JP2008052537A - Electronic mail processing system, electronic mail processing method and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electronic mail processing system or the like suitable to hold secret of an electronic mail even when receiving Web mail service on a display terminal of an Internet cafe available to a third party by use of a mobile terminal such as a camera-equipped cellphone. <P>SOLUTION: The mobile terminal 103 generates a public key and a private key in starting a service, the public key is stored in a server device 102 functioning as a Web mail server, and the private key is stored in the mobile terminal 103. The electronic mail received by the server device 102 is encrypted by the public key, and thereafter is two-dimensionally encoded to generate an encoded image. A display terminal 104 displays the encoded image through the Web mail service. When a user photographs the encoded image displayed on the display terminal 104, the mobile terminal 103 decodes a two-dimensional code for the photographed image, decrypts it using the private key, and acquires and displays contents of the electronic mail. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention provides an electronic mail suitable for maintaining the confidentiality of an electronic mail even when receiving a web mail service at a display terminal of an Internet cafe that can be used by a third party using a mobile terminal such as a mobile phone with a camera. The present invention relates to a processing system, an e-mail processing method, a server device, a portable terminal, and a program for realizing these on a computer and a portable terminal.

Conventionally, an encryption system using a two-dimensional bar code such as a QR code (registered trademark) has been proposed. The inventors have proposed an encryption system using a mobile phone in the following document.
Nikkei Sangyo Shimbun, December 14, 2005, page 1, "Encrypting mobile images Chaosware safe transmission system"

  In the technique disclosed in [Non-Patent Document 1], an encryption key used for encryption is converted into a two-dimensional barcode, and this is captured by the camera of the mobile phone, and the encryption key is taken into the mobile phone. When transmitting an image taken with a mobile phone camera, the image is acquired after being encrypted with the encryption key and decrypted with the encryption key on the receiving side, and the encryption key is secured. Information leakage in transmission and communication paths is prevented.

  On the other hand, web mail services using Internet browsers are being widely used. In webmail, an Internet browser is used as an interface for displaying e-mails, so there is an advantage that the contents of e-mails addressed to itself can be displayed even on terminals of other people or terminals of Internet cafes. is there.

  However, if the content of the e-mail is displayed as it is on a terminal used by a third party, the e-mail content remains in the cache of the Internet browser, for example, or the e-mail content is activated by spyware run by another person. There is a risk of information leakage, such as leakage.

  Therefore, there is a great demand for reducing the risk of information leakage while maintaining the advantage of the web mail service that can be used anywhere.

  The present invention solves the above-mentioned problems, and when using a mobile terminal such as a camera-equipped mobile phone, even when receiving a web mail service on a display terminal of an Internet cafe that can be used by a third party, It is an object of the present invention to provide an electronic mail processing system, an electronic mail processing method, and a program for realizing these on a computer and a portable terminal, which are suitable for maintaining the secret of electronic mail.

  In order to achieve the above object, the following invention is disclosed in accordance with the principle of the present invention.

  An electronic mail processing system according to a first aspect of the present invention includes a server device and a mobile terminal, and is configured as follows.

  That is, the mobile terminal includes a key generation unit, a public key transmission unit, a secret key storage unit, an image photographing unit, a decryption unit, a decryption unit, and a mail display unit.

  Here, the key generation unit generates a pair of a public key and a secret key for the user of the mobile phone.

  On the other hand, the public key transmission unit transmits the generated public key to the server device.

  Further, the secret key storage unit stores the generated secret key.

  On the other hand, the server device includes a public key reception unit, a public key storage unit, a mail reception unit, an encryption unit, an encoding unit, and an image transmission unit.

  Here, the public key receiving unit receives the public key transmitted from the portable terminal.

  On the other hand, the public key storage unit stores the received public key.

  Further, the mail receiving unit receives an electronic mail transmitted from the mail sender to the user of the mobile terminal.

  Then, the encryption unit encrypts the received electronic mail with the stored public key, and outputs the result of the encryption as an encrypted message.

  On the other hand, the encoding unit performs two-dimensional image encoding on the output encrypted message and outputs the result of the encoding as an encoded image.

  Further, the image transmission unit transmits the output encoded image to the display terminal, and causes the display terminal to display the encoded image.

  On the other hand, the image capturing unit captures the encoded image received and displayed by the display terminal.

  On the other hand, the decoding unit decodes the captured encoded image by inverse transformation with respect to the two-dimensional image encoding, and outputs the decoding result as a decoded message.

  Further, the decryption unit decrypts the output decrypted message with the stored secret key, and outputs the decrypted result as a received electronic mail.

  Then, the mail display unit displays the output received electronic mail.

  In the electronic mail processing system of the present invention, the server device transmits an encoded image to the display terminal by a web mail service via an Internet browser, and the display terminal is encoded by the Internet browser. An image can be received and displayed.

  In the electronic mail processing system of the present invention, the server device further includes a mail storage unit for storing the received electronic mail, and after the request for the web mail service is requested from the display terminal, the stored electronic mail is stored. The encryption and the encoding can be performed, and the encoded image can be transmitted as a response to the web mail service.

  A server device according to another aspect of the present invention is a server device in the electronic mail processing system.

  The portable terminal which concerns on the other viewpoint of this invention is a portable terminal in said electronic mail processing system.

  An electronic mail processing method according to another aspect of the present invention is executed by a server device and a mobile terminal, and the mobile terminal includes a key generation unit, a public key transmission unit, a secret key storage unit, an image photographing unit, and a decryption unit. The server device has a public key reception unit, a mail reception unit, a public key storage unit, an encryption unit, an encoding unit, and an image transmission unit. Key transmission process, private key storage process, image photographing process, decryption process, decryption process, mail display process, public key reception process, mail reception process, public key storage process, encryption process, encoding process, image transmission process The configuration is as follows.

  That is, in the mobile terminal, in the key generation process, the key generation unit generates a pair of a public key and a private key for the user of the mobile phone.

  On the other hand, in the public key transmission step, the public key transmission unit transmits the generated public key to the server device.

  Further, in the secret key storage step, the secret key storage unit stores the generated secret key.

  On the other hand, in the public key receiving step, the public key receiving unit receives the public key transmitted from the portable terminal.

  In the public key storage step, the public key storage unit stores the received public key.

  Further, in the mail receiving step, the mail receiving unit receives an electronic mail transmitted from the mail sender to the user of the mobile terminal.

  On the other hand, in the encryption step, the encryption unit encrypts the received e-mail with the stored public key, and outputs the result of the encryption as an encrypted message.

  Further, in the encoding step, the encoding unit performs two-dimensional image encoding on the output encrypted message, and outputs the result of the encoding as an encoded image.

  Then, in the image transmission step, the image transmission unit transmits the output encoded image to the display terminal, and causes the display terminal to display the encoded image.

  On the other hand, in the image capturing process at the portable terminal, the image capturing unit captures the encoded image received and displayed by the display terminal.

  Further, in the decoding step, the decoding unit decodes the captured encoded image by inverse transformation with respect to the two-dimensional image encoding, and outputs the decoding result as a decoded message.

  In the decryption step, the decryption unit decrypts the output decrypted message with the stored secret key, and outputs the decryption result as a received electronic mail.

  On the other hand, in the mail display process, the mail display unit displays the output received electronic mail.

  In the electronic mail processing method of the present invention, the server device transmits an encoded image to the display terminal by a web mail service via an Internet browser, and the display terminal is encoded by the Internet browser. An image can be received and displayed.

  Further, in the electronic mail processing method of the present invention, the server device further includes a mail storage unit for storing the received electronic mail, and after the request for the web mail service is requested from the display terminal, the stored electronic mail is stored. The encryption and the encoding can be performed, and the encoded image can be transmitted as a response to the web mail service.

  A program according to another aspect of the present invention is configured to cause a computer to function as the server device or the mobile terminal.

  The program can be recorded on a computer-readable information recording medium (including a compact disk, flexible disk, hard disk, magneto-optical disk, digital video disk, magnetic tape, or semiconductor memory).

  The information recording medium can be distributed and sold independently of the computer, and the program itself can be distributed and sold via a computer communication network such as the Internet.

  According to the present invention, even when a web mail service is received at a display terminal of an Internet cafe that can be used by a third party using a mobile terminal such as a camera-equipped mobile phone, it is suitable for maintaining the secrecy of e-mail. An electronic mail processing system, an electronic mail processing method, a server device, a portable terminal, and a program that realizes these on a computer and a portable terminal can be provided.

  Embodiments of the present invention will be described below. The embodiments described below are for illustrative purposes and do not limit the scope of the present invention. Accordingly, those skilled in the art can employ embodiments in which each or all of these elements are replaced with equivalent ones, and these embodiments are also included in the scope of the present invention. .

  FIG. 1 is an explanatory diagram showing a schematic configuration of an embodiment of a cryptographic communication system according to the present invention. Hereinafter, a description will be given with reference to FIG.

  In the present embodiment, the e-mail processing system 101 includes a server device 102 that functions as a web mail server, and a display terminal 104 that can use a browser for displaying web mail prepared in an Internet cafe or the like. In addition to the connection via the mobile terminal 103, communication to upload the public key is performed from the mobile terminal 103 realized by a mobile phone with a camera to the server apparatus 102.

  In addition, the display terminal 104 and the mobile terminal 103 are not connected so as to be directly communicable with each other, but by capturing an image displayed on the screen of the display terminal 104 using a digital camera included in the mobile terminal 103, information can be obtained. Exchange.

  Generally, at travel destinations, especially overseas, it is possible to keep privacy by bringing your own mobile phone to send and receive e-mail, but the amount of packet communication is often extremely high. On the other hand, fees for using Internet cafes are generally low. However, using webmail at an Internet cafe often has problems from a privacy perspective.

  This embodiment has an advantage that a low-priced Internet cafe can be used while maintaining privacy when reading an email in consideration of such a price difference.

  FIG. 2 is an explanatory diagram showing a schematic configuration of the mobile terminal according to the present embodiment. Hereinafter, a description will be given with reference to FIG.

  The portable terminal 103 includes a key generation unit 201, a public key transmission unit 202, a secret key storage unit 203, an image photographing unit 204, a decryption unit 205, a decryption unit 206, and a mail display unit 207. These are typically realized by executing a program on the mobile terminal 103.

  FIG. 3 is a flowchart showing the control flow of the registration request process executed by the mobile terminal 103. This process is executed only once when the user starts using the electronic mail processing system of the present embodiment. Hereinafter, a description will be given with reference to FIG.

  When this process is started, the key generation unit 201 of the mobile terminal 103 generates a public / private key pair for the user of the mobile phone (step S301).

  In a public key system such as RSA encryption, it is typical that a user inputs a passphrase and uses the passphrase as a secret key. In this embodiment, a pair of a secret key and a public key is used as a portable terminal. 103 generates. Information corresponding to the passphrase may be generated using a random number or the like, or may be obtained by observing an appropriate input state from the user.

  Next, the public key transmission unit 202 transmits the generated public key to the server apparatus 102 (step S302).

  A program that can be executed by a mobile phone cannot communicate with a general server from the viewpoint of security, but is often configured to communicate with a server provided with the program. Therefore, the server apparatus 102 of this embodiment is configured to provide the program. In the present embodiment, only the public key is transmitted to the server apparatus 102.

  Next, the secret key storage unit 203 stores the generated secret key (step S303) and ends this process.

  Typically, the secret key is stored in a non-volatile memory such as a flash EEPROM provided in the mobile phone. When actually reading an e-mail, it is possible to obtain a secret key associated with the public key registered in the server apparatus 102 by accessing such a nonvolatile memory.

  Processing in the image capturing unit 204, the decoding unit 205, the decoding unit 206, and the mail display unit 207 will be described later.

  FIG. 4 is an explanatory diagram showing a schematic configuration of the server apparatus 102 in the present embodiment. Hereinafter, a description will be given with reference to FIG.

  The server apparatus 102 includes a public key receiving unit 401, a public key storage unit 402, a mail receiving unit 403, an encryption unit 404, an encoding unit 405, an image transmission unit 406, a mail storage unit 411, and an image storage unit 412.

  The server apparatus 102 provides a general web mail service as a normal service, and provides a service with enhanced privacy and security protection by applying the present invention. Therefore, a known technique can be applied as it is to a basic element for providing the web mail service. In addition, processing of each unit of the server apparatus 102 is realized by executing a program prepared in advance on the server computer.

  FIG. 5 is a flowchart showing a control flow of the registration acceptance process executed by the server apparatus 102. Hereinafter, a description will be given with reference to FIG.

  First, the public key receiving unit 401 receives the public key transmitted from the mobile terminal 103 (step S501).

  This public key is paired with the secret key generated by the mobile terminal 103 when the user of the mobile terminal 103 starts using the electronic mail processing system.

  Next, the public key storage unit 402 stores the received public key and ends this process (step S502). Usually, it is stored in a nonvolatile manner in a hard disk or the like in association with user information of the user of the portable terminal 103.

  Since the server apparatus 102 functions as a kind of web mail server, as user information, an e-mail address, billing information, or an e-mail received in the past (may be encrypted by the function of this system or select an option) In some cases, raw data may be stored / provided as it is.) Information on various settings is managed in the same way as a normal web mail server.

  In addition, if the phone number of the mobile phone functioning as the mobile terminal 103 is also stored in the same manner, which phone should a user with multiple mobile phones use when displaying webmail on the display terminal 104? It ’s easier to check.

  In this way, when the registration request process is executed by the portable terminal 103 and the registration acceptance process is executed by the server apparatus 102, the “initialization” of the electronic mail processing system is completed, and thereafter, the electronic mail itself is processed. Is called.

  FIG. 6 is a flowchart showing the control flow of the mail storage process executed by the server apparatus 102. This process is started when an e-mail is transferred from another mail server to a user managed by the server apparatus 102 based on the SMTP (Simple Mail Transfer Protocol) protocol or the like. Hereinafter, a description will be given with reference to FIG.

  First, the mail receiving unit 403 receives an e-mail transmitted from the mail sender to the user of the mobile terminal 103 (step S601), and temporarily stores it in the mail storage unit 411 (step S602). This process is the same as the e-mail reception executed by a normal web mail server.

  Next, the encryption unit 404 encrypts the received electronic mail with the stored public key, and outputs the result of the encryption as an encrypted message (step S603).

  The public key is generated by the mobile terminal 103, and a secret key stored in the mobile terminal 103 is necessary to decrypt the encrypted message. For this encryption, techniques used in various public key cryptosystems such as RSA cryptography can be applied.

  At this time, the information on the e-mail to be encrypted can include a title, a sender, and the like in addition to the e-mail body. In the following description, it is assumed that all information of the electronic mail is encrypted.

  Further, the encoding unit 405 performs two-dimensional image encoding on the output encrypted message, outputs the result of the encoding as an encoded image (step S604), and associates the code with the user. The converted image is stored in the image storage unit 412 (step S605). At this time, it is desirable to store information on the time when the electronic mail is received (this is not “information included in the electronic mail”).

  The two-dimensional image coding here corresponds to a so-called two-dimensional (bar) code. For example, the most popular two-dimensional bar code at present in Japan is a QR code. In addition, various two-dimensional codes such as PDF417, DataMatrix, and MaxiCode can be used. All of these two-dimensional codes are standardized by AIM International and ISO.

  For example, in a QR code, 7089 numbers can be stored in one encoded image, 4296 alphanumeric characters, 2953 binary data, and 1817 Chinese characters. Therefore, when the size of the mail is larger than this, processing such as dividing the electronic mail or omitting the latter half is performed.

  Then, the server apparatus 102 deletes the e-mail that is the source of the encoded image from the mail storage unit 411 (step S606), and ends this process.

  In this way, the encoded image obtained by image-encrypting the e-mail is managed by the server apparatus 102 in association with the user. Since the server device 102 is a kind of web mail server, as with a normal web mail server, when there is a request for displaying “e-mail” via a browser from a display terminal 104 such as a computer of an Internet cafe or various computers, An “e-mail” addressed to the user will be provided. In this process, authentication by a user name and a password is performed in the same manner as normal web mail.

  However, in the present embodiment, since the “e-mail” text itself has been deleted from the mail storage unit 411, the text of the “e-mail” itself is not provided.

  Instead, the image transmission unit 406 transmits the encoded image stored in the image storage unit 412 to the display terminal 104 and causes the display terminal 104 to display the encoded image.

  FIG. 7 is an explanatory diagram showing a display example of the encoded image displayed on the display terminal 104 by such processing. Hereinafter, a description will be given with reference to FIG.

  The browser screen 701 displays a list of encoded images 703 corresponding to the date and time 702 at which the e-mail was received and the e-mail text (including the sender and title).

  For the email received after the user displayed this list by the previous webmail service, the reception date and time 702 is highlighted, so that it is clear which mail is unread. .

  In addition, the total number of emails and the mobile phone number of the mobile terminal 103 that generated the public key of the user are also displayed.

  As described above, even if the user displays the encoded image on the screen using the display terminal 104 in which privacy and security are not necessarily ensured, there is no possibility that the contents are known. This is because the content of the e-mail is encrypted by public key cryptography.

  A user who wants to read the contents of an electronic mail causes the portable terminal 103 to execute the following mail decryption process.

  FIG. 8 is a flowchart showing the flow of control of mail decryption processing executed by the mobile terminal 103. Hereinafter, a description will be given with reference to FIG.

  When this process is started by a user instruction, the image capturing unit 204 captures an encoded image received and displayed by the display terminal 103 (step S801).

  As described above, this photographing is typically performed by a digital camera or a scanner provided in a mobile phone that constitutes the mobile terminal 103. Bar code reading functions and QR code reading functions have already been incorporated into mobile phones, and various technologies can be applied.

  Next, the decoding unit 205 decodes the captured encoded image by inverse transformation with respect to the two-dimensional image encoding, and outputs the decoding result as a decoded message (step S802).

  This is related to the recognition of the two-dimensional code, and the decoding corresponding to the reverse process of the encoding is performed according to the QR code standard.

  Further, the decryption unit 206 decrypts the output decrypted message with the stored secret key, and outputs the decryption result as a received electronic mail (step S803).

  The secret key is paired with the public key generated at the start of system use. Since the server apparatus 102 is encrypted with the public key, the secret key can be decrypted.

  Then, the mail display unit 207 displays the output received electronic mail (step S804), and ends this process. Typically, the content of the e-mail is displayed as character information on the display screen of the mobile terminal 103.

  In the electronic mail processing system of the present invention, the server apparatus 102 transmits the encoded image to the display terminal 104 by a web mail service via an Internet browser, and the display terminal 104 transmits the encoded image by the Internet browser. An encoded image can be received and displayed.

  In the above description, one server computer is assumed as the server apparatus 102. However, each process may be distributed to a plurality of computers. For example, a mail addressed to a non-web mail address that is temporarily used during travel is forwarded to an encryption code server, and the encryption code server encrypts and encodes the image. It is a form in which a free web mail server is accessed from a cafe, a screen is taken with a mobile phone, and a mail text is obtained. In this case, the encryption code server and the free webmail server work together to function as the server apparatus 102 of the above embodiment.

  In the above description, every time the server apparatus 102 receives an e-mail, encryption using a public key and encoding into a two-dimensional code are performed. However, the following modes may be used.

  That is, when an e-mail is received, it is the same as in the above embodiment until it is stored in the mail storage unit 411 in a nonvolatile manner. The opportunity to start encryption and encoding is a request for the web mail service made from the display terminal 103. The generated encoded image is immediately transmitted to the display terminal 104.

  In this case, the e-mail text may not be deleted from the mail storage unit 411 after the encoded image is generated, or the image storage unit 412 may not be provided.

  This embodiment is suitable for providing a web mail service that can temporarily change whether an e-mail display method is to display raw data or to display an encoded image by option setting. is there.

  As described above, according to the present invention, even when a web mail service is received at a display terminal of an Internet cafe that can be used by a third party using a mobile terminal such as a mobile phone with a camera, the secret of the e-mail is kept. An electronic mail processing system, an electronic mail processing method, a server device, a portable terminal, and a program that realizes these on a computer and a portable terminal can be provided, and is applied to the field of cryptographic communication be able to.

1 is a schematic diagram showing a schematic configuration of an electronic mail processing system according to an embodiment of the present invention. It is explanatory drawing which shows schematic structure of the portable terminal which concerns on this embodiment. It is a flowchart which shows the flow of control of the registration request process performed with a portable terminal. It is explanatory drawing which shows schematic structure of the server apparatus in this embodiment. It is a flowchart which shows the flow of control of the registration reception process performed with a server apparatus. It is a flowchart which shows the flow of control of the mail preservation | save process performed with a server apparatus. It is explanatory drawing which shows the example of a display of the encoded image displayed on the display terminal. It is a flowchart which shows the flow of control of the mail decoding process performed with a portable terminal.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 E-mail processing system 102 Server apparatus 103 Portable terminal 104 Display terminal 111 Internet 201 Key generation part 202 Public key transmission part 203 Private key memory | storage part 204 Image photographing part 205 Decoding part 206 Decryption part 207 Mail display part 401 Public key receiving part 402 Public key storage unit 403 Mail reception unit 404 Encryption unit 405 Encoding unit 406 Image transmission unit 411 Mail storage unit 412 Image storage unit 701 Browser screen 702 Reception date and time 703 Encoded image

Claims (10)

An e-mail processing system comprising a server device and a mobile terminal,
(A) The mobile terminal
A key generation unit that generates a pair of a public key and a private key for the user of the mobile phone;
A public key transmitter that transmits the generated public key to the server device;
A secret key storage unit for storing the generated secret key,
(B) The server device
A public key receiving unit for receiving a public key transmitted from the portable terminal;
A public key storage unit for storing the received public key;
A mail receiving unit that receives an e-mail transmitted from the mail sender to the user of the mobile terminal;
An encryption unit that encrypts the received e-mail with the stored public key and outputs a result of the encryption as an encrypted message;
An encoding unit that encodes the output encrypted message into a two-dimensional image and outputs a result of the encoding as an encoded image;
An image transmission unit that transmits the output encoded image to the display terminal and causes the display terminal to display the encoded image;
(C) The mobile terminal
An image capturing unit that captures an encoded image received and displayed by the display terminal;
A decoding unit that decodes the captured encoded image by inverse transformation with respect to the two-dimensional image encoding, and outputs a result of the decoding as a decoded message;
Decrypting the output decrypted message with the stored secret key, and outputting the decrypted result as a received electronic mail;
An e-mail processing system further comprising: a mail display unit that displays the output received e-mail. The e-mail processing system according to claim 1,
The server device transmits an encoded image by a web mail service via an Internet browser to the display terminal,
The electronic mail processing system, wherein the display terminal receives and displays the encoded image by the Internet browser. An e-mail processing system according to claim 2,
The server device
A mail storage unit for storing the received e-mail;
After the request for the web mail service is made from the display terminal, the encryption and the encoding of the stored electronic mail are performed, and the encoded image is transmitted as a response of the web mail service. E-mail processing system featuring.   The server apparatus in the electronic mail processing system of any one of Claim 1 to 3.   The portable terminal in the electronic mail processing system of any one of Claim 1 to 3. An electronic mail processing method executed by a server device and a mobile terminal, wherein the mobile terminal includes a key generation unit, a public key transmission unit, a secret key storage unit, an image photographing unit, a decryption unit, a decryption unit, The server device has a public key receiving unit, a public key storage unit, a mail receiving unit, an encryption unit, an encoding unit, an image transmission unit,
(A) In the mobile terminal,
A key generation step in which the key generation unit generates a pair of a public key and a secret key for the user of the mobile phone;
A public key transmitting step in which the public key transmitting unit transmits the generated public key to the server device;
The secret key storage unit includes a secret key storage step of storing the generated secret key;
(B) In the server device,
A public key receiving step in which the public key receiving unit receives a public key transmitted from the mobile terminal;
A public key storage step in which the public key storage unit stores the received public key;
A mail receiving step in which the mail receiving unit receives an email transmitted from a mail sender to the user of the mobile terminal;
An encryption step in which the encryption unit encrypts the received e-mail with the stored public key and outputs the result of the encryption as an encrypted message;
An encoding step in which the encoding unit encodes the output encrypted message into a two-dimensional image and outputs a result of the encoding as an encoded image;
The image transmission unit further includes an image transmission step of transmitting the output encoded image to the display terminal and causing the display terminal to display the encoded image.
(C) In the mobile terminal,
An image capturing step in which the image capturing unit captures an encoded image received and displayed by the display terminal;
A decoding step in which the decoding unit decodes the captured encoded image by inverse transformation with respect to the two-dimensional image encoding, and outputs a result of the decoding as a decoded message;
A decrypting step in which the decrypting unit decrypts the output decrypted message with the stored secret key and outputs the decrypted result as a received electronic mail;
The e-mail processing method, wherein the e-mail display unit further includes a mail display step of displaying the output received e-mail. The e-mail processing method according to claim 6,
The server device transmits an encoded image by a web mail service via an Internet browser to the display terminal,
The e-mail processing method, wherein the display terminal receives and displays the encoded image by the Internet browser. The e-mail processing method according to claim 7,
The server device
A mail storage unit for storing the received e-mail;
After the request for the web mail service is made from the display terminal, the encryption and the encoding of the stored electronic mail are performed, and the encoded image is transmitted as a response of the web mail service. E-mail processing method characterized.   A program that causes a computer to function as each unit of the server device according to claim 4.   A program for causing a computer to function as each unit of the mobile terminal according to claim 5.

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