JP2010028733A - Image data encryption apparatus, encrypted image data decryption apparatus, image data encryption method, encrypted image data decryption method, and encrypted image data transmission method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce a processing load and to maintain high confidentiality and tampering resistance. <P>SOLUTION: An image data encryption apparatus 10 for encrypting image data 50 having a management information part 51a including time stamp information and a data body part 52, includes: a first key generation unit 130 for generating a first key by applying a first arithmetic operation to the management information part 51a; an encryption key generation unit 150 for generating an encryption key by applying a second arithmetic operation to the first key and a predetermined second key; an encryption unit 160 which uses the encryption key to encrypt the data body part in accordance with a common key system; and an encrypted image data output unit 170 for outputting, as encrypted image data 70, the management information part 51a and the encrypted data body part 72. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image data encryption device, an encrypted image data decryption device, an image data encryption method, an encrypted image data decryption method, and an encrypted image data transmission method.

  In recent years, communication networks represented by the Internet have become widespread, and transmission speeds have also been improved. For this reason, data having a large capacity such as still image data and moving image data is often transmitted via a communication network.

On the other hand, since many communication networks such as the Internet can be used by an unspecified number of users, it is important to ensure security when transmitting highly confidential image data. For example, Patent Literature 1 describes that image data is encrypted by a transmission device and decrypted by a reception device to prevent image data from being leaked to the outside or falsified.
JP 2006-352265 A

  In Patent Document 1, in order to facilitate management of a key used for encryption, an ID is assigned to the key used for encryption in advance, and the encrypted transmission apparatus encrypts the user data area of the image data. It is described that the receiving device that received the image data inserts the key ID of the key used for the encryption and specifies the key used for the encryption based on the key ID inserted in the user data area. Has been.

  However, since the technique described in Patent Document 1 can specify the key used for encryption from the plaintext key ID inserted in the user data area, there is a problem that confidentiality and tamper resistance are impaired. There is. In addition, when continuously transmitting / receiving encrypted image data by a monitoring system or the like, it is desirable that the amount of computation in encryption processing and decryption processing be as small as possible in order to reduce the load on the apparatus.

  The present invention has been made in view of such circumstances, and has a light processing load, high confidentiality and tamper resistance, an image data encryption device, an encrypted image data decryption device, an image data encryption method, an encryption An object of the present invention is to provide a method for decrypting encrypted image data and a method for transmitting encrypted image data.

  In order to solve the above-described problem, an image data encryption device according to a first aspect of the present invention is an image data for encrypting image data having a management information section including predetermined information different for each frame and a data body section. A first key generating means for generating a first key by performing a first calculation on the management information section; and a first key and a predetermined second key. An encryption key generating means for generating an encryption key by performing the operation of 2; an encryption means for encrypting the data main body using a common key encryption method using the encryption key; and the management information section; Encrypted image data output means for outputting the encrypted data body as encrypted image data.

  According to the present invention, the first key generation, the encryption key generation, and the encryption can be performed without going through complicated procedures, so that the processing load of the image data encryption apparatus can be reduced. Further, since the encryption key is generated using the management information part other than the data main body part, tamper resistance can be improved. Furthermore, since the management information part includes different information for each frame, the encryption key differs for each process. For this reason, confidentiality can be improved.

  In order to solve the above problems, an image data encryption device according to a second aspect of the present invention is an image data encryption device that encrypts image data having a management information section and a data body section, and the management Management information preprocessing means for inserting predetermined different information for each frame into a predetermined area of the information section; first key generation means for generating a first key by performing a first calculation on the management information section; An encryption key generating means for generating an encryption key by performing a second operation on the first key and a predetermined second key; and a common key encryption method using the encryption key. And encryption means for encrypting the data body portion, and encrypted image data output means for outputting the management information portion and the encrypted data body portion as encrypted image data.

  In the first aspect and the second aspect, the predetermined information different for each frame can be, for example, time stamp information.

  In order to solve the above-described problem, an encrypted image data decryption apparatus according to a third aspect of the present invention includes a management information unit including predetermined information that differs for each frame, and a first operation is performed on the management information unit. A data main body encrypted by a common key encryption method using an encryption key generated by performing a second operation on a first key generated in advance and a predetermined second key; An encrypted image data decrypting device for decrypting encrypted image data comprising: first key generating means for generating a first key by performing the first operation on the management information section; and an encryption side A second key setting means for specifying the second key determined in advance, and a cipher for generating an encryption key by performing the second operation on the first key and the specified second key Encryption key generating means and the encryption key And a decoding means for decoding the data body portion by the common key decryption scheme used.

  According to the present invention, the first key generation, the encryption key generation, and the encryption can be performed without going through a complicated procedure, so that the processing load of the encrypted image data decryption apparatus can be reduced. In addition, since the decryption cannot be performed if the management information part is falsified, it can be easily known that the falsification has occurred. Here, the predetermined information different for each frame can be, for example, time stamp information.

  In order to solve the above-mentioned problem, an image data encryption method according to a fourth aspect of the present invention is an image in which the image data encryption apparatus has a management information section and a data body section including predetermined information that differs for each frame. An image data encryption method for encrypting data, wherein a first key generation step of generating a first key by performing a first operation on the management information section, and the first key are predetermined. An encryption key generating step for generating an encryption key by performing a second operation on the second key; and an encryption step for encrypting the data body using a common key encryption method using the encryption key. And an encrypted image data output step for outputting the management information part and the encrypted data body part as encrypted image data.

  In order to solve the above problems, an image data encryption method according to a fifth aspect of the present invention is an image data encryption method in which an image data encryption device encrypts image data having a management information section and a data body section. A management information pre-processing step of inserting predetermined different information for each frame into a predetermined area of the management information section, and generating a first key by performing a first operation on the management information section A first key generation step, an encryption key generation step for generating an encryption key by performing a second operation on the first key and a predetermined second key, and using the encryption key An encryption step of encrypting the data body portion by a common key encryption method, and an encrypted image data output step of outputting the management information portion and the encrypted data body portion as encrypted image data. Yes That.

  In the fourth aspect and the fifth aspect, the predetermined information different for each frame can be, for example, time stamp information.

  In order to solve the above-described problem, an encrypted image data decryption method according to a sixth aspect of the present invention includes a management information unit including predetermined information different for each frame, and a first operation is performed on the management information unit. A data main body encrypted by a common key encryption method using an encryption key generated by performing a second operation on a first key generated in advance and a predetermined second key; Are encrypted image data decrypting methods in which the encrypted image data decrypting device decrypts the encrypted image data, and a first key is generated by performing the first operation on the management information section. Performing the second calculation on a key generation step, a second key setting step for specifying the second key predetermined on the encryption side, and the first key and the specified second key. Generate an encryption key It has a No. encryption key generating step, and a decoding step of decoding the data body portion by the common key decryption scheme using the encryption key. The predetermined information different for each frame may be time stamp information, for example.

  In order to solve the above-mentioned problem, in the image data transmission method according to the seventh aspect of the present invention, image data having a management information part and a data body part including predetermined information different for each frame is encrypted on the transmission side. Transmission method for transmitting encrypted encrypted image data to a reception side via a transmission path, wherein the transmission side performs a first calculation on the management information unit to generate a first key A generating step, an encryption key generating step for generating an encryption key by performing a second operation on the first key and a predetermined second key, and a common key encryption using the encryption key An encryption step for encrypting the data body portion by an encryption method, and an encrypted image data output step for outputting the management information portion and the encrypted data body portion as the encrypted image data. The dark The image data is transmitted to the receiving side via the transmission path. The predetermined information different for each frame may be time stamp information, for example.

  According to the present invention, it is possible to reduce the processing load and to keep confidentiality and tamper resistance high.

  Embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing an outline of the configuration of the image data transmission system of the present embodiment. As shown in FIG. 1, the image data transmission system includes an image data encryption device 10 and an encrypted image data decryption device 20. The image data encryption device 10 and the encrypted image data decryption device 20 are connected via a communication network 40 such as the Internet, for example.

  The image data encryption device 10 can be configured using a general-purpose information processing device or a dedicated device having a CPU, a memory, a communication control device, an input / output interface, and the like, and inputs image data 50 to be transmitted. The encrypted image data 70 is output.

  The image data 50 is configured in a predetermined format, and includes a management information unit 51 including image related information and a data main body unit 52 which is a substantial image data part. The encrypted image data 70 is image data encrypted by applying the present invention, and includes a plaintext management information section 51a and an encrypted encrypted data body section 72.

  The encrypted image data decryption device 20 can be configured using a general-purpose information processing device or a dedicated device provided with a CPU, a memory, a communication control device, an input / output interface, and the like. The decoded image data 50a is output.

  The decrypted image data 50a is image data obtained by decrypting the encrypted image data 70, and includes a management information section 51a and a data main body section 52a that is a substantial image data section. The data body 52a of the decrypted image data 50a has the same contents as the data body 52 of the image data 50 input to the image data encryption device 10.

  Here, it is assumed that the data body 52 of the image data 50 is compressed by the JPEG method, and the format of the image data 50 is a JFIF format which is a standard format of JPEG image data. However, the present invention is not limited to this, and various image compression formats such as GIF and TIF can be used. Moreover, it is not limited to a still image format, and may be a moving image format such as MPEG.

  FIG. 2 is a block diagram illustrating a functional configuration of the image data encryption device 10. As shown in FIG. 2, the image data encryption device 10 includes an image data input unit 110 that inputs image data 50 including a management information unit 51 and a data body unit 52, and a management information unit 51 prior to encryption. A management information preprocessing unit 120 that inserts additional information such as a time stamp, and a first key generation unit 130 that generates a first key based on the management information unit 51a output from the management information preprocessing unit 120; A second key storage unit 140 for storing the second key, an encryption key generation unit 150 for generating an encryption key based on the first key and the second key, and a data body unit 52 using the encryption key. The encrypted image data to be output as the encrypted image data 70 by integrating the encryption unit 160 for encrypting the encrypted data, the pre-processed management information unit 51a, and the encrypted data main body 72 output by the encryption unit 160. And an output unit 170.

  The management information preprocessing unit 120 inserts time stamp information and encryption flag information into the user data area of the management information unit 51, for example, a comment segment. Here, the time stamp information is a time (year / month / day / second / millisecond) to which the time stamp information is added. However, the time when the image data 50 is created, the time when the image data is compressed, the time when the encryption is performed, and the like may be used. Further, when the type stamp information is already recorded in the management information section 51, it is not necessary to insert it again. In order to perform encryption in the image data encryption device 10, the encryption flag information is inserted in a flag-on state. If it is clear that all the image data input to the encrypted image data decryption apparatus 20 is encrypted, the encryption flag information may be omitted.

  The management information preprocessing unit 120 can further insert model name information, version information, MAC address information, size information of the data main body unit 52, and the like into the user data area of the management information unit 51. The management information preprocessing unit 120 may insert a different numerical value or character string for each image data instead of the time stamp information. This different numerical value may be a random number or an incrementing numerical value. As will be described later, since the first key is generated using the data string that constitutes the management information unit 51, it is more secure that the information is different for each image data in the management information unit 51 and the confidentiality of encryption and tamper resistance. Will increase.

  The first key generation unit 130 performs checksum, CRC (Cyclic Redundancy Check), SHA (Secure Hush Algorithm), md5 (Message) on the data string (x0, x1,..., Xn) constituting the management information unit 51a. A first key fx (x0, x1,..., Xn) is generated by applying a one-way function fx such as a hash function such as (Digest Algorithm). Since the management information part 51a includes time stamp information, the generated first key has a different value for each process.

  The second key storage unit 140 stores a predetermined second key. For example, the second key has a unique value that is different for each model and version of the image data encryption device 10. Can do. However, a common value may be used for each model.

  The encryption key generation unit 150 generates the encryption key gx (first key, second key) by applying the one-way function gx as described above using the first key and the second key as variables. Since the first key is generated with a different value for each process, the encryption key also has a different value for each process.

  The encryption unit 160 encrypts the data main body unit 52 using the encryption key generated by the encryption key generation unit 150 to generate an encrypted data main body unit 72. The encryption unit 160 performs encryption using a common key method that uses the same key during encryption processing and decryption processing. As the common key method, for example, Blowfish, DES (Data Encryption Standard), or the like can be used.

  As described above, in this embodiment, the data main body 52 is encrypted using the encryption key derived from the management information unit 51a, and the management information unit 51a is not encrypted. Since the management information unit 51a includes time stamp information, the encryption key has a different value for each image data. For this reason, encryption confidentiality and tamper resistance are increasing.

  FIG. 3 is a block diagram showing a functional configuration of the encrypted image data decryption apparatus 20. As shown in FIG. 3, the encrypted image data decryption apparatus 20 includes an encrypted image data input unit 210 that inputs encrypted image data 70 including a management information unit 51 a and an encrypted data body 72, and management information. A first key generation unit 130 that generates a first key based on the unit 51a and a second key that is used to generate an encryption key when the data body unit 52 is encrypted in the image data encryption device 10 are set. A second key setting unit 240 that performs encryption, an encryption key generation unit 250 that generates an encryption key based on the first key and the second key, and decryption that decrypts the encrypted data body unit 72 using the encryption key Unit 260, and a decoded image data output unit 270 that integrates the management information unit 51a and the decoded data main body 52a output from the decoding unit 260 and outputs the result as decoded image data 50a.

  The encrypted image data input unit 210 checks whether or not the encryption flag information is included in the user data area of the management information unit 51a, and if it is included, the encrypted image data decryption device Decoding process 20 is performed. If not included, the decryption process in the encrypted image data decryption apparatus 20 is not performed. However, if it is clear that the input image data is encrypted, the encryption flag information may not be checked.

  The first key generation unit 230 is the same as the conversion function used by the first key generation unit 130 of the image data encryption device 10 for the data string (x0, x1,..., Xn) constituting the management information unit 51a. The first key fx (x0, x1,..., Xn) is generated by applying the one-way function fx. Therefore, the first key generated by the first key generation unit 230 is the same as the first key generated by the first key generation unit 130 of the image data encryption device 10 for the management information unit 51a.

  The second key setting unit 240 sets a second key used for generating an encryption key when the data body unit 52 is encrypted in the image data encryption device 10. The second key setting unit 240 includes, for example, a second key setting table as shown in FIG. 4A. From the model name, version, etc. of the image data encryption device 10 specified by the management information unit 51a. The second key can be set.

  Note that the second key setting method is not limited to the table method. For example, as illustrated in FIG. 4B, the image data encryption device 10 may acquire the image data encryption device 10 at the start of communication between the image data encryption device 10 and the encrypted image data decryption device 20. Or you may make it acquire from the management server 80 separately provided on the communication network 40. FIG. Furthermore, when a uniform value is used as the second key, a predetermined second key can be stored in the second key setting unit 240. Since the second key is not a direct encryption key, even if the second key leaks, confidentiality and robustness against tampering can be maintained.

  The encryption key generation unit 250 performs encryption by applying the same one-way function gx as the conversion function used by the encryption key generation unit 150 of the image data encryption device 10 using the first key and the second key as variables. A key gx (first key, second key) is generated. For this reason, the encryption key generated by the encryption key generation unit 250 is the same as the encryption key generated by the encryption key generation unit 150 of the image data encryption device 10.

  The decryption unit 260 decrypts the encrypted data body 72 using the encryption key generated by the encryption key generation unit 250, and generates a decrypted data body 52a. Since the encrypted data main body 72 is encrypted by the common key method, the decryption unit 260 uses the generated encryption key to perform encryption using the encryption unit 160 of the image data encryption device 10. By performing decryption using the same encryption method as the method, the encrypted data body 72 can be decrypted to obtain the decrypted data body 52a.

  Next, encryption processing in the image data encryption apparatus 10 will be described with reference to the flowchart of FIG. 5 and FIG. First, the image data input unit 110 inputs image data 50 from a photographing apparatus or the like (S101). The management information preprocessing unit 120 inserts additional information such as a time stamp into the management information unit 51 of the image data (S102), and inserts the encryption flag in an ON state (S103).

  FIG. 6 is a diagram showing a format of the image data 50 in which additional information such as a time stamp is inserted. This figure shows the format of the image data 50 when JFIF using the JPEG format is used. The image data 50 includes a management information part 51a in which additional information is inserted and a data body part 52 composed of frame data 504 compressed in the JPEG format, and an SOI (Start Of Image) indicating the start of the image data 50. ) A marker 501 and an EOI (End Of Image) marker 505 indicating the end of the image data 50 are attached. The SOI marker 501 is indicated by 2 bytes in which 0xFF is combined with 0xFF which is a key code of JFIF, and the EOI marker 505 is indicated by 2 bytes in which 0xD9 is combined with 0xD9. In FIG. 6, the management information unit 51a includes the comment segment 502 and the application segment 503, but is not limited thereto, and may include other segments.

  In the comment segment 502 of the management information section 51a, a COM (Comment) marker 512a indicating that it is a comment segment is indicated by 2 bytes obtained by combining 0xFF and 0xFE of the key code, and the subsequent 2-byte Length 512b indicates the comment segment. The data length is indicated. The management information preprocessing unit 120 inserts time stamp information, encryption flag information, model name, version, and MAC address into the main body part 512c of the comment segment 502a. However, as described above, it is sufficient that time stamp information is included in the management information section 51a, and the time information indicated by the time stamp information is not limited.

  Next, the first key generation unit 130 generates a first key based on the management information unit 51a (S104). In the example illustrated in FIG. 7, the first key generation unit 130 obtains the first key fx (x0, x1,..., Xn) from the data string (x0, x1,..., Xn) configuring the management information unit 51a. Is generated. The first key may be generated by including the data string of the SOI marker 501 in the management information unit 51a.

  Then, the second key is acquired from the second key storage unit 140 (S105), and the encryption key generation unit 150 generates an encryption key from the first key and the second key (S106). When the encryption key is generated, the encryption unit 160 encrypts the data body unit 52 using the generated encryption key (S107).

  As shown in FIG. 7, the encrypted image data output unit 170 combines the management information unit 51a into which the additional information is inserted and the encrypted data main body unit 72 composed of the encrypted frame data 706. The encrypted image data 70 is output to the encrypted image data decrypting apparatus 20 via the communication network 40 (S108).

  The image data encryption device 10 repeats the above processing until the image data to be transmitted ends (S109). As described above, since the encryption key is different every time it is repeated, the confidentiality and tamper resistance of the encryption are increased. Further, the image data encryption device 10 can perform the calculation for generating the first key, the calculation for generating the encryption key, and the encryption process without going through complicated procedures. Even in the case of transmission, the processing load of the image data encryption device 10 is light.

  Next, decryption processing in the encrypted image data decryption apparatus 20 will be described with reference to the flowchart of FIG. 8 and FIG. First, the encrypted image data input unit 210 inputs the encrypted image data 70 from the image data encryption device 10 via the communication network 40 (S201). If the input image data does not include the encryption flag in the on state, the subsequent decryption process is not performed.

  When the encrypted image data 70 is input, the first key generation unit 230 generates a first key based on the management information unit 51a (S202). In the example shown in FIG. 9, the first key generation unit 230 obtains the first key fx (x0, x1,..., Xn) from the data string (x0, x1,..., Xn) constituting the management information unit 51a. Is generated.

  Then, the second key setting unit 240 sets the second key used for generating the encryption key when the data body unit 52 is encrypted in the image data encryption device 10 (S203). When the second key is set, the encryption key generation unit 250 generates an encryption key from the first key and the second key (S204).

  Since this encryption key matches the encryption key used when encrypting the data main body 52 in the image data encryption device 10, the decryption unit 260 uses the generated encryption key to perform encryption. The data body 72 is decrypted (S205).

  As shown in FIG. 9, the decoded image data output unit 270 combines the management information unit 51a and the decoded data main body unit 52a composed of the decoded frame data 504a to obtain decoded image data 50a. It outputs to an image display apparatus etc. (S206).

  The encrypted image data decryption apparatus 20 repeats the above processing until the transmitted image data is completed (S207). The encrypted image data decryption apparatus 20 can perform the calculation for generating the first key, the calculation for generating the encryption key, and the decryption process without complicated procedures. Even in the case of transmission, the processing load of the encrypted image data decryption apparatus 20 is light.

  FIG. 10 is a diagram showing an embodiment in which a network video monitoring system is constructed using the image data encryption device 10 and the encrypted image data decryption device 20 described above. In this example, two image data encryption devices (image data encryption device A 10a and image data encryption device B 10b) and one encrypted image data decryption device 20 are used.

  The image data encryption device A10a encrypts the image data photographed by the photographing device A30a and outputs the encrypted image data to the encrypted image data decryption device 20 via the communication network 40. The image data encryption device B10b is photographed by the photographing device B30b. The encrypted image data is encrypted and output to the encrypted image data decryption apparatus 20 via the communication network 40.

  An image display device A50a and an image display device B50b are connected to the encrypted image data decryption device 20, and the encrypted image data decryption device 20 is input from the image data encryption device A10a and the image data encryption device B10b, respectively. The encrypted image data is decrypted and displayed on the image display device A50a and the image display device B50b, respectively.

  As shown in FIG. 10, in the encrypted image data decryption device 20, the encrypted image data of frame 0, frame 1... Frame n input from the image data encryption device A 10a is encrypted from the management information unit 51a. Encryption key A0, encryption key A1,... Decryption is performed using encryption key An, and encrypted image data of frame 0, frame 1... Frame n input from image data encryption apparatus B10b is obtained from management information section 51a. The encryption key B0, the encryption key B1,... Can be decrypted with the encryption key Bn.

  At this time, since each management information section 51 includes time stamps indicating different times, the encryption key A0, the encryption key A1,... The encryption key An, the encryption key B0, and the encryption key B1. ... the encryption keys Bn are all different values. Therefore, the confidentiality of the network video monitoring system is high. Further, if the management information part 51a is falsified, it becomes impossible to decrypt the encrypted image data, so that the tamper resistance is high.

  Furthermore, when model name information, MAC address information, etc. are included in the management information part used for generating the encryption key, for example, when the information of the image data encryption device 10 is intentionally replaced or rewritten. The encryption key cannot be reproduced, and the encrypted image data cannot be decrypted. For this reason, the discovery of tampering becomes easier, and the deterrence effect of tampering becomes higher.

  Further, the above-described embodiment can be effectively applied to an image distribution system, a video conference system, and the like, similarly to the network video monitoring system that is the above-described example.

It is a block diagram which shows the outline | summary of a structure of the image data transmission system which is embodiment of this invention. It is a block diagram which shows the function structure of an image data encryption apparatus. It is a block diagram which shows the function structure of an encryption image data decoding apparatus. It is a figure explaining the setting method of a 2nd key. It is a flowchart explaining the encryption process in an image data encryption apparatus. It is a figure explaining the additional information of a management information part. It is a figure explaining the format of image data and encryption image data. It is a flowchart explaining the decoding process in an encryption image data decoding apparatus. It is a figure explaining the format of encrypted image data and decoded image data. It is a schematic block diagram of the network video surveillance system which is an Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Image data encryption apparatus, 20 ... Encrypted image data decryption apparatus, 30 ... Imaging apparatus, 40 ... Communication network, 50 ... Image display apparatus, 80 ... Management server, 110 ... Image data input part, 120 ... Before management information Processing unit 130 ... first key generation unit 140 ... second key storage unit 150 ... encryption key generation unit 160 ... encryption unit 170 ... encrypted image data output unit 210 ... encrypted image data input unit , 230 ... first key generation unit, 240 ... second key setting unit, 250 ... encryption key generation unit, 260 ... decryption unit, 270 ... decrypted image data output unit

Claims (12)

An image data encryption device for encrypting image data having a management information part and data body part including predetermined information different for each frame,
First key generating means for generating a first key by performing a first operation on the management information section;
An encryption key generating means for generating an encryption key by performing a second operation on the first key and a predetermined second key;
An encryption means for encrypting the data body using a common key encryption method using the encryption key;
Encrypted image data output means for outputting the management information part and the encrypted data body part as encrypted image data;
An image data encryption apparatus comprising: An image data encryption device for encrypting image data having a management information part and a data body part,
Management information preprocessing means for inserting predetermined information different for each frame into a predetermined area of the management information section;
First key generating means for generating a first key by performing a first operation on the management information section;
An encryption key generating means for generating an encryption key by performing a second operation on the first key and a predetermined second key;
An encryption means for encrypting the data body using a common key encryption method using the encryption key;
Encrypted image data output means for outputting the management information part and the encrypted data body part as encrypted image data;
An image data encryption apparatus comprising:   3. The image data encryption apparatus according to claim 1, wherein the predetermined information different for each frame is time stamp information. A management information part including predetermined information different for each frame, a first key generated by performing a first calculation on the management information part, and a second key determined in advance are applied to the second key. An encrypted image data decrypting device for decrypting encrypted image data, comprising: a data main body encrypted by a common key encryption method using the generated encryption key,
First key generating means for generating a first key by performing the first calculation on the management information section;
Second key setting means for specifying the second key predetermined on the encryption side;
Encryption key generating means for generating an encryption key by performing the second operation on the first key and the identified second key;
Decryption means for decrypting the data body using a common key decryption method using the encryption key;
An encrypted image data decrypting device comprising:   5. The encrypted image data decrypting apparatus according to claim 4, wherein the predetermined information different for each frame is time stamp information. The image data encryption device is an image data encryption method for encrypting image data having a management information part and a data body part including predetermined information different for each frame,
A first key generation step of generating a first key by performing a first operation on the management information section;
An encryption key generating step of generating an encryption key by performing a second operation on the first key and a predetermined second key;
An encryption step of encrypting the data body with a common key encryption method using the encryption key;
An encrypted image data output step for outputting the management information part and the encrypted data body part as encrypted image data;
An image data encryption method characterized by comprising: The image data encryption device is an image data encryption method for encrypting image data having a management information part and a data body part,
A management information pre-processing step of inserting different predetermined information for each frame into a predetermined area of the management information section;
A first key generation step of generating a first key by performing a first operation on the management information section;
An encryption key generating step of generating an encryption key by performing a second operation on the first key and a predetermined second key;
An encryption step of encrypting the data body with a common key encryption method using the encryption key;
An encrypted image data output step for outputting the management information part and the encrypted data body part as encrypted image data;
An image data encryption method comprising:   8. The image data encryption method according to claim 6, wherein the predetermined information different for each frame is time stamp information. A management information part including predetermined information different for each frame, a first key generated by performing a first calculation on the management information part, and a second key determined in advance are applied to the second key. An encrypted image data decryption method in which an encrypted image data decryption apparatus decrypts encrypted image data comprising a data main body portion encrypted by a common key encryption method using the generated encryption key Because
A first key generation step of generating a first key by performing the first calculation on the management information section;
A second key setting step for specifying the second key predetermined on the encryption side;
An encryption key generating step for generating an encryption key by performing the second operation on the first key and the identified second key;
A decrypting step of decrypting the data body using a common key decryption method using the encryption key;
A method of decrypting encrypted image data, comprising:   10. The encrypted image data decrypting method according to claim 9, wherein the predetermined information different for each frame is time stamp information. A transmission method for transmitting encrypted image data obtained by encrypting image data having a management information part and data main body part including predetermined information different for each frame on a transmission side to a reception side via a transmission path. ,
The sender is
A first key generation step of generating a first key by performing a first operation on the management information section;
An encryption key generating step of generating an encryption key by performing a second operation on the first key and a predetermined second key;
An encryption step of encrypting the data body with a common key encryption method using the encryption key;
An encrypted image data output step for outputting the management information portion and the encrypted data body portion as the encrypted image data, and the encrypted image data is transmitted to the receiving side via the transmission path. And transmitting the encrypted image data.   12. The method of transmitting encrypted image data according to claim 11, wherein the predetermined information different for each frame is time stamp information.