WO2013097326A1

WO2013097326A1 - Electronic mail encryption method, mail server, and system

Info

Publication number: WO2013097326A1
Application number: PCT/CN2012/071316
Authority: WO
Inventors: 陈颖棠; 黄重阳
Original assignee: 盈世信息科技(北京)有限公司
Priority date: 2011-12-29
Filing date: 2012-02-20
Publication date: 2013-07-04
Also published as: CN103188129A

Abstract

Disclosed is an email encryption method comprising: acquiring mail information of a mail transmitted by a terminal, where the mail information comprises a recipient, a subject, a body, and an attachment; determining if the mail information comprises an encryption password, and if yes, encrypting the mail on the basis of the mail information, where the encrypted mail comprises a header, a template body, an encrypted body, and an encrypted attachment, and where the header also comprises an encryption identifier corresponding to the mail. Employment of the present invention expands a standard format for email, allows each mail to be provided with an independent encryption password, and greatly increases mail data security. At the same time, because the entire encrypted data is placed within the original text of the email, the email can thus be downloaded independently and decrypted independently. In addition, utilization of the Rijndael encryption method for the encryption of emails effectively guarantees the security of entity data of each mail.

Description

E-mail encryption method, mail server and system

The present invention relates to the field of communication security, and in particular, to an email encryption method, server, and system. Background technique

Nowadays, with the development and popularization of the Internet, e-mail has become an important communication tool, and its security has received more and more attention.

In addition to the information that is delivered to another user by one user, the email must also contain additional service information. The mail server uses this information to deliver the message, and the client's mail receiving software uses this information to classify the message.

At present, the shortcoming of the mail server is that the protection method for the mail security is relatively simple, and the security of all the mails is mainly managed through the login password of the mailbox, and the content of the stored mail is basically only encoded in plain text or simply by Base64, and depends on the user. A password or other single authentication method determines whether the user has permission to view the content of the email. If there is a problem with the authentication or the mail server is modified, the data of all the users' emails will be completely exposed, and the security of the user's email is seriously threatened. At the same time, once the address of the mail server is made public, it is easy to become the target of the hacker, and the chance of the server data being stolen is increased. For example, when the user selects the password remember function of the browser, as long as the user's computer password is stolen, the user's mailbox can be freely logged in, and the security of the email in the user's mailbox cannot be guaranteed.

According to conventional thinking, the mail server often adopts the method of passing the authentication, so that all the data of the user in the system can be accessed. However, many users lack sufficient security awareness, and the password is too simple, and the password of the mailbox is often stolen. In this case, the mail data is also easily stolen. Summary of the invention

The technical problem to be solved by the present invention is to provide an email encryption method and a mail service. Servers and systems, by extending the standard format of e-mail, each e-mail can have a separate encrypted password, and Rijndael encryption is used to ensure the security of each mail entity data.

In order to solve the above technical problem, the present invention provides an email encryption method, including: acquiring email information of a mail sent by a terminal, the mail information including a recipient, a title, a body, and an attachment; determining whether the email information is The encrypted password is included, and when the determination is yes, the email is encrypted according to the email information, and the encrypted email includes a header, a template body, an encrypted text, and an encrypted attachment, where the header further includes The encrypted identifier corresponding to the email.

As an improvement of the foregoing solution, the step of encrypting the email according to the email information includes: generating an encrypted identifier for the email to be encrypted; adding the recipient, a title, and an encrypted identifier to the header; The preset template content is added to the template body; the encrypted text and the encrypted attachment are generated according to the encrypted password, the body and the attachment.

As an improvement of the foregoing solution, the method for generating an encrypted text and an encrypted attachment according to an encrypted password, a text, and an attachment includes: encrypting a text and an attachment by using Rijndael encryption according to the encrypted password; and encrypting the text and the attached by the Rijndael encryption method. Perform Base64 encoding.

As an improvement of the foregoing solution, the method for generating an encrypted text and an encrypted attachment according to an encrypted password, a text, and an attachment further includes: the text and the attachment generate the verification information by using an MD5 algorithm.

Correspondingly, the present invention further provides a mail server, comprising: an acquiring unit for acquiring mail information of a mail sent by a terminal, the mail information including a recipient, a title, a body and an attachment; The determining unit is connected to the determining unit for determining whether the email information includes an encrypted password; and is connected to the determining unit, and configured to: when the determining unit determines that the email information includes an encrypted password, according to the mail The information is an encryption unit that encrypts the email, and the encrypted email includes a header, a template body, an encrypted text, and an encrypted attachment, and the header further includes an encrypted identifier corresponding to the email.

As an improvement of the foregoing solution, the encryption unit includes: an identifier generation subunit for generating an encryption identifier for the email to be encrypted; and the identifier generation subunit is connected to the recipient, the title, and a header generating subunit added to the header of the header; a template generating subunit for adding preset template content to the template body; and configured to generate an encrypted body according to the encrypted password, the text, and the attachment Encrypted subunit of the encrypted attachment. As an improvement of the foregoing solution, the encryption subunit includes:

a first encryption subunit for encrypting the text and the attachment by the Rijndael encryption method; and a second encryption subunit connected to the first encryption subunit for Base64 encoding the text and the attachment encrypted by the first encryption subunit .

As an improvement of the foregoing solution, the encryption subunit further includes: a verification information generation subunit for generating verification information according to the text and the attachment by using the MD5 algorithm.

Correspondingly, the present invention further provides an e-mail encryption system, comprising: a terminal for transmitting or receiving a mail; a mail server, configured to acquire mail information of a mail sent by the terminal, and determine the mail information Whether or not the encrypted password is included, and when it is judged as YES, the mail is encrypted according to the mail information.

The implementation of the present invention has the following beneficial effects: The standard format of the e-mail is extended, so that each e-mail can have a separate encrypted password, so that even if the e-mail password is stolen or the data of the mail server is stolen, an encrypted password is required. Viewing the full content of an email greatly improves the security of your email data. At the same time, because the entire encrypted data is placed in the original text of the email, the email can be downloaded and decrypted separately, which is convenient for users to decrypt on different mail servers or clients. In addition, the use of Rijndael encryption to encrypt emails effectively ensures the security of each email entity. DRAWINGS

1 is a flow chart of a first embodiment of an email encryption method according to the present invention;

2 is a flow chart of a second embodiment of an email encryption method according to the present invention;

3 is a flow chart of a third embodiment of an email encryption method according to the present invention;

4 is a schematic structural diagram of an email encryption system according to the present invention;

5 is a schematic structural diagram of a mail server 1 in an email encryption system according to the present invention; FIG. 6 is another schematic diagram of a mail server 1 in an email encryption system according to the present invention; Another structural schematic diagram of the mail server 1 in the system. detailed description

In order to make the objects, technical solutions and advantages of the present invention more clear, the present invention will be described below with reference to the accompanying drawings. The details are further described in detail.

1 is a flow chart of a first embodiment of an email encryption method according to the present invention, including:

5100. Obtain the mail information of the mail sent by the terminal.

The mail information includes a recipient, a title, a body, and an attachment. The user sends a mail to the mail server through the terminal, wherein the mail information includes the recipient, the title and the body, and the user can add an attachment in the mail, and the number of the attachments can be one or more.

5101. Determine whether the encrypted information is included in the email information.

It should be noted that not all emails need to be encrypted. Users only encrypt emails that need to be encrypted and submit encrypted passwords. When users submit encrypted passwords, encrypted passwords are stored in email messages. After the mail server obtains the mail information of the mail sent by the terminal, it is necessary to determine whether the mail information includes an encrypted password.

5102. When the determination is yes, the email is encrypted according to the mail information.

When the mail server determines that the email message does not contain an encrypted password, it indicates that the email does not need to be encrypted, and may be directly sent to the terminal; when the email server determines that the email information contains an encrypted password, it indicates that the email needs to be encrypted. Therefore, the mail server should encrypt the mail.

The encrypted email includes a header, a template body, an encrypted text, and an encrypted attachment, and the header further includes an encrypted identifier corresponding to the email.

It should be noted that, the encrypted identifier is used to determine whether the email is an encrypted email. When the terminal receives the email sent by the email server, the terminal may determine whether the email is an encrypted email by using an encrypted identifier, and when determining that the email is an encrypted email, Prompt the user to enter the password; when it is judged that it is not an encrypted mail, the mail information can be directly read.

Preferably, the mail server encrypts the mail using Rijndael encryption and Base64 encoding.

For example, user A needs to send an encrypted mail to user B, wherein the mail contains an attachment, and user A uploads the attachment through the terminal and writes the recipient, the title, the body, and the like in the mail, and simultaneously inputs the encrypted password. After the mail server obtains the mail information of the terminal and judges that the mail information contains the encrypted password, the mail needs to be encrypted. Therefore, the mail server encrypts the mail by Rijndael encryption and Base64 encoding, and the encrypted mail includes the header, the template body, and the encryption. The text and the encrypted attachment further include an encrypted identifier corresponding to the mail. Mail server will encrypt the mail Sent to user B. After user B obtains the email sent by user A, the email body knows that the email is an encrypted email. The email server determines that the email is an encrypted email according to the encrypted identifier in the template header, and requires user B to input the decryption password, and user B inputs the decryption password. Read the message. The decryption password entered by user B is the same as the encrypted password of user A.

It should be noted that since the text and the attachment are independently encrypted in the encryption process, the decryption is also performed separately when decrypting.

As another example, user A needs to send unencrypted mail to user B, where the mail contains an attachment. User A uploads the attachment through the terminal and writes the recipient, title, and body in the email. After the mail server obtains the mail information of the terminal, it determines that the mail information does not contain the encrypted password, and the mail does not need to be encrypted, so the mail server directly sends the mail to the user B. After User B obtains the email sent by User A, it can directly read the email.

2 is a flow chart of a second embodiment of an email encryption method according to the present invention, including:

5200, Obtain the mail information of the mail sent by the terminal.

The mail information includes a recipient, a title, a body, and an attachment.

5201. Determine whether the encrypted information is included in the mail information.

5202. Generate an encryption identifier for the email to be encrypted.

It should be noted that, the encrypted identifier is used to determine whether the email is an encrypted email. When the terminal receives the email sent by the email server, the terminal may determine whether the email is an encrypted email by using an encrypted identifier, and when determining that the email is an encrypted email, Prompt the user to enter the password; when it is judged that it is not an encrypted mail, the mail information can be directly read. In the encryption process, when the mail server determines that the email message contains an encrypted password, it indicates that the email needs to be encrypted. At this time, the mail server generates an encrypted identifier, where the encrypted identifier may be "EncType=undetach"; When the mail server determines that the encrypted information is not included in the mail information, it indicates that the mail does not need to be encrypted. At this time, the mail server does not generate an encrypted identifier;

5203. Add the recipient, the title, and the encrypted identifier to the letterhead.

5204. Add preset template content to the template body.

It should be noted that the template content includes a text description, so that the recipient can clearly know that the email is an encrypted email after receiving the email from the template body of the email.

5205. Generate an encrypted text and an encrypted attachment according to the encrypted password, the body, and the attachment.

The mail server generates an encrypted body based on the encrypted password and the body text, and then generates an encrypted attachment based on the encrypted password and the attachment.

It should be noted that the attachment may be one or more, and the mail server traverses the text and the attachment, and sequentially encrypts the text and the attachment to generate a corresponding encrypted text and an encrypted attachment. Since the text and attachments are independently encrypted during the encryption process, the body and attachments can be downloaded and decrypted separately during decryption.

For example, user A needs to send encrypted mail to user B, where the mail contains attachment C and attachment D, and user A uploads the attachment through the terminal and writes the recipient, title and body in the mail, and simultaneously inputs the encrypted password. After the mail server obtains the mail information of the terminal, it determines that the mail information contains an encrypted password, and the mail needs to be encrypted. Therefore, the mail server generates an encrypted identifier "EncType=undetach" and adds the recipient, the title, and the encrypted identifier to the letterhead. The preset template content is added to the template body, and the text and the attachment C and the attachment D are sequentially encrypted by using Rijndael encryption method and Base64 encoding, and the encrypted text, the encrypted attachment C and the encrypted attachment D are generated. The mail server sends the encrypted mail to User B. After user B obtains the email sent by user A, the email body knows that the email is an encrypted email, and the email server determines that the email is an encrypted email according to the encryption identifier "EncType=undetach" in the template header, and requires user B to input the decryption password. User B selects the encrypted text or encrypted attachment that needs to be decrypted according to actual needs, and enters the decryption password to read the encrypted text or encrypted attachment. The decryption password entered by user B is the same as the encrypted password of user A. 3 is a flow chart of a third embodiment of an email encryption method according to the present invention, including:

5300. Obtain the email information of the email sent by the terminal.

The mail information includes a recipient, a title, a body, and an attachment.

5301. Determine whether the encrypted information is included in the email information.

It should be noted that not all emails need to be encrypted. Users only encrypt emails that need to be encrypted and submit encrypted passwords. When users submit encrypted passwords, encrypted passwords are stored in email messages. After the mail server obtains the mail information of the mail sent by the terminal, it is necessary to determine whether the mail information includes an encrypted password. When the mail server determines that the email message does not contain an encrypted password, it indicates that the email does not need to be encrypted, and may be directly sent to the terminal; when the email server determines that the email information contains an encrypted password, it indicates that the email needs to be encrypted. Therefore, the mail server should encrypt the mail.

5302. Generate an encryption identifier for the email to be encrypted.

In the encryption process, when the mail server determines that the email message contains an encrypted password, it indicates that the email needs to be encrypted. At this time, the mail server generates an encrypted identifier, where the encrypted identifier may be "EncType=undetach"; When the mail server determines that the encrypted information is not included in the mail information, it indicates that the mail does not need to be encrypted. At this time, the mail server does not generate an encrypted identifier.

5303. Add the recipient, the title, and the encrypted identifier to the letterhead.

5304. Add preset template content to the template body.

5305. Encrypt the text and attachments according to the encrypted password using Rijndael encryption.

It should be noted that the attachment may be one or more, and the mail server traverses the text and the attachment, and encrypts the text and the attachment in sequence.

5306, Performing Base64 encoding on the body and the attachment encrypted by the Rijndael encryption method. During the encryption process, the mail server encrypts the text and attachments by Rijndael encryption and base64 encodes the text and attachments encrypted by Rijndael encryption to generate the encrypted text and Encrypt attachments.

Since the attachment may be one or more, the mail server traverses the text and the attachment, and encrypts the text and the attachment separately to generate a corresponding encrypted text and an encrypted attachment. The body and attachments are independently encrypted during the encryption process, so when decrypting, the body and attachments can be downloaded separately and decrypted separately.

For example, user A needs to send encrypted mail to user B, where the mail contains attachment C and attachment D, and user A uploads the attachment through the terminal and writes the recipient, title and body in the mail, and enters the encrypted password. After the mail server obtains the mail information of the terminal, it determines that the mail information contains an encrypted password, and the mail needs to be encrypted. Therefore, the mail server generates an encrypted identifier "EncType=undetach" and adds the recipient, the title, and the encrypted identifier to the letterhead. The preset template content is added to the template body, the text is encrypted by Rijndael encryption, and the body encrypted by Rijndael encryption is Base64 encoded to generate an encrypted body, and the attachment C is encrypted by Rijndael encryption and passed through Rijndael. The encrypted C-encrypted accessory C performs Base64 encoding to generate the encrypted attachment C, encrypts the attached D by Rijndael encryption, and performs Base64 encoding on the attached D encrypted by Rijndael encryption to generate the encrypted attachment D. The mail server sends the encrypted mail to User B. After user B obtains the email sent by user A, the email body knows that the email is an encrypted email, and the email server encrypts the email according to the template header.

"EncType=undetach" determines that the email is an encrypted email, and requires user B to input the decryption password. User B selects the encrypted text to be decrypted, encrypts attachment C or encrypts attachment D according to actual needs, and inputs the decryption password to read the encrypted text of the email. Encrypt attachment C or encrypt attachment D. The decryption password entered by user B is the same as the encrypted password of user A.

More preferably, in the encryption process, the text and the attachment use the MD5 algorithm to generate verification information to ensure that the correctness of the password can be verified during decryption.

4 is a schematic structural diagram of an email encryption system according to the present invention, including:

Terminal 2 for sending or receiving mail.

The mail server 1 is configured to obtain mail information of the mail sent by the terminal 2 and determine whether the mail information includes an encrypted password. When the determination is yes, the mail is encrypted according to the mail information.

The mail information includes a recipient, a title, a body and an attachment; the encrypted mail includes a letter header, a template body, an encrypted text, and an encrypted attachment, and the header further includes the email pair The encryption ID should be.

It should be noted that the mail server 1 encrypts the text and the attachment sequentially by using the Rijndael encryption method and the Base64 encoding.

FIG. 5 is a schematic structural diagram of a mail server 1 in an email encryption system according to the present invention, which includes:

An obtaining unit 11 for obtaining mail information of a mail transmitted by the terminal 2.

The mail information includes a recipient, a title, a body, and an attachment.

The determining unit 12 is connected to the obtaining unit 11 for determining whether the mail information includes an encrypted password.

It should be noted that not all emails need to be encrypted. Users only encrypt emails that need to be encrypted and submit encrypted passwords. When users submit encrypted passwords, encrypted passwords are stored in email messages.

The determining unit 12 is connected to the encryption unit 13 for encrypting the mail according to the mail information when the determining unit 12 determines that the encrypted information is included in the mail information.

When the judging unit 12 judges that the e-mail message does not contain the encrypted password, it indicates that the e-mail does not need to be encrypted, and can be directly sent to the terminal; when the judging unit 12 judges that the e-mail contains the encrypted password, it indicates that the e-mail needs to be encrypted. Operation, so the encryption unit 13 should encrypt the mail.

The mail server 1 obtains the mail information of the mail sent by the terminal 2 through the obtaining unit 11, and the determining unit 12 determines whether the mail information includes the encrypted password, and the determining unit 12 determines that the mail information includes the encrypted password. At this time, the encryption unit 13 encrypts the mail based on the mail information.

It should be noted that the encryption unit 13 uses the Rijndael encryption method and the Base64 encoding to sequentially encrypt the text and the attachment and respectively generate the encrypted text and the encrypted attachment.

FIG. 6 is a schematic diagram of another structure of the mail server 1 in an email encryption system according to the present invention. The encryption unit 13 includes:

An identifier generating sub-unit 131 for generating an encrypted identifier for the mail to be encrypted.

In the encryption process, when the judging unit 12 judges that the e-mail message contains an encrypted password, it indicates The email needs to perform an encryption operation. In this case, the identifier generation sub-unit 131 generates an encrypted identifier, where the encrypted identifier may be "EncType=undetach"; when the determining unit 12 determines that the email information does not contain the encrypted password, the identifier The mail does not need to perform an encryption operation. At this time, the identifier generation sub-unit 131 does not generate an encryption identifier.

The identifier generating sub-unit 131 is connected to the header generating sub-unit 132 for adding the recipient, the title and the encrypted identifier to the header.

A template generation sub-unit 133 for adding preset template content to the template body. The template content includes a text description, so that the recipient can clearly know that the email is an encrypted email after receiving the email from the template body of the email.

An encryption subunit 134 for generating an encrypted text and an encrypted attachment based on the encrypted password, body, and attachment.

It should be noted that the attachment may be one or more, and the mail server traverses the text and the attachment, and sequentially encrypts the text and the attachment to generate a corresponding encrypted text and an encrypted attachment. Since the body and attachments are independently encrypted during the encryption process, the body and attachments can be downloaded separately and decrypted separately during decryption.

During the encryption process, the encryption sub-unit 134 encrypts the text and attachments by Rijndael encryption and base64 encodes the text and attachments encrypted by Rijndael encryption to generate an encrypted text and an encrypted attachment.

The mail server 1 acquires the mail information of the mail transmitted by the terminal 2 through the obtaining unit 11, and the judging unit 12 judges whether or not the encrypted mail is included in the mail information. When the determining unit 12 determines that the encrypted information is included in the mail information, the identifier generating sub-unit 131 in the encrypting unit 13 generates an encrypted identifier "EncType=undetach", and the recipient is generated by the header generating sub-unit 132. The header and the encryption identifier are added to the header, and the template generation sub-unit 133 adds the preset template content to the template body, and the encryption sub-unit 134 sequentially encrypts the text and the attachment by using the Rijndael encryption method and the Base64 encoding. Generate the corresponding encrypted text and encrypted attachments. Finally, the header, template body, encrypted body, and encrypted attachments are combined to form an encrypted message.

FIG. 又一 is another schematic structural diagram of the mail server 1 in an email encryption system according to the present invention. The encryption subunit 134 includes:

The first plus for encrypting text and attachments using Rijndael encryption based on encrypted passwords The subunit unit 1341.

Connected to the first encryption subunit 1341, a second encryption subunit 1342 for Base64 encoding the text and the attachment encrypted by the first encryption subunit 1341.

In the encryption process, the first encryption sub-unit 1341 encrypts the text and the attachment by Rijndael encryption, and the second encryption sub-unit 1342 performs Base64 encoding on the text and the attachment encrypted by the Rijndael encryption method to generate an encrypted text and an encrypted attachment. .

It should be noted that the attachment may be one or more, and the mail server traverses the text and the attachment, and sequentially encrypts the text and the attachment to generate a corresponding encrypted text and an encrypted attachment.

Preferably, the encryption subunit 134 further includes: a verification information generation subunit 1343 for generating verification information according to the text and the attachment by using the MD5 algorithm to ensure that the correctness of the password can be verified during decryption.

During operation, the mail server 1 obtains the mail information of the mail sent by the terminal 2 through the obtaining unit 11, and the determining unit 12 determines whether the encrypted information is included in the mail information. When the determining unit 12 determines that the encrypted information is included in the mail information, the identifier generating sub-unit 131 in the encrypting unit 13 generates an encrypted identifier "EncType=undetach", and the recipient is generated by the header generating sub-unit 132. The header and the encryption identifier are added to the header, and the template generation sub-unit 133 adds the preset template content to the template body, and the first encryption sub-unit 1341 encrypts the sequential text and the attachment by Rijndael encryption method, and is encrypted by The second encryption sub-unit 1342 performs Base64 encoding on the body and the attachment encrypted by the Rijndael encryption method to respectively generate the encrypted text and the encrypted attachment. At the same time, the verification information generating subunit 1343 generates the verification information using the MD5 algorithm. Finally, the header, template body, encrypted text, and encrypted attachments are combined to form an encrypted message.

As can be seen from the above, the present invention extends the standard format of an email to consist of a header, a template body, an encrypted body, and an encrypted attachment, so that each email can have a separate encrypted password, and an encrypted password is required to view the email. The complete content of the encrypted text and encrypted attachments greatly improves the security of the mail data. At the same time, because the entire encrypted data is placed in the encrypted text and encrypted attachments, the user can separately download and separately decrypt the encrypted text and encrypted attachments. To a certain extent, the user can decrypt on different mail servers or clients. In addition, the use of Rijndael encryption to encrypt emails effectively ensures the security of each email entity.

The above is a preferred embodiment of the present invention, it should be noted that it is common to the art. Many modifications and refinements can be made by the skilled person without departing from the principles of the invention, and such modifications and refinements are also considered to be within the scope of the invention.

Claims

Claim

An email encryption method, comprising:

Obtaining mail information of a mail sent by the terminal, where the mail information includes a recipient, a title, a body, and an attachment;

Determining whether the encrypted information is included in the mail information, and if the determination is yes, encrypting the mail according to the mail information, where the encrypted mail includes a letter header, a template body, an encrypted text, and an encrypted attachment, the letter The header also includes an encrypted identifier corresponding to the mail.

2. The method of encrypting an email according to claim 1, wherein the step of encrypting the email according to the email information comprises:

Generating an encrypted identifier for the mail to be encrypted;

Adding the recipient, the title, and the encrypted identifier to the header;

Add preset template content to the template body;

An encrypted text and an encrypted attachment are generated based on the encrypted password, body, and attachment.

The method for encrypting an email according to claim 2, wherein the method for generating an encrypted text and encrypting an attachment according to an encrypted password, a text, and an attachment includes:

Encrypt the text and attachments according to the encrypted password using Rijndael encryption method;

Base64 encoding the body and attachments encrypted by Rijndael encryption.

The method for encrypting an email according to claim 2, wherein the method for generating an encrypted text and an encrypted attachment according to the encrypted password, the text, and the attachment further comprises: generating the verification information by using the MD5 algorithm in the text and the attachment .

5. A mail server, characterized in that it comprises:

An obtaining unit for obtaining mail information of a mail sent by the terminal, where the mail information includes a recipient, a title, a body, and an attachment;

And a determining unit, configured to determine whether the email information includes an encrypted password, connected to the acquiring unit;

And the judging unit is configured to be used as an encryption unit for encrypting the e-mail according to the mail information when the judging unit determines that the e-mail information includes an encrypted password, where the encrypted mail includes a letter header, The template body, the encrypted body, and the encrypted attachment, and the header further includes an encrypted identifier corresponding to the mail.

The mail server according to claim 5, wherein the encryption unit comprises:

An identifier generating subunit for generating an encrypted identifier for the mail to be encrypted;

And the identifier generating subunit, configured to add the recipient, the title, and the encrypted identifier to the header generating subunit of the header;

a template generation subunit for adding preset template content to the template body; An encryption subunit for generating an encrypted text and an encrypted attachment based on the encrypted password, body, and attachment.

7. The mail server according to claim 6, wherein the encryption subunit comprises:

a first encryption subunit for encrypting a text and an attachment by using Rijndael encryption according to the encrypted password; and being connected to the first encryption subunit for performing Base64 encoding on the text and the attachment encrypted by the first encryption subunit The second cryptographic subunit.

The mail server according to claim 7, wherein the encryption subunit further comprises: a verification information generation subunit for generating verification information by using an MD5 algorithm according to the text and the attachment.

9. An email encryption system, comprising:

a terminal for sending or receiving mail;

A mail server according to any one of claims 5 to 8.