KR20190139483A - Method and apparatus for multiple image encryption and decryption - Google Patents

Abstract

A method and apparatus for multiple image encryption and decryption are disclosed. According to an embodiment of the present invention, the apparatus for multiple image encryption obtains secret images and private keys generated from multiple original images, respectively, performs a phase shift on the secret images to generate phase coded images from the secret images, and may generate an encrypted image that encrypts the multiple original images by overlapping the phase coded images.

Description

METHOD AND APPARATUS FOR MULTIPLE IMAGE ENCRYPTION AND DECRYPTION}

The embodiments below relate to a method and apparatus for encrypting and decrypting multiple images.

Many techniques for encrypting image or digital information have been proposed. A technique for restoring the original image by dividing the original image into a plurality of masks by using the interference principle and by overlapping the divided masks has been proposed. Existing cryptography requires iterative computer computations, which limits the efficiency and speed of processing.

Various multi-image encryption schemes have been proposed, which have a problem that there is a silhouette problem and the influence of crosstalk between images. In addition, the technique using the orthogonal code has a limitation that is applicable only to the binary image. There is a need for an efficient encryption technique that can increase the performance of encryption and decryption and reduce computational complexity.

An encryption and decryption method according to an embodiment is intended to perform image encryption and decryption in which there is substantially no difference between original information and decrypted information.

An encryption and decryption method according to an embodiment is to propose a technique that is easily implemented digitally or optically.

An encryption and decryption method according to an embodiment is intended to minimize the influence of crosstalk between images and provide robust encryption and decryption performance.

According to an embodiment, a method of encrypting a multi-image may include obtaining secret images and private keys generated from multiple original images, respectively; Performing phase shift on the secret images to generate phase coded images from the secret images; And overlapping the phase coded images to generate an encrypted image obtained by encrypting the multiple original images.

According to an embodiment, the generating of the phase coded images may include performing a phase shift of the secret images based on a matrix satisfying an orthogonality condition.

를 만족하는 n차 하다마드 행렬(Hadamard matrix) H이고, 상기

는 상기 H의 전치행렬이고, 상기 I는 n x n의 항등 행렬이고, 상기 H의 원소들은 1 또는 -1일 수 있다.According to one embodiment, the matrix is

Is an n-order Hadamard matrix H satisfying

Is a transpose matrix of H, I is an identity matrix of nxn, and the elements of H may be 1 or -1.

According to an embodiment, the generating of the phase coded images may include shifting the phases of the pixels included in the secret images by 0 degrees or 180 degrees using a binary phase mask. have.

According to an embodiment, the generating of the phase coded images may include: dividing pixels of the secret images into segments; And applying the elements of the Hadamard matrix to the segments, respectively, to shift the phases of the segments, wherein generating the encrypted image overlaps the shifted phases by segment. It may include the step of generating.

According to an embodiment, the secret images include a first secret image, a second secret image, a third secret image, and a fourth secret image, and the generating of the phase coded images may be performed by (m) of the first secret image. dividing n) of pixels into four first segments; Dividing the pixel of (m, n) of the second secret image into four second segments; Dividing the pixel of (m, n) of the third secret image into four third segments; Dividing the pixel of (m, n) of the fourth secret image into four fourth segments; Applying respective elements of a first row in a 4 x 4 Hadamard matrix to the first segments to shift the first phases of the first segments; Applying respective elements of a second row in the Hadamard matrix to the second segments to shift the second phases of the second segments; Applying respective elements of a third row in the Hadamard matrix to the third segments to shift the third phases of the third segments; And applying the elements of the fourth row in the Hadamard matrix to the fourth segments, respectively, to shift the fourth phases of the fourth segments, wherein generating the encrypted image comprises: performing the transformed second transform; The method may include generating an encrypted image by overlapping the first phases, the shifted second phases, the shifted third phases, and the shifted fourth phases by segments of the same position.

According to one embodiment, generating the phase coded images includes passing laser beams in a structure in which binary phase masks are superimposed on the secret images, wherein the encrypted image is generated based on the passed laser beams. Can be.

According to one embodiment, the secret image and the private key may be a first phase image and a second phase image decomposed from the original image through interference.

According to an embodiment, in the complex plane, the vector of the original image may be the sum of a vector of secret images and a private key having the same amplitude and different phases.

According to an embodiment, there is provided a method of decrypting a multiple image, including: obtaining an encrypted image obtained by encrypting multiple original images; Identifying an original image to be decoded among the multiple original images; Performing a phase shift on the encrypted image, the phase shift corresponding to the identification result, to generate a secret image; And generating an original image from the secret image based on the private key corresponding to the identification result.

According to one embodiment, the original images may correspond to binary phase masks and private keys, respectively.

According to an embodiment, the generating of the secret image may include obtaining a matrix satisfying an orthogonal characteristic condition; Obtaining at least one element corresponding to the identification result from the matrix; And shifting phases of pixels included in the encrypted image based on the obtained element.

According to an embodiment, the pixels of the encrypted image are each divided into segments, and the shifting phases of the pixels may be performed by shifting the phases of the segments by applying the obtained element to the segments. The generating of the original image may include generating an original image by overlapping segments belonging to the same pixel.

According to an embodiment, the generating of the secret image may include obtaining a binary phase mask corresponding to the identification result among binary phase masks respectively corresponding to the original images; And shifting phases of pixels included in the encrypted image by using the obtained binary phase mask.

According to an embodiment, the generating of the original image may include: obtaining a private key corresponding to the identification result among private keys respectively corresponding to the original images; And generating an original image through interference between the obtained private key and the secret image.

According to an embodiment, the encrypted image is generated by superimposing phase-coded images, the phase-coded images are generated from the secret images by performing a phase shift on secret images, and the secret images and the private keys are generated. Each of the multiple original images may be generated.

According to an embodiment, there is provided a method of encrypting multiple digital information, the method comprising: obtaining secret information and private keys generated from multiple original digital information, respectively; Performing phase shift on the secret digital information to generate phase coded digital information from the secret digital information; And overlapping the phase coded digital information to generate encrypted digital information that encrypts the multiple original digital information.

According to an embodiment, there is provided a method of decrypting multiple digital information, the method comprising: obtaining encrypted digital information obtained by encrypting multiple original digital information; Identifying original digital information to be decoded among the multiple original digital information; Performing a phase shift on the encrypted digital information, the phase shift corresponding to the identification result, to generate secret digital information; And generating original digital information from the secret digital information based on the private key corresponding to the identification result.

The apparatus according to one embodiment may be controlled by a computer program stored in a medium in combination with hardware to carry out the method of any one of the aforementioned methods.

The encryption and decryption method according to an embodiment may perform image encryption and decryption in which there is substantially no difference between original information and decrypted information.

Encryption and decryption method according to an embodiment may propose a technique that is easily implemented digitally or optically.

The encryption and decryption method according to an embodiment may minimize the influence of crosstalk between images and provide robust encryption and decryption performance.

1 is a flowchart illustrating a method of encrypting multiple images, according to an exemplary embodiment.
2 is a diagram for describing a decomposition operation of an original image, according to an exemplary embodiment.
3 is a conceptual diagram illustrating an encryption operation of multiple images.
4 is a diagram for describing an operation of generating a phase-coded image, according to an exemplary embodiment.
5 is a diagram for describing a method of encrypting multiple images, according to an exemplary embodiment.
6 is a flowchart illustrating a decoding method of multiple images, according to an exemplary embodiment.
7A is a conceptual diagram illustrating a decoding operation of multiple images.
7B is a diagram for describing an operation of generating a secret image in a method of decoding a multiple image, according to an exemplary embodiment.
7C is a diagram for describing an operation of generating an original image in a method of decoding a multiple image, according to an exemplary embodiment.
8 to 13 are diagrams for explaining an embodiment of encryption and decryption.
14 is an exemplary diagram of a configuration of an apparatus according to an embodiment.

Specific structural or functional descriptions of the embodiments are disclosed for purposes of illustration only, and may be practiced in various forms. Accordingly, the embodiments are not limited to the specific disclosure, and the scope of the present specification includes changes, equivalents, or substitutes included in the technical idea.

Terms such as first or second may be used to describe various components, but such terms should be interpreted only for the purpose of distinguishing one component from another component. For example, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component.

When a component is referred to as being "connected" to another component, it should be understood that there may be a direct connection or connection to that other component, but there may be other components in between.

Singular expressions include plural expressions unless the context clearly indicates otherwise. As used herein, the terms "comprise" or "have" are intended to designate that the described feature, number, step, operation, component, part, or combination thereof exists, but includes one or more other features or numbers, It is to be understood that it does not exclude in advance the possibility of the presence or addition of steps, actions, components, parts or combinations thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art. Terms such as those defined in the commonly used dictionaries should be construed as having meanings consistent with the meanings in the context of the related art, and are not construed in ideal or excessively formal meanings unless expressly defined herein. Do not.

Hereinafter, exemplary embodiments will be described in detail with reference to the accompanying drawings. Like reference numerals in the drawings denote like elements.

1 is a flowchart illustrating a method of encrypting multiple images, according to an exemplary embodiment.

Referring to FIG. 1, an encryption apparatus of a multiple image may acquire secret images and private keys generated from multiple original images, respectively (101). An apparatus for encrypting multiple images is an apparatus for encrypting multiple images, for example, may be implemented as a software module, a hardware module, or a combination thereof. Hereinafter, an encryption device of multiple images will be referred to as an encryption device.

Multiple original images may include different original images. Here, the original images may be separate images that are not related to each other. According to an embodiment, the encryption apparatus may perform encryption with high efficiency by encrypting different original images and generating a single encrypted image including the encrypted information. Since the information encrypted by the encryption apparatus is not generated for each of the original images, communication efficiency may be increased because only a single encrypted image is transmitted and received between different subjects. For example, the encryption apparatus may generate a single encrypted image by encrypting the plurality of original images shown in FIG. 8. A server or a terminal requiring a plurality of original images may increase processing efficiency by recording or transmitting and receiving only a single encrypted image.

According to one embodiment, the original image can be decomposed into a secret image and a private key. Hereinafter, a decomposition operation of the original image through interference will be described with reference to FIG. 2.

2 is a diagram for describing a decomposition operation of an original image, according to an exemplary embodiment.

According to an embodiment, the original image may be decomposed into a first phase image and a second phase image through interference. The secret image and the private key may be a first phase image and a second phase image, respectively. The encryption device can decompose the original image into a secret image and a private key. The encryption apparatus may obtain a pre-decomposed secret image and a private key. Embodiments of the subject of the decomposition operation via the interference principle are not limited.

According to one embodiment, the original image may be a gray scale two-dimensional image. The original image can be decomposed into two pure phase-only images through interference.

는 2개의 위상 이미지의 벡터들

및

로 분해될 수 있다. 위상 이미지의 진폭은 픽셀 전체에 걸쳐 균일해야 하므로,

의 진폭은 정규화를 통해 최대치가 2가 되도록 설정될 수 있다. 복소 평면에서,

는

및

의 합이다.

및

는 크기가 크기(amplitude)가 서로 같고, 위상이 서로 다르다.

는 단위 반지름의 원에 있는 두 점의 합으로 표시될 수 있다.

는 수학식 1과 같이 정의될 수 있다.2, the vector of the original image

Are vectors of two phase images

And

Can be decomposed into Since the amplitude of the phase image must be uniform across the pixels,

The amplitude of may be set such that the maximum value becomes 2 through normalization. In the complex plane,

Is

And

Sum of

And

Are equal in magnitude and different in phase.

Can be expressed as the sum of two points in a circle of unit radius.

May be defined as in Equation 1.

이고, (x, y)는 원본 이미지의 주어진 픽셀의 공간 좌표이다.

및

는 2개의 위상 이미지들에 각각 대응하는데,

는 비밀 이미지의 벡터이고,

는 개인 키의 벡터이다. 복소 평면에서,

및

는 각각 비밀 이미지의 위상과 개인 키의 위상이다. 도 2를 참조하면,

는

및

의 합으로 표시된다. here,

Where (x, y) is the spatial coordinate of the given pixel of the original image.

And

Respectively corresponds to two phase images,

Is a vector of secret images,

Is the vector of private keys. In the complex plane,

And

Are the phase of the secret image and the phase of the private key, respectively. 2,

Is

And

It is expressed as the sum of.

및

의 관계는 수학식 2와 같다.By the relational expression of the trigonometric function,

And

The relationship of is as shown in Equation 2.

와

사이의 각은 상수이고, 두 벡터의 합은 원본 이미지의 픽셀의 진폭을 나타내기 때문에,

와

중 하나는 무작위로 정해질 수 있다. 이러한 방식으로,

와

모두는 무작위의 위상 분포를 가질 수 있다.Two positions vector

Wow

Since the angle between is constant and the sum of the two vectors represents the amplitude of the pixels in the original image,

Wow

One can be randomly chosen. In this way,

Wow

All may have a random phase distribution.

According to an embodiment, the encryption apparatus may obtain secret images and private keys for each of the plurality of original images.

Referring back to FIG. 1, the encryption apparatus may perform phase shift on secret images to generate phase coded images from secret images (102). According to one embodiment, the encryption apparatus may shift the phases included in the pixels of the secret images. The pixels of the secret image may include information of size and phase, and the encryption device may shift the phase included in the pixels of the secret image. The phase coded image is an image whose phase is shifted from the secret image.

According to an embodiment, the encryption apparatus may perform phase shift of secret images based on a matrix satisfying an orthogonality condition. The matrix that satisfies the orthogonal characteristic condition may be an n-th order Hadamard matrix H. The matrix H satisfies Equation 3.

는 H의 전치행렬이고, I는 n x n의 항등 행렬이고, H의 원소들은 1 또는 -1이다. H는 행들 사이에 서로 직교하는 n차 정사각 행렬이다.

Is the transpose of H, I is the identity matrix of nxn, and the elements of H are 1 or -1. H is an n-th order square matrix that is orthogonal to each other between the rows.

An example of H is shown in Equation 4.

The Hadamard matrix has the following characteristics:

(a) Equation 3 is satisfied even if two rows or two columns are exchanged.

(b) Equation 3 is satisfied even if the sign of the row or column is reversed.

The 4-order Sylvester Hadamard matrix is represented by Equation 5.

The n-th order Hadamard matrix satisfies an orthogonal characteristic condition as shown in Equation (6).

는 하다마드 행렬 H의

번째 원소이다.

은 크로네커 델타 함수(Kronecker delta function)이다.

Of the Hadamard matrix H

Element.

Is the Kronecker delta function.

According to an embodiment, the encryption apparatus may shift the phases of the pixels included in the secret images by 0 degrees or 180 degrees by using a binary phase mask. The binary phase mask can be designed based on the Hadamard matrix. The binary phase mask can have elements 1 or -1 in the Hadamard matrix, and the encryption apparatus can apply the binary phase mask to the secret image to shift the phases of the pixels in the secret image. An embodiment regarding the phase shift will be described later with reference to FIG. 4.

Referring to FIG. 1, the encryption apparatus may generate an encrypted image obtained by encrypting multiple original images by overlapping phase-encoded images (103). The encryption apparatus may generate the single encrypted image by overlapping the phase-coded images for the same pixels. Various techniques may be employed in the manner of superimposing the phase coded images, where the technique is not limited. According to an embodiment, the encryption apparatus may add phases for each pixel in the phase encoded images and overlap the phase encoded images. The encryption apparatus may generate an encrypted image according to the superimposition result, where the encrypted image is an image obtained by encrypting multiple original images. The encryption apparatus may generate an encrypted image including encrypted information from multiple original images to be encrypted at once. Hereinafter, a process of encrypting and decrypting multiple images will be described with reference to FIGS. 3A and 3B.

3 is a conceptual diagram illustrating an encryption operation of multiple images.

로 표기되고, 4개의 이진 위상 마스크들은 각각

로 표기되어 있다. BS는 빔 스플리터(Beam Splitter)이고, M은 미러(Mirror)이다. Referring to FIG. 3, the four two-dimensional secret images are each

4 binary phase masks,

It is indicated by. BS is a beam splitter and M is a mirror.

에 이진 위상 마스크들

이 각각 겹쳐진 구조로 레이저 빔들이 통과되면, 비밀 이미지들의 위상이 부호화된 위상 부호화 이미지들이 생성될 수 있다. 일실시예에 따르면, (m, n) 번째 픽셀에 있어서,

의 4개의 세그먼트들에 대응하는 위상들은

의 4개의 원소들에 의해 변이되어 부호화될 수 있다. 4개의 세그먼트들의 위상들은 각각 같은 위치의 원소들에 의해 부호화될 수 있다. 일실시예에 따르면, 이진 위상 마스크의 원소들은 하다마드 행렬의 원소들일 수 있다.As shown in FIG. 3, secret images

Binary phase masks

When the laser beams pass through the respective superimposed structures, phase-encoded images in which phases of secret images are encoded may be generated. According to one embodiment, for the (m, n) th pixel,

Phases corresponding to the four segments of

It may be mutated and encoded by four elements of. The phases of the four segments may each be encoded by elements of the same location. According to an embodiment, the elements of the binary phase mask may be elements of the Hadamard matrix.

The encrypted image may be generated by superimposing phase coded images generated as the laser beams pass. The phase detection system may measure phase information of overlapping beams using an interferometer. According to one embodiment, it is possible to obtain an encrypted image generated by the passage of the laser beam.

4 is a diagram for describing an operation of generating a phase-coded image, according to an exemplary embodiment.

According to an embodiment, the encryption apparatus may generate a phase-coded image by performing a phase shift for each segment of pixels of the secret image. First, the encryption apparatus may acquire secret images and divide the pixels of the secret images into segments. The encryption apparatus may divide one pixel into a plurality of segments of the same size.

According to an embodiment, the encryption apparatus may determine the number of segments based on the size of the Hadamard matrix employed for the phase shift. For example, if the size of the Hadamard matrix is n x n, the encryption device may divide the pixel of the secret image into n segments.

According to an embodiment, the encryption apparatus may apply the elements of the Hadamard matrix to the segments divided from the pixels, respectively, to shift the phases of the segments. The segments divided from the pixels each have phase information of the corresponding pixel, and the encryption apparatus may shift the phases of the segments by adding the phases of the elements of the Hadamard matrix for each segment. The encryption apparatus may generate an encrypted image by overlapping the phase shifted for each segment.

의 (m, n)의 픽셀을 4개의 동일한 크기의 제1 세그먼트들로 분할한다. 4개의 제1 세그먼트들의 위상은 원본 픽셀과 동일한 위상

를 갖는다. Referring to FIG. 4, an embodiment will be described on the assumption that secret images include a first secret image, a second secret image, a third secret image, and a fourth secret image. 4 (a) and 4 (b), the encryption device may include a first secret image.

A pixel of (m, n) of is divided into four equally sized first segments. The phase of the four first segments is in phase with the original pixel

Has

의 (m, n)의 픽셀에 속한 4개의 제1 세그먼트들은 4차 하다마드 행렬의 첫 번째 행의 4개의 원소들에 따라 각각 위상변이가 된다. 여기서, 원소 1 또는 -1은 광학적으로

또는

만큼의 위상변이에 대응한다. 그 결과로서 도 4(c)에 나타낸 바와 같이 해당 픽셀의 제1 세그먼트들 중 첫 번째의 제1 세그먼트는

의 위상 정보를 갖게 된다. 여기서

는 하다마드 행렬의 첫 번째 행의 첫 번째의 원소에 대응하는 위상이다. Referring to FIG. 4C, the encryption apparatus may apply the elements of the first row in the 4 × 4 Hadamard matrix to the first segments to shift the first phases of the first segments. Of the first secret image

The four first segments belonging to the pixel of (m, n) of are phase shifted according to the four elements of the first row of the fourth order Hadamard matrix. Where element 1 or -1 is optically

or

It corresponds to the phase shift by. As a result, as shown in Fig. 4C, the first first segment of the first segments of the pixel

Will have phase information. here

Is the phase corresponding to the first element of the first row of the Hadamard matrix.

According to an embodiment, the encryption apparatus may apply different Hadamard matrices to different pixels in the first secret image, which randomly swap rows or columns of the fourth-order Sylvester Hadamard matrix. Or it can be generated by reversing the sign of the row or column.

Similarly, the encryption device divides the pixel of (m, n) of the second secret image into four equally sized second segments. The encryption device divides the pixel of (m, n) of the third secret image into four equally sized third segments. The encryption device divides the pixel of (m, n) of the fourth secret image into four equally sized fourth segments. Referring to FIG. 4 (d), the encryption apparatus is configured to apply the second HAMAD matrix to the second secret image, the third secret image, and the fourth secret image to each pixel of the same Hadamard matrix used at the same position of the first secret image. The four elements of the third and fourth rows can be applied to shift the phases of the segments, respectively.

As shown in Fig. 4 (d), the fourth segments of the pixel of (m, n) of the fourth secret image are 4 of the fourth row of the same Hadamard matrix used in the pixel at the same position of the first secret image. Phase-encoded according to the elements. Here, the binary phase mask represents four elements of each row of the Hadamard matrices belonging to the Hadamard matrix set in the form of a 2 × 2 binary phase pattern. Finally, the encryption apparatus may overlap the four phase-encoded images with each other to generate one encrypted image.

The encrypted image at the (m, n) th pixel may be expressed as Equation (7).

은 암호화된 이미지의 (m, n) 번째 픽셀의 첫 번째 세그먼트를 통과하는 빔의 복소수 진폭,

은 a번째 비밀 이미지의 (m, n) 번째 픽셀의 위상이다.

는 4차 하다마드 행렬

의 전치행렬로서, 수학식 8과 같이 표현될 수 있다.Where (m, n) is the x and y coordinate of the pixel in the encrypted image,

Is the complex amplitude of the beam passing through the first segment of the (m, n) th pixel of the encrypted image,

Is the phase of the (m, n) th pixel of the a th secret image.

Is a quadratic Hadamard matrix

The transpose matrix of may be expressed as Equation (8).

는 하다마드 행렬의 (i, j)번째 원소인 1 또는 -1에 대응하는 위상(

또는

의 위상 변이)이다.here

Is the phase corresponding to 1 or -1, which is the (i, j) th element of the Hadamard matrix

or

Phase shift).

5 is a diagram for describing a method of encrypting multiple images, according to an exemplary embodiment.

은 각각 하다마드 행렬 내 원소들

,

,

및

에 의해 위상 변이가 수행된다. 이와 마찬가지로, 제2 비밀 이미지 내 픽셀들 중 상술한 픽셀과 같은 위치의 픽셀 내 세그먼트들

은 각각 하다마드 행렬 내 원소들

,

,

및

에 의해 위상 변이가 수행된다. 제3 비밀 이미지 내 픽셀들 중 상술한 픽셀과 같은 위치의 픽셀 내 세그먼트들

은 각각 하다마드 행렬 내 원소들

,

,

및

에 의해 위상 변이가 수행된다. 제4 비밀 이미지 내 픽셀들 중 상술한 픽셀과 같은 위치의 픽셀 내 세그먼트들

은 각각 하다마드 행렬 내 원소들

,

,

및

에 의해 위상 변이가 수행된다. 상술한 바와 같이, 암호화 장치는 위상 변이된 세그먼트들을 같은 위치에 속하는 세그먼트들 별로 중첩시켜, 암호화된 이미지를 생성할 수 있다. Referring to FIG. 5, segments in any one of the pixels in the first secret image

Are each element in the Hadamard matrix

,

,

And

Phase shift is performed by Similarly, the segments in the pixel at the same position as the aforementioned one of the pixels in the second secret image

Are each element in the Hadamard matrix

,

,

And

Phase shift is performed by Segments in the pixel at the same position as the aforementioned one of the pixels in the third secret image

Are each element in the Hadamard matrix

,

,

And

Phase shift is performed by Segments in the pixel at the same position as the aforementioned one of the pixels in the fourth secret image

Are each element in the Hadamard matrix

,

,

And

Phase shift is performed by As described above, the encryption apparatus may generate the encrypted image by overlapping the phase shifted segments for each segment belonging to the same position.

6 is a flowchart illustrating a decoding method of multiple images, according to an exemplary embodiment.

Referring to FIG. 6, an apparatus for decrypting multiple images according to an embodiment (hereinafter, referred to as a decryption apparatus) may obtain an encrypted image in which multiple original images are encrypted (601). The encrypted image is an image encrypted by the encryption method described above.

Referring to FIG. 6, the decoding apparatus may identify an original image to be decoded among multiple original images (602). When the multiple original images include the first original image to the fourth original image, the decoding apparatus may identify that the original image to be decoded from the first original image to the fourth image is the second original image.

Referring to FIG. 6, the decryption apparatus may generate a secret image by performing a phase shift on an encrypted image (603). Here, the phase shift corresponds to the identification result. The original images may correspond to binary phase masks and private keys, respectively. The decryption apparatus may obtain information about the binary phase masks and the private keys used in the encryption operation.

According to an embodiment, the decoding apparatus may obtain a matrix satisfying an orthogonal characteristic condition. The decoding apparatus may obtain at least one element corresponding to the identification result from the obtained matrix. When the original image to be decrypted corresponding to the identification result is the second original image, the decryption apparatus may obtain at least one element of the matrix used to encrypt the second original image. The decryption apparatus may shift the phases of the pixels included in the encrypted image based on the obtained element and generate a secret image.

According to an embodiment, the decoding apparatus may obtain a binary phase mask corresponding to an identification result among binary phase masks respectively corresponding to the original images. The decryption apparatus may shift the phases of the pixels included in the encrypted image by using the obtained binary phase mask.

According to one embodiment, the pixels of the encrypted image may each be divided into segments. The decoding apparatus may shift the phases of the segments by applying an element obtained from a matrix satisfying an orthogonal characteristic condition to segments in a pixel.

Referring to FIG. 6, the decryption apparatus may generate an original image from a secret image based on the private key corresponding to the identification result (604). As described above, when the original image to be decrypted is the second original image, the decryption apparatus may obtain a private key corresponding to the second original image. The decryption apparatus may generate the original image through the interference between the obtained private key and the secret image. According to an embodiment, the decoding apparatus may generate an original image by overlapping segments belonging to the same pixel.

7A is a conceptual diagram illustrating a decoding operation of multiple images.

가 겹쳐진 구조로 레이저 빔이 통과되면, p번째의 비밀 이미지가 복원될 수 있다. 예를 들어, 도 7a를 참조하여 설명된

중

와 암호화 이미지가 겁쳐진 구조로 레이저 빔이 통과되면, 비밀 이미지

가 복원될 수 있다. According to an embodiment, the decryption apparatus may generate an original image to be decrypted from an encrypted image in which multiple original images are encrypted. Referring to FIG. 7A, the p-th binary phase mask in the encrypted image

When the laser beam passes through the overlapped structure, the p-th secret image may be restored. For example, as described with reference to FIG. 7A

medium

And encrypted image is scared when the laser beam passes into the structure, the secret image

Can be restored.

According to one embodiment, the phase shift may be performed according to the four elements of the p-th row of the Hadamard matrix for the 2x2 segments of each pixel in the encrypted image. Interference between the restored secret image paper and the p-th private key may be performed to generate the p-th original image. The decoding apparatus may obtain the p-th original image and convert four segments within the same pixel into a single pixel. In this case, the (m, n) th pixel of the reconstructed image may be expressed as in Equation (9).

는 (m, n) 번째 픽셀에서의 a번째 복원된 이미지의 진폭이다.

은 a번째 비밀 이미지의 (m, n) 번째 픽셀의 위상이다.

은 a번째 개인 키의 (m, n) 번째 픽셀의 위상이다.

Is the amplitude of the a-th reconstructed image at the (m, n) th pixel.

Is the phase of the (m, n) th pixel of the a th secret image.

Is the phase of the (m, n) th pixel of the a th private key.

7B is a diagram for describing an operation of generating a secret image in a method of decoding a multiple image, according to an exemplary embodiment.

,

,

및

를 적용할 수 있다. 복호화 시 사용되는 원소들은 해당 세그먼트들에 대한 암호화 수행 시에 채용된 원소들에 대응한다. 복호화 장치는 세그먼트들의 위상 변이를 수행하고, 위상 변이된 세그먼트들을 단일의 픽셀로 중첩시켜 제2 비밀 이미지를 생성할 수 있다.Referring to FIG. 7B, the original image that the decryption apparatus intends to decrypt from the encrypted image in which the multiple original images are encrypted is the second original image. The decryption apparatus comprises elements in the Hadamard matrix, respectively, in segments in any one of the pixels in the encrypted image.

,

,

And

Can be applied. Elements used in decryption correspond to elements employed in performing encryption on the corresponding segments. The decoding apparatus may perform a phase shift of the segments, and generate the second secret image by overlapping the phase shifted segments with a single pixel.

7C is a diagram for describing an operation of generating an original image in a method of decoding a multiple image, according to an exemplary embodiment.

Referring to FIG. 7C, an original image that the decryption apparatus intends to decrypt from an encrypted image in which multiple original images are encrypted is a second original image. The decryption apparatus may obtain a second private key corresponding to the second original image of the private keys. The decryption apparatus may generate the second original image by interfering the phase shifted segments based on the second private key. Alternatively, the decryption apparatus may generate the second original image through interference of the second secret image and the second private key in which the phase shifted segments are superimposed on a single pixel.

The decryption apparatus may quickly and easily restore an image to be decrypted from an encrypted image in which multiple original images are encrypted. Although encryption and decryption for an image have been described above, the object of encryption and decryption is not limited to the image and can be extended to various information. According to an embodiment, the encryption apparatus may generate encrypted digital information by encrypting multiple original digital information by using the above-described technique. The decryption apparatus may generate the original digital information to be decrypted from the encrypted digital information in which the multiple original digital information are encrypted by employing the above-described technique.

8 to 13 are diagrams for explaining an embodiment of encryption and decryption.

8 (a) to 8 (d) are original images, respectively. 9A to 9D are binary phase masks for phase encoding, respectively. The encryption apparatus may generate an encrypted image obtained by encrypting original images of FIGS. 8A to 8D using the binary phase masks of FIGS. 9A to 9D.

10 (a) to 10 (d) are images decrypted from an encrypted image using correct binary phase masks and correct private keys. The decryption apparatus may generate the decrypted images of FIGS. 10 (a) to 10 (d) from the encrypted image.

11 (a) to 11 (d) are images decrypted from an encrypted image using erroneous binary phase masks and correct private keys. Even if the private keys are suitable for decryption, if binary phase masks are applied incorrectly, decryption will not be performed correctly.

12 (a) to 12 (d) are images decrypted from an encrypted image using correct binary phase masks and wrong private keys. Even if binary phase masks are suitable for decoding, if individuals are applied incorrectly, decoding will not be performed correctly.

13A to 13D are images decrypted from an encrypted image using the second binary phase mask and correct private keys. Only the second original image corresponding to the second binary phase mask may be reconstructed.

The encryption apparatus can easily encrypt multiple original images using binary phase masks and private keys, and can easily restore the original image to be decrypted using the binary phase masks and private keys employed in encryption. .

14 is an exemplary diagram of a configuration of an apparatus according to an embodiment.

Referring to FIG. 14, an apparatus 1401 may include a processor 1402 and a memory 1403. In the memory 1402, a program for processing instructions related to encryption or decryption may be recorded, and instructions for executing the operations described with reference to FIGS. 1 to 13 may be recorded. The processor 1402 may load and execute a program recorded in the memory 1403. Here, the above-described embodiments may be applied to the operations of the processor 1402.

The embodiments described above may be implemented as hardware components, software components, and / or combinations of hardware components and software components. For example, the apparatus, methods and components described in the embodiments may be, for example, processors, controllers, arithmetic logic units (ALUs), digital signal processors, microcomputers, field programmable gates (FPGAs). It may be implemented using one or more general purpose or special purpose computers, such as an array, a programmable logic unit (PLU), a microprocessor, or any other device capable of executing and responding to instructions. The processing device may execute an operating system (OS) and one or more software applications running on the operating system. The processing device may also access, store, manipulate, process, and generate data in response to the execution of the software. For ease of understanding, the processing device may be described as one used, but those skilled in the art will appreciate that the processing device includes a plurality of processing elements and / or a plurality of types of processing elements. It can be seen that it may include. For example, the processing device may include a plurality of processors or one processor and one controller. In addition, other processing configurations are possible, such as parallel processors.

The software may include a computer program, code, instructions, or a combination of one or more of the above, and configure the processing device to operate as desired, or process it independently or in combination. You can command the device. Software and / or data may be any type of machine, component, physical device, virtual equipment, computer storage medium or device in order to be interpreted by or to provide instructions or data to the processing device. Or may be permanently or temporarily embodied in a signal wave to be transmitted. The software may be distributed over networked computer systems so that they may be stored or executed in a distributed manner. Software and data may be stored on one or more computer readable recording media.

The method according to the embodiment may be embodied in the form of program instructions that can be executed by various computer means and recorded in a computer readable medium. The computer readable medium may include program instructions, data files, data structures, and the like, alone or in combination. The program instructions recorded on the media may be those specially designed and constructed for the purposes of the embodiments, or they may be of the kind well-known and available to those having skill in the computer software arts. Examples of computer-readable recording media include magnetic media such as hard disks, floppy disks, and magnetic tape, optical media such as CD-ROMs, DVDs, and magnetic disks, such as floppy disks. Magneto-optical media, and hardware devices specifically configured to store and execute program instructions, such as ROM, RAM, flash memory, and the like. Examples of program instructions include machine code, such as produced by a compiler, as well as high-level language code that can be executed by a computer using an interpreter or the like. The hardware device described above may be configured to operate as one or more software modules to perform the operations of the embodiments, and vice versa.

Although the embodiments have been described with reference to the accompanying drawings, those skilled in the art may apply various technical modifications and variations based on the above. For example, the described techniques may be performed in a different order than the described method, and / or components of the described systems, structures, devices, circuits, etc. may be combined or combined in a different manner than the described method, or other components. Or, even if replaced or substituted by equivalents, an appropriate result can be achieved.

Therefore, other implementations, other embodiments, and equivalents to the claims are within the scope of the claims that follow.

Claims (21)

Obtaining secret images and private keys generated from multiple original images, respectively;
Performing phase shift on the secret images to generate phase coded images from the secret images; And
Superimposing the phase-encoded images to generate an encrypted image obtained by encrypting the multiple original images
Containing
How to encrypt multiple images.
The method of claim 1,
Generating the phase coded images
Performing a phase shift of the secret images based on a matrix satisfying an orthogonality condition
Including,
How to encrypt multiple images.
The method of claim 2,
The matrix is

Is an n-order Hadamard matrix H satisfying
remind

Is a transpose matrix of H, I is an identity matrix of nxn,
The elements of H are 1 or -1,
How to encrypt multiple images.
The method of claim 1,
Generating the phase coded images
Shifting the phases of the pixels included in the secret images by 0 or 180 degrees using a binary phase mask
Including,
How to encrypt multiple images.
The method of claim 1,
Generating the phase coded images
Dividing the pixels of the secret images into segments; And
Varying the phases of the segments by applying the elements of a Hadamard matrix to the segments, respectively
Including,
Generating the encrypted image
Superimposing the shifted phases for each segment to generate an encrypted image
Including,
How to encrypt multiple images.
The method of claim 1,
The secret images include a first secret image, a second secret image, a third secret image and a fourth secret image,
Generating the phase coded images
Dividing the pixel of (m, n) of the first secret image into four first segments;
Dividing the pixel of (m, n) of the second secret image into four second segments;
Dividing the pixel of (m, n) of the third secret image into four third segments;
Dividing the pixel of (m, n) of the fourth secret image into four fourth segments;
Applying respective elements of a first row in a 4 × 4 Hadamard matrix to the first segments to shift the first phases of the first segments;
Applying respective elements of a second row in the Hadamard matrix to the second segments to shift the second phases of the second segments;
Applying respective elements of a third row in the Hadamard matrix to the third segments to shift the third phases of the third segments; And
Shifting the fourth phases of the fourth segments by applying the elements of a fourth row in the Hadamard matrix to the fourth segments, respectively
Including,
Generating the encrypted image
Generating the encrypted image by overlapping the shifted first phases, the shifted second phases, the shifted third phases, and the shifted fourth phases by segments of the same position.
Including,
How to encrypt multiple images.
The method of claim 1,
Generating the phase coded images
Passing laser beams in a structure in which binary phase masks are superimposed on the secret images
Including,
The encrypted image is generated based on the passed laser beams,
How to encrypt multiple images.
The method of claim 1,
The secret image and private key are first phase image and second phase image, which are decomposed from the original image through interference,
How to encrypt multiple images.
The method of claim 1,
In the complex plane, the vector of the original image is the sum of the vectors of the private key and the vector of the secret key with the same amplitude, different phase,
How to encrypt multiple images.
Obtaining an encrypted image in which multiple original images are encrypted;
Identifying an original image to be decoded among the multiple original images;
Performing a phase shift on the encrypted image, the phase shift corresponding to the identification result, to generate a secret image; And
Generating an original image from the secret image based on the private key corresponding to the identification result
Containing
Method of decoding multiple images.
The method of claim 10,
The original images respectively corresponding to binary phase masks and private keys,
Method of decoding multiple images.
The method of claim 10,
Generating the secret image
Obtaining a matrix that satisfies an orthogonal characteristic condition;
Obtaining at least one element corresponding to the identification result from the matrix; And
Shifting phases of pixels included in the encrypted image based on the obtained element
Including,
Method of decoding multiple images.
The method of claim 12,
The pixels of the encrypted image are each divided into segments,
Shifting the phases of the pixels
Applying the obtained element to the segments to shift the phases of the segments
Including,
Generating the original image
Creating an original image by overlapping segments belonging to the same pixel
Including,
Method of decoding multiple images.
The method of claim 10,
Generating the secret image
Obtaining a binary phase mask corresponding to the identification result among binary phase masks respectively corresponding to the original images; And
Shifting phases of pixels included in the encrypted image by using the obtained binary phase mask
Including,
Method of decoding multiple images.
The method of claim 10,
Generating the original image
Obtaining a private key corresponding to the identification result among private keys respectively corresponding to the original images; And
Generating an original image through interference between the obtained private key and the secret image
Including,
Method of decoding multiple images.
The method of claim 10,
The encrypted image is generated by overlaying phase coded images,
The phase coded images are generated from the secret images by performing a phase shift on secret images,
The secret images and private keys are each generated from the multiple original images,
Method of decoding multiple images.
Obtaining secret information and private keys generated from multiple original digital information, respectively;
Performing phase shift on the secret digital information to generate phase coded digital information from the secret digital information; And
Superimposing the phase coded digital information to generate encrypted digital information of the multiple original digital information;
Containing
How to encrypt multiple digital information.
Obtaining encrypted digital information encrypted with multiple original digital information;
Identifying original digital information to be decoded among the multiple original digital information;
Performing a phase shift on the encrypted digital information, the phase shift corresponding to the identification result, to generate secret digital information; And
Generating original digital information from the secret digital information based on the private key corresponding to the identification result;
Containing
Method of decoding multiple digital information.
19. A computer program stored in a recording medium in combination with hardware to carry out the method of any one of claims 1-18.
Obtain secret images and private keys, respectively generated from multiple original images,
Perform phase shift on the secret images to generate phase coded images from the secret images,
A processor for superimposing the phase coded images to generate an encrypted image obtained by encrypting the multiple original images
Containing
Encryption device for multiple images.
Multiple original images to obtain an encrypted encrypted image,
Identifying an original image to be decoded among the multiple original images,
Perform a phase shift on the encrypted image, the phase shift corresponding to the identification result, to generate a secret image,
A processor for generating an original image from the secret image based on the private key corresponding to the identification result
Containing
Device for decoding multiple images.

Images