JP2009177304A - Data file ciphering system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a data file ciphering system capable of easily and efficiently transferring a data file sufficiently securing security by software processing. <P>SOLUTION: A ciphered data file is prepared by ciphering a data file by a common key system using a part of a randomly generated master random number as temporary key information. Also, after executing prescribed work to the master random number using a master random number control value extracted from a public passport file, the worked master random number is ciphered by the public key system using a public key extracted from the public passport file to prepare a ciphered master random number, and the ciphered data file and the ciphered master random number are transmitted to the reception side together with cipher management information. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a data file encryption system capable of transferring a data file with sufficient security secured simply and efficiently by software processing.

  When a data file including confidential information is attached to an e-mail and sent, the corresponding data file is often encrypted using file encryption software. Incidentally, data file encryption is generally performed using a predetermined password between the file transmission source (transmission side) and the transmission destination (reception side), and decryption of the encrypted data file is also performed. The above password is used (see, for example, Patent Documents 1 and 2). This type of encryption is called a common key scheme. However, in order to make it easy to remember a password that should be kept secret, a simple phrase such as a telephone number is often adopted as a password. Moreover, since there are many notes to prevent forgetting passwords, there are concerns about security issues.

In this regard, software for encrypting the e-mail itself has been developed, but there are not many cases where it is used due to differences in software infrastructure among companies.
JP 2006-237908 A JP 2004-297755 A

  By the way, it is considered to use a phrase that cannot be guessed as a password used for encryption, and to change this type of password frequently. However, in this case, the management of the password becomes complicated and it is very difficult to perform this artificially. Therefore, it has been proposed to use a one-time password that changes every time, a so-called one-time password. However, in order to use a one-time password, dedicated hardware and a dedicated network system are often required, and the fact is that they cannot be used easily.

  The present invention has been made in consideration of such circumstances, and its object is to provide a data file encryption that enables transfer of a highly secure data file using a one-time password without using dedicated hardware. Is to provide a system.

  In order to achieve the above-described object, the data file encryption system according to the present invention conceptually includes a public key / private key used in a public key scheme, a randomly generated random number as a part of a master random number, and a temporary key. It is used as information (one-time password), and the data file is encrypted using the temporary key information using the common key method, and the master random number is encrypted using the public key. It is characterized by.

That is, the data file encryption system according to the present invention is:
<a> The data file receiving side includes a public passport file including a public key used in advance in a public key method and a randomly generated master random number control value, and a secret key and the master random number control paired with the public key. A secret passport file including a value and notifying the public passport file to the data file sender,
<b> The transmission side uses a part of the randomly generated master random number as temporary key information to encrypt the data file by a common key method, and uses the master random number control value extracted from the public passport file. The master random number is subjected to predetermined processing, and then the processed master random number is encrypted by a public key method using a public key extracted from the public passport file, and the encrypted data file and the encrypted master random number are Sent to the receiving side together with encryption management information,
<c> The receiving side uses the public key method to decrypt the encrypted master random number using the received encryption management information and the secret key extracted from the secret passport file, and then extracts the encrypted master random number from the secret passport file. The temporary key information is extracted from the decrypted master random number using a master random number control value, and the encrypted data file is decrypted by a common key method using the extracted temporary key information.

Preferably, the secret passport file and the public passport file are respectively encrypted by a common key method using pre-shared key information shared in advance between the receiving side and the transmitting side,
<b1> The transmission unit decrypts the public passport file using the pre-shared key information to extract the public key and the master random number control value, and uses the pre-shared key information to extract the encryption management information. Encrypt and notify the recipient,
<c1> The receiving unit decrypts the encryption management information from the received data using the pre-shared key information, and uses the pre-shared key information to obtain the secret key and the master random number control value from the secret passport file, respectively. It is configured to be extracted and used for decoding the received data.

  The master random number control value is given as a master random number management unit offset value for offsetting the master random number, or a master random number mask value for masking the master random number by exclusive OR. The pre-shared key information and the temporary key information include, for example, an encryption initial vector, an encryption key, a message authentication code initial vector, and a message authentication code key necessary for encryption by a common key method. In addition, the temporary key information includes, for example, byte data at a predetermined position in the master random number as the random number management unit including an encryption initial vector offset, an encryption key offset, a message authentication code initial vector offset, and a message authentication code key offset. It is obtained by giving an offset.

Further, it is desirable that the encryption management information is encrypted by the common key method using pre-shared key information, including the version of the encryption method, the number of master random numbers, and the size of the data file before encryption. .
Also, the above-described encryption master random number is created using the master random number control value and public key extracted from the public passport file respectively notified from a plurality of receiving sides, and all of the plurality of encryption master random numbers created. May be transferred to the plurality of receivers together with the encrypted data file.

  According to the data file encryption system having the above configuration, the public key obtained from the public passport file notified from the transmission destination (reception side) and a part of the randomly generated master random number are used as temporary key information (one-time password). And using this temporary key information to encrypt the data file by a common key method, and processing the master random number using the master random number control value extracted from the public passport file, and then processing the processed master Since the random number is encrypted using the public key, even if the encryption using the public key takes a long time, the encryption range is limited to the master random number. It is possible to ensure sufficient performance.

  In particular, since the data file is simply encrypted using the common key method using the temporary key information (one-time password), it can be processed at high speed even when the size of the data file is large. Therefore, it is possible to perform processing in a short time in combination with only a small master random number as the range of encryption by the public key method. That is, in the data file encryption system according to the present invention, a data file is encrypted as temporary key information (one-time password) using a part of the master random number in a common key method, and the master random number is obtained from a public passport file. After performing predetermined processing according to the random number control value, encryption is performed using the public key. Therefore, it is possible to efficiently execute the transfer of the data file that simply and effectively secures the confidentiality.

  Also, each of the plurality of encryption master random numbers created by using the master random number control value and the public key extracted from the public passport file respectively notified from the plurality of receiving sides, respectively. By transferring the encrypted data file together with the plurality of receiving sides at once, so-called broadcast of the same data file to a plurality of transmission destinations becomes possible.

Hereinafter, an embodiment of a data file encryption system according to the present invention will be described with reference to the drawings.
FIG. 1 shows the concept of a data file encryption system according to the present invention. In this system, a public passport file (public passport) Ppk and a secret passport file (secret passport) Psk paired with the public passport file Ppk are respectively created in advance on the receiving side R that receives the data file, and preliminarily assumed data This is realized by notifying (disclosing) the public passport file Ppk to the file transmission side T. The transmission side T basically encrypts the data file using the public passport file Ppk notified from the reception side R in advance and transmits it to the reception side R, while receiving the encrypted data file. The receiving side R decrypts the encrypted data file using the secret passport file Psk.

  Incidentally, the public passport file Ppk and the secret passport file Psk are, for example, a master random number as a public key PK used in the public key scheme and a secret key SK paired with the public key PK, and a randomly generated master random number control value. It includes a management unit offset OF and a master random number mask value to be described later. Specifically, as shown in FIG. 2, the public passport file Ppk is a file including a public key PK and a master random number management unit offset OF, and the secret passport file Psk is a secret key SK and the master random number management. Each file is generated as a file including the part offset OF.

  Note that key information used for encryption of the public key PK, the secret key SK, and the like includes, for example, an encryption initial vector, an encryption key, a MAC (message authentication code) initial vector, and a MAC key. The master random number management unit offset OF is composed of, for example, a randomly generated random number value, and is used as a master random number offset to be described later. These public passport file Ppk and secret passport file Psk are respectively encrypted by a common key method using key information (pre-shared key information) CK shared in advance between the receiving unit R and the transmitting unit T. Of these, only the encrypted public passport file Ppk is notified (transmitted) from the receiving side R to the transmitting side T in advance. Incidentally, since there is no confidentiality about the contents of the public passport file Ppk, there is no need to give special consideration to its handling.

  The transmitting side T encrypts the data file to be transmitted to the receiving side R as follows. That is, the transmitting side T first uses a part of a randomly generated master random number (random number value) MR as an offset value for obtaining temporary key information TK used for encryption by the common key method. Incidentally, the offset value obtained as a part of the master random number (random number value) MR is an encryption initial for giving an offset to the above-mentioned encryption initial vector, encryption key, MAC initial vector and MAC key constituting the temporary key information TK. It consists of a vector offset, encryption key offset, MAC initial vector offset, and MAC key offset.

  Specifically, the offset value is, for example, as shown in FIG. 3, the first 4 bytes of a 256-byte master random number (random number value), one byte at a time for the encryption initial vector offset, the encryption key offset, the MAC initial vector offset, and the MAC key. Each is extracted as an offset and defined as a random number manager. Using the random number management unit (offset value) defined in this manner, a numerical value of the necessary number of bytes is extracted from the master random number (random number value) MR described above and used as temporary key information TK.

  For example, when the encryption initial vector offset is given as [251], the 256-byte master random number MR described above is extracted cyclically over 16 bytes from the 251st byte as shown in FIG. Byte data is obtained as the encryption initial vector. Other encryption keys, MAC initial vectors, and MAC keys are also part of the master random number MR from each byte position of the master random number MR specified by the encryption key offset, MAC initial vector offset, and MAC key offset, respectively. Are obtained in a similar manner by cyclically extracting each over the required number of bytes. The encryption initial vector, encryption key, MAC initial vector, and MAC key thus obtained are used as temporary key information (one-time password) TK used for encryption by the common key method.

  Thereafter, the data file to be transmitted to the receiving unit R is encrypted by the common key method using the temporary key information (one-time password) TK obtained as described above, and the encrypted file is sent to the receiving unit R. To do. As described above, since the data file is encrypted by the common key method, even if the size of the data file is large, the encryption process can be performed at high speed.

  At this time, as shown in FIG. 5, for example, 16-byte encryption management information indicating the version of the encryption method, the number of master random numbers MR, and the size of the data file is created, and this encryption information is stored in the encrypted file. Attach. Also, for the master random number MR used for the above-described encryption, for example, the master random number MR is encrypted and notified to the receiving unit R. For the encryption of the master random number MR, for example, the public passport file Ppk is decrypted by using the pre-shared key information CK described above to obtain the master random number management unit offset OF and the public key PK. Then, the master random number (random number value) MR is first rotated (offset) in the positive direction as shown in FIG. 6 using the master random number management unit offset OF obtained by decrypting the public passport file Ppk. Thereafter, the master random number (random number value) MR rotated as described above using the decrypted public key PK is encrypted by the public key method. Then, the encrypted master random number (random number value) MR ′ may be transmitted to the receiving side R together with the above-described encrypted file and encryption management information.

  The receiving side R that receives the encrypted file as described above basically performs the decryption by executing the reverse process of the encryption procedure. That is, the encryption management information is extracted from the received file, and the extracted encryption management information is decrypted using the pre-shared key information CK. By decrypting the encryption management information, the version of the encryption method, the number of master random numbers MR, and the size of the data file are obtained. Next, after extracting an encrypted master random number MR ′ from the received file according to the number of master random numbers MR, the encrypted master random number MR ′ is decrypted using the secret key SK obtained from the secret passport file Psk. To do. Then, the master random number MR used for the encryption process is obtained by reversely rotating the decrypted master random number MR using the master random number management unit offset OF described above. Note that the master random number management unit offset OF is obtained by decrypting the secret passport file Ppk using the pre-shared key information CK.

  Then, from the restored master random number MR, the first 4 bytes of data are first extracted as the encryption initial vector offset, the encryption key offset, the MAC initial vector offset, and the MAC key offset as described above. Next, the temporary key information TK used for encryption is obtained by extracting the numerical value of the necessary number of bytes from the master random number (random number value) MR using the random number management unit (offset value) obtained from the master random number MR. Thereafter, the data file encrypted by the common key method is decrypted using the temporary key information TK obtained as described above.

  As described above, in the data file encryption system according to the present invention, the data file is basically encrypted by the common key method, and the master random number MR used for the encryption is encrypted by the public key method. Management information is encrypted by a common key method. Of these, encryption by the public key method generally requires a very long processing time, but in this system, only the master random number MR having a small data size is the target of encryption by the public key method. Processing in a short time is possible. In addition, a data file with a large data size is encrypted using a common key method, so that high-speed processing is possible. Moreover, since the temporary key information (one-time password) TK described above is used for the encryption, the secrecy is sufficient. It is possible to ensure.

  The encryption management information is encrypted using pre-shared key information CK that is fixedly given. However, since the encryption management information does not include secret information, there is no problem in terms of security. Therefore, by using the one-time password (temporary key information) TK created based on the master random number MR as described above, it is possible to transfer a highly secure data file with sufficiently secured secrecy. In addition, the encryption process can be executed without using dedicated hardware. In other words, it is possible to easily execute transfer of a highly secure data file while utilizing the features of the common key method and the public key method by software processing.

  7 and 8 schematically show the encryption processing procedure and its processing concept according to a specific embodiment of the present invention, and FIGS. 9 and 10 show the decryption according to the specific embodiment of the present invention. The processing procedure and its processing concept are shown schematically. The overall flow of the encryption process on the transmission side T and the decryption process on the reception side R described above with reference to FIGS. Here, a case where a plurality of data files are collectively transmitted to a plurality of transmission destinations (reception side R) will be described as an example.

  The encryption process is started by first archive-compressing a plurality of data files to be transmitted and creating an archive file [step S1]. On the other hand, the public passport file Ppk of the file transmission destination (reception side R) is selected [step S2]. When there are a plurality of file transmission destinations, a plurality of public passport files Ppk respectively obtained from the transmission destinations are obtained. In the example shown in FIG. 8, there are three destinations (X, Y, Z), and the public passport file Ppk is obtained from each of these destinations. Then, each of the public passport files is decrypted using pre-shared key information CK that is fixedly determined in advance with the transmission destination, and public keys that are disclosed by the three transmission destinations (X, Y, Z), respectively. Each of SK and master random number management unit offset OF is obtained [step S3].

  When the above preprocessing is completed, a master random number MR having a predetermined number of bytes is obtained from a random number seed that is randomly generated using a random number generator [step S4]. Then, a part of the extracted master random number MR is extracted as the temporary key information TK, for example, as described above, for example, as described above [step S5]. Then, the temporary key information TK is used to calculate a MAC (message authentication code) for the archive file, and the calculated MAC is added to the archive file [step S6]. Next, the archive file to which the MAC is added is encrypted by the common key method using the temporary key information (one-time password) TK obtained as described above [step S7].

  Thereafter, or in parallel with the encryption of the archive file described above, the master random number MR is positively rotated in accordance with the master random number manager offset OF described above [step S8], and the master random number manager offset OF is obtained as a pair. The rotated master random number MR ′ is encrypted by the public key method using the public key PK [Step S9]. The encryption of the master random number MR is repeatedly executed for each of the plurality of transmission destinations described above by checking whether or not the next passport exists [step S10].

  The encryption management information indicating the version of the encryption method, the number of master random numbers, and the size of the data file indicating the contents of the encryption processing described above is then encrypted by the common key method using the pre-shared key information CK described above. [Step S11]. Then, the encrypted encryption management information, the encrypted master random number MR, and the encrypted archive file (data file) are concatenated to form one encrypted data file [step S12]. To each of the plurality of transmission destinations (reception side R).

  On the other hand, in the transmission destination (receiving side R) that has received the encrypted data file described above, first, the encrypted encryption management information is extracted from the encrypted data file, and the extracted encryption management information is used as the pre-shared key information CK. [Step S21]. Also, a secret key SK which is paired with the public passport file Ppk disclosed to the transmitting side T, and which decrypts the secret passport file (secret passport) Psk owned only by the receiving side R and is paired with the public key PK, The master random number management unit offset OF described above is obtained [step S22].

  Next, the encrypted master random number MR ′ is extracted from the encrypted data file, and the master random number MR is decrypted using the secret key SK [step S23]. Then, it is determined whether or not the master random number MR has been successfully decrypted. If the master random number MR cannot be decrypted, the next master random number MR ′ is similarly decrypted using the secret key SK [steps S24 and S25]. . In other words, since the encrypted data file may be transmitted to a plurality of destinations at the same time, it is possible to determine whether the encrypted data file is self-determined by determining whether or not the decryption process has been performed normally. The master random number MR is obtained while confirming whether or not the data is transmitted to.

  When the master random number MR ′ is normally decrypted, the master random number MR ′ decrypted using the master random number management unit offset OF described above is reverse-rotated, and thereby the master random number MR used for encryption is obtained. Restore [Step S26]. Thereafter, the temporary key information TK extracted as described above is obtained from the restored master random number MR [Step S27], and the data file encrypted using the temporary key information TK is decrypted by the common key method to be an archive file. [Step S28].

  Thereafter, the MAC of the decrypted archive file is calculated [step S29], and it is determined whether or not the calculated MAC matches the MAC attached to the archive file [step S30]. When the MACs match, this is recognized as a legitimate received file, the archive file is decompressed, and a plurality of data files compressed as archive files are obtained [step S31]. If the above-described decoding of the master random number MR fails over all the master random numbers included in the received data file, and the MAC of the decoded archive file does not match, the file is not sent to itself. The decoding process ends.

  As described above, the transmission side T encrypts and transmits the data file, and the reception side R decrypts the encrypted file, thereby transferring a plurality of data files while ensuring sufficient security. It becomes possible. In addition, data files can be transmitted to a plurality of destinations at once, and security can be ensured for each individual destination.

  The present invention is not limited to the embodiment described above. In the embodiment, the public / private passport file Ppk / Psk including the public key PK / secret key SK and the master random number management unit offset OF is generated, but the master random number mask value MM is used instead of the master random number management unit offset OF. The public / private passport file Ppk / Psk may be generated. In this case, the master random number MR is subjected to exclusive OR processing (XOR) using the master random number mask value MM, and the same effect as the rotation described above can be obtained.

  The size of the data file, the number of files to be integrated as an archive file, and the number of destinations to which the files are sent in a batch can be determined according to the transfer purpose of the data file, and are limited in particular. Never happen. Furthermore, with regard to the encryption initial vector offset, the encryption key offset, etc., it is generally sufficient to allow 1 byte for each, but it is of course possible to assign a larger number of bytes. For the encryption initial vector and the encryption key itself, for example, data of about 16 bytes is sufficient, and this is not particularly limited. In addition, the present invention can be variously modified and implemented without departing from the scope of the invention.

The figure which shows the concept of the data file encryption system which concerns on one Embodiment of this invention. The figure which shows the relationship between a secret passport file and a public passport file. The figure which shows the example of the random number management part extracted from a master random number. The figure which shows the example of the encryption initial vector calculated | required from a master random number. The figure which shows the structural example of encryption management information. The figure which shows the processing example of the master random number by rotation. The figure which shows the example of the encryption processing procedure which concerns on specific embodiment of this invention. The figure which shows typically the concept of the encryption process shown in FIG. The figure which shows the example of the decoding process procedure which concerns on specific embodiment of this invention. The figure which shows typically the concept of the decoding process shown in FIG.

Explanation of symbols

Psk private passport file Ppk public passport file SK private key PK public key TK temporary key information (one-time password)
CK Pre-shared key information MR Master random number OF Master random number manager offset (Master random number control value)

Claims (6)

The data file receiving side includes a public passport file including a public key used in advance in a public key method and a randomly generated master random number control value, and a secret key paired with the public key and the master random number control value. Generating a secret passport file each including the public passport file and notifying the data file sender;
The transmission side uses a part of the randomly generated master random number as temporary key information to create an encrypted data file by encrypting the data file with a common key method, and extracts the master random number extracted from the public passport file After performing a predetermined process on the master random number using a control value, the processed master random number is encrypted by a public key method using a public key extracted from the public passport file to create an encrypted master random number, Means for transmitting the encrypted data file and the encrypted master random number together with encryption management information to the receiving side;
The receiving side uses the public key method to decrypt the encrypted master random number using the received encryption management information and the secret key extracted from the secret passport file, and then extracts the master random number control extracted from the secret passport file. A data file cipher comprising: means for extracting the temporary key information from the decrypted master random number using a value, and decrypting the encrypted data file by a common key method using the extracted temporary key information System. The secret passport file and the public passport file are respectively encrypted by a common key method using pre-shared key information shared in advance between the receiving side and the transmitting side,
The transmitting side decrypts the public passport file using the pre-shared key information to extract the public key and the master random number control value, and encrypts the encryption management information using the pre-shared key information. Notify the recipient,
The receiving side decrypts the encryption management information from the received data using the pre-shared key information, and extracts the secret key and the master random number control value from the secret passport file using the pre-shared key information, respectively. The data file encryption system according to claim 1, wherein the data file encryption system is used for a decryption process of the received data.   The data file according to claim 1, wherein the master random number control value is given as a master random number management unit offset value for offsetting the master random number, or a master random number mask value for masking the master random number by exclusive OR. Encryption system. The pre-shared key information and the temporary key information each include an encryption initial vector, an encryption key, a message authentication code initial vector, and a message authentication code key necessary for encryption by a common key method,
The temporary key information is obtained by adding an offset to the master random number as a random number management unit including byte data at a predetermined position in the master random number, which is an encryption initial vector offset, encryption key offset, message authentication code initial vector offset, and message authentication code key offset. The data file encryption system according to claim 1, wherein the data file encryption system is obtained.   2. The encryption management information includes an encryption method version, the number of master random numbers, and a size of a data file before encryption, and is encrypted by a common key method using pre-shared key information. Data file encryption system.   The creation of the encrypted master random number is performed using the master random number control value and the public key extracted from the public passport file respectively notified from the plurality of receiving sides, and all of the plurality of created encrypted master random numbers are performed. The data file encryption system according to claim 1, wherein the data file encryption system transfers the encrypted data file to the plurality of receiving sides.

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