Encryption and decryption system, decryption device, and decryption program

Abstract

To provide an encryption / decryption system, a decryption device and a decryption program for embedding information invisible to a human being in an image visible to the human being, and for reading the invisible information without making it necessary to add any component as compared with a conventional technology.SOLUTION: A smartphone 1 as a decoding device includes reading means C11 for reading an embedded image in which a pattern image in which a first periodic pattern is allocated to a place where a cell value of a two dimensional code is high and a second periodic pattern is allocated to a place where the cell value is low is embedded, ternarization means C12 for reducing an influence of the embedded image from a read image 51, emphasis processing means C13 for emphasizing one of the first periodic pattern and the second periodic pattern and attenuating the other with respect to an image after ternarization processing, interference-fringe elimination processing means C14 for eliminating an interference-fringe from the image after the emphasis processing, and decoding means C15 for decoding the two dimensional code from the image subjected to the interference-fringe elimination processing.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to an encryption / decryption system, a decoding device, and a decoding program that encrypt and decrypt information, and in particular to an encryption / decryption system, a decoding device, and a decoding program that can encrypt and embed information in images attached to visible objects such as merchandise, goods, advertisements, bulletin boards, and digital signage, and decrypt the embedded encrypted information. [Background technology]

[0002] Barcodes and two-dimensional codes are known as technologies for encrypting information. When an encrypted image such as a barcode is printed on a product, a notice, or an advertisement, it is common to separate the barcode into a dedicated space to make it easier to read. However, reserving a dedicated space for the barcode can lead to problems such as a loss of aesthetic appearance and design of the product.

[0003] The techniques described in Patent Documents 1 and 2 and Non-Patent Documents 1 and 2 are known as techniques for embedding some information into an image visible to humans (an embedded image) in a form that is difficult for humans to see. Patent Document 1 (JP 2004-328496 A) describes a technique for embedding a two-dimensional code (sub-information) in a face image (main information) for personal authentication by applying a digital watermarking technique. In the technique described in Patent Document 1, positioning marks (204) used for complementing the sub-information are recorded in the four corners of the face image (202) for personal authentication.

[0004] Patent Document 2 (JP 2007-164715 A) describes a technique for printing invisible information such as a two-dimensional code on a printed material using stealth ink, superimposing it on visible information. In Patent Document 2, the printed invisible information is read by illuminating the stealth ink with an ultraviolet light-emitting diode (a so-called black light).

[0005] Non-Patent Document 1 describes a technology in which an original image is divided into multiple blocks vertically and horizontally, two 2D sign pattern images with 90-degree rotational symmetry are combined in the raster scan order of the blocks to generate a watermark pattern, and the watermark pattern, which has the same vertical and horizontal dimensions as the original image, is multiplied by an embedding strength and embedded into the original image. Non-Patent Document 1 embeds information after adding (encoding) an error correction code to a binary code (watermark information). Furthermore, in Non-Patent Document 1, as in Patent Document 1, a QR (registered trademark) code finder pattern and alignment pattern are formed at the four corners of the watermarked image to deal with out-of-sync and projection distortion due to the shooting angle.

[0006] Non-Patent Document 2, like Non-Patent Document 1, describes a technique for embedding a watermark pattern in an original image according to the raster scan order. In Non-Patent Document 2, a captured watermarked image is compared with an image registered in a database to obtain the coordinates of the four corners, and then a planar projective transformation is performed based on the coordinates of the four corners, thereby addressing projection distortion due to the shooting angle without the need to add a finder pattern or alignment pattern as in Non-Patent Document 1. Note that Non-Patent Document 2, like Non-Patent Document 1, embeds information after adding (encoding) an error correction code to a binary code. Note that the technique for embedding information after adding (encoding) an error correction code to a binary code is disclosed in, for example, Non-Patent Document 3, etc., and is publicly known, so a detailed description thereof will be omitted. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-328496 ("0022"-"0023", Figure 2) [Patent Document 2] JP 2007-164715 A ("0014" to "0019") [Non-patent literature]

[0008] [Non-Patent Document 1] Kenji Yamanaka and two others, "Study on Digital Watermarking Methods for Printed Materials," 2013, The Institute of Electronics, Information and Communication Engineers, SCIS2013 The 30th Symposium on Cryptography and Information Security, Kyoto, Japan, Jan. 22-25, 2013, pp. 1-7 [Non-patent document 2] Hiroaki Ogawa and two others, "A digital watermarking method that can extract watermarks from printed materials without position detection markers using image search," 2016, The Institute of Electronics, Information and Communication Engineers, SCIS2016 2016 Symposium on Cryptography and Information Security, Kumamoto, Japan, Jan. 19-22, 2016, pp. 1-7 [Non-patent document 3] Takao Nakamura and three others, "High-speed watermark detection method from analog images using camera-equipped mobile phones," December 2004, IEICE Transactions on Electrical, Information and Communication Engineers, Vol. J87-D-II, No. 12, pp. 2145-2155 Summary of the Invention [Problem to be solved by the invention]

[0009] (Problems with the prior art) The technology of adding a positioning mark or finder pattern as in Patent Document 1 and Non-Patent Document 1 still has the problem of impairing the aesthetic appearance of the product. The technology in Patent Document 2 requires a black light for reading, which increases the number of parts and costs. In particular, the embedded information cannot be obtained by simply reading the image with a camera built into a mobile phone or smartphone, which poses a problem in terms of convenience. The technology described in Non-Patent Document 2 involves matching with a database, which requires communication with the database, registration of the watermarked image and coordinates in the database, and management and maintenance of the database, which results in problems such as an increase in the overall configuration and overall costs.

[0010] The technical object of the present invention is to embed information that is invisible to humans in an image that is visible to humans, while making it possible to read the invisible information without requiring the addition of any additional components compared to conventional techniques. [Means for solving the problem]

[0011] In order to solve the above technical problem, the encryption / decryption system of the invention described in claim 1 is: an encryption means for encrypting the embedding target information into a two-dimensional code; a pattern image conversion means for converting the image of the two-dimensional code into a pattern image in which, according to cell values ​​of the image of the two-dimensional code, a first periodic pattern is assigned to a portion where the cell value is higher than a predetermined first threshold value, and a second periodic pattern is assigned to a portion where the cell value is lower than the first threshold value; an embedding means for embedding the information to be embedded in the image to be embedded by superimposing the pattern image on the image to be embedded at a predetermined transparency; a reading means for reading the embedded image in which the pattern image is embedded; a ternarization processing means for converting each pixel value of the read image read by the reading means into three values ​​of positive, zero, and negative based on each pixel value of the read image, thereby reducing the influence of the embedded image; an enhancement processing means for performing a process on the image converted by the ternary processing means to enhance one of the first periodic pattern and the second periodic pattern and attenuate the other; an interference fringe removal processing means for removing interference fringes of the first periodic pattern and the second periodic pattern from the image processed by the enhancement processing means; a decoding means for reading the two-dimensional code from the image processed by the interference fringe removal processing means and decoding the two-dimensional code to obtain the information to be embedded; The present invention is characterized by the following features.

[0012] The invention described in claim 2 is the encryption / decryption system described in claim 1, the interference fringe removal processing means for removing interference fringes of the first periodic pattern and the second periodic pattern by applying a Roberts filter to the image processed by the enhancement processing means in order to extract edges of the image, binarizing each pixel of the image after application of the Roberts filter based on a predetermined threshold, and applying an averaging filter to the binarized image in order to reduce a difference in pixel values ​​between adjacent pixels; The present invention is characterized by the following features.

[0013] The invention described in claim 3 is the encryption / decryption system described in claim 1, The two-dimensional code is a QR (registered trademark) code. The present invention is characterized by the following features.

[0014] In order to solve the above technical problem, the decoding device of the invention described in claim 4 comprises: a reading means for reading the embedded image in which a two-dimensional code in which information to be embedded is encrypted is converted into a pattern image in which a first periodic pattern is assigned to a portion where the cell value of the two-dimensional code image is higher than a predetermined first threshold value and a second periodic pattern is assigned to a portion where the cell value is lower than the first threshold value, according to the cell values ​​of the two-dimensional code image, and the converted pattern image is embedded in the embedded image; a ternarization processing means for converting each pixel value of the read image read by the reading means into three values ​​of positive, zero, and negative based on each pixel value of the read image, thereby reducing the influence of the embedded image; an enhancement processing means for performing a process on the image converted by the ternary processing means to enhance one of the first periodic pattern and the second periodic pattern and attenuate the other; an interference fringe removal processing means for removing interference fringes of the first periodic pattern and the second periodic pattern from the image processed by the enhancement processing means; a decoding means for reading the two-dimensional code from the image processed by the interference fringe removal processing means and decoding the two-dimensional code to obtain the information to be embedded; The present invention is characterized by the following features.

[0015] The invention described in claim 5 is the decoding device described in claim 4, a display means for displaying the embedding target information decoded by the decoding means; The present invention is characterized by the following features.

[0016] In order to solve the above technical problem, the decoding program of the invention described in claim 6 is: Computer, a ternarization processing means for converting an embedded image into a pattern image in which a two-dimensional code in which information to be embedded is encrypted is converted into a pattern image in which a first periodic pattern is assigned to areas where the cell values ​​of the two-dimensional code image are higher than a predetermined first threshold value and a second periodic pattern is assigned to areas where the cell values ​​are lower than the first threshold value, and for converting each pixel value into three values: positive, zero, and negative, based on each pixel value of a read image in which the embedded image is read, thereby reducing the influence of the embedded image; an enhancement processing means for performing processing on the image converted by the ternary processing means to enhance one of the first periodic pattern and the second periodic pattern and attenuate the other; an interference fringe removal processing means for removing interference fringes of the first periodic pattern and the second periodic pattern from the image processed by the enhancement processing means; a decoding means for reading the two-dimensional code from the image processed by the interference fringe removal processing means and decoding the two-dimensional code to obtain the embedding target information; The present invention is characterized in that it functions as a [Effects of the Invention]

[0017] According to the inventions described in claims 1 and 6, it is possible to embed information that is invisible to humans in an image that is visible to humans, and to read the invisible information without requiring the addition of any components, as compared with the prior art. According to the invention of claim 2, after applying a Roberts filter and binarizing, an averaging filter can be applied to remove interference fringes. According to the invention of claim 3, it is possible to reduce the failure to read invisible information by utilizing the error correction function of the QR (registered trademark) code itself. According to the inventions set forth in claims 4 and 5, information that is invisible to humans and that is embedded in an image that is visible to humans can be read without requiring any additional components, as compared to the prior art. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is an explanatory diagram of the entire encryption / decryption system according to the first embodiment of the present invention. [Figure 2] FIG. 2 is a functional block diagram of the server in the encryption / decryption system of the first embodiment. [Figure 3] 3A and 3B are explanatory diagrams of examples of periodic patterns according to the first embodiment, where FIG. 3A is an explanatory diagram of a first periodic pattern and FIG. 3B is an explanatory diagram of a second periodic pattern. [Figure 4] 4A and 4B are explanatory diagrams of an example of pattern image conversion in the first embodiment, where FIG. 4A is an explanatory diagram of an example of a two-dimensional code before conversion, and FIG. 4B is an explanatory diagram of an example of a pattern image after pattern image conversion. [Figure 5] FIG. 5 is an explanatory diagram of embedding a pattern image, where FIG. 5A is an explanatory diagram of an example of an embedded image, and FIG. 5B is an explanatory diagram of an example of an outer surface image after the pattern image has been embedded. [Figure 6] FIG. 6 is a functional block diagram of the decryption device in the encryption / decryption system of the first embodiment. [Figure 7] 7A and 7B are explanatory diagrams of the ternarization process of the first embodiment, in which FIG. 7A is an explanatory diagram of an example of a read image, and FIG. 7B is an explanatory diagram of an image after the ternarization process. [Figure 8]8A is an explanatory diagram of an example of an image after ternarization processing, FIG. 8B is an explanatory diagram of an example of the enhancement processing, and FIG. 8C is an explanatory diagram of an image after enhancement processing. [Figure 9] 9A is an explanatory diagram of an example of an image after enhancement processing, FIG. 9B is an explanatory diagram of an image after application of an edge filter, FIG. 9C is an explanatory diagram of an image after binarization processing, and FIG. 9D is an explanatory diagram of an image after application of an averaging filter. DETAILED DESCRIPTION OF THE INVENTION

[0019] Next, specific examples of embodiments of the present invention (hereinafter referred to as examples) will be described with reference to the drawings, but the present invention is not limited to the following examples. In the following description using the drawings, illustrations of components other than those necessary for the description are omitted as appropriate to facilitate understanding. [Example]

[0020] FIG. 1 is an explanatory diagram of the entire encryption / decryption system according to the first embodiment of the present invention. 1, an encryption / decryption system S of the present invention has a smartphone 1 as an example of a decryption device. The smartphone 1 of Example 1 has a main body 2, a touch panel 3 as an example of a display means and an example of an input means, an outer camera 4 as an example of a reading device, and an inner camera 5 as an example of a reading device.

[0021] In the encryption / decryption system S, exterior patterns 11a-13a are applied as an example of an exterior image to the exterior surfaces of products 11-13, which are examples of objects. Examples of products 11-13 include a triangular prism-shaped sandwich 11, a rectangular parallelepiped confectionery box 12, and a cylindrical beverage bottle 13. The products are not limited to food products, but can be any kind of item. Furthermore, the shapes of the products are not limited to those exemplified, but can be any shape, such as a bag-shaped container, a can, or a bottle. Furthermore, although the exterior patterns 11a-13a are applied to the exterior surfaces of product packaging in the example, the patterns are not limited to this, and can also be applied to patterns applied directly to the exterior surfaces of the products themselves.

[0022] The encryption / decryption system S also has a server 21 as an example of an information processing device. The server 21 is configured to be able to send and receive information to and from the smartphone 1 via a communication line 20. The server 21 has a display 22 as an example of a display means, and a keyboard 23 and a mouse 24 as examples of an input means. A printer 26 capable of printing the exterior patterns 11a to 13a is also connected to the server 21.

[0023] (Explanation of the control unit of the server 21 in the first embodiment) FIG. 2 is a functional block diagram of the server in the encryption / decryption system of the first embodiment. In FIG. 2, the control unit 21a of the server 21 of the first embodiment is composed of a computer device having an I / O (input / output interface) that inputs and outputs signals from and to the outside and adjusts input / output signal levels, a ROM (read-only memory) that stores programs and data for performing necessary startup processing, a RAM (random access memory) that temporarily stores necessary data and programs, a CPU (central processing unit) that performs processing according to the startup program stored in the ROM, etc., and a clock oscillator, etc., and can realize various functions by executing the programs stored in the ROM and RAM, etc. The control unit 21a stores basic software for controlling basic operations, a so-called operating system OS, an encryption program P1 as an example of an application program, and other software (not shown).

[0024] (Elements connected to the control unit 21a in the first embodiment) Output signals from signal output elements such as a keyboard 23 and a mouse 24 are input to the control unit 21a. Furthermore, the control unit 21a of the first embodiment outputs control signals to controlled elements such as the display 22 and the printer 26.

[0025] (Function of control unit 21a) The encryption program P1 of the control unit 21a of the first embodiment has the following functional means (program modules) C1 to C3.

[0026] The encryption means C1 encrypts the information to be embedded into a two-dimensional code as an example of binary data. The encryption means C1 of the first embodiment encrypts information about each of the products 11 to 13 (such as the product name, ingredient names, expiration date, allergy information, and the URL of the information disclosure website) as the information to be embedded into a QR (registered trademark) code as an example of a two-dimensional code. Note that the encryption of QR (registered trademark) codes is well known and therefore will not be described in detail.

[0027] 3A and 3B are explanatory diagrams of examples of periodic patterns according to the first embodiment, where FIG. 3A is an explanatory diagram of a first periodic pattern and FIG. 3B is an explanatory diagram of a second periodic pattern. 4A and 4B are explanatory diagrams of an example of pattern image conversion in the first embodiment, where FIG. 4A is an explanatory diagram of an example of a two-dimensional code before conversion, and FIG. 4B is an explanatory diagram of an example of a pattern image after pattern image conversion. The pattern image conversion means C2 converts the two-dimensional code created by the encryption means C1 into a pattern image in which a first periodic pattern is assigned to areas where the cell value is higher than a predetermined first threshold, and a second periodic pattern is assigned to areas where the cell value is lower than the first threshold, depending on the cell value. In FIG. 3, in the first embodiment, a sine wave (sine wave) with a wave progression direction from upper left to lower right as shown in FIG. 3A is used as an example of the first periodic pattern, and a sine wave (sine wave) with a wave progression direction from lower left to upper right as shown in FIG. 3B is used as an example of the second periodic pattern. Note that each periodic pattern is not limited to the example shown, and the first periodic pattern and the second periodic pattern may be combined in reverse, or the first periodic pattern may be a sine wave with a top-to-bottom direction and the second periodic pattern may be a sine wave with a left-to-right direction. It is also possible to adopt a periodic pattern other than a sine wave. Note that when a periodic pattern different from the periodic pattern exemplified in the embodiment is adopted, it may be necessary to adjust or change the filter processing used during decoding (described later) as appropriate (for example, not use a Roberts filter, etc.) depending on the periodic pattern to be adopted.

[0028] The pattern image conversion means C2 identifies the cell values, i.e., the black portions (cell values ​​"1") and white portions (cell values ​​"0") of the two-dimensional code 41 shown in FIG. 4A. The pattern image conversion means C2 then assigns a first periodic pattern to areas (bright value areas) where the cell value ("1" or "0") is higher than a first threshold value (e.g., "0.5"). The pattern image conversion means C2 also assigns a second periodic pattern to areas (dark value areas) where the cell value ("1" or "0") is lower than the first threshold value (e.g., "0.5"). In this way, the pattern image conversion means C2 converts the two-dimensional code 41 shown in FIG. 4A into the pattern image 42 shown in FIG. 4B.

[0029] FIG. 5 is an explanatory diagram of embedding a pattern image, where FIG. 5A is an explanatory diagram of an example of an embedded image, and FIG. 5B is an explanatory diagram of an example of an outer surface image after the pattern image has been embedded. The embedding unit C3 embeds the pattern image 42 converted by the pattern image conversion unit C2 into the embedded image to generate an exterior pattern (11a-13a). The embedding unit C3 of the first embodiment embeds the pattern image 42 by superimposing it on the embedded image 43 at a predetermined transparency (transmittance), for example. For example, by superimposing the embedded image 43 of FIG. 5A and the pattern image 42 of FIG. 4B at an image density of 1:0.2, an exterior pattern is generated in which the pattern image 42 is embedded in the embedded image 43 at a predetermined transparency (0.2). Depending on the size of the exterior pattern, the pattern image 42 can be set to the maximum size that does not result in partial loss of the square two-dimensional code 41, but is not limited to this. For example, a configuration is possible in which pieces of a predetermined size (e.g., 2 cm x 2 cm) repeatedly arranged vertically and horizontally are embedded in the embedded image 43. The exterior patterns 11a to 13a generated for the products 11 to 13, respectively, are applied (printed or printed out) by a printer 26 to the packaging and labels of the products 11 to 13.

[0030] (Explanation of the control unit of the smartphone 1 according to the first embodiment) FIG. 6 is a functional block diagram of the decryption device in the encryption / decryption system of the first embodiment. 6, the control unit 1a of the smartphone 1 of Example 1 is configured with an I / O (input / output interface) that inputs and outputs signals to and from the outside and adjusts input / output signal levels, a ROM (read-only memory) that stores programs and data for performing necessary startup processing, a RAM (random access memory) that temporarily stores necessary data and programs, a CPU (central processing unit) that performs processing according to the startup program stored in the ROM, etc., a computer device having a clock oscillator, etc., a so-called microcomputer. Various functions can be realized by executing the programs stored in the ROM and RAM, etc. The control unit 1a stores basic software for controlling basic operations, a so-called operating system OS, a decoding program P2 as an example of an application program, and other software (not shown).

[0031] (Elements connected to the control unit 1a in the first embodiment) The control unit 1a receives output signals from signal output elements such as a touch panel 3, an outer camera 4, an inner camera 5, and buttons (not shown). Furthermore, the control unit 1a of the first embodiment outputs a control signal to controlled elements such as the touch panel 3 and an external output terminal (not shown).

[0032] (Function of control unit 1a) The decoding program P2 of the control unit 1a of the first embodiment has the following functional means (program modules) C11 to C16. The reading means C11 reads the exterior patterns 11a to 13a of the products 11 to 13 based on the image captured by the outer camera 4 or the inner camera 5. That is, it reads the exterior patterns 11a to 13a, which are images in which the pattern image 42 is embedded in the embedded image 43. In the first embodiment, the reading means C11 reads the image as a monochrome (single color) image. Note that the image reading is not limited to monochrome, and a full color image can also be read.

[0033] 7A and 7B are explanatory diagrams of the ternarization process of the first embodiment, in which FIG. 7A is an explanatory diagram of an example of a read image, and FIG. 7B is an explanatory diagram of an image after the ternarization process. The ternarization means C12 converts each pixel value of the read image 51, which is read by the reading means C11, into three values—positive, zero, and negative—based on the pixel values ​​of the read image 51, thereby reducing the influence of the embedded image 43. The ternarization means C12 of the first embodiment performs edge processing in image processing. Specifically, the edge processing applies a filter to the image to output a ternary pixel value—positive, negative, or zero. Note that it is also possible to convert each pixel value (brightness value) of the read image 51 into three values—“+ (positive),” “0,” and “− (negative)”—based on a predetermined second threshold. Therefore, as shown in FIG. 7B , the influence of the embedded image 43 is reduced in the converted ternarized image 52 (the embedded image 43 is almost completely removed), resulting in an image similar to the pattern image 42.

[0034] 8A is an explanatory diagram of an example of an image after ternarization processing, FIG. 8B is an explanatory diagram of an example of the enhancement processing, and FIG. 8C is an explanatory diagram of an image after enhancement processing. The enhancement processing means C13 performs processing on the image (ternarized image 52) converted by the ternarization means C12, emphasizing either the first periodic pattern or the second periodic pattern and attenuating the other. In Example 1, a filter (enhancement filter) is applied to each pixel of the ternarized image 52 so as to emphasize the first periodic pattern and attenuate the second periodic pattern. Thus, the ternarized image 52 illustrated in FIG. 8A can be converted into an enhanced image 53 as shown in FIG. 8C by applying a filter F that emphasizes the first periodic pattern and attenuates the second periodic pattern as shown in FIG. 8B. Therefore, the two-dimensional code 41 appears to emerge in the enhanced image 53. While it is possible to attempt to decode the two-dimensional code 41 at the enhanced image 53 stage, decoding at this stage is extremely difficult because the interference fringes are also recognized as part of the two-dimensional code pattern.

[0035] 9A is an explanatory diagram of an example of an image after enhancement processing, FIG. 9B is an explanatory diagram of an image after application of an edge filter, FIG. 9C is an explanatory diagram of an image after binarization processing, and FIG. 9D is an explanatory diagram of an image after application of an averaging filter. The interference fringe removal processing means C14 has a Roberts filter application means C14a, a binarization means C14b, and an averaging filter application means C14c, and removes interference fringes of the first periodic pattern and the second periodic pattern, so-called moire, from the image (enhanced processed image 53) processed by the enhancement processing means C13. A Roberts filter application means C14a, which is an example of an edge filter application means, applies a Roberts filter, which is an example of an edge filter, to the enhancement-processed image 53. Since the Roberts filter is a conventionally known example of an edge filter, a detailed description thereof will be omitted. By applying the Roberts filter, the enhancement-processed image 53 shown in FIG. 9A is converted into an edge-filtered image 54, as shown in FIG. 9B. In FIG. 9B, the edge-filtered image 54 appears as if it has been entirely filled in compared to the enhancement-processed image 53, resulting in a reduction in diagonal moire.

[0036] The binarization means C14b binarizes each pixel of the image (edge-filtered image 54) after the Roberts filter application means C14a has applied the Roberts filter, based on a predetermined threshold. In the first embodiment, as an example, if white (the minimum pixel value) is set to "0" and black (the maximum pixel value) is set to "1," the threshold can be set to "0.8" or "0.9." The binarization means C14b converts the edge-filtered image 54, which appears entirely filled in as shown in FIG. 9B, into a binarized image 56 (see FIG. 9C) in which the black and white portions of the two-dimensional code 41 are clearly defined. The averaging filter application means C14c applies an averaging filter to the binarized image (binarized image 56) to reduce (average) the difference in pixel values ​​between adjacent pixels. Note that the averaging filter itself is conventionally known, so a detailed description thereof will be omitted. By applying the averaging filter, the binarized image 56 shown in FIG. 9C is converted into the moiré-removed image 57 shown in FIG. 9D. By applying the averaging filter, the diagonal moiré is further reduced in the moiré-removed image 57 compared to the binarized image 56.

[0037] The decoding means C15 reads the two-dimensional code 41 from the moire-removed image 57, decodes the two-dimensional code, and acquires the information to be embedded. The decoding means C15 of the first embodiment decodes a QR (registered trademark) code, which is an example of the two-dimensional code 41, and acquires the information to be embedded. Note that since the decoding of the QR (registered trademark) code is conventionally known, a detailed description thereof will be omitted. The decoding result display means C16 displays the embedding target information decoded by the decoding means C15 on the touch panel 3, which is an example of a display means.

[0038] (Function of Example 1) In the encryption / decryption system S of Example 1 having the above configuration, a two-dimensional code 41 is converted into a pattern image 42, and the image embedded in the embedded image 43 is applied to the outer surfaces of the products 11-13 as exterior patterns 11a-13a. Therefore, the pattern image 42 is less recognizable to humans than the embedded image 43. In other words, the two-dimensional code 41 is embedded invisibly in the embedded image 43, which is a visible image. In particular, although unencrypted character information or graphic information can also be used as embedded information, encrypted two-dimensional codes can embed more information than unencrypted codes. In other words, a larger amount of embedded information can be embedded. Furthermore, in the encryption / decryption system S of the first embodiment, there is no need to reserve a space dedicated to the barcode, as compared to conventional cases where the barcode is directly attached to the exterior. Furthermore, in the first embodiment, no positioning marks or the like as in Patent Document 1 and Non-Patent Document 1 are generated. Therefore, the aesthetic appearance of the exterior of the products 11 to 13 is prevented from being impaired.

[0039] Furthermore, in the encryption / decryption system S of Example 1, when the exterior patterns 11a-13a are read by the cameras 4 and 5 of the smartphone 1, the embedded image 43 is almost completely removed by the ternarization means C12, the two-dimensional code 41 emerges by the enhancement processing means C13, and the interference fringes (moiré) are removed by the interference fringe removal processing means C14. The two-dimensional code 41 is then decoded from the moiré-removed image 57 from which the interference fringes have been removed, thereby acquiring and displaying the embedded information. Therefore, Example 1 does not require the addition of dedicated components such as a black light as in Patent Document 2, and can acquire the embedded information that is invisible to the general cameras 4 and 5 without requiring additional components. This improves convenience. Furthermore, decryption does not require collation with a database or the like, and can be executed by the decryption program P2 of the smartphone 1, eliminating the expense and effort required for a database.

[0040] In particular, due to the relationship between the two periodic patterns used when converting into the pattern image 42, simply reducing the influence of the embedded image 43 by ternarization processing leaves the influence of interference fringes, making it difficult to mechanically decode by the decoding means C15. In contrast, in the first embodiment, the interference fringes are removed by the interference fringe removal processing means C14, making it possible to decode by the decoding means C15. Furthermore, in the first embodiment, a QR (registered trademark) code is used as an example of the two-dimensional code 41. The QR (registered trademark) code itself has an advanced error correction function, and even if a part is missing when read or a defective part occurs in part of the two-dimensional code 41 during the processing by the ternarization means C12 to the interference fringe removal processing means C14, the error correction function can correct it. Therefore, compared to when the QR (registered trademark) code is not used, it is possible to embed a large amount of information and it is easy to decode by the decoding means C15. Therefore, even if the ambient light or the shooting method changes, decoding is easy using the error correction function.

[0041] (Example of change) Although the embodiments of the present invention have been described above in detail, the present invention is not limited to the above embodiments and various modifications can be made within the scope of the gist of the present invention as set forth in the claims. Modifications (H01) to (H05) of the present invention are exemplified below. (H01) In the above embodiment, the server 21 and the smartphone 1 are connected via the communication line 20, but a non-connected configuration is also possible. Also, in the first embodiment, the smartphone 1 is configured to perform centralized processing using the decoding program P2, but the present invention is not limited to this. In a configuration in which the smartphone 1 is connected to the server 21 via the communication line 20, some or all of the ternarization means C12 to the decoding means C15 of the decoding program P2 can be processed on the server 21 side, that is, a distributed processing configuration is also possible.

[0042] (H02) In the above-described embodiments, the specific numerical values ​​exemplified can be changed arbitrarily according to the design, specifications, etc. (H03) In the above embodiment, the interference fringe removal processing means C14 uses a Roberts filter application means C14a, a binarization means C14b, and an averaging filter application means C14c, but is not limited to this. For example, any interference fringe removal process that can remove moire to the extent that it can be decoded from the enhancement-processed image 53 can be applied. For example, a process for removing interference fringes using deep learning, a blurring process, or the like can be used. (H04) In the above embodiment, the two-dimensional code 41 is encrypted into a QR (registered trademark) code, but this is not limiting. For example, any encryption method, such as a barcode as an example of binary data, can be used.

[0043] (H05) In the above embodiment, the smartphone 1 is given as an example of a decoding device, but the present invention is not limited to this. For example, the present invention can be applied to any device equipped with a reading means such as a camera or scanner, such as a tablet terminal, a laptop computer, a smart camera, a network camera, a scanner capable of reading codes, or a cash register. [Explanation of symbols]

[0044] 1...Decoding device, 3...display means, 11~13...products, 41...2D code, 42...Pattern image, 43...embedded image, 51...Read image, 52...Image after conversion by the ternary processing means, 53...Image after processing by enhancement processing means, 54...Image after applying Roberts filter, 56...Image after binarization, 57...Image processed by interference fringe removal processing means, C1...encryption means, C2: Pattern image conversion means, C3: Embedding means, C11...Reading means, C12...Ternarization means, C13...emphasis processing means, C14...interference fringe removal processing means, C15...decryption means, P2: Decryption program, S...Encryption / decryption system.

Claims

1. an encryption means for encrypting the embedding target information into a two-dimensional code; a pattern image conversion means for converting the image of the two-dimensional code into a pattern image in which, according to cell values ​​of the image of the two-dimensional code, a first periodic pattern is assigned to a portion where the cell value is higher than a predetermined first threshold value, and a second periodic pattern is assigned to a portion where the cell value is lower than the first threshold value; an embedding means for embedding the information to be embedded in the image to be embedded by superimposing the pattern image on the image to be embedded at a predetermined transparency; a reading means for reading the embedded image in which the pattern image is embedded; a ternarization processing means for converting each pixel value of the read image read by the reading means into three values ​​of positive, zero, and negative based on each pixel value of the read image, thereby reducing the influence of the embedded image; an enhancement processing means for performing a process on the image converted by the ternary processing means to enhance one of the first periodic pattern and the second periodic pattern and attenuate the other; an interference fringe removal processing means for removing interference fringes of the first periodic pattern and the second periodic pattern from the image processed by the enhancement processing means; a decoding means for reading the two-dimensional code from the image processed by the interference fringe removal processing means and decoding the two-dimensional code to obtain the information to be embedded; An encryption / decryption system comprising:

2. the interference fringe removal processing means for applying a Roberts filter to the image processed by the enhancement processing means in order to extract edges of the image, binarizing each pixel of the image after application of the Roberts filter based on a predetermined threshold, and applying an averaging filter to the binarized image in order to reduce a difference in pixel values ​​between adjacent pixels, thereby removing interference fringes of the first periodic pattern and the second periodic pattern; 2. The encryption / decryption system according to claim 1, comprising:

3. The two-dimensional code is a QR (registered trademark) code.

2. The encryption / decryption system according to claim 1, comprising:

4. a reading means for converting a two-dimensional code in which information to be embedded is encrypted into a pattern image in which a first periodic pattern is assigned to a portion where the cell value is higher than a predetermined first threshold value according to a cell value of an image of the two-dimensional code, and a second periodic pattern is assigned to a portion where the cell value is lower than the first threshold value, and the pattern image is embedded in an image to be embedded, and reading the image to be embedded in which the pattern image is embedded; a ternarization processing means for converting each pixel value of the read image read by the reading means into three values ​​of positive, zero, and negative based on each pixel value of the read image, thereby reducing the influence of the embedded image; an enhancement processing means for performing a process on the image converted by the ternary processing means to enhance one of the first periodic pattern and the second periodic pattern and attenuate the other; an interference fringe removal processing means for removing interference fringes of the first periodic pattern and the second periodic pattern from the image processed by the enhancement processing means; a decoding means for reading the two-dimensional code from the image processed by the interference fringe removal processing means and decoding the two-dimensional code to obtain the information to be embedded; A decoding device comprising:

5. a display means for displaying the embedding target information decoded by the decoding means; 5. The decoding device according to claim 4, further comprising:

6. Computer, a ternarization processing means for converting an embedded image into a pattern image in which a two-dimensional code in which information to be embedded is encrypted is converted into a pattern image in which a first periodic pattern is assigned to portions where the cell values ​​of the two-dimensional code image are higher than a predetermined first threshold value and a second periodic pattern is assigned to portions where the cell values ​​are lower than the first threshold value, in accordance with the cell values ​​of the image of the two-dimensional code, and converting each pixel value into three values: positive, zero, and negative, based on the pixel values ​​of an image obtained by reading the embedded image, thereby reducing the influence of the embedded image; an enhancement processing means for performing processing on the image converted by the ternary processing means to enhance one of the first periodic pattern and the second periodic pattern and attenuate the other; an interference fringe removal processing means for removing interference fringes of the first periodic pattern and the second periodic pattern from the image processed by the enhancement processing means; a decoding means for reading the two-dimensional code from the image processed by the interference fringe removal processing means and decoding the two-dimensional code to obtain the embedding target information; A decoding program characterized by causing the program to function as a

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