JPS6220444A - Destination concealing communication system - Google Patents

Abstract

PURPOSE:To transmit communication texts to the other party of communication while concealing contents of communication texts from intermediate repeater stations by putting a ciphered text, which is preliminarily acknowledged between a transmitter and receiver, in the address position of data of one transmission unit. CONSTITUTION:A pair of a enciphering key K 302 and a deciphering key K' 305 are made different from each other. A normal text M 301 is enciphered with the enciphering key K 302 by a enciphering part 303, and this enciphered text EK (M) 304 is deciphered with the deciphering key K' 305 by a deciphering part 306 to obtain an original normal text M 307. The enciphering key K 302 and the deciphering key K' 305 are generated in a receiver 308, and the enciphering key K 302 is opened to a transmitter 309, and the deciphering key K' 305 is held secretly by the receiver 308.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention is directed to a communication system having a public relations communication function, in which data can be communicated to a receiving destination while the destination is kept secret during the transmission route. Concerning confidential communication methods.

[Background of the invention]

Conventionally, when introducing encryption into a data communication system consisting of multiple terminals and computers, one of the following three introduction methods has been adopted.

(1) Link-link method: The link-link method is a method that performs encryption processing for relay lines, and is a method in which an encryption device is introduced between a modem and a terminal station on the relay line. If the message passes through several relay stations,
per relay station.

There are two link configurations: a terminal station/relay station and a relay station/terminal station, and four encryption devices are required. At this time, the relay station decodes the communication data, reads the route information, and
Perform predetermined control. This method has the advantage of being easy to implement because it can be considered independently of the system, but has the disadvantage that it is susceptible to eavesdropping and tampering because it is processed in plain text at the relay station.

(2) Node-node method: There is a node-note method as a method to supplement the processing of the plaintext state at the intermediate node, which has the disadvantage of the link-link method.

This method is the same as the link-link method in that an encryption device is inserted between the terminal station and the relay station, but a protection mechanism for encryption and decryption is built into the relay station. The operation of this protection function is to decrypt the sender's ciphertext and encrypt it again for the receiver, but of the plaintext message created by decryption, only the route information is passed through a filter and processed by the relay station. passed to. Therefore, in the node-node system, information other than route information can be prevented from being wiretapped or tampered with, but relay stations have the disadvantage that route information is susceptible to wiretapping and tampering.

(3) End-to-end method: The end-to-end method is a method in which the ciphertext encrypted at the transmitting end station is not decrypted until it reaches the receiving end station.

In this method, the route information required by the relay station is left in plain text, and a message is created with only the data in cipher text. This method has the advantage that it is possible to prevent wiretapping and falsification of communication data other than route information, and that key management is easier than the link-link method and the node-node method. However, the end
The end method also has the disadvantage that route information is susceptible to eavesdropping and falsification.

Both of the above methods have the disadvantage that the route information is in plain text at the relay station and is susceptible to eavesdropping and falsification of the route information. In particular, in communication systems such as satellite communications and local area networks that have a public relations communication function that allows the receiving end station to receive the message by once publicizing the communication, a third party can eavesdrop on the communication data. It is relatively easy to do so, but if the route information is obtained in plain text, there are drawbacks such as the fact that the content of the communication data, which should originally be kept secret, can be inferred by a third party through statistical processing or the like.

[Purpose of the invention]

The purpose of the present invention is to eliminate such conventional drawbacks in a communication system having a public relations communication function, to encrypt messages including route information, and to encrypt the contents of messages including route information even at intermediate relay stations. To provide a destination concealed communication method that allows a message to arrive at a communication partner while being kept confidential.

[Summary of the invention]

In order to achieve the above object, the destination concealed communication method according to the present invention enables communication with the destination kept confidential by having the sender and receiver of the message perform the following actions in a communication system having a public relations communication function. Have them do it. The main points are described below.

1. The sender satisfies the predefined sentence format, and
A plaintext with different content than previously used is encrypted using the recipient's encryption key and placed in the address position of the message. Furthermore, the sender 6 broadcasts the message thus obtained in the communication system. The encryption performed by the sender must be able to be decrypted by the recipient who receives the ciphertext, and cannot be decrypted by a third party. Here, deciphering refers to illegally decrypting a ciphertext by a third party. As one method for creating such a ciphertext, the sender may encrypt it using the recipient's public key encryption 9r.

2. When the receiver receives the advertised message, he first decodes the route information in the message using his own decoding axis. Next, if the decrypted text satisfies a predefined text format, it is determined that it is a message addressed to the user, and the message is taken in. If the decrypted text does not satisfy the predetermined text format, the user determines that the message is not addressed to him and rejects the message. When public key cryptography is used as an encryption method, the recipient creates an encryption key and decryption key for public key encryption in advance, discloses the encryption key to others, and keeps the decryption key private. Keep it.

By implementing the above communication method, if a third party other than the sender and receiver obtains the message, the route information in the message will be encrypted and cannot be deciphered by the third party.
The original destination of the message cannot be read from the route information.

Furthermore, when the communication system is connected to another communication system having a public relations communication function via one relay station, by having the transmission source, relay station, and reception destination perform the following operations. Communication can be performed while keeping the destination secret.

3. The sender first satisfies the predefined sentence format,
In addition, first, the plaintext with content different from the content used previously is encrypted using the relay station's encryption key to obtain first route information, and it is placed in the address position of the message. Next, the plaintext with content different from the content used previously is encrypted using the recipient's encryption key to create second route information, and it is placed in the position next to the address position.

It is assumed that the position following the address position is a user communication information portion that is not used for communication control.

Thereafter, the sender transmits the message created in this way by public relations communication.

4. When the relay station receives the advertised message.

First, the first route information in the message is decrypted using its own decryption axis. If the decrypted plaintext matches the specified sentence format, the first root information is deleted and the second root information is replaced with the address position to fill in the deleted part, resulting in re-ellipsing. The received message is sent as a public relations communication within the recipient's communication system. If the decrypted plaintext does not match the specified sentence format, the station determines that it is not a message that should be processed by its own station, and rejects the message.

5. When the recipient receives the advertised message, first,
Decrypt the route information at the address location using your own decryption key. If the decrypted plaintext matches the specified text format, it is determined that the message is addressed to the local station, and the message is taken in.

If the decrypted plaintext does not match the specified sentence format, it is determined that it is not a message addressed to the local station, and
The correspondence shall be rejected.

By expanding and applying the above method to three or more communication systems having a public relations communication function, three or more communication systems having a plurality of public relations communication functions can be formed into a multi-link configuration using the relay station of each communication system as a connection point. , the route information is encrypted so that even if a third party other than the sender and receiver obtains the message, it cannot be decrypted with the third party's decryption key. , a third party cannot peek at the destination of the message.

[Embodiments of the invention]

FIG. 1 shows a communication system having a destination secret communication function showing an embodiment of the present invention.

In Figure 1, a communication satellite 103, an earth station (relay station)
Communication is carried out between terminal stations 101 and 105 through data lines 106 and 107 via terminal stations 102 and 104, respectively.

This embodiment will be described below in the order in which communication data is transmitted.

1. As a preliminary preparation in this embodiment, each terminal station and
Each earth station independently creates an encryption key and a decryption key using public key cryptography, of which the encryption key is made public and the decryption key is kept private. Accordingly, each station is assumed to hold the encryption keys of all other stations. It is also assumed that each station and each earth station have a common format shown in FIG. Second
The format of the diagram has a total length of 64 bits, and the first 1
The 2 bits and the trailing 12 bits are each a bit string "101010101010".

Note that the public key cryptosystem used here satisfies the following.

(1) Encryption and decryption follow the flow shown in Figure 3,
302 for the pair of encryption keys and ' 30 for the decryption key
5 is different and any plaintext M301
The following is satisfied for .

M=DK' (Ek (M)) That is, after the plaintext M301 is encrypted by the encryption unit 303 using 302 as the encryption key, the ciphertext Ek (M)
304 as the decryption key' 305 as the decryption key 306
When decrypted, the original plaintext M307 is returned.

(2) In FIG. 3, an encryption key 302 and a decryption key 305 are created at the recipient 308,
Thereafter, the encrypted @1jk 302 is disclosed to the sender 309, and the decryption key '305 is kept secret at the receiver 308.

(3) Decryption Iak″3 corresponding to encryption #k 302
Even if the ciphertext Ek (M) 304 is decrypted with the decryption key 306 using a decryption key k'' other than 05, it will not return to the original plaintext.In other words, if k'≠k'', then Mf-Dk ″
(Ek(M)) (4) Even if a third party other than the recipient receives the encryption key k 301, the plain text M301, and the encrypted Ek
Even if you obtain (M)304, it is very difficult to know the decryption key '.

(5) In FIG. 3, the flow shown by the dotted line from right to left is established. That is, plaintext data M307 is used as the decryption key'
305 and the decryption key 304, and then the decrypted pk' (M) is encrypted by the encryption unit 303 using the encryption key k to return to the original plaintext.

M=Ek (Dk' (M)) 2. Assume that data is transmitted from the source terminal station 101 to the destination terminal station 104 in FIG. The operation in the source terminal station 101 at this time will be described in detail using FIG.

In FIG. 4, data line 401 is an enlarged representation of data line 106 in FIG. Source terminal station 40
9 is an enlarged view of the source terminal station 101 in FIG. The station 409 includes a register 402, a decryption key 403, an encryption section 404, a header addition section 406,
It consists of a public key selection section 407 and an address control section 408.

(1) When input data is input from the user, the user terminal 405 first creates data in the format shown in FIG. The data in Figure 5 is the destination earth station number 501 (10 in Figure 1).
4), a destination station number 502 (corresponding to 105 in FIG. 1), and an information section 503 containing data that the user intends to transmit. After creating the data in the format shown in FIG. 5, the user terminal 405 transmits the destination earth station number 501 and the destination end station number 502 to the public key selection unit 407.

At the same time, the user terminal transmits the entire data in the format shown in FIG. 5 to the encryption unit 404.

(2) When the public key selection unit 407 receives the destination earth station number 501 and the destination end station number 502, the public key selection unit 407 selects each earth station and each non-terminal station that have already been published and stored in the public key selection unit 407. Among the encryption keys, 2 is selected as the encryption key of the earth station corresponding to the destination earth station number 501 and 3 is selected as the encryption key of the terminal station corresponding to the destination end station 502, and transmitted to the encryption unit 404. .

(3) The encryption unit 404 sets the encryption key to 2 and k3.
2, generates a random number with the same bit length as the binary data 202 in FIG. 2 from among the data in the common format shown in FIG. Replace with the binary data of At this time, the data in the updated format shown in FIG.
The encryption key ko of the local station (source terminal station), which is already stored in
Then, using the encrypted fikl of the source earth station stored in the public encryption unit 404, A's ciphertext Eko is
After creating (A) and Ekl(A), A's ciphertext Ek2 (A) using 2 as the encryption key, and
Dark+([Jf! k 3 Use A's ciphertext Ek3(
A), and further creates a ciphertext EkO(M) in the information section 503 using its own encryption key kO, and transmits it to the header addition section 406.

(4) The header addition part has four types of A's ciphertext EkO(A)
, Ekl (A), Ek2 (A), Ek3 (A), and EkO (M), data in the format shown in FIG. 6 is created. The data in Figure 6 includes a start delimiter (SD) 601 indicating the start of the packet, a control section (CT) 602 indicating the type of packet, and a source earth station address section (
SAI) 603, source terminal station address section (SA2) 60
4. Destination earth station address section (DAI) 605, destination end station address section (DA2) 606, information section (INFO) 60
7. Frame check sequence (Fe2) 608
, an end delimiter (ED) 609 indicating the end of the packet. The header addition unit 406 provides the next data and the sixth
After creating the data in the format shown in the figure, it is transmitted on the data [401].

SD: “01111110” CT: “01” (Indicates forward transmission data) SAI: Ekl (A) SA2: EkO (A) DAl: Ek2 (A) DA2: Ek3 (A) INFO: EkO ( M) Fe2: Check bit of cyclic code ED: “0111.1110” Data in the format shown in Figure 6 created in this way is DA
Call it TA1.

Furthermore, to ensure data transparency.

When transmitting a packet, the packet transmitter shall always insert a 1-bit "0" after the five consecutive "1"s for data on the transmission path other than the transmit delimiter and end delimiter, and The receiving side shall always delete the 1-bit 110 I+ after the following five HI 11s from data on the transmission path other than the transmission delimiter and end delimiter when receiving.

3. The operation of the source earth station 102 shown in FIG. 1 will be described in detail using FIG.

In FIG. 7, a data line 701 is an enlarged representation of the data line 106 in FIG. Source earth station 7
02 is an enlarged display of the source earth station 102 in FIG. The earth station 702 has a transmitting and receiving antenna 7o.
3. It consists of an address determination section 706, a data reconstruction section 704, and a decryption key 705.

(1) The source earth station 702 first stores DATA 1 transmitted by the source terminal station 101 in the data reconfiguration unit 704.

(2) The decryption key 705 has already been created and using the local station's decryption #ak1' kept secretly in the decryption key 705, DATA 1 (7) is sent to the destination earth station shown in Figure 6. Decode the data in the address field 605 and decode result B
is transmitted to the address determination section 706.

(3) When the address determination unit 706 receives B, the address determination unit 706 selects the leading and trailing 12-bit strings “10101010” of the common format data shown in FIG.
1010'' and the 12 bit strings at the beginning and end of B. If they match, DATAI
The destination earth station is determined to be the local station, and a signal indicating "data addressed to the local earth station" is transmitted to the data reconstruction unit 704.

If they do not match, it is determined that the destination earth station of DATA 1 is another earth station, and a signal indicating "data addressed to another earth station" is transmitted to the data reconstruction unit 704. In this example, the data in the destination earth station address field 605 shown in FIG. 6 out of DATA1 is Ek2 (A
), so B and A do not match. That is, A-f-Dkl' (Ek2 (A))=B Furthermore,
B is the total of the beginning and end of the common format data in Figure 2, 2
The probability of a 4-bit match is extremely small at 1/2" to 17 millionths. Therefore, in this example, it is almost certain that a signal indicating "r=data addressed to the T-baseball station" is transmitted. be done.

(4) When the data reconstruction unit 704 receives a signal indicating the data j addressed to the own earth station, it deletes the destination earth station address part 605 shown in FIG. 6 from DATA 1, and converts it into the data format shown in FIG. After creating DATA2 changed to
ATA2 is transmitted on data line 701. When the data reconstruction unit 704 receives a signal indicating “data addressed to another earth station,” it transmits DATA 1 stored in the data reconstruction unit directly to the satellite 103 via the transmitting/receiving antenna 703 without changing it.

4. The satellite 103 in FIG. 1 performs the following operations6:
After receiving DATA 1, send DATA to each earth station.
1 will be transmitted as a publicity.

56 It is assumed that the source earth station 101 and the destination earth station 104 in FIG. 1 have the same configuration. Accordingly, the operation of destination earth station 104 of FIG. 1 will be described in detail using FIG. However, the data line 701 in FIG. 7 is an enlarged version of the data line 107 in FIG. 1, and the destination earth station 702 in FIG. 7 is an enlarged version of the destination earth station 104 in FIG. Suppose there is.

(1) When the destination earth station 702 receives DATA l through the transmitting/receiving antenna 703 of the satellite 103, first,
DATA I is stored in the data reconfiguration unit 704.

(2) The decryption key 705 is transmitted from the transmitting/receiving antenna 703
When TA 1 is received, first, a signal indicating "satellite reception" is transmitted to address determination section 706. Next, the decryption key 705 uses 2' for its own decryption key, which has already been created and is kept secretly within the decryption key 705.
1, the data in the destination earth station address field 605 shown in FIG.

(3) The address determining unit 706 determines that “When receiving the signal indicating reception J from the satellite and the signal C, the address determining unit 706
1010101010 1010101010
10" and the 12-bit bit strings at the beginning and end of C. If they match, it is determined that the destination earth station of DATA 1 is the local station, and the data reconstruction unit 70
4, a signal indicating "data addressed to own earth station" is transmitted. If they do not match, it is determined that the destination earth station of DATA 1 is another station, and a signal indicating "data rejection" is transmitted to the data reconfiguration unit 704. In this example, DATA
The data in the destination earth station address field 605 shown in FIG.
Since this is Ek2(A) which is the encrypted version of the common format data A shown in the figure, C and A match. That is, A=D2' (Ek2 (A))=C Therefore, C
is the total of 24 at the beginning and end of the common format data in Figure 2.
Match in bits.

Therefore, in this example, a signal indicating "data addressed to own earth station" is transmitted.

(4) When the data reconstruction unit 704 receives a signal indicating "data addressed to own earth station," it deletes the destination earth station address part 605 shown in FIG. 6 from DATA 1 and formats the data as shown in FIG. 8. After creating DATA 2 changed to
DATA 2 is transmitted on data line 701. The data in FIG. 8 includes a start delimiter (S D
) 801, a control section (CT
) 802, source earth station address section (SAI) 803,
Source terminal address section (SAD) 804, destination station address section (DA2) 1305, information section (INF○) 80G
, Frame Check Silkens (Fe2) 807,
It consists of an end delimiter (ED) 808 indicating the end of the packet. When the data reconstruction unit 704 receives a signal indicating “rejection data”, the data reconstruction unit 704
Delete TA 1.

6. It is assumed that the source terminal station 101 and the destination station 105 in FIG. 1 have the same configuration. Therefore, the operation of destination station 105 in FIG. 1 will be described in detail using FIG. 4.

However, the data line 401 in FIG. 4 is the data line 1 in FIG.
It is assumed that the destination station 409 in FIG. 4 is an enlarged display of the destination station 105 in FIG. 1.

(1) Transmit data on v&401! riDATA
2 is first stored in register 402.

(2) The decryption key 403 uses 3' for the decryption key of the local station that has been created and is stored in the decryption key 403.
Of A2, the data in the destination station address section 804 in FIG. 8 is decoded, and the decoded data D is sent to the address determination section 408.

(3) When the address determination unit 408 receives D, the address determination unit 408 selects the leading and trailing 12-bit bit strings “10101” of the common format data shown in FIG.
0101010'' and the 12-bit bit strings at the beginning and end of C are compared.

If the two match, it is determined that the destination station of DATA 2 is the own station, and a signal indicating "data addressed to the own station" is transmitted to the register 402.

If they do not match, it is determined that the destination station of DATA 2 is another terminal station, and a signal indicating "data addressed to another terminal station" is transmitted to the register 402. In this example, DAT
Of A2, the data in the destination station address field 804 shown in FIG. 8 is Ek3(A), which is obtained by encrypting the common format data A in FIG. D and A match. That is, A=Dk3' (E
k3 (A)=D Therefore, D matches the common format data shown in FIG. 2 with a total of 24 bits at the beginning and end.

Therefore, in this example, a signal indicating "data addressed to own station" is transmitted.

(4) When the register 402 receives a signal indicating "data addressed to its own station," it uses the decoding fik 3' of its own station to
The information part 805 in FIG. 8 of the ATA 2 is decoded, and the decoded data E is transmitted to the user terminal 405. Here, E is the same as data M input to the user terminal of the source terminal station 101. Namely.

E=Dk3' (Ek3 (M))=M register 40
When 2 receives a signal indicating "data addressed to another terminal station," it transfers DATA 2 stored in register 402 to data line 4.
Transmit again on 01.

7. Single-error correction and double-error detection
This is done by using a check sequence as a check bit. At this time, the following operation is performed.

(1) If a single bit error occurs during data transmission, the earth station or terminal station that detects it automatically corrects the single bit error and then continues transmission.

(2) If a double bit error occurs during data transmission,
At the earth station or terminal station that checked it, the 9th
The retransmission request packet shown in the figure is created and sent. The data in Figure 9 includes a start delimiter (
SD) 901, the type of the packet is a control section (CT) 902 indicating that it is a retransmission request packet, the source earth station address section (SAI) 903, the source terminal station address section (SA2) 904, the destination earth Station address part (D
AI) 905, destination station address section (DA2) 906,
It consists of a frame check sequence (Fe2) 907 and an end delimiter (ED) 908 indicating the end of the packet. In particular, the control unit 902 contains a bit string indicating that it is a retransmission request packet, for example, CT="
10'' (indicating data in the opposite direction).By doing this, the retransmission request packet is transmitted to the terminal station that sent the original data, and
The destination station that has received the retransmission request packet can confirm that it is a retransmission request packet from the bit string "10''" in the control section of the packet. Furthermore, since the source end station address field 903 in FIG. 9 is the same as the destination end station address field 606 that the destination end station previously transmitted, it can be known that this is a retransmission request for the packet. .

〔Effect of the invention〕

According to 1 to 7 above, the data input to the user terminal of the source terminal station 101 is correctly delivered to the destination station 105, and is not only transmitted to other terminal stations and relay stations, but also to third parties that intentionally eavesdrop. Even the recipient will not know the address. That is, (1) For the source terminal station 101 and other terminal stations connected by the same data line 106 and for the source earth station 102, among the transmitted DATA 1 in the format shown in FIG. Earth station address 605 and destination station address 6
06 is a bit string that cannot be deciphered by the terminal station, and even if data transmitted more than once from the same source terminal station is compared, the bit pattern of the destination address changes each time. It is difficult to identify the original terminal station. In this embodiment, if a 40-bit random number is placed in the 40-bit portion 202 of FIG. 2, the probability that the same bit pattern will appear twice in the destination address is 1/
2", that is, approximately one trillionth, is extremely small and can be ignored.

(2) For other earth stations different from the source earth station 102, among the transmitted DATA 1 in the format shown in FIG. 6, the destination earth station address 605 and the destination earth station address 6
06 is a bit string that cannot be deciphered by the earth station, and even if data transmitted more than once from the same source terminal station is compared, the bit pattern of the destination address changes each time. It is difficult to fix terminal stations.

:3) For other terminal stations connected to the destination station 105 by the same data line 107, the transmitted D in the format shown in FIG.
The destination station address 804 of the ATA 2 is a bit string that cannot be deciphered by the terminal station, and
Even if data transmitted more than once from the same source terminal station is compared, the bit pattern of the destination address changes each time, making it difficult to fix the destination station.

(4) For terminal stations other than those mentioned above, data is not transmitted from the earth station connected by the same data line, so of course,
The destination station cannot be fixed.

Additionally, the method can address bit errors during transmission by utilizing the frame check sequences of FIGS. 6 and 8.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a communication system having a destination secret communication function showing an embodiment of the present invention, Fig. 2 is a diagram showing a common format held by each earth station in Fig. 1, and Fig. 3 is a diagram showing the present embodiment. A flowchart showing the processing procedure for encryption and decryption using the public key cryptosystem used in the example, Figure 4 is a block configuration diagram of the source terminal in Figure 1, and Figure 5 is created by the user terminal in Figure 4. 6 is a diagram showing the format of data created by the header addition section in FIG. 4. FIG. 7 is a block diagram of the source earth station in FIG. 1.
The figure shows the format of data created by the data reconfiguration section in FIG. 7, and FIG. 9 shows the format of a retransmission request packet.
7/-1,2'-\ Agent Patent Attorney Ogawa Sumi 2-'' 6 Go- 201?o2203 No. 4 B No. B Country No. 7 No. 8 Concave

Claims (1)

[Claims] 1. In a communication system having a public relations communication function, route control is performed by placing a ciphertext agreed upon in advance between the sender and the receiver at the address position of one transmission unit of data. A destination secret communication method characterized by the following. 2. The above-mentioned ciphertext is an encrypted plaintext that satisfies a predefined text format in the communication system, and the sender encrypts the plaintext that satisfies the text format each time it is sent and that the previously used plaintext 2. The destination secret communication method according to claim 1, wherein plain text having a content different from that of the destination is encrypted. 3. The ciphertext is encrypted by public key cryptography, and each subscriber in the communication system creates an encryption key and a decryption key in advance and uses the encryption The key is made public to others, the decryption key is kept secret, and then when a sender sends data to a receiver, the sender uses the receiver's published encryption key. After encrypting the plaintext that satisfies the above text format using the encryption key, the data is sent via public relations communication, and each subscriber who receives the data can then use his or her own decryption key to encrypt the ciphertext. It is determined whether or not the decrypted sentence matches the sentence format, and if it matches, it is determined that the data is addressed to itself and the data is received; if it does not match, it is determined that the data is not addressed to itself. 2. The destination secret communication method according to claim 1, wherein the destination confidential communication method determines that there is no such data and rejects the data. 4. A certain subscriber in the communication system is also a relay station with another communication system having a public relations communication function,
When a transmission source belonging to one communication system transmits data to a reception destination belonging to another communication system, the transmission source:
The first route information obtained by encrypting the plaintext that satisfies the text format using the relay station's published encryption key is placed in the address position, and then the reception destination's published encryption After creating one transmission unit of data by placing the second route information obtained by encrypting the plain text that satisfies the above-mentioned sentence format using the public key in the next position of the above-mentioned address position, After transmitting the data, the relay station receives the data using the method, and since the plaintext decoded using the method matches the text format, the relay station transmits the data through the another communication system. After that, the first route information is deleted from the data part, and the second route information that was placed next to the address position is added to the new address part. After reconfiguring one transmission unit of data as the content, the data is transmitted by public relations communication within the other communication system, thereby enabling communication between communication systems having different public relations communication functions. Claim 1
Destination secret communication method described in section. 5. Three or more communication systems having a public relations communication function are connected in a multiple ring shape using a relay station in each communication system as a connection point, and a transmission source belonging to one communication system is connected to another communication system. When transmitting data to another receiving destination belonging to the data transmission route, a relay station existing in the data transmission route and multiple relay stations that encrypt the plain text in the above text format using each published encryption key of the receiving destination. 5. The destination secret communication system according to claim 4, wherein the ciphertexts of 1 and 2 are successively placed in order from the address position, and the message is delivered to the sender.