or not the error counter err is 0 (S413), and determines that it is 0. The process ends, and when it is determined that it is not 0, the mail address of each destination subject to error processing is acquired from the record number stored in step S408, and an error mail is transmitted to the transmission source (S414).

  FIG. 10 is a diagram illustrating an example of contents described in the error mail. As shown in FIG. 10, for example, the e-mail transmission time, the list of e-mail addresses of the destinations sent by deleting the attached file, the fact that the attached file has been deleted, and the reason for deletion, as shown in FIG. Is at least described.

It is a block block diagram which shows typically one Example of the electronic mail transmitter by this invention. It is a flowchart explaining the process which a reception process part performs. It is a flowchart explaining the example of a process which acquires an encryption key from an encryption key storage part based on an e-mail address. It is explanatory drawing which shows the structure of the record in which an encryption key storage part stores an encryption key. FIG. 4 is a flowchart corresponding to FIG. 3 in a configuration in which the encryption key can be stored in the external server in addition to the encryption key storage unit. It is a flowchart explaining the process example which the attachment file encryption part performs among encryption attachment file e-mail preparation transmission processes. It is explanatory drawing of the record structure in which an attached file storage part stores the mail address of a destination. It is a flowchart explaining the transmission process among encryption attachment file e-mail preparation transmission processes. It is a figure which shows an example of the content added to an email main body in an error process. It is a figure which shows an example of the content described in an error mail.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electronic mail transmitter 2 Encryption key storage part 3 External server 11 Mail transmission / reception part 12 Reception processing part 13 Attached file encryption part 14 Encryption key acquisition part 15 Attached file storage part 16 Transmission processing part 20 Client 30 Network 401 Destination mail address 402 Encryption key 701 Source mail address 702 Time stamp 703 Destination mail address 704 Attached file M E-mail

Claims (5)

  A mail transmission / reception unit that receives an e-mail and transmits a predetermined e-mail, a reception processing unit that determines whether or not an attachment file is attached to the received e-mail, and an attachment file of the received e-mail Attached file encryption unit that creates an encrypted attached file by encrypting for each destination with an encryption key specified based on a transmission source and a destination, an encryption key storage unit that stores an encryption key, and the attachment file encryption An encryption key acquisition unit that acquires an encryption key from the encryption key storage unit in response to a request from the unit, and an attachment file storage unit that stores the encrypted attachment file corresponding to the transmission source and destination of the electronic mail And acquiring the encrypted attached file specified based on the source and destination of the received e-mail from the attached file storage unit, and sending the e-mail of the destination A transmission processing unit that creates an e-mail that can be transmitted by replacing the attached file, and the e-mail transmission / reception unit receives the e-mail that the transmission processing unit has created for the e-mail with the attached file An e-mail transmitting apparatus that transmits the received e-mail to an e-mail that has been transmitted and has no attached file.   When the attached file encryption unit could not encrypt the attached file, the transmission processing unit creates an e-mail from which the attached file is deleted as an e-mail to be transmitted to a corresponding destination, and the e-mail transmitting / receiving unit The e-mail transmission apparatus according to claim 1, wherein the e-mail from which the attached file is deleted is transmitted by the transmission processing unit.   When the e-mail with the attached file deleted is created as an e-mail to be sent to the corresponding destination by the transmission processing unit, the e-mail sending / receiving unit adds the fact that the attached file has been deleted. 3. The electronic mail transmitting apparatus according to claim 1, wherein the electronic file to which the file is deleted is transmitted.   When the e-mail with the attached file deleted is created as an e-mail to be sent to the corresponding destination by the transmission processing unit, the e-mail transmitting / receiving unit notifies the sender that the attached file has been deleted from the e-mail at the destination. The electronic mail transmitting device according to any one of claims 1 to 3, wherein the electronic mail transmitting device is configured.   The electronic mail transmitting device according to any one of claims 1 to 4, wherein the encryption key storage unit is configured as an external server that is communicably connected via the network.

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