JPH0797381B2 - Electronic trading method - Google Patents

Description

TECHNICAL FIELD The present invention relates to an electronic transaction system for conducting electronic transactions using a computer message.

[Conventional technology]

As prior art sentences, the methods of Document 1 and Document 2 below are known.

1) Takaragi et al .: Proposal of a stamping method for electronic transactions in information networks, 1985 National Conference of the Institute of Electronics and Communication Engineers, 1985
November. 2) Day Double Davis and Double L
Price: Digital Signature Updater: Proc of the Seventh International Conferencing on Computer Comunication North Holland Publishing Company, 1984, 10.30-11.2, Sydney Australia, pp8
45-849 (DWDavies and WLPrice: Digital signature
-An update: Proc.of the Seventh International Confe
rencn on Computer Communication, North-Holland Publ
ishing Company, 1984,10.30 ~ 11.2, Sydney Australia, p
p845-849.) When exchanging contract documents with signatures and seals via a communication system such as VAN, a method called digital signature is used.

Traditionally, a signature written by hand on a contract document or a seal imprinted using red ink indicates the identity of the issuer of the document and at the same time proves that the issuer has consented to the content of the document. is there.

Similarly, a digital signature sent via a communication system indicates where the message came from, and the message is a person other than the issuer.
It also proves the infallibility that it has not been modified by a spontaneous error.

The RSA digital signature is well known as an example of realizing the digital signature. Suppose you want to create an RSA digital signature for a message of 500 bits. At this time, RSA
The encryption key is, for example, 355-bit data. The RSA digital signature is a 500-bit ciphertext obtained by encrypting the above-mentioned 500-bit plaintext message with the above-mentioned 355-bit RSA encryption key.

This 500-bit digital signature is a sequence of "0" or "1" bits that, when viewed by humans, are meaningless. However, if the computer once inputs the 500-bit digital signature and then performs the RSA decryption with the 278-bit RSA decryption key, the original 500-bit plaintext message is restored and displayed to a human.

From the fact that a person can decrypt with the above 278-bit RSA decryption key, a person knows that the originator of this digital signature is the owner of the RSA encryption key paired with the RSA decryption key. .

Here, if you are informed of the RSA decryption key, there may be a concern that you may be informed of the other RSA encryption key based on it, but this is not a problem. In other words, in the case of the above message length, even if the currently known fastest algorithm and fastest super computer are used, after the RSA decryption key is inserted, the corresponding RSA encryption key is output. , Computer 4
We have to keep it moving for more than 0,000 years. Therefore,
The RSA encryption key can be kept sufficiently confidential within the validity period of the realistic contract, and the security of the digital signature that depends on this confidentiality is guaranteed.

As an application example of the digital signature, an electronic seal, a tally (above document 1), an electronic check (above document 2), and the like are considered. These are effective in a system in which computers exchange contract documents with each other via an information network such as VAN to confirm the validity of signatures and seals.

[Problems to be solved by the invention]

However, the digital signature has two drawbacks as compared with the conventional red stamp.

The first drawback is that even if a person looks at a digital signature, it is not intuitively known whether the person has imprinted it.

The second drawback is that you can copy any number of slips with digital signatures, and the same effect will be exhibited.

(1) Point that judgment by human intuition does not work It is the human who finally confirms the signature and the seal.

The human confirms the digital signature only after seeing the computer's calculation result. This is because the digital signature itself is a bit string that does not make sense to humans as described above, so it is necessary to have the computer process it and convert it into a human-readable form.

Here, the following problems occur. In other words, it is not possible for a human being to judge whether or not a computer has processed through a legitimate procedure simply by reading the message of the computer.

For example, in the past, the officers of a bank settled by looking at a customer's stamp that had already been stamped. However, in the case of a digital signature in which the red stamp is replaced with a computer message, the officers cannot easily confirm the validity of the digital signature as in the conventional case. Even if the computer that causes the digital signature to be decrypted is reliable, it may not be tampered with before the output slip of the computer reaches the office. Moreover, even if tampering occurs, the officers cannot detect the fact of tampering just by looking at the character string of the digital signature, which originally has no meaning.

As described above, the digital signature has a disadvantage as compared with the conventional handwritten signature and the red stamp, in that the check by the human eye is not easy. In particular, important contract documents are often viewed by executives and seniors who do not know how to operate the computer, and the characteristic that "the processing of the computer is required to confirm the digital signature" is practical. It was an open road.

(2) Ease of copying It was easy to copy many vouchers with digital signatures. This was just as difficult as writing a number of contracts with red stamps, which would be inconvenient.

An object of the present invention is to provide an electronic marking method that solves the above-mentioned problems of the prior art.

[Means for solving problems]

In order to achieve the above object, the electronic transaction system of the present invention is characterized in that a digital signature reflecting transaction content information and accompanying information of a transaction document is adopted.

That is, in the electronic transaction system of the present invention, the terminal device, which is the issuer of the transaction document, issues the one-way encrypted information generated from the document information indicating the transaction content and the document information associated with the transaction at the issuer. The information obtained by encrypting with the secret encryption key is used as a digital signature, and this is sent together with the document information indicating the transaction content and the transaction accompanying information to the transaction terminal, and the transaction terminal device receives it. The transaction content document information, transaction accompanying information, and digital signature are output as a transaction document in a predetermined format.

As an encryption method for generating the digital signature, for example, a public key encryption method is adopted.

That is, the issuing terminal device encrypts the one-way encrypted information and the document information accompanying the transaction with the secret key in the public key encryption method, and the correspondent terminal device uses the one-way encryption from the received transaction content document information. In addition to generating the encrypted information, the received digital signature is decrypted with the public key corresponding to the issuer, and the decrypted information is collated with the generated one-way encrypted information to validate the digital signature. Check the sex.

The transaction partner can identify the issuer of this transaction document from the fact that the ciphertext encrypted with the secret key known only to the issuer can be decrypted with the public key corresponding to this secret key.
Further, from the fact that the one-way encrypted information generated from the received transaction content document information was included in the decrypted digital signature, it is convinced that the issuer created the document information of the transaction content. Can be obtained.

Further, as incidental information (symbol string) to be printed as a transaction document, for example, serial number, name, and other information that can be visually identified by humans are included, and these incidental information are set as a part of the constituent information of the digital signature. This makes it possible to confirm the correspondence between the format information of the transaction document and the digital signature.

After confirming the received transaction document with eyes, when confirming the legitimacy of the digital signature, the business partner must input the digital signature into the computer and have the computer judge the legitimacy of the digital signature. I have to.

In order to facilitate such a judgment process, for example, by attaching a memory directly accessible by the computer to the output form of each transaction document and recording the transaction original text and the digital signature therein, The efficiency of data input can be improved.

[Action]

According to the configuration of the present invention, the digital signature received by the customer terminal device together with the transaction information can be created only by the issuer who is the owner of the encryption key. A customer who does not have the encryption key cannot tamper with the digital signature for his own convenience.

However, upon receipt of the digital signature, the business partner can decrypt using the decryption key and obtain the original transaction text. From the fact that the business partner could decrypt with the decryption key,
It can be seen that the creator of the digital signature is the owner of the encryption key that makes up the decryption key pair. Further, the digital signature can be used at any time as proof that the issuer has authorized the transaction.

Further, according to the present invention, part of the original text of the digital signature includes the one-way encrypted information of the transaction content and a symbol string such as a serial number, which is additional information unique to each transaction document. Therefore, if the digital signature is copied to another sheet and reused, the digital signature is decrypted with the public key and it is checked whether or not the symbol string of the sheet is included to reuse the digital signature. The fact of can be detected.

Being able to prevent the reuse of digital signatures has exactly the same effect as copying and not reusing a stamped document. For example, it is possible for a bank to issue a cash voucher by an electric signal from a remote place to a terminal for which a printed slip sheet is set in advance.

Further, the accompanying information of each transaction document used for a part of the digital signature in the present invention, that is, the character string printed in advance on each transaction document is meaningful to the human eye.
In which it indicates whether the distributed beforehand which destination. As long as the business partner believes that the terminal keeps the printed matter safely and does not pass it to an unrelated third party as a blank sheet for use, the transaction text is processed by the terminal in a predetermined manner. After that, you can believe that it was completed.

Furthermore, it is difficult for a transaction source to forge an illegal transaction text and make it appear as if it is a legitimate transaction text. If the transaction source counterfeits an illegal transaction text, the transaction partner decrypts the transaction text by a computer, knows that it is not a valid document, and creates an illegal document. You can blame. Therefore, the transaction source must be prepared for considerable danger in order to send an illegal transaction statement. In this sense, the business partner can trust the transaction text to a large extent when he receives the printed matter and sees it with his own eyes.

〔Example〕

 FIG. 1 is a slip showing an embodiment of the present invention.

FIG. 2 shows a financial system using this slip.

The slip 101 has a certain arabesque pattern that is difficult to forge, and
The serial number 102 is printed. The slip 101 is set on the printing machine 205 of the customer.

In order to carry out a transaction using this slip 101, the transaction source 201, via the transaction source terminal 202, the communication network 203, and the trading partner terminal 204, in the printing machine 205, the transaction original text 1 is printed on the blank portion 103 of this slip 101.
04 and fill in the digital signature 105.

The digital signature 105 is created by public key cryptography, the cryptographic key 206 is kept secret by the transaction source 201, and the decryption key 20
It is assumed that the customer terminal 204 and related persons are informed of 8.

In the transaction original text 104, the transaction original text “transfer request ...” is entered.

The digital signature 105 is the one-way encryption of the transaction original text 104, the serial number "WC808972GA", and the data obtained by connecting the data indicating the transaction status such as the issue date and time, the name, etc., with the encryption key 206 of the transaction source 201. It was done.

Note that one-way-cipher is a cipher that can be encrypted but cannot be decrypted. There are various one-way ciphers, but here, the feedback back one-way cipher is used.

The feedback one-way cipher is generated using a block cipher. Now, if the block length and the key length of the block encryption machine are m bits, and the m-bit ciphertext obtained by encrypting the m-bit plaintext X with the m-bit key K is Y, then Y = E (K , X).

In the generation of the feed back one-way cipher, the transaction text is divided into _n m bit length blocks M ₁ , M ₂ , ..., M _n in advance. In the generation of the final division M _n , when the rest of the transaction original text is less than m bits, the necessary number of bits “0” are packed to generate a block of m bit length, which is M _n .

A block I _{0 having} a predetermined m-bit length is encrypted with a key M ₁ to create a ciphertext, C ₁ = E (M ₁ , I ₀ ). Next, the above ciphertext C ₁ is encrypted with the key M ₂ , and the block encryption is repeatedly performed, and so on.

Then, the finally obtained C _n is the one-way encryption for the transaction original text.

When the transaction source 201 transmits the transaction original text and the digital signature via the transaction source terminal 202 and the communication network 203, the customer terminal 204 first sends the transaction original text in the same procedure as above. Create a one-way cipher.

Next, the customer terminal 204 decrypts the digital signature with the decryption key 208, checks the decryption result, and confirms that the transaction status data and the same data as the one-way encryption created by the customer terminal 204 earlier. If it appears, it is determined that the transaction source text and the digital signature are correctly created by the customer 201.

Then, the supplier terminal 204 enters the transmitted transaction original text 10 in the entry field 103 of the slip 101 set in the printing machine 205.
4, and the digital signature 105 is printed.

The slip 101 printed in this way is
Delivered to 210.

The delivery member 210 delivers the slip 101 to the official seat 211.

The official seat 211 looks at the transaction original text 104 printed on the slip 101 and verifies the transaction content.

Further, the official seat 211 looks at the arabesque pattern printed on the slip 101 and determines whether the slip 101 is a forged one. If it can be determined that the voucher is not a counterfeit one, the transaction original text 104 processed by the customer terminal 204 and the digital signature 105 are as long as the belief that the management in the security equipment 200 is performed correctly. You can believe that it is legitimate.

Modified Example of Embodiment As shown in FIG. 3, a memory section 106 that can be directly accessed by a computer is added to the slip shown in FIG.
When printing to the memory, the same content as
It may also be recorded in 106 to facilitate the data input to the computer, which is required when confirming the legitimacy of the transaction in detail later.

〔The invention's effect〕

 According to the present invention, the following effects can be obtained.

1. Improving security against malicious third parties Even if a malicious third party tries to forge the transaction document, in order for the action to succeed, the printed matter must be obtained illegally and You must get the ciphertext illegally. It is generally difficult to do this double fraud. Therefore, the security against malicious third parties is improved.

2. Prevention of transaction fraud (1) Detection of falsification of transaction text The digital signature entered by the publisher on the printed matter can only be created by the publisher who owns the encryption key. A customer who does not have the encryption key cannot tamper with the digital signature for his own convenience.

However, upon receipt of the digital signature, the business partner can decrypt using the decryption key and obtain the original transaction text. From the fact that the business partner could decrypt with the decryption key,
It can be seen that the creator of the digital signature is the owner of the encryption key that makes up the decryption key pair. Further, the digital signature can be used at any time as proof that the issuer has authorized the transaction.

(2) Prevention of reuse of digital signature A part of the original text of the digital signature includes a symbol string such as a serial number printed in advance so that the slip is difficult to forge. Therefore, if the digital signature is copied to another sheet and reused, the digital signature is decrypted with the public key and it is checked whether or not the symbol string of the sheet is included to reuse the digital signature. The fact of can be detected.

Being able to prevent the reuse of digital signatures has exactly the same effect as copying and not reusing a stamped document. For example, it is possible for a bank to issue a cash voucher by an electric signal from a remote place to a terminal for which a printed slip sheet is set in advance.

3. string that is pre-printed on the check the printed matter by the human eye, which means seen in the human eye lead, in which indicates whether the distributed beforehand which destination. As long as the business partner believes that the terminal keeps the printed matter safely and does not pass it to an unrelated third party as a blank sheet for use, the transaction text is processed by the terminal in a predetermined manner. After that, you can believe that it was completed.

Furthermore, it is difficult for a transaction source to forge an illegal transaction text and make it appear as if it is a legitimate transaction text. If the transaction source counterfeits an illegal transaction text, the transaction partner decrypts the transaction text by a computer, knows that it is not a valid document, and creates an illegal document. You can blame. Therefore, the transaction source must be prepared for considerable danger in order to send an illegal transaction statement. In this sense, the business partner can trust the transaction text to a large extent when he receives the printed matter and sees it with his own eyes.

[Brief description of drawings]

FIG. 1 is an example of a slip showing an embodiment of the present invention, FIG. 2 is a block diagram of a financial system using the slip shown in FIG. 1,
FIG. 3 is a modification of a slip for carrying out the present invention.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Makoto Okumura 6-23-15 Minamioi, Shinagawa-ku, Tokyo Inside Omori Software Factory, Hitachi, Ltd. (56) References International Publication 85/03787 (WO, A)

Claims (3)

[Claims] 1. An electronic transaction system for converting a transaction document into a computer message and transmitting / receiving the computer message, wherein a terminal device which is an issuer of the transaction document and one-way encrypted information generated from document information indicating transaction content and the transaction. The information obtained by encrypting the document information associated with the transaction with the encryption key concealed by the issuer is used as a digital signature, and this is used together with the document information indicating the transaction content and the transaction associated information together with the transaction terminal. The transaction terminal device outputs the received transaction content document information, transaction incidental information and digital signature as a transaction document in a predetermined format. 2. The issuer terminal device generates the digital signature by encrypting the one-way encryption information and the document information accompanying the transaction with a secret key in a public key encryption method, The destination terminal device generates one-way encrypted information from the received transaction content document information, and decrypts the received digital signature with a public key corresponding to the issuer,
The electronic transaction system according to item 1, wherein the validity of the digital signature is confirmed by collating the decrypted information with the generated one-way encrypted information. 3. The transaction terminal device prints out the received transaction content document information, transaction incidental information, and digital signature on a transaction document in a predetermined format, and integrates these information into the transaction document. The first term or the second aspect characterized in that the information is electronically stored in a computerized memory means.
Electronic trading method described in paragraph.