JPH096235A - Encphering device and deciphering device - Google Patents

Abstract

PURPOSE: To make it possible to enhance secrecy of communication contents, to enhance the cipher intensity without sending out the number of involution steps onto a communication channel, by setting variably a number of involution steps in addition to use of a usual cipher key. CONSTITUTION: In the enciphering/deciphering device 6 for facsimile device, when a cipher is transmitted or a cipher is received, involution is applied, which uses a cipher key and is reciprocally reverse to that of an opposite party, to original data or enciphered data by a number of steps corresponding to a counted value of a counter provided for every communicating party. Enciphering and deciphering are thereby accomplished. A counted value of the counter is incremented by '+1' once every enciphering or deciphering. Accordingly, a receiving partly can apply reverse involution to enciphered data by the same number of steps as number of involution steps established by a transmitting party.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an encryption device for obtaining encrypted data by subjecting original data to multiple stages of encrypted involution, and to multiple stages of plain culture involution to encrypted data. By this, it relates to a plain culture device for obtaining plain culture data corresponding to original data.

[0002]

2. Description of the Related Art Conventionally, especially in the field of communication,
From the viewpoint of maintaining confidentiality of communication data, so-called encrypted communication is performed in which encrypted data is created by transmitting an encryption process to a communication data using a predetermined encryption key and then transmitted. One method of encrypted communication is, for example, DES (Da
There is a public algorithm method using a ta Encryption Standard type encryption device.

FIG. 6 is a block diagram showing an electrical configuration of the DES type encryption device. The DES type encryption device includes a pre-processing unit B0, a stirring processing unit B1, a post-processing unit B2, and a key scheduling unit KS. Key scheduling section KS, based on the encryption key K, to create a plurality of unit cryptographic key _{k a, k 0 ~k 7,} k b, the pre-processing unit B0, gives the stirring processing section B1 and the post-processing unit B2.

The data D _in to be encrypted is stored _in the preprocessor B0.
, The exclusive OR between k _a , which is one of the plurality of unit encryption keys, is taken by the gate G _in and then divided into two. One of the two divided data is provided as it is to the agitation processing unit B1 as the data L ₀ .
Further, in the agitation processing unit B1, data R ₀ obtained by taking an exclusive OR between the two divided data is gate G.
given by _p .

In the stirring processing section B1, the key schedulin
Unit encryption key k created by the KS section ₀~ K₇Is each
Given arithmetic unit E₁~ E₈(When collectively referred to below,
Arithmetic section E ") and gate G₁~ G₈(Hereinafter generically
"Gate G") is provided. Disturbance
In the agitation processing unit B1, one computing unit E and one gate G are provided.
Then, the involution of one step is executed. And
This involution can be repeated multiple times.
The encryption process is achieved by and.

The above involution will be described in more detail. In the arithmetic unit E, the data R _{0 to} R ₇ is used as one input, and the unit encryption keys k _{0 to} k ₇ are used as the other inputs, and the arithmetic operation by the predetermined f function is executed. On the other hand, at the gate G,
The data L _{0 to} L ₇ are used as one input, and the calculation result in the calculation unit E is used as the other input, and the data L _{0 to} L ₇ and the calculation result of the calculation unit E are exclusive ORed.

The data R _{1 to} R ₇ are respectively the exclusive OR of the operation result in the gate G for the involution of the preceding stage, that is, the input data L _{0 to} L ₆ and the outputs of the operation units E _{1 to} E _7. Correspond. Also, the data L _{1 to} L ₇
Is input data R _{0 to} R ₆ to the arithmetic units E _{1 to} E ₇ in the previous stage.
And are respectively the same. That is, in the agitation processing unit B1, when the involution of the first stage is completed, the processing result is exchanged, and the arithmetic unit E and the gate G of the next stage are exchanged.
Is given to the calculation unit E and the gate G in the next stage, and the result of the involution process in the previous stage is subjected to involution. As a result, the data L completely different from the original data L ₀ and R ₀ given to the agitation processing unit B1.
₈ and R ₈ are created. These data L ₈ and R ₈ are given to the post-processing unit B2.

In the post-processing unit B2, the gate G _a takes the exclusive OR of the data L ₈ and R ₈ . As a result, the output data of the gate G _a and the data L ₈ are combined into one data. Then, an exclusive OR between the collected data and the unit encryption key k _b is obtained at the gate G _out . As a result, encrypted data D _out that is completely different from the original data D _in is obtained.

On the other hand, the plain culture process for obtaining the plain culture data from the received encrypted data is achieved by performing the data shuffling in a procedure opposite to the data shuffling process executed in the encryption process. In the public algorithm method, the contents of the f-function and the contents of the encryption algorithm including the number of stages of involution are made public. The parties who carry out the cryptographic communication have a secret cryptographic key in advance. Then, by setting the common encryption key K in the communication device on the transmission side and the communication device on the reception side, the encrypted communication is achieved.

[0010]

By the way, the above-mentioned DES
In the type encryption device, the number of stages of the involution is fixed. Moreover, the contents of the f-function and the overall processing flow including involution and data exchange are open to the public. Therefore, in the above-mentioned DES type encryption device, the encryption strength (degree of encryption) may not always be sufficient, and it is considered that further improvement of the encryption strength is desired.

Therefore, a first object of the present invention is to solve the above-mentioned technical problem and to improve the encryption strength by using information other than the encryption key instead of or together with the encryption key. An object of the present invention is to provide an encryption device that can be achieved. A second object of the present invention is to provide a flat culture device capable of obtaining plain culture data corresponding to original data by performing plain culture on encrypted data created using information other than an encryption key. It is to be.

[0012]

According to a first aspect of the present invention, there is provided an encryption device for obtaining encrypted data by subjecting original data to a plurality of stages of encryption involution. Therefore, the input means that can input arbitrary identification information and the number of stages of encrypted involution can be variably set, and the encrypted involution of the set number of stages is applied to the original data, which is obtained The encryption means for outputting the encrypted data and the count value corresponding to each of the plurality of identification information are held, the identification information is input from the input means, and the original data is encrypted by the encryption means. On the condition that the counter value updates the count value corresponding to the input identification information according to a predetermined rule, and the counter means of the counter means. Based on the cement value, characterized in that it comprises a stage number setting means for setting the number of stages of encryption involution performed in the encryption means.

Further, the plain culture device according to the second aspect of the invention has a plain culture inversion opposite to the encryption involution for the encrypted data obtained by subjecting the original data to a plurality of stages of encryption involution. This is a device for performing plain culture on encrypted data to obtain plain culture data equivalent to the original data by applying a volition, and an input means for inputting arbitrary identification information and a plain culture involution. It is possible to variably set the number of rounds, and the plain culture involution of the set number of rounds is applied to the encrypted data, and the plain culture means for outputting the obtained flat culture data and the count corresponding to each of the plurality of identification information While holding the value, the identification information is input from the input means, and the encrypted data is encrypted by the encryption method. Under the condition, and a counter means for updating the count value corresponding to the input identification information according to a predetermined rule, and based on the count value of the counter means, the flat culture involution executed in the flat culture means. And a step number setting means for setting the step number.

[0014]

In the structure according to the above-mentioned claim 1, while the identification information is input from the input means, the encrypted involution of the number of steps set by the step number setting means is applied to the original data, thereby creating the encrypted data. To be done. The number of stages of the encrypted involution is set based on the count value of the counter means corresponding to the input identification information. The count value of the counter means is updated according to a predetermined rule. That is, the number of encryption involution steps is variably set. Therefore, the encryption strength can be improved as compared with the conventional technique in which the number of encryption involution stages is fixed.

Moreover, even when the encryption involution is executed using a fixed encryption key, a sufficient encryption strength can be obtained by using an encryption key having a sufficiently large amount of information. The encrypted data created by the encryption device according to the first aspect can be plainly written by the flat culture device according to the second aspect. That is, the flat culture device according to claim 2 includes a stage number setting means for setting the number of stages of the plain culture involution based on the count value corresponding to the input identification information in the counter means, and the stage number set by the stage number setting means. A plain culture means for obtaining the plain culture data by applying the plain culture involution to the encrypted data is provided.

Since the counter means updates the count value according to a predetermined rule, if the count value is updated according to the same rule as the count value in the encrypting apparatus according to claim 1, it is possible to perform the encryption. An equal number of flat culture involutions will be applied to the encrypted data.
As a result, the encrypted data created by the encryption device according to the first aspect can be plainly written.

[0017]

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a block diagram showing an electrical configuration of a facsimile apparatus according to one embodiment of the present invention.
This facsimile apparatus includes a reading unit 1 that optically reads a document to be transmitted and outputs original image data. The original image data output from the reading unit 1 is subjected to predetermined image processing by the image processing unit 2. The original image data that has been subjected to image processing is given to the encoding / decoding device 4 via the control unit 3, and the MH (Modified Huffman) and MR (Modi
fied READ, READ: Relative Element Address Designat
The compression coding necessary for facsimile communication such as e) is performed and converted into a transmission code. In the case of normal facsimile communication, this transmission code is directly given to the modem 5. On the other hand, in the case of encrypted communication, the transmission code is given to the encryption / plaintext device 6 and converted into encrypted data. Then, this encrypted data is given to the modem 5. In the modem 5, a transmission signal is created by subjecting the transmission code or the encrypted data to a predetermined modulation process. The created transmission signal is sent to the public telephone line 8 via the network control unit (NCU) 7.

On the other hand, when data is received, the received signal is given to the modem 5 via the network controller 7 and demodulated into a received code. If the received code is not encrypted,
That is, in the case of normal facsimile communication, the received code is decoded (decompressed) by the encoding / decoding device 4 and restored to the original image data. On the other hand, when the received code is encrypted, that is, in the case of encrypted communication, the received code is converted into plain culture data by the encryption / plain culture device 6 and then decoded by the encoding / decoding device 4, It is restored to the original image data. The restored original image data is given to the recording unit 9, and the received image is recorded on the paper.

The transmission function unit 10 is for executing line connection control and transmission protocol processing during transmission. The reception function unit 11 is for executing line connection control and reception protocol processing at the time of reception.
The facsimile apparatus also includes an operation unit 12 that functions as an input unit when the apparatus serves as a calling side device for encrypted communication. The operation unit 12 includes a numeric keypad 12a for inputting numerical data such as a facsimile number of a communication partner, a start key 12b for instructing the start of facsimile communication, and an encrypted communication key 12c for instructing encrypted communication. Has been done. The above-described types of keys in the operation unit 12 are examples, and keys for other functions may be added or the arrangement of the keys may be changed as necessary.

When the device is the called device,
The encoding / decoding device 4 and the encryption / plaintext device 5 are grasped as input means. The facsimile machine further includes an image memory 13 composed of a DRAM or the like. A part of the storage area of the image memory 13 can be used as a confidential box used during confidential communication. In the confidential communication, the data transmitted from the sending facsimile machine is temporarily stored in the memory, the data is read from the memory in response to the input of a predetermined personal identification number (ID), etc. Based on this, the received image is printed out.

As shown in FIG. 1, the image memory 13 has a plurality of confidential boxes BOX ₁ , BOX ₂ ,.
BOX _n is made available. Confidential Box BOX
Are given different box numbers. In the cryptographic communication, for example, a fictitious confidential box number different from the number assigned to the confidential box BOX in the image memory 13 may be used. That is, the confidential box number for encrypted communication is predetermined for each communication partner,
The confidential box corresponding to the confidential box number for encrypted communication does not exist in the image memory 13.

By associating the confidential box number for encrypted communication with the confidential box existing in the image memory 13, encrypted communication can be performed using the confidential function. In the control unit 3, counters CNT ₁ , CNT ₂ , ..., CNT _n (hereinafter collectively referred to as “counter CNT”) that perform counting operation according to a predetermined rule are associated with a confidential box number for encrypted communication. Are provided for each. In this embodiment, the confidential box number for encrypted communication corresponds to the identification information. The counter CNT may be a software counter realized by setting a part of the memory area of the memory included in the control unit 3 as a counter and changing the stored value of the counter area by the program processing by the control unit 3. Good. When executing the encryption / plain-text processing, the control unit 3 corresponds to the communication partner based on the count value C of the counter CNT corresponding to the encrypted communication confidential box number corresponding to the communication partner, as described later. Step number selection data P corresponding to the confidential box number for encrypted communication is obtained, and a selection signal SEL corresponding to the obtained step number selection data P is given to the encryption / plaintext device 6.

The facsimile machine also includes a memory 14 composed of an EEPROM or the like. The memory 14 stores an encryption key K required for encryption / plaintext processing in association with a confidential box number for encrypted communication. The encryption key K is a secretly negotiated agreement between parties involved in encrypted communication so as not to be leaked to a third party. The negotiated encryption key K is, for example, the ten key 12
By an input operation from a, it is registered in the memory 14 in association with the determined encrypted communication confidential box number.

The encoding / decoding device 4 has an A terminal connected to the encryption / decryption device 6 and a B connected to the modem 5.
And a terminal. When executing normal facsimile communication, the control unit 3 gives the encoding / decoding device 4 a control signal for instructing to select the B terminal. At this time, the control unit 3 gives an OFF signal to the encryption / plaintext device 6 to prohibit its operation. As a result, the transmission code output from the encoding / decoding device 4 is directly given to the modem 5.
Further, the reception code output from the modem 5 is given to the encoding / decoding device 4 and restored to the original image data.

Further, the control section 3 gives a control signal for instructing the encoding / decoding apparatus 4 to select the A terminal when executing the encrypted communication. At this time, the control unit 3 sets the encryption key K stored in the memory 14 of the encryption / plaintext device 6 and the count value C of the counter CNT corresponding to the confidential box number for encrypted communication corresponding to the communication partner. Selection signal SE corresponding to the stage number selection data P obtained based on
While giving L, it gives an ON signal. As a result, the transmission code output from the encoding / decoding device 4 is given to the encryption / plain culture device 6 and converted into encrypted data. Then, this encrypted data is given to the modem 5. The received code output from the modem 5 is given to the encryption / plain culture device 6 and converted into plain culture data. Then, this plain culture data is encoded / decoded by the encoding / decoding device 4
And is restored to the original image data.

FIG. 2 is a block diagram showing the electrical configuration of the encryption / plaintext device 6. The encryption / plain culture device 6 is provided with an encryption / plain culture block unit 61 for performing encryption / plain culture processing on the original / encrypted data D _in to obtain encryption / plain culture data candidates. ing. The encryption / plain culture block unit 61 is a typical encryption / symmetric encryption system.
DES (Data Encryption Standard), which is a flat culture method
Performs encryption / plain culture based on, line 6
Five types of encrypted / flat culture data candidates are output to 2a to 62e and given to the selector unit 63. The selector unit 63 outputs any one of the encrypted / plain culture data candidates as the encrypted / plain culture data D _out based on the selection signal SEL corresponding to the stage number selection data P given from the control unit 3.

FIG. 3 shows the encryption / plain culture block section 6 described above.
2 is a block diagram showing an electrical configuration of 1. FIG. The encryption / flat culture block unit 61 includes a pre-processing unit B0 and a stirring processing unit B.
1, a post-processing unit B2 and a key scheduling unit KS are provided. Key scheduling section KS, based on the encryption key K, a plurality of unit cryptographic key _{k a, k 0 ~k 7,} k b
Is prepared and given to the pretreatment unit B0, the stirring treatment unit B1, and the posttreatment unit B2.

The original data D _in to be encrypted is stored _in the preprocessing unit B.
At 0, an exclusive OR with one of the plurality of unit encryption keys k _a is taken at the gate G _in and then divided into two. One of the two divided data is provided as it is to the agitation processing unit B1 as the data L ₀ . Further, the agitation processing unit B1 is further supplied with data R ₀ obtained by taking the exclusive OR of the divided data from the gate G _p .

In the agitation processing section B1, the key schedulin
Unit encryption key k created by the KS section ₀~ K₇Is each
Given arithmetic unit E₁~ E₈(When collectively referred to below,
Arithmetic section E ") and gate G₁~ G₈(Hereinafter generically
"Gate G") is provided. Disturbance
In the agitation processing unit B1, one computing unit E and one gate G are provided.
Then, the involution of one step is executed. And
This involution can be repeated multiple times.
The encryption process is achieved by and.

The above involution will be described in more detail. In the arithmetic unit E, the data R _{0 to} R ₇ is used as one input, and the unit encryption keys k _{0 to} k ₇ are used as the other inputs, and the arithmetic operation by the predetermined f function is executed. On the other hand, at the gate G,
With the data L _{0 to} L ₇ as one input and the calculation result in the calculation unit E as the other input, the exclusive OR of the data L _{0 to} L ₇ and the calculation result of the calculation units E _{1 to} E ₇ is obtained. To be

The data R _{1 to} R ₇ are respectively the result of the operation in the gate G for the involution in the previous stage, that is, the exclusive OR of the input data L _{0 to} L ₆ and the outputs of the operation units E _{1 to} E _7. Correspond. Also, the data L _{1 to} L ₇
Is input data R _{0 to} R ₆ to the arithmetic units E _{1 to} E ₇ in the previous stage.
And are respectively the same. That is, in the agitation processing unit B1, when the involution of the first stage is completed, the processing result is exchanged, and the arithmetic unit E and the gate G of the next stage are exchanged.
Is given to the calculation unit E and the gate G in the next stage, and the result of the involution process in the previous stage is subjected to involution. As a result, the original data L ₀ and R ₀ given to the agitation processing unit B1 can be sufficiently agitated.

When the involution in the final-stage arithmetic unit E ₈ and the gate G ₈ is completed, the data L ₈ and R _{8 as} the processing result of the involution are given to the post-processing unit B2. The post-processing unit B2, the exclusive OR of the data L _8, R ₈ is taken in the gate G1 _a.
A gate G1 _a of the output data and the data L ₈ are combined into a single data are combined. Then, the exclusive OR between the collected data and the unit encryption key k _b (64 bits) is obtained at the gate G1 _out . As a result, the encrypted data candidate D1 that is completely different from the original data D _in
out is created.

In the post-processing section B2 of this embodiment, the fourth processing unit
Arithmetic unit E in the third to seventh stages_Four~ E₇And gate G
_Four~ G₇For the result of the involution in
However, the same post-processing as described above is performed. Sand
The process of involution from the 4th stage to the 7th stage
As a result, the gate G2_a~ G5 _a
And gate G2_out~ G5_outExclusive OR in
Is taken and further data combination is executed,
Encrypted data candidate D2_out~ D5_outIs created.

On the other hand, the received encrypted data D_inKarahira
Cultural data candidate D1_out~ D5_outCreate a culture
The above is the unit encryption key k₀~ K₈, K_a, K_bIs calculated
Part E ₁~ E₈, Gate G_in, Gate G1_out~ G5_out
Instead of giving₈~ E₁,Gate
G1_out~ G5_out, Gate G_inReach by giving to
Is made. That is, the data executed in the encryption process
Data agitation is performed in the reverse order of data agitation processing.
And achieves the flat culture processing.

Incidentally, in FIG. 3, the arithmetic unit E is used during the flat culture process.
The unit encryption keys k _{0 to} k ₈ , k _a , and k _b given to the above are written in parentheses. Returning to FIG. 2, the encryption / plain culture data candidate D1 created by the encryption / plain culture block unit 61 is generated.
_{out to} D5 _out are sent to the lines 62a to 62e, respectively. Therefore, the encrypted / plaintext data candidates D1 _{out to} D5 _out having different involution stages are transmitted to the lines 62a to 62e, respectively.

The selector section 63 responds to the selection signal SEL corresponding to the stage number selection data P, from the lines 62a.about.
Any one of 62e is selected. As a result, the encrypted / plaintext data candidate sent to the selected line is extracted as the encrypted / plaintext data D _out . That is, the encrypted / flat culture data D _out in which the involution has been executed by the number of stages corresponding to the stage number selection data P is extracted.

The step number selection data P is sent to the control section 3 by the control section 3.
It is obtained by the calculation shown in equation (1) below. P = P _min + α (1) Here, P _min is the minimum number of involution steps required to create encrypted data that is not likely to be decrypted even if intercepted. In this embodiment, P _min =
5 is set.

The parameter α is the counter CN
It is obtained by performing a predetermined calculation on the count value C of T. In this embodiment, the count value C is directly used as the parameter α as shown in the following equation (2). α = C (2) The counter CNT is such that the count value C is incremented each time encrypted communication is performed with the communication partner corresponding to the counter CNT. This counter CNT
The count width to be incremented in 1 may be set appropriately, but is set to "+1" in this embodiment.

The count value C of the counter CNT is cleared when it reaches a predetermined value C _TH which is equal to the maximum number of involution steps of the encryption / plain culture block section 61. In the present embodiment, the maximum number of involutions of the encryption / plain culture block unit 61 is 8, so C _TH = 3 is set so that 0 ≦ α <4. Generally, the maximum number of involution steps of the encryption / plaintext block unit 61 may be determined based on the processing speed. If the number of stages of involution is too large, it takes a long time to perform the processing for encryption / plain culture, which may lead to a longer communication time.

FIG. 4 is a flow chart showing the transmission operation in the facsimile apparatus. When executing facsimile communication, the operator first sets the original document on the facsimile device. After that, the facsimile number on the receiving side is input from the ten key 12a provided in the operation unit 12, and the start key 12b is operated. When performing encrypted communication, the encrypted communication key 12c is operated prior to the operation of the start key 12b, and the confidential box number for encrypted communication, which is pre-arranged with the receiving side so that the sender can be specified by the receiving facsimile machine. Is input from the ten keys 12a.

Subsequent to the operation of the start key 12b, the transmission function unit 10 performs the line connection processing. When the line with the facsimile machine on the receiving side is connected, it is determined whether or not the encrypted communication is performed based on whether or not the encrypted communication key 12c is operated (step S1). As a result, when it is determined that the communication is not encrypted communication, it is determined that the communication is normal facsimile communication, the transmission control process is executed, and then the transmission signal corresponding to the original image data is transmitted (step S1).
0). On the other hand, if it is determined that the communication is cipher communication, the cipher transmission process is executed after the transmission control process is executed (steps S2 to S10).

The above transmission control processing is performed by NSS (Non-Standar).
This corresponds to pre-processing including transmission of transmission control signals such as d facilities Set-up). A plurality of specific bits are assigned to the NSS in order to write the number data indicating the confidential box number for encrypted communication. Further, the NSS is assigned in advance for a flag indicating whether or not a specific 1 bit is encrypted communication. In the case of normal facsimile communication, the NSS in which the number data is not written and the flag is not set is transmitted. In the case of encrypted communication, the number data is written and the flagged NSS is transmitted.

In the cipher transmission process, the control section 3
First, the confidential box for encrypted communication entered from the numeric keypad 12a
The secret box number for encrypted communication based on the
Read the associated encryption key K from the memory 14
Put out (step S4). The confidential box number for encrypted communication is
Since it is set for each communication destination, the read encryption
The key K corresponds to the facsimile machine on the receiving side.
The read encryption key K is stored in the encryption / plain culture block unit 61.
Given to the encryption / plain culture block section 61
Original data D_inIs encrypted and the encrypted data is
Candidate D1_out~ D5 _outIs created (step S
5).

On the other hand, the control unit 3 reads the count value C from the counter CNT corresponding to the confidential box number for encrypted communication based on the confidential box number for encrypted communication input from the ten-key 12a (step S2), and reads it. Based on the count value C thus obtained, the parameter α is obtained as shown in the above equation (2) (step S3). And
Based on the obtained parameter α, the stage number selection data P is obtained as shown in the equation (1). After that, the selection signal SEL corresponding to the obtained stage number selection data P is selected.
To the selector unit 63.

As a result, in the selector section 63, the encrypted data candidate D sent to the lines 62a to 62e is sent.
One of _out D5 _out, the number selected by involution stages corresponding to the data P is performed encrypted data candidate is extracted as the encrypted data D _{ou t.} Then, the extracted encrypted data D _out is converted into a transmission signal by the modem 5, and the transmission signal is sent to the public telephone line 8 via the network control unit 7 (step S10).

When the encryption processing is executed, the count value C of the counter CNT required for obtaining the stage number selection data P is incremented by a constant "+1" which is the count width (step S6). After that, 0 ≦ α <4
In order to satisfy the condition of, it is judged whether or not the predetermined value C _TH has been reached (step S7). As a result, the count value C
If is less than the predetermined value C _TH , the count value C is held as it is (step S9). On the other hand, if the count value C has reached the predetermined value C _TH , the count value C is cleared (step S8).

FIG. 5 is a flow chart showing the receiving operation in the facsimile apparatus. In the facsimile machine, when the line with the transmitting facsimile machine is connected, first, the NSS received prior to the signal corresponding to the original image data is referred to. Then, based on whether or not the flag indicating whether or not the encrypted communication is in the NSS is set, it is determined whether or not the encrypted communication is performed (step T1). If the result of this determination is that it is normal facsimile communication, normal reception processing is performed and the received image is recorded on paper (step T10).

On the other hand, when it is determined that the encrypted communication is performed, the NSS is further referred to and the confidential box number for encrypted communication is acquired based on the number data included in the NSS.
The encryption key K stored in association with the acquired confidential box number for encrypted communication is read from the memory 14 (step T4). Since the confidential box number for encrypted communication is set for each communication partner, the read encryption key K corresponds to the sending facsimile machine.
The read encryption key K is given to the encryption / plain culture block unit 61, and the encryption / plain culture block unit 61 repeatedly performs involution on the encrypted data D _in to perform the plain culture process, Plain culture data candidate D1
_{out to} D5 _out are created (step T5).

On the other hand, the control unit 3 reads the count value C of the counter CNT corresponding to the confidential box cipher for encrypted communication (step T2), and the read count value C.
Based on the above, the parameter α is obtained according to the above equation (2) (step T3). Then, based on the parameter α, the stage number selection data P is obtained as shown in the equation (1). Thereafter, the selection signal SEL corresponding to the stage number selection data P is given to the selector section 63.

As a result, in the selector section 63, the plain culture in which the number of stages corresponding to the stage number selection data P among the plain culture data candidates D1 _{out to} D5 _out transmitted to the lines 62a to 62e has been executed. The data candidates are extracted as the plain culture data D _out corresponding to the original data. Then, the extracted plain culture data D _out is given to the encoding / decoding device 4 to restore the original image data. The recording unit 9 performs a printout operation based on the restored original image data to reproduce the original image.

Counter CN of the facsimile machine on the receiving side
The count value C of T is
The constant "+1" which is the count width is incremented (step T6). That is, the counter CNT of the facsimile machine on the receiving side operates exactly like the counter CNT of the facsimile machine on the transmitting side. Therefore, the counters CNT of the sending side and receiving side facsimile machines
The count values C are equal. Therefore, the receiving side facsimile apparatus performs the same number of involutions as the transmitting side facsimile apparatus and the opposite number of revolutions as the transmitting side facsimile apparatus. As a result, the original image data can be faithfully restored. Therefore, the original document can be accurately reproduced.

After updating the count value C, the control unit 3 sets 0 ≦
In order to satisfy the condition of α <4, it is determined whether or not the count value C has reached a predetermined value C _TH (= 3) (step T
7). As a result, if it is less than the predetermined value C _TH , the count value C is held as it is (step S9), and if it has reached the predetermined value C _TH , the count value C is cleared (step S8).

As described above, according to the facsimile apparatus of this embodiment, not only the normal encryption key K but also the number of involution steps, which is a processing unit of encryption processing, is variably set, so that the encryption strength is improved. Can be planned. Further, the number of involution steps is the counter CNT provided in each of the facsimile machines on the transmitting side and the receiving side.
Is determined by the count value C. In other words, the number of stages of involution is not transmitted to the public communication line 8. Therefore, the number of steps of involution is not known to a third party.

Therefore, the confidentiality of the communication contents can be improved. The description of the embodiment of the present invention is as described above, but the present invention is not limited to the above-described embodiment. For example, in the above-described embodiment, in the transmission / reception operation shown in FIGS. 4 and 5, the count value C is incremented after the encryption / plain culture processing is executed, but it is determined that the communication is encrypted communication, for example. It may be performed immediately after being performed. That is, you may insert the process which performs the increment of the count value C between step S1 and step S2 of FIG. 4, and between step T1 and step T2 of FIG. Further, in the above embodiment, the count width to be incremented in the counter CNT is set to the constant "+1", but other constants such as the constants "+2", "+3", "-1", "-2" are set. ,-
3 "may be set as the count width.

Further, for example, the number of predetermined digits of the facsimile number of the communication partner may be used as the count width.
Further, the count width may be a month or a day when executing encrypted communication. For example, when the encrypted communication is in February, the count width may be "+2". In addition, when the encrypted communication is set on the 24th, the count width is "+24".
It may be.

Furthermore, a new count value may be obtained by multiplying or dividing the count value C by a predetermined constant, or the month or day when executing encrypted communication.
However, in this case, the initial value C ₀ of the count value C is C ₀ ≠
It is necessary to satisfy the condition of 0. Also, the parameter α
Can be obtained by a predetermined arithmetic expression based on the count value C, but a table showing the correspondence between the count value C and the parameter α is stored in the memory 13 and the parameter α is obtained by referring to the table. You may do it.

In the above embodiment, the encryption key K is changed according to the communication partner, but it may be fixed regardless of the communication partner. With this configuration, the capacity required for encrypted communication in the capacity of the memory 13 can be reduced. Specifically, the encryption key K is usually represented by 64 bits or 128 bits, whereas the count value C of the counter CNT for setting the number of stages of involution is, for example, 2 bits (0, 1). , 2, 3 can be expressed), the larger the number of communication destinations, the smaller the capacity required for encrypted communication.

If the encryption key K is fixed in this way,
Without conspiring with the correspondent about cryptographic information,
Cryptographic communication can be realized. Moreover, the encryption strength is sufficiently high because the encryption is performed using the encryption key K having a sufficiently large amount of information, although the value is constant. Further, in the above embodiment, the encryption processing and the plain culture processing are executed in the dedicated encryption / plain culture apparatus 6, but the encryption / plain culture processing is realized by the software processing in the control unit 3, for example. May be.

Specifically, when executing the encryption process, the control unit 3 reads the count value C from the counter CNT corresponding to the facsimile number of the communication destination, and the parameter α based on the read count value C. Ask for. Next, the stage number selection data P is obtained based on this parameter α. Further, the encryption key K corresponding to the facsimile number of the communication partner is read from the memory 13. Then, the encrypted data is created by performing the involution on the original data by the number of stages corresponding to the obtained stage number selection data P. The same applies when executing the flat culture process.

Further, in the above embodiment, as a configuration for reading the encryption key K and the step number selection data P corresponding to the transmitting side facsimile apparatus, the encryption key K is provided for each communication partner and the confidential box for encrypted communication is provided. The confidential box number for encrypted communication is stored in the memory 14 in association with the number, and the confidential box number for encrypted communication is acquired based on the number data included in the NSS transmitted from the transmitting side facsimile device. Although the corresponding encryption key K is read out, for example, the encryption key K is stored in association with the facsimile number of the communication partner, and the TSI (Trans
The encryption key K corresponding to this facsimile number may be read based on the facsimile number included in the mitting subscriber identification).

Furthermore, although the above embodiment has been described by taking a facsimile device as an example, the present invention can be widely applied to devices capable of handling data, such as a personal computer and a word processor. For example, in a personal computer, when data is stored in a hard disk which is an external storage medium, the present invention may be applied when data is encrypted and stored in order to prevent data leakage to a third party. .

More specifically, for example, it is conceivable to input a user ID as identification information and then encrypt the data and store it in a storage medium. That is,
A data writing counter is prepared for each user ID, and the count value of the data writing counter corresponding to the input user ID is incremented. Then, the number of stages of the encrypted involution is set based on the count value of this counter, and the encrypted involution of the set number of stages is applied to the data to be saved to create the encrypted data. Good.

On the other hand, when reading out the stored encrypted data, the user ID is input. Then, a data reading counter is prepared for each user ID, and the count value of the data reading counter corresponding to the input user ID is incremented. By doing so, the count value of the data read counter becomes equal to the count value of the data write counter when the encrypted data was created. Therefore, the number of steps of the plain culture involution may be set based on the count value of the data reading counter, and the set number of steps of the plain culture involution may be applied to the stored encrypted data. . As a result, the data before saving can be restored.

When data encryption / plain culture is performed using this user ID, the update rule of the count value in the data writing counter and the data reading counter is changed for each user ID. Good. Further, in the above embodiment, the original image data is described as an example of the data to be transmitted, but the present invention can be applied when transmitting data other than the original image data.

Other various design changes can be made within the scope described in the claims.

[0066]

As described above, according to the encryption device of the first aspect, since the number of stages of the encryption involution executed for the encrypted data is variably set, the number of stages of the encryption involution is It is possible to improve the encryption strength as compared with the fixed conventional technique.

Moreover, since the number of stages of the encrypted involution is set based on the count value of the counter means updated according to a predetermined rule, it changes every time the corresponding identification information is input. Therefore, the number of encryption involution steps is not known to a third party.
Therefore, for example, when the encryption device of the present invention is used for encrypted communication, the confidentiality of communication contents can be improved.

Further, in the case of executing the encryption involution using the fixed encryption key, the purpose of using other information in place of the encryption key can be achieved. In this case, if an encryption key having a sufficiently large amount of information is used, sufficient encryption strength can be obtained. According to the flat culture device of claim 2,
The encryption created by the encryption device according to claim 1 by inputting identification information corresponding to the identification information input when creating encrypted data by the encryption device according to claim 1. Data can be written in plain text.

[Brief description of drawings]

FIG. 1 is a block diagram showing an electrical configuration of a facsimile apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram showing an electrical configuration of an encryption / plain culture device forming a part of the facsimile device.

FIG. 3 is a block diagram showing an electrical configuration of an encryption / plain culture block unit forming a part of the encryption / plain culture device.

FIG. 4 is a flowchart showing a transmission operation in the facsimile device.

FIG. 5 is a flowchart showing a receiving operation in the facsimile device.

FIG. 6 is a block diagram showing an electrical configuration of a conventional DES type encryption device.

[Explanation of symbols]

 3 control unit 6 encryption / plain culture device 61 encryption / plain culture block unit 62 line 63 selector unit CNT counter P stage number selection data SEL selection signal

Claims (2)

[Claims] Claim: What is claimed is: 1. An apparatus for obtaining encrypted data by subjecting original data to a plurality of stages of encrypted involution, the input means being capable of inputting arbitrary identification information, and the encrypted involution. It is possible to variably set the number of steps of the, the encryption involution of the set number of steps is applied to the original data, the encryption means that outputs the encrypted data obtained by it, and the count value corresponding to each of the multiple identification information. The count value corresponding to the input identification information in accordance with a predetermined rule, provided that the identification information is input from the input means and the original data is encrypted by the encryption means. And a encryption means executed by the encryption means based on the count value of the counter means. An encryption device, comprising: a step number setting means for setting the step number of the solution. 2. The encrypted data is obtained by subjecting the encrypted data obtained by subjecting the original data to a plurality of stages of encrypted involution, to a plain culture involution opposite to the encrypted involution. It is an apparatus for performing plain culture and obtaining plain culture data equivalent to the original data, and an input means capable of inputting arbitrary identification information, and the number of stages of the plain culture involution can be variably set, The plain culture means that applies the set number of plain culture involutions to the encrypted data and outputs the plain culture data obtained by that, and the count value corresponding to each of multiple identification information are held, and the above input In accordance with the prescribed rules, provided that the identification information is input from the means and the encrypted data is encrypted by the above described encryption method. Counter means for updating the count value corresponding to the inputted identification information, and a step number setting means for setting the step number of the flat culture involution executed in the flat culture means based on the count value of the counter means. A flat culture device characterized by including and.