JP6085978B2 - Mail processing method, mail processing program, and mail processing apparatus - Google Patents

Description

  The present invention relates to a mail processing method, a mail processing program, and a mail processing apparatus.

  In recent years, there has been an increase in targeted emails that identify parties to whom emails are sent, and steal confidential information or leak personal information using malicious programs embedded in emails. The characteristics of targeted emails are that the recipient may seem to open unexpectedly, using a sender pretending to be a real person, the subject of the email, or the name of the attached file, etc. It is difficult to prevent attacks by targeted emails simply by checking email headers. If the recipient of the email opens the attachment or link destination without noticing the email header forgery, the malicious program is executed and the information stored on the recipient's computer is leaked, or the recipient's computer In some cases, I was infected with a computer virus.

  Conventional countermeasure techniques have two kinds of countermeasures, one for taking countermeasures on the mail server side and one for taking countermeasures on a client basis.

  For example, there is “transmission domain authentication” as a countermeasure on the mail server side. This is a technology for realizing the validity of the outgoing mail server and the trail of the transmission path on a server basis. Specifically, this is a technology for checking the domain of an e-mail address, verifying whether the e-mail is transmitted from a legitimate server, and proving that the sender's address is legitimate. There are mainly two types of sender domain authentication: authentication by IP address and authentication by electronic signature.

  For authentication by IP address, for example, with SPF (Sender Policy Framework) / Sender ID, the association (SPF record) between the domain of the email server and the IP address of the sender is disclosed to the DNS (Domain Name System) server and received. There has been a technique for confirming that the sender's address is valid by inquiring the DNS server for the sender's IP address from time to time and performing collation.

  As authentication by electronic signature, for example, the public key information of the electronic mail server is disclosed to the DNS server by DKIM (DomainKeys Identified Mail), the electronic signature is combined with the private key, and the electronic mail is transmitted. There has been a technique for confirming that a sender's address is authentic by inquiring public key information to a DNS server at the time of reception and performing verification. In addition, there is a method of determining the legitimacy of a mail at a relay server that relays a mail transmitted from a sender to a receiver, and adding the determination result to a mail header or the like (for example, Non-Patent Document 1, (See Non-Patent Document 2, JP-A-2006-94422).

  On the other hand, there was a detection method using anti-virus software as a countermeasure for the client base, but conventional anti-virus software registered problematic programs as signatures and detected matching ones as illegal emails. However, it is difficult to prevent targeted e-mails even with anti-virus software that cannot be detected by programs without signatures and that anticipates malicious programs.

  In order to solve the above problems, the inventors have invented a mail delivery system for detecting illegal mail such as targeted attack mail on a client basis (Japanese Patent Application No. 2012-108092, hereinafter “First”). It is referred to as “the claimed invention”). In the invention of the prior application, the receiving side cooperates with the transmitting and receiving terminals, shares secret information that the attacker cannot know, and combines the secret information generated based on the mail header transmitted on the transmitting terminal side with the mail header. Proposes a method of judging the possibility of illegal mail by verifying the mail header with secret information.

Sender Policy Framework Project Overview, Internet <http: // www. openspf. org /> DKIM. org, Internet <http: // www. dkim. org />

JP 2006-94422 A

  However, since the transmission address of the targeted email is also camouflaged, the identity cannot be secured when it is transmitted using a legitimate server. In addition, it is necessary to install a DNS server, and there is a problem that operation costs increase.

  Further, in the invention of the prior application, when the mail header is replaced with good intentions such as combining a unique item such as a serial number at the head of the subject (Subject) as in the mailing list, the secret information and the mail header generated by the transmitting terminal are exchanged. In some cases, it becomes impossible to verify at the receiving terminal.

  Therefore, in one aspect, to provide a method of detecting an illegal mail, a detection program thereof, and a detection device thereof, in which the mail header can be verified at the receiving terminal even when the mail header is rewritten by mailing list software. Objective.

In one proposal, a mail processing method includes: processing for generating verification information based on a target header item of transmitted mail and secret shared information; processing for combining meta information of the target header item with the verification information; A process of combining the verification information combined with the meta information with the mail header of the outgoing mail is executed by the first computer that transmits the mail, and the verification information and the meta information are separated from the mail header of the received mail. Processing to acquire the target header item from the mail header based on the separated meta information, processing to regenerate verification information based on the acquired target header item and the secret shared information, and separation wherein a process of comparing the verification information and the regenerated the verification information, executes the second computer for receiving the mail, the first computer that has the verification In the process of combining the meta information of the target header item with the information, the feature information calculated from a predetermined part of the target header item is further combined with the verification information, and the second computer performs the process of separating The feature amount is further separated from the mail header of the received mail, the feature amount is calculated from the acquired target header item, and the calculated feature amount is compared with the separated feature amount. To do .

  According to one aspect, it is possible to provide a method of detecting an illegal mail, a detection program thereof, and a detection device thereof in which the mail header can be verified at the receiving terminal even when the mail header is rewritten by mailing list software. it can.

System Configuration E-mail sending terminal configuration diagram Configuration diagram of verification information generation device of e-mail transmission terminal Configuration of e-mail receiving terminal E-mail receiving terminal verification device configuration diagram Flow chart showing the management process of the target header item Target header item candidate list Flow chart showing processing of the verification information generation device Flow chart showing processing of verification device The figure explaining verification information generation processing in a 1st embodiment The figure explaining the verification process in 1st Embodiment The figure explaining the verification information generation process in 2nd Embodiment The figure explaining the verification process in 2nd Embodiment The figure explaining the verification information generation process in 3rd Embodiment The figure explaining the verification process in 3rd Embodiment

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  First, a system configuration according to the present embodiment will be described with reference to FIG. FIG. 1 is an example of a system configuration diagram.

  In FIG. 1, an e-mail sending terminal 2 used by a sender and an e-mail receiving terminal 5 used by a receiver are sent by a sending mail (SMTP) server 3 and a receiving mail (POP) server 4 via a network 1. Send and receive.

  SMTP (Simple Mail Transfer Protocol) is an application layer protocol used to send e-mails. When sending e-mails from the e-mail software included in the e-mail sending terminal 2 to the sending mail server 3. The protocol used. POP (Post Office Protocol) is an application layer protocol used to receive an e-mail. When e-mail software included in the e-mail receiving terminal 5 receives an e-mail from the received mail server 4, the POP (Post Office Protocol) is used. The protocol used.

  In FIG. 1, the e-mail transmission terminal 2 and the e-mail reception terminal 5 are illustrated as being connected to the network 1 via the transmission mail server 3 and the reception mail server 4, respectively. The sending terminal 2 and the e-mail receiving terminal 5 may be connected to the network 1 and connected to the sending mail server 3 and the receiving mail server 4 on the network 1 via the network 1.

  Next, details of the e-mail transmission terminal 2 will be described with reference to FIG. FIG. 2 is a configuration diagram showing an example of the configuration of the e-mail transmission terminal.

  In FIG. 2, the e-mail transmission terminal 2 includes e-mail software 21, a verification information generation device 22, and a communication device 23.

  The e-mail software 21 is software in which a sender issues an e-mail creation and transmission instruction, and is a mailer, for example. The verification information generation device 22 generates “verification information” to be included in a mail transmitted from the electronic mail transmitting terminal 2 to the electronic mail receiving terminal 5. The verification information is information used when the electronic mail receiving terminal 5 determines whether there is a possibility of target mail. The communication device 23 is an interface device for transmitting electronic mail to the transmission mail server 3. When the e-mail software 21 transmits a transmission mail to the verification information generation device 22 and receives the transmission mail with verification information, the electronic mail software 21 transmits the transmission mail to the transmission mail server 3 via the communication device 23.

  Next, details of the verification information generation device 22 will be described with reference to FIG. FIG. 3 is a configuration diagram showing an example of the configuration of the verification information generation device 22 of the e-mail transmission terminal.

  In FIG. 3, the verification information generation device 22 includes a request reception unit 221, a management unit 222, a secret information management unit 223, and a verification information generation unit 224.

  The request receiving unit 221 includes an input / output unit 2211, receives a transmission mail input from the electronic mail software 21, and outputs a reply mail combined with verification information to the electronic mail software 21. The management unit 222 includes a target header item management unit 2221 and manages target header items to be described later.

  The secret information management unit 223 includes a secret information storage unit 2231 and handles secret information used when generating verification information. The secret information needs to be shared in advance between the email sending terminal 2 and the email receiving terminal 5.

  For example, the secret information is created by the secret information management unit 223 and is shared with the electronic mail receiving terminal 5 in advance. Alternatively, the verification device 52 of the electronic mail receiving terminal 5 may create the same algorithm and share the same secret information. Since the attacker cannot generate the verification information without knowing the secret information, the sent mail can be safely verified.

  The created secret information is stored in the secret information storage unit 2231. The stored confidential information must be stored securely so as not to leak outside. Therefore, the secret information storage unit 2231 encrypts and stores the secret information, for example.

  The verification information generation unit 224 includes a feature amount information generation unit 2241, a verification information generation unit 2242, and a verification information combination unit 2243, generates verification information, and combines the verification information created in the reply mail.

  Next, details of the electronic mail receiving terminal 5 will be described with reference to FIG. FIG. 4 is a configuration diagram showing an example of the configuration of the e-mail receiving terminal.

  In FIG. 4, the e-mail receiving terminal 5 includes e-mail software 51, a verification device 52, a communication device 53, and a display device 54.

  The e-mail software 51 is software in which the recipient gives an instruction to receive e-mail from the receiving server 4, and is a mailer, for example. The verification device 52 verifies the verification information combined with the received electronic mail. The communication device 53 is an interface for receiving electronic mail from the received mail server 4. The display device 54 displays the verification result by the verification device 52.

  Next, details of the verification device 52 will be described with reference to FIG. FIG. 5 is a configuration diagram showing an example of the configuration of the verification device 52 of the electronic mail receiving terminal.

  In FIG. 5, the verification device 52 includes a request reception unit 521, a secret information management unit 522, and a verification unit 523.

  The request receiving unit 521 includes an input / output unit 5211, receives a reception mail with verification information input from the electronic mail software 51, and outputs a verification result to the electronic mail software 51.

  The secret information management unit 522 includes a secret information storage unit 5221 and manages secret information used for verification of verification information.

  The verification unit 523 includes a feature amount information generation unit 5231 and a verification unit 5232, and generates feature amount information from the target header item and verifies the verification information.

  Next, a method of managing the target header item by the management unit 222 described with reference to FIG. 3 will be described with reference to FIG. FIG. 6 is an example of a flowchart showing the management processing of the target header item.

  In FIG. 6, the verification information generation device 22 generates a target header item (S3001). The target header item is an item of an e-mail header that is a target of e-mail verification. The target header item is generated according to a target header item generation policy (not shown in FIG. 3) provided in the verification information generation device 22, for example. The target header item policy represents a method of generating a target header item, and the verification information generating device 22 generates the target header item by applying the target header item policy to the input outgoing mail. By using the target header item policy, an appropriate target header item corresponding to the outgoing mail is generated. The target header item policy can be uniformly applied to, for example, a plurality of electronic mail transmission terminals. The uniform target header item policy can be automatically applied to outgoing mail regardless of whether there is an instruction from the sender, for example. For example, a predetermined target header item policy can be automatically applied to an outgoing mail having a specific word such as “confidential” or “confidential”. On the other hand, the sender may select and generate the target header item individually.

  For the target header item, for example, the importance level of the outgoing mail is defined in advance, and the target header item can be generated according to the importance level. FIG. 7 is a list for explaining an example of the target header item candidate list.

  In FIG. 7, the sent mails are classified as having an importance level of A, B, C, and D, and patterns 1, 2, 3, and 4 of header items are assigned to the respective importance levels. Each pattern includes the header items “From”, “To”, “Subject”, “Received”, “Date”, “Message-ID”, “X-Mailer”, “Body”, and “File”. Is set. For example, when the importance level C is selected, the header item is uniquely generated as “From, Subject, Date, Body”. For example, the sender can appropriately select the importance of the mail. Moreover, it can select automatically by the target header item policy mentioned above.

  Returning to FIG. 6, the generated target header item is stored by the target header item management unit 2221 (S3002), and the management processing of the target header item is ended.

  Next, the operation of the verification information generation process in the verification information generation apparatus 22 will be described with reference to FIG. FIG. 8 is a flowchart illustrating an example of processing of the verification information generation apparatus.

  In FIG. 8, as a start condition, a sender first activates the e-mail software 21 of the e-mail transmission terminal 2 to create a mail for transmission. The electronic mail software 21 inputs a transmission mail including header information and text information to the request reception unit 221 via the input / output unit 2211 of the verification information generation device 22.

  First, the request accepting unit 221 to which the mail is input issues a verification information generation request to the verification information generating unit 224 (S4001). At this time, the request reception unit 221 transmits the transmission mail information including the header information and the text information received from the electronic mail software 21 to the verification information generation unit 224.

  The verification information generation unit 224 receives the verification information generation request (S4002), and transmits a secret information acquisition request including the header information of the transmission mail to the secret information management unit 223 (S4003).

  The secret information management unit 223 receives the secret information acquisition request from the verification information generation unit 224 (S4004), acquires the secret information from the secret information storage unit 2231 (S4005), and further uses the acquired secret information as the verification information generation unit. It transmits to 224 (S4006).

  The verification information generation unit 224 receives the secret information from the secret information management unit 223 (S4007), and transmits a target header item acquisition request to the management unit 222 (S4008).

  The management unit 222 receives the target header item acquisition request from the verification information generation unit 224 (S4009), acquires the target header item stored by the target header item management unit 2221 described in FIG. 6 (S4010), and further Then, the target header item is transmitted to the verification information generating means 224 (S4011).

  The verification information generation unit 224 acquires the target header item from the management unit 222 (S4012). The verification information generation unit 224 generates verification information with secret information for the target header item (S4013). A method for generating verification information and a verification method will be described later with reference to FIGS.

  The verification information combining unit 2243 of the verification information generating unit 224 newly adds a header item in the “pattern 3 format” acquired simultaneously with the acquisition of the target header item from the target header item management unit 2221, and is generated in the added header item. The verification information is combined (S4014). The “pattern 3 format” is a format in which information about the target header item is added to the header item by adding a separate header item, instead of describing the target header item directly in the header. The target header item is specified to generate verification information when verifying the received mail at the mail receiving terminal, but if the target header item is described directly in the header, the attacker impersonates the target header item described Verification information can be generated and combined with the header. If the target header items are combined in the “pattern 3 format”, it is possible to prevent generation of verification information disguised by an attacker. The verification device 52 on the mail receiving terminal side also manages and shares the target header item candidate list described in FIG.

  The verification information generation unit 224 transmits the information of the mail with the verification information header to the request reception unit 221 (S4015).

  The request reception unit 221 receives the information of the mail with the verification information header from the verification information generation unit 224, transmits the information of the mail with the verification information header to the electronic mail software 21 (S4016), and the verification described in FIG. The process of the information generating device is terminated.

  As described with reference to FIG. 2, when the e-mail software 21 receives the information of the mail with the verification information header from the request receiving unit 221, the e-mail software 21 transmits the transmission mail with the verification information to the transmission mail server 3 via the communication device 23. A mail is transmitted to the mail receiving terminal 5 via the mail server 4.

  Next, the verification process in the verification device 52 of the mail receiving terminal 5 will be described with reference to FIG. FIG. 9 is a flowchart showing an example of processing of the verification device 52.

  In FIG. 9, the request receiving unit 521 that has received the received mail with verification information from the electronic mail software 51 transmits a verification request to the verification unit 523 (S5001).

  The verification unit 523 receives the verification request from the request reception unit 521 (S5002), and analyzes the header information and text information of the mail with verification information (S5003). The verification unit 523 acquires the target header item from the header information (S5004). The verification unit 523 further transmits a secret information acquisition request to the secret information management unit 522 (S5005).

  When the secret information management unit 522 receives the secret information acquisition request from the verification unit 523 (S5006), the secret information management unit 522 acquires the secret information managed by the secret information storage unit 5221 (S5007), and verifies the acquired secret information by the verification unit 523. (S5008).

  When the verification unit 5232 receives the secret information from the secret information management unit 522 (S5009), the verification unit 5232 regenerates the verification information from the secret information based on the information of the target header item acquired in S5004 (S5010). Next, the verification unit 523 acquires verification information from the header item combined with the header information by the verification information generation unit 224 (S5011).

  The verification unit 3232 of the verification unit 523 compares the regenerated verification information with the verification information acquired from the header item, and checks whether they match (S5012). The verification unit 523 transmits the verification result to the request reception unit 521 (S5013).

  Upon receiving the verification result from the verification unit 523 (S5014), the request reception unit 521 transmits the verification result to the email software 51, and the email software 51 verifies the recipient via the output device 54. Inform the results.

Next, details of the verification information generation process in the electronic mail transmission terminal 2 and the verification process in the electronic mail reception terminal 5 will be described in three embodiments. The first embodiment will be described with reference to FIGS. 10 and 11. The second embodiment will be described with reference to FIGS. 12 and 13. Furthermore, the third embodiment will be described with reference to FIGS. 14 and 15. Note that step numbers indicated by (S4010) in the figure correspond to the step numbers in the flowcharts described in FIGS.
[First embodiment]

  In the first embodiment, a verification information header is generated by verifying the verification information by combining the character string size of the “Subject:” header item of the transmission mail information with the verification information.

  FIG. 10 is a diagram illustrating an example of the verification information generation process in the first embodiment. In FIG. 10, the verification information generation unit 2242 includes a “From:” header, a “To:” header, a “Subject:” header, a “Date:” header, a “Body:” text information (in the text information). Generates verification information for the five header items (including “File:” attachment). The verification information generation unit 2242 generates verification information “BC73DA1254231F” from the above five header items based on the secret information acquired from the secret information storage unit 2233. Here, the verification information generated from the header item is referred to as “first verification information”.

  As an algorithm for generating the verification information, for example, a one-way hash function is used. However, a generation algorithm other than a hash function may be used. The secret information and the generation algorithm used when generating the verification information are shared with the verification unit 5232 of the verification device 52 in order to ensure consistency at the time of verification.

  With regard to the “Subject:” header, there is a possibility that characters such as serial numbers may be combined in a mailing list (hereinafter abbreviated as “ML”) server. In this embodiment, the character string size “18” (x18: hexadecimal number) of the contents of the original “Subject:” header before the characters are combined by the ML server is calculated and combined with the first verification information. To do. The first verification information combined with the character string size is referred to as “second verification information”.

  In this embodiment, a case is described in which characters are combined with the “Subject:” header by the ML server. For example, when a change is made to other header items by the ML server, a predetermined item in the mail header is used. Alternatively, the size of the character string may be acquired and combined with the first verification information. Further, metadata relating to header items other than the size of the character string may be acquired and combined with the first verification information. The metadata in this case may identify the header item before the change of the header item and identify the header item before the change by the verification process in the mail receiving terminal. Other than the number of characters, for example, information for specifying the beginning and end of the character string, the number of bytes of the beginning character and the character string, and the like can be used. Further, as a method for combining the first verification information, the present embodiment describes a method of combining metadata behind the generated first verification information. You may combine metadata. Note that the format definition (the type of metadata to be combined and the combining method) of these verification information is shared with the verification unit 5232 of the verification device 52.

  The verification information combining unit 2243 generates an “X-Inbound Target Head:” header as new header information of the target header item, and combines “pattern 3” that is the target header item. Further, the verification information combining unit 2243 generates an “X-InboundMAC:” header as new header information of the verification information, and combines “BC73DA1254231F18” serving as verification information (S4014).

  FIG. 11 is a diagram for explaining an example of the verification process in the first embodiment.

  In FIG. 11, the verification unit 523 refers to the “X-BoundTargetHead:” header that specifies the target header item, and checks which header item is the generation target of verification information. In this embodiment, “From:” header, “To:” header, “Subject:” header, “Date:” header, and “Body:” body information (corresponding to “pattern 3”) The five header items (including the “File:” attached file) are target header items.

  Here, it is assumed that the character string [cybersec00112] is added to the “Subject:” header by the ML server. If the verification information is regenerated using the target header field of the received mail as it is, it is different from the original mail header created by the mail transmission terminal 2, so the character string of the target header field is added by the ML server. Mail will be judged as illegal mail.

  In this embodiment, with reference to the “X-InboundMAC:” header combined with the header information, the character size information is separated from the verification information combined with the character size information, which is metadata, and “Subject: By acquiring the character size separated from the rear part of the “header”, the original “security vulnerability report” character string can be acquired.

  The verification unit 5232 regenerates verification information using the secret information acquired from the secret information management unit 522 based on the character string of the “Subject:” header and other target header items. In this embodiment, “BC73DA1254231F” is regenerated as the verification information.

  Next, the verification unit 5232 compares “BC73DA1254231F”, which is verification information separated from the “X-InboundMAC:” header, with the regenerated verification information, and confirms that they match. If the verification information matches, the received mail can be verified as being sent from a valid sender.

In the first embodiment, verification information can also be generated by replacing the character string of the “Subject:” header with feature amount information using a one-way hash function or the like. By using the “Subject:” header as feature amount information, generation of impersonation identification information by an attacker can be prevented.
[Second Embodiment]

  In the second embodiment, in addition to the character size information of the “Subject:” header content, the feature amount information of the “Subject:” header content is combined with the verification information to generate a verification information header, and the verification is performed. It is.

  In the second embodiment, verification processing can be performed even when some characters are added after the “Subject:” header by the ML server.

  FIG. 12 is a diagram for explaining an example of verification information generation processing in the second embodiment. Differences between the verification information generation process in the second embodiment and the verification information generation process in the first embodiment described with reference to FIG. 10 are as follows. In the first embodiment, the character string size of the “Subject:” header is calculated and combined with the verification information. On the other hand, in the second embodiment, the feature amount information generation unit 2241 calculates the feature amount of the character string that is the content of the “Subject:” header, and verifies the character string size of the “Subject:” header. In addition to combining with the verification information, the calculated feature amount is further combined with the verification information.

  In the present embodiment, the feature amount “52A6A39C33” is calculated from the character string of “Security Vulnerability Report” in the “Subject:” header, and is combined with the verification information. Note that the method of combining the verification information is not limited to the present embodiment as in the first embodiment.

  FIG. 13 is a diagram for explaining an example of the verification process in the second embodiment. The verification processing in the second embodiment described with reference to FIG. 13 is based on the verification processing in the first embodiment described in FIG. 11 and the character string of “Security Vulnerability Report” in the “Subject:” header, “52A6A39C33”. The feature amount is calculated and compared with the feature amount combined with the verification information. By comparing the feature amounts, it is possible to confirm whether or not the character string of the “security vulnerability report” acquired based on the character size information combined with the verification information is correct. For example, when the feature amount of the character that has acquired the character size from the end of the character string of the “Subject:” header is different from the feature amount combined with the verification information, the acquisition position is set to the beginning of one character from the end of the character string. Shift and re-acquire and compare the amount of information. By repeating this operation, the original character string can be found even if some characters are added after the “Subject:” header by the ML server, for example. The verification unit 5232 can regenerate the verification information together with the other four target header items by using the correct “Subject:” header character string.

  In this embodiment, the metadata combined with the verification information is character size information, and character strings corresponding to the character size are sequentially extracted from the back of the “Subject:” header. If the last character of the column and the character size are used as metadata, the correct original character string can be obtained without repeating processing by extracting the character size from the location where the characters matched in the “Subject:” header. Extraction is possible.

The other operations are the same as the verification process in the first embodiment described in FIG.
[Third embodiment]

  In the third embodiment, verification information is generated and verified in addition to the character size information of the contents of the “Subject:” header, which is the target header item, and the feature amount information of the contents of the “Subject:” header. is there.

  In the third embodiment, for example, the verification process can be performed even when the ML server deletes part of the back of the “Subject:” header. In mail transmission / reception in a mobile environment such as a mobile phone, a tablet terminal, or a smartphone, if the character string of the “Subject:” header exceeds a predetermined size, a part of the back may be deleted. According to the third embodiment Verification processing is possible.

  FIG. 14 is a diagram illustrating an example of the verification information generation process in the third embodiment. Differences between the verification information generation process in the third embodiment described in FIG. 14 and the verification information generation process in the second embodiment described in FIG. 12 are as follows. In the second embodiment, the size of all original character strings in the “Subject:” header and the feature values of all character strings are combined with the verification information. On the other hand, in the third embodiment, the size and the feature amount of the designated portion of the character string of the “Subject:” header are combined with the verification information. The character string can be specified by, for example, a method of specifying “from the first character in the character string to the character size”. Further, the designation method may be changed according to the size of all the original character strings, and the designation method may be combined with the verification information as metadata. For example, a designation method of “designate all characters within 20 characters and top 10 characters when greater than 20 characters” is possible. As a result, it is possible to perform verification processing in consideration of the case where the number of characters in the “Subject:” header that can be received differs depending on the specifications of the mobile phone carrier.

  In this embodiment, the character of “vulnerability report” is designated from the contents of the “Subject:” header, and the designated character size “0C” and the feature amount “293B294CDA” of the designated character are combined with the verification information. Yes. Further, the verification information “CF743A24D94C930C293B294CDA” is combined with the “X-BoundMAC:” header, which is new header information of the verification information.

  Other processes are the same as those in the second embodiment described with reference to FIG.

  FIG. 15 is a diagram for explaining an example of the verification process according to the third embodiment. The verification process in the third embodiment described with reference to FIG. 15 is different from the verification process in the second embodiment described with reference to FIG. 13 in the method of specifying characters of the “Subject:” header. In the second embodiment, all the character strings in the header are the target of feature amount calculation and the target of verification information regeneration. In the third embodiment, the character specified in the header is the target. It becomes. Therefore, the verification process can be performed even when the number of characters is limited and some characters are deleted.

The other processes are the same as those described with reference to FIG.
Note that when sending / receiving mails to / from a plurality of terminals, secret information and the like may be different for each terminal of the other party. In that case, a transmission destination is specified by the “To:” header, and a mail header with verification information corresponding to the transmission destination is created. In addition, for a transmission mail in which a plurality of destinations are described, a mail to be transmitted may be created for each destination and sequentially transmitted.

  Further, the mail transmission terminal 2 described in the present embodiment is configured separately from the verification information device 22 and the mail software 21, and the mail reception terminal 5 is configured separately from the verification device 52 and the mail software 51. Therefore, the mail software can be selected by the user as appropriate, and normal mail can be transmitted / received to / from a transmission / reception destination not equipped with the verification device 52 or the like.

  Note that the function of the verification information device 22 and the function of the verification device 52 may be implemented by an add-on function of mail software.

  In the embodiment described above, mail verification is performed on a client basis. For example, secret information is managed by a management server connected to the network, and each transmitting / receiving terminal acquires secret information by connecting to the management server as appropriate. You may do it.

  As mentioned above, although the form for implementing this invention was explained in full detail, this invention is not limited to such specific embodiment, In the range of the summary of this invention described in the claim, Various modifications and changes are possible.

The present invention may have the following configurations as described below.
(Appendix 1)
Processing to generate verification information based on the target header item of the outgoing mail and the secret sharing information,
A process of combining meta information of the target header item with the verification information;
A first computer that transmits a mail executes processing for combining the verification information combined with the meta information with a mail header of the transmitted mail;
A process of separating verification information and meta information from the mail header of the received mail;
A process of acquiring a target header item from the mail header based on the separated meta information;
Processing to regenerate verification information based on the acquired target header item and the secret shared information;
A mail processing method executed by a second computer that receives a mail, the process of comparing the separated verification information and the regenerated verification information.
(Appendix 2)
The first computer is
In the process of combining the meta information of the target header item with the verification information, further combining the feature amount calculated from a predetermined portion of the target header item with the verification information,
The second computer is
In the separation process, the feature amount is further separated from the mail header of the received mail,
Processing for calculating a feature value from the acquired target header item;
The mail processing method according to claim 1, further comprising: a process of comparing the calculated feature quantity with the separated feature quantity.
(Appendix 3)
The first computer is
The mail processing method according to attachment 2, wherein in the calculation process, a feature amount is calculated for a specified portion of the target header item.
(Appendix 4)
When a computer sends an e-mail,
An input / output unit for inputting / outputting information;
A verification information generating unit that generates verification information based on the target header item of the outgoing mail and the secret shared information, and combines the verification information with meta information of the target header item;
A mail processing program that causes the verification information combined with the meta information to function as a processing unit that combines the verification information with a mail header of the transmission mail.
(Appendix 5)
The computer,
Further function as a feature amount information generation unit that calculates a feature amount from a predetermined portion of the target header item,
The mail processing program according to attachment 4, wherein the verification information generation unit further combines the feature quantity with the verification information.
(Appendix 6)
The mail processing program according to appendix 5, wherein the feature amount information generation unit calculates a feature amount for a specified portion of the target header item.
(Appendix 7)
When a computer receives an e-mail,
An input / output unit for inputting / outputting information;
The verification information and the meta information are separated from the mail header of the received mail, the target header item is acquired from the mail header based on the separated meta information, and the acquired target header item and the secret shared information are based on the acquired header information. A mail processing program that regenerates the verification information and causes the verification information to function as a verification unit that compares the separated verification information with the regenerated verification information.
(Appendix 8)
The computer,
Further function as a feature amount information generation unit that calculates a feature amount from the target header item,
The verification unit
In addition to the verification information and the meta information, the feature amount is further separated from the mail header of the received mail,
The mail processing program according to appendix 7, which compares the calculated feature quantity with the separated feature quantity.
(Appendix 9)
The mail processing program according to appendix 8, wherein the feature amount information generation unit calculates a feature amount for a specified portion of the target header item.
(Appendix 10)
A verification information generation unit that generates verification information based on the target header item of the outgoing mail and the secret shared information;
A mail processing apparatus comprising: a verification information combining unit that combines meta information of the target header item with the verification information, and combines the verification information combined with the meta information with a mail header of the outgoing mail.
(Appendix 11)
The verification information and the meta information are separated from the mail header of the received mail, the target header item is obtained from the mail header based on the separated meta information, and the obtained target header item and the secret shared information are obtained. A mail processing apparatus comprising: a verification unit that regenerates verification information and compares the separated verification information with the regenerated verification information.
(Appendix 12)
Processing to generate verification information based on the target header item of the outgoing mail and the secret sharing information,
A process of combining meta information of the target header item with the verification information;
A mail processing method executed by a computer that transmits a mail, wherein the verification information combined with the meta information is combined with a mail header of the transmission mail.
(Appendix 13)
A process of separating verification information and meta information from the mail header of the received mail;
A process of acquiring a target header item from the mail header based on the separated meta information;
Processing to regenerate verification information based on the acquired target header item and the secret shared information;
The mail processing method which the computer which receives mail performs the process which compares the said verification information isolate | separated and the said regenerated verification information.

1 Network 2 E-mail sending terminal
21 E-mail Software 22 Verification Information Generation Device 23 Communication Device 221 Request Reception Unit 222 Management Unit 223 Secret Information Management Unit 224 Verification Information Generation Unit 2211 Input / Output Unit 2221 Target Header Item Management Unit 2231 Secret Information Storage Unit 2241 Feature Quantity Information Generation Unit 2242 Verification information generating unit 2243 Verification information combining unit 3 Sending mail (SMTP) server 4 Received mail (POP) server 5 Email receiving terminal 51 Email software 52 Verification device 53 Communication device 54 Display device 521 Request receiving means 522 Secret information management Means 523 Verification means 5211 Input / output unit 5221 Confidential information storage unit 5231 Feature quantity information generation unit 5232 Verification unit

Claims (8)

Processing to generate verification information based on the target header item of the outgoing mail and the secret sharing information,
A process of combining meta information of the target header item with the verification information;
A first computer that transmits a mail executes processing for combining the verification information combined with the meta information with a mail header of the transmitted mail;
A process of separating verification information and meta information from the mail header of the received mail;
A process of acquiring a target header item from the mail header based on the separated meta information;
Processing to regenerate verification information based on the acquired target header item and the secret shared information;
A process of comparing the separated verification information and the regenerated verification information is executed by a second computer that receives the mail ,
The first computer is
In the process of combining the meta information of the target header item with the verification information, further combining the feature amount calculated from a predetermined portion of the target header item with the verification information,
The second computer is
In the separation process, the feature amount is further separated from the mail header of the received mail,
Processing for calculating a feature value from the acquired target header item;
A mail processing method for executing a process of comparing the calculated feature quantity with the separated feature quantity . The first computer is
The mail processing method according to claim 1 , wherein in the calculation process, a feature amount is calculated for a designated portion of the target header item. When a computer sends an e-mail,
An input / output unit for inputting / outputting information;
A verification information generating unit that generates verification information based on the target header item of the outgoing mail and the secret shared information, and combines the verification information with meta information of the target header item;
The verification information combined with the meta information is made to function as a processing unit that combines with the mail header of the outgoing mail ,
The verification information generation unit is a mail processing program that combines the verification information with a feature amount calculated from a predetermined portion of the target header item . When a computer receives an e-mail,
An input / output unit for inputting / outputting information;
A separation unit that separates verification information, meta information, and feature values from the mail header of the received mail ;
An acquisition unit that acquires a target header item from the mail header based on the separated meta information ;
A regenerating unit for regenerating the verification information based on the acquired the target header item and the secret shared information,
A verification unit for comparing the amount released was the verification information and the re-generated the verification information,
A feature amount calculation unit for calculating a feature amount from the acquired target header item;
A mail processing program that functions as a comparison unit that compares the calculated feature quantity with the separated feature quantity . A verification information generation unit that generates verification information based on the target header item of the outgoing mail and the secret shared information;
A verification information combining unit that combines meta information of the target header item with the verification information, and combines the verification information combined with the meta information with a mail header of the outgoing mail ;
The verification information generation unit is a mail processing device that further combines a feature amount calculated from a predetermined portion of the target header item with the verification information . A separation unit that separates verification information, meta information, and feature values from the mail header of the received mail ;
An acquisition unit that acquires a target header item from the mail header based on the separated meta information ;
A regenerating unit for regenerating the verification information based on the acquired the target header item and the secret shared information,
A verification unit for comparing the amount released was the verification information and the re-generated the verification information,
A feature amount calculation unit for calculating a feature amount from the acquired target header item;
An email processing apparatus comprising a comparison unit that compares the calculated feature quantity with the separated feature quantity . Processing to generate verification information based on the target header item of the outgoing mail and the secret sharing information,
A process of combining meta information of the target header item with the verification information;
A process of combining the verification information combined with the meta information with a mail header of the outgoing mail, and a computer that transmits the mail ,
A mail processing method , wherein in the process of combining meta information of the target header item with the verification information, a feature amount calculated from a predetermined portion of the target header item is further combined with the verification information . A process of separating verification information and meta information from the mail header of the received mail;
A process of acquiring a target header item from the mail header based on the separated meta information;
And the acquired target header item and process to regenerate verification information based on the secret sharing information,
A process of comparing the separated verification information with the regenerated verification information;
In the separation process, the feature amount is further separated from the mail header of the received mail,
Processing for calculating a feature value from the acquired target header item;
A mail processing method executed by a computer that receives a mail , the process of comparing the calculated feature quantity and the separated feature quantity .

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