JP2004040819A - Image encryptor/reproducer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image encryptor/reproducer which can enhance secrecy of picture information recorded on a sheet of medium. <P>SOLUTION: An original manuscript to be encrypted or the original manuscript to be encrypted, recorded, and decoded is read by a reading section 1 and stored in an image storage section 3 via an A/D converter 2. Whether encryption mode or decoding mode is selected with a process mode and a password entered from a password input section 9. The input process mode and the password are analyzed by a number analysis section 10. According to this process mode, an address calculation section 12 calculates a transfer destination address of a picture element for encryption process or decoding process using a method like deriving a solution of a polynomial calculation based on the password. A pixel rearrangement/reconstruction section 5 replaces the image data stored in the image storage section 3 based on the destination address. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to an image encryption / reproduction device that encrypts image data and reproduces the encryption into an original image.

Conventionally, as an image encryption / reproduction device of this type, there is a technology disclosed in, for example, Japanese Patent Application Laid-Open No. 3-123988. The disclosed technique relates to a reproducing apparatus that accurately reproduces high-definition bit information recorded on a sheet-like medium and outputs the information as a good image and audio signal. This apparatus records character, voice and image information on a sheet-like medium as an optically readable code or bit string information, and transmits the same via, for example, existing mail means. It is configured to reproduce text, audio and image information. Further, in order to improve the handling of information, it has been proposed to add start data, end data, and identification code data in addition to bit information of character, voice, and image information.

Further, although the contents of the image can be kept secret in the digital signal processing device until the image read by the scanner is printed, an encryption method suitable for facsimile communication is described in, for example, Journal of Image Communication Society, Vol. No. (1988), "Secure facsimile communication using image scrambling method", and an encryption method suitable for digital images is disclosed in, for example, Transactions of the Institute of Electronics and Communication Engineers, '86 / 11 @ Vol. J69-B No. 11 "A Method of Data Encryption Suitable for Digital Images".

These methods are inadequate in terms of processing speed even if they are applied to images using encryption methods such as a public key method and a common key method, and extremely strong cipher breaking in computer networks. Therefore, we are trying to solve the problem that the system scale becomes large. For these purposes, a method has been proposed in which the image data is processed at a high speed with a relatively high encryption strength by a simple method.

However, in the above-mentioned conventional encryption / reproduction device, even if the bit string information recorded on the sheet medium is apparently secret, the bit string information can be easily reproduced with the reproduction device. So you can't maintain confidentiality. In the above-mentioned encryption method for facsimile communication and digital image, since the method is for an image signal to be electrically processed, the encryption is performed via a sheet-like medium which is easy to handle, and the encryption is performed on the original image. Can not be played.

The present invention has been made in view of the above-mentioned conventional problems, and has as its object to provide an image encryption / reproduction apparatus capable of improving the confidentiality of image information recorded on a sheet medium.

In order to achieve the above object, the first means is a reading means for optically reading an image recorded on a sheet medium, a storing means for storing the image read by the reading means, and a password input. Along with, input means capable of selecting an encryption process and a decryption process, an address calculation unit that derives a solution of a polynomial operation based on the input personal identification number, and calculates a transfer destination address from the derived solution, When an encryption process is selected via the input unit, the encryption unit encrypts the image stored in the storage unit based on the transfer destination address calculated by the address calculation unit; and Decryption means for decrypting an image stored in the storage means based on the transfer destination address when the decryption processing is selected via the transfer destination address; Wherein the image or the decoded image by the decoding means and output means for outputting the printout sheet-like medium.

The second means is the first means, wherein the encryption means encrypts the image stored in the storage means by replacing the image in a two-dimensional area for each pixel, and the decryption means is stored in the storage means. The decoding is performed by returning the image to the original position for each pixel.

The third means is that, in the first means, the encrypting means calculates the white and black run lengths of the image stored in the storage means, and replaces the whole area in units of a range in which the same pixel is continuous. The image is encrypted by storing the image in the storage unit, and the decryption unit decrypts the image stored in the storage unit by returning the image to the original position for each of the ranges.

A fourth means is the first means, wherein the encryption means calculates a prediction error of the multi-valued image stored in the storage means, quantizes the prediction error, and replaces the quantized data line by line. Wherein the decoding means returns the quantized data to the original line and dequantizes the image stored in the storage means into a prediction error, and decodes a multi-valued image from the prediction error. And

The fifth means specifies a specific two-dimensional area in the image area for the image stored in the storage means in the first means, and inputs an instruction to encrypt or decrypt the two-dimensional area Means, the encrypting means encrypts the image of the designated two-dimensional area and combines it with an unencrypted image of another area, and the decrypting means decrypts the encrypted image of the two-dimensional area. And combining the image with an unencrypted image in another area.

A sixth means is that, in the first to fifth means, the encrypting means adds an outer frame indicating a horizontal direction and a vertical direction of the area of the encrypted image, and the decrypting means performs the encryption stored in the storage means. The decoded image is decoded after being returned to the original direction by the outer frame.

{Seventh means is characterized in that in the first to fifth means, the encryption means adds the direction of the encrypted image.

The eighth means is characterized in that, in the first to fifth means, the decryption means emphasizes the high-frequency component before decrypting the encrypted image.

In the first means, a solution of a polynomial operation is derived based on a password, a transfer destination address is calculated from the derived solution, and encryption and decryption of an image on a sheet-like medium are performed based on this address. Since this is performed, the confidentiality of the image information recorded on the sheet-like medium can be improved.

In the second means, the confidentiality of the image information recorded on the sheet-shaped medium can be improved by the password, and the image on the sheet-shaped medium is encrypted because each pixel is encrypted in the two-dimensional area. It is completely illegible and can be processed at high speed.

According to the third means, the confidentiality of the image information recorded on the sheet medium can be improved by the password, and the run length of black and white is calculated to determine the range in which the same pixel continues in all areas. Since the data is exchanged in units and stored in the storage means and encrypted, the image on the sheet medium becomes completely illegible, and high speed and data compression can be realized.

In the fourth means, the confidentiality of the image information recorded on the sheet-like medium can be improved by the password, and the multi-valued image is encrypted by the prediction error. It becomes completely illegible and can achieve high speed and data compression.

In the fifth means, confidentiality of image information recorded on a sheet medium can be improved by a password, and a specific two-dimensional area in the image area is designated, and the two-dimensional area is encrypted. Therefore, it is possible to keep secret according to the purpose and value of the image, and it is possible to prevent deterioration of the image quality of the non-encrypted image.

According to the sixth means, the security of the image information recorded on the sheet medium can be improved by the password, and the encrypted image is decrypted after being returned to the original direction by the outer frame. Therefore, it is possible to correctly decrypt the encrypted image and improve the accuracy of information transmission.

According to the seventh means, the security of the image information recorded on the sheet-like medium can be improved by the password, and the direction of the encrypted image is added on the sheet-like medium. The operation at the time of reading is simplified, and therefore, the accuracy of information transmission can be improved.

According to the eighth means, the confidentiality of the image information recorded on the sheet-like medium can be improved by the password, and the high-frequency component is emphasized before decryption. Correct decoding can be performed without losing the components.

As described above, according to the present invention, the image information recorded on the sheet-like medium by performing the encryption process and the decryption process based on the input personal identification number because the configuration is as described above. Confidentiality can be improved.

According to the present invention, since the image is encrypted for each pixel in the two-dimensional area, the image on the sheet-shaped medium becomes completely unreadable and can be processed at high speed.

Further, according to the present invention, the run lengths of black and white are calculated, and the same pixels are replaced in a continuous range unit for the entire area and stored in the storage means for encryption. Can be completely illegible, and high speed and data compression can be realized.

According to the present invention, since the multi-valued image is encrypted by the prediction error, the image on the sheet-shaped medium becomes completely unreadable, and high-speed and data compression can be realized.

Further, according to the present invention, a specific two-dimensional area in the image area is designated and the two-dimensional area is encrypted, so that it can be kept secret according to the purpose and value of the image. It is possible to prevent the image quality of the encrypted image from deteriorating.

According to the present invention, since the encrypted image is decrypted after being returned to the original direction by the outer frame, the encrypted image can be correctly decrypted and the accuracy of information transmission can be improved.

Further, according to the present invention, since the direction of the encrypted image is added on the sheet-like medium, the operation at the time of reading the encrypted image is simplified, and therefore, the accuracy of information transmission can be improved. it can.

{Furthermore, according to the present invention, the high-frequency component is emphasized before decryption, so that it is possible to correctly decrypt the encrypted image without damaging the high-frequency component.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of an image encryption / reproduction apparatus according to the present invention, FIG. 2 is a flowchart for explaining the operation of the image encryption / reproduction apparatus of FIG. 1, and FIG. FIG. 4 is an explanatory diagram showing an operation when encrypting an image for each pixel, FIG. 5 is an explanatory diagram showing an operation when encrypting an image for each run length, and FIG. FIG. 7 is an explanatory diagram showing an operation when encrypting a multi-valued image, FIG. 7 is an explanatory diagram showing an operation when selectively encrypting all or part of an image, and FIG. 8 is a diagram for synthesizing a plurality of encrypted images. FIG. 9 is an explanatory diagram showing an operation when separating and decoding a combined image. FIG. 9 is an explanatory diagram showing an operation when combining an unencrypted image and an encrypted image and separating and decoding the combined image. FIG. 10 is an explanatory diagram showing an operation for identifying an area of an encrypted image, and FIG. Explanatory view showing a technique to recognize that it is an image, FIG. 12 is an explanatory diagram showing a high-frequency emphasis at the time of decrypting the encrypted image.

In FIG. 1, the outline is described. As shown by an arrow, an original image is read and encrypted by the device, the encrypted image is recorded on a sheet-like medium, and the encrypted image is read and decrypted. The decoded image is recorded on a sheet-like medium and reproduced. Next, the detailed configuration and operation of this embodiment will be described with reference to FIGS. 1 and 2. The document to be encrypted or the document to be encrypted and recorded and decrypted is read by the image reading unit 1. And converted into an electric signal. Next, the electric signal is converted into a digital signal by the A / D converter 2 and stored in the image storage unit 3.

{Circle around (2)} The encryption mode or the decryption mode is selected based on the processing mode and the password input through the password input unit 9. In this case, the number analysis unit 10 analyzes the input processing mode and the password (step 13 shown in FIG. 2), and the encryption / decryption control unit 11 selects a processing mode according to the analysis result (step 14). ).

The address calculation unit 12 calculates a destination address of a pixel for moving an image to be encrypted or decrypted in a block unit, a pixel unit, a line unit, or the like in accordance with the processing mode, based on a password. (Steps 15 and 19), and the pixel rearrangement / reconstruction unit 5 replaces the image data stored in the image storage unit 3 with the transfer destination address (encryption or decryption). (Steps 16 and 20).

In the case of decryption, the address calculation unit 12 calculates an address by a method of deriving a solution of a polynomial operation based on the password, and the pixel rearrangement / reconstruction unit 5 converts this address into the encrypted image. Identify the destination. The encrypted or decrypted image data is stored in the image storage unit 7, and is recorded on a sheet-like medium by the output unit 8 and output.

In the case of the encryption process, the circumscribed frame creating unit 6 surrounds the image area rearranged by the pixel rearrangement / reconstruction unit 5 to define the horizontal direction and the vertical direction of the encrypted image. The surrounding area is surrounded by a solid line frame (step 17), and in the case of decryption processing, the frame line recognition unit 4 allows the pixel rearrangement / reconstruction unit 5 to correctly reconstruct the encrypted image. Next, the direction of the encrypted area is identified by recognizing the solid frame (step 18).

(4) Since the image on the sheet medium is encrypted and decrypted by the password, the confidentiality of the image information recorded on the sheet medium can be improved.

Next, the operation in the case of encrypting each block will be described with reference to FIG. First, the entire area when encrypting the original image 27 as shown in FIG. 3B is calculated (step 21), and then the original image 27 is divided into blocks (step 22). The size of this block can be set by default, or can be set via, for example, the password input unit 9.

Next, each divided image is rotated according to the result of the calculation by performing a polynomial operation based on the personal identification number (step 23), and each of the divided rotated images is transferred to the destination address calculated by the address calculation unit 12. Is stored in the image storage unit 7 in accordance with (steps 24 and 25). Then, the circumscribed frame creating unit 6 creates a solid line frame 28a for surrounding the periphery of each divided rotated image and stores it in the image storage unit 7 of the address (step 26).

Therefore, according to this embodiment, since the original image 27 is rotated and encrypted for each block, the image on the sheet medium can be roughly kept secret. The blocks of the encrypted image 28 shown in FIG. 3B are slightly larger for ease of explanation, but the confidentiality can be improved by making the blocks smaller.

Next, the operation in the case of encrypting each pixel of the image will be described with reference to FIG. 4. First, the entire area in the case of encrypting the original image 33 as shown in FIG. 29). Next, each pixel in this area is stored in the image storage unit 7 according to the destination address calculated by the address calculation unit 12, thereby generating an encrypted image 34 as shown in FIG. 31) Further, the circumscribed frame creating unit 6 generates a solid line frame 34a for surrounding the entirety of the encrypted image 34 and stores it in the image storage unit 7 of the address (step 32).

(4) Therefore, in this example, since each pixel is replaced, processing can be performed at a high speed, and even if printed on a sheet-like medium as shown in FIG.

Next, the operation for encrypting an image for each run length will be described with reference to FIG. First, the entire area when the original image 40 as shown in FIG. 5B is encrypted is calculated (step 35), and the white and black run lengths of the area to be encrypted are calculated. A range where the same pixel continues is specified (step 36). Next, the same pixel is replaced in a continuous range unit for the entire area and stored in the image storage unit 7 to generate an encrypted image 41 as shown in FIG. 5B. A solid frame 41a for surrounding the entirety of the encrypted image 41 is generated and stored in the image storage unit 7 at that address (steps 38 and 39).

Therefore, in this example, since the data is encrypted for each run length, the image on the sheet-shaped medium becomes completely unreadable, and high speed and data compression can be realized.

Next, the operation for encrypting the multi-valued image 67 as shown in FIG. 6B will be described. First, the entire area in the case of encrypting the multi-valued image 67 is calculated (step 61), and a prediction error is calculated by previous value prediction or plane prediction (step 62), and the prediction error is quantized. (Step 63). Next, the quantized data of the prediction error is replaced for each line and stored in the image storage unit 7 to generate an encrypted image 68 as shown in FIG. 6B (steps 64 and 65). The frame creation unit 6 creates a solid frame 68a for surrounding the entire periphery of the encrypted image 68 and stores it in the image storage unit 7 at that address (step 66).

Therefore, in this example, since the multi-valued image is encrypted by the prediction error, the image on the sheet-like medium becomes completely unreadable, and high speed and data compression can be realized.

Next, the operation when selectively encrypting all or a part of the original image 78 will be described with reference to FIG. The specification for encrypting a part of the image 78 may be performed via the input unit 9 together with the personal identification number and the processing mode, or the solid line frame specified in advance on the document may be designated by the frame line recognition unit 4. It can be recognized by recognizing or specifying via a tablet.

First, the processing area is determined in step 71 shown in FIG. 7A. If the entire area has been designated, the process proceeds from step 72 to step 73 or less. Proceed to. If the entire area is designated, an encrypted image 79a of the entire area is generated as shown in FIG. 7B by the encryption processing as shown in FIGS. 3 to 6 (step 74). In addition, the circumscribed frame creating unit 6 creates a solid line frame 79c for surrounding the periphery of the encrypted image 79a.

On the other hand, if a part of the area is specified, first, the encryption area is specified (step 75). When the area is specified via the tablet, the encrypted area can be specified by the address specified by the tablet. 7B, an image 79b in which only the designated area is encrypted is generated by the processing shown in FIGS. 3 to 6, and the circumscribed frame creating unit 6 generates the image 79b. A frame 79c of a solid line for enclosing the periphery of is generated.

Therefore, in this example, since a part of the image is encrypted, it can be kept secret according to the purpose and value of the image, and the deterioration of the image quality of the non-encrypted image can be prevented.

Next, the operation when combining a plurality of encrypted images will be described with reference to FIG. First, when an original image is input (step 81), the original image is stored in the image storage unit 3 and then encrypted by the processing shown in FIGS. 3 to 7 (step 82). Then, the encrypted image is synthesized by performing an exclusive OR operation together with a decryption key derived according to the number of images already synthesized by the same method and the number of synthesized images and the order of processing, based on the password. (Step 83).

Next, in order to use the decryption key for decryption at the time of the next composition, the number of composites is counted (step 84). Is generated (step 86), and the number of combined images is recorded outside the frame of the solid line (step 87).

Next, with reference to FIG. 8B, an operation in the case of separating and decoding the composite image will be described. First, the number of combined images is identified (step 88), and a solid frame surrounding the encrypted area is identified (step 89). Next, the first encrypted image corresponding to the decryption key derived from the number of combined images, the order of the combined images, and the password is separated from the combined image (step 90), and the encrypted image is reproduced by decryption processing (step 90). Step 91). Then, by repeating the processing of steps 90 and 91, all the encrypted images are separated and reproduced (step 92).

Therefore, in this example, a plurality of encrypted images are combined and further encrypted, so that a large number of confidential information can be recorded on one sheet-shaped medium to increase the density of the information.

Next, referring to FIG. 9A, a case where an encrypted image 94 is spatially dispersed and combined with an unencrypted combined image 93 as shown in FIG. The operation will be described. First, the image 94 to be encrypted is encrypted (step 101), and then the encrypted image is randomly stored in a memory at an address based on a random number generated by a pseudo-random number generator (not shown) (step 102). , 103). Then, a composite image 95 as shown in FIG. 9C is generated by ORing this image and the non-encrypted image 96 (step 104). Note that an image 96 on the composite image 95 shown in FIG. 9C shows a case where the image 94 is encrypted and randomly arranged, and has the same properties as a white noise.

Next, the operation of separating the composite image 95 will be described with reference to FIG. 9B. First, when the composite image 95 is input (step 105), the non-encrypted image 93 passes through the low-pass filter. The random image 96 similar to a white noise is separated through a high-pass filter (steps 106 to 108). Then, the random image 96 is rearranged at the original position based on the random number at the time of synthesis and restored to an encrypted image (step 109), and the encrypted image is reproduced by a decryption process as described later. (Step 110).

Therefore, in this example, since the randomized encrypted image 96 and the non-encrypted image 93 are synthesized, there is an effect that the encrypted image is not known to a third party by the non-encrypted image.

Next, an operation for identifying an area of an encrypted image as shown in FIG. 10B will be described with reference to FIG. As described above, this region is surrounded by the solid line 118 in the horizontal direction and the solid line 119 in the vertical direction. Therefore, when the encrypted image is read by the reading unit 1 and stored in the image storage unit 3, first, the frame is The line segments 118 and 119 are determined by the line recognition unit 4 (step 111). Then, the line segments 118 and 119 are separated and extracted into a horizontal line segment 118 and a vertical line segment 119 (steps 112 and 113), and a circumscribed frame is determined based on a connection state of the line segments 118 and 119 (step 114).

Next, the amount of inclination in the horizontal direction (step 115) and the amount of inclination in the vertical direction (step 116) are calculated from the address of the circumscribed frame stored in the image storage unit 3, and the image storage unit 3 is calculated based on the amount of inclination. Is corrected by shifting and rotating the encrypted image stored in (step 117). Therefore, even if the encrypted image recorded on the sheet-like medium is rotated and read, the encrypted image can be corrected to the original position and correctly decoded.

As a method for recognizing the encrypted image, as shown in FIG. 11, by visually recording an arrow 119b indicating the origin 119a of the sheet medium, the owner can set the sheet medium correctly in the image reading unit 1. Thus, the encrypted image can be read in the correct direction. Also, by visually recording the mark 120 indicating that the image is an encrypted image, it is possible to notify that the image can be reproduced if the owner inputs a correct password. The arrow 119b and the mark 120 can be recorded on a sheet-like medium by storing each pattern in advance and developing it in the image storage unit 7 after creating a circumscription at the time of encryption.

(4) Since the direction of the encrypted image is added to the sheet-like medium, the operation for reading the encrypted image is simplified, and the accuracy of information transmission can be improved.

Here, as shown in the upper part of FIG. 12B, the high-frequency component 126 is missing in the encrypted image 125. Then, the encrypted image 125 recorded on the sheet medium is read again by the image reading unit 1 (step 121), converted into a digital signal by the A / D converter 2 (step 122), and stored in the image storage unit 3. (Step 123) As shown in the lower part of FIG. 12B, the change point and the change amount of the signal are extracted by the differential filter in both the horizontal and vertical directions, and the encrypted image 125 stored in the image storage unit 3 is extracted. By synthesizing, the image 127 in which the high frequency component is emphasized can be reproduced (step 124).

FIG. 1 is a block diagram showing an embodiment of an image encryption / reproduction device according to the present invention. 2 is a flowchart for explaining the operation of the image encryption / reproduction device of FIG. 1. FIG. 9 is an explanatory diagram illustrating an operation when an image is encrypted for each block. FIG. 9 is an explanatory diagram illustrating an operation when an image is encrypted for each pixel. FIG. 9 is an explanatory diagram illustrating an operation when an image is encrypted for each run length. FIG. 9 is an explanatory diagram illustrating an operation when encrypting a multi-valued image. FIG. 9 is an explanatory diagram showing an operation when selectively encrypting all or a part of an image. FIG. 9 is an explanatory diagram showing an operation in a case where a plurality of encrypted images are combined and a combined image is separated and decrypted. FIG. 9 is an explanatory diagram showing an operation in a case where an unencrypted image and an encrypted image are combined, and the combined image is separated and decrypted. FIG. 9 is an explanatory diagram showing an operation when an area of an encrypted image is identified. FIG. 4 is an explanatory diagram illustrating a method of recognizing an encrypted image. FIG. 4 is an explanatory diagram illustrating high-frequency emphasis when decrypting an encrypted image.

Explanation of reference numerals

REFERENCE SIGNS LIST 1 image reading unit 2 A / D converter 3, 7 image storage unit 4 frame line recognition unit 5 pixel rearrangement / reconstruction unit 6 circumscribed frame creation unit 8 output unit 9 password input unit 10 number analysis unit 11 encryption / Decryption control unit 12 Address calculation unit

Claims (8)

Reading means for optically reading an image recorded on a sheet-like medium,
Storage means for storing an image read by the reading means,
Input means for inputting a personal identification number and selecting encryption processing and decryption processing;
An address calculation unit that derives a solution of a polynomial operation based on the input password, and calculates a destination address from the derived solution,
When an encryption process is selected via the input unit, an encryption unit that encrypts an image stored in the storage unit based on the destination address calculated by the address calculation unit;
When decoding processing is selected via the input means, decoding means for decoding the image stored in the storage means based on the transfer destination address,
Output means for printing out and outputting the image encrypted by the encryption means or the image decrypted by the decryption means to a sheet-like medium,
An image encryption / reproduction device comprising: The encryption unit encrypts the image stored in the storage unit by replacing the image in a two-dimensional area for each pixel, and the decryption unit returns the image stored in the storage unit to the original position for each pixel. 2. The image encryption / reproduction apparatus according to claim 1, wherein the decryption is performed by: The encryption unit encrypts by calculating the run length of black and white of the image stored in the storage unit, replacing the same pixel in the entire area in a continuous range unit, and storing the same in the storage unit. 2. The apparatus according to claim 1, wherein the decryption unit decrypts the image stored in the storage unit by returning the image to an original position for each of the ranges. The encryption unit calculates a prediction error of the multi-valued image stored in the storage unit, quantizes the prediction error, and performs encryption by replacing the quantized data for each line. 2. The image encryption / reproduction according to claim 1, wherein the image stored in the means is dequantized into a prediction error by returning the quantized data to the original line, and a multi-valued image is decoded from the prediction error. apparatus. Means for designating a specific two-dimensional area within the image area for the image stored in the storage means, and inputting an instruction to encrypt or decrypt the two-dimensional area; The image of the two-dimensional area is encrypted and combined with an unencrypted image of another area, and the decryption unit decrypts the encrypted image of the two-dimensional area and combines it with the unencrypted image of the other area. 2. The image encryption / reproduction apparatus according to claim 1, wherein: The encrypting means adds an outer frame indicating the horizontal direction and the vertical direction of the area of the encrypted image, and the decrypting means returns the encrypted image stored in the storage means to the original direction by the outer frame. The image encryption / reproduction apparatus according to any one of claims 1 to 5, wherein decryption is performed afterwards. 6. The apparatus according to claim 1, wherein the encrypting means adds a direction of the encrypted image. 6. The image encryption / reproduction apparatus according to claim 1, wherein said decryption means emphasizes a high-frequency component of the encrypted image before decrypting the encrypted image.

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