KR100349520B1 - System and method for holographic-image encryption and decoding - Google Patents

Abstract

The present invention relates to a holographic image encryption and decryption system and method for digitally encrypting private information and optically decrypting an encrypted image.

In a holographic image encryption and decryption system, a digital encryption system is composed of a processor for processing an original image and converting the original image into encrypted data, and a memory for recording encrypted data by the processor.

The decoding system includes a secondary input plane for outputting a cryptographic key image, a secondary Fourier transform lens for Fourier transforming the output cryptographic key image, a cryptographic card for outputting a product of the joint power spectrum and a Fourier transform value and a joint power spectrum An inverse Fourier transform lens for performing inverse Fourier transform on the product, and a secondary optical detector for recording the inverse Fourier transform value.

According to the present invention, it is possible to digitally encrypt an image and restore an original image in real time, and when digitally encrypting, interference noise is separated from an original image by selection of two parameter values can do.

Description

[0001] System and method for holographic image encryption and decoding [0002]

The present invention relates to a holographic image encryption and decryption system and method for digitally encrypting private information and optically decrypting an encrypted image.

Generally, photographs, faces, fingerprints and the like are used as means for checking forgery of passports, credit cards, various ID cards, etc. Recently, with the development of computers, image processing and printer technologies, It is becoming a serious social problem in modern credit society as it is elaborated.

In recent years, holograms have been widely used in credit cards and passports, but they can not be reproduced theoretically because they are searched by human eyes. However, in actual cases, the hologram pattern is a CCD (Charge- Coupled Device), it is possible to synthesize and replicate new holograms.

Therefore, in recent years, existing optical intensity detectors, such as CCDs, have not been able to reproduce or reproduce a complex function type A new optical security technique using a random phase pattern is proposed.

P. Refregier, "Optical Image Encryption and Fourier Plane Random Encoding by Input Plane", presents a new image encryption scheme that encrypts the original image with two random phase masks.

That is, one of the two random masks is located on the input plane and the other is located on the spatial frequency plane, and ultimately the original image is converted into a stationary white noise form. In the decoder system, the cryptographic card image is optically Fourier transformed , And the converted value is multiplied by the conjugate complex value of the random phase mask corresponding to the cryptographic key.

However, since the encrypted image has a complex number, it is difficult to produce a card, and a decoder requires a spatial light modulator (SLM) capable of displaying a complex value.

On the other hand, B. Javidi "Optical Pattern Recognition for Validation and Security Verification" presented a simple method of encrypting by attaching a random phase mask on the original image.

In the decoder, a reference image corresponding to a cryptographic card and a random phase mask is JFT (Joint Fourier Transform), detects JTPS (Joint Transform Power Spectrum), and then transforms the reference image into inverse Fourier transform.

Therefore, it is possible to determine whether the card is falsified by checking the correlation peak value. This method is advantageous in that it is easy to manufacture a decoder because it is not so sensitive to system alignment as compared with the method of Refregier, It is possible to falsify the card if the phase mask is removed by a careless manner.

SUMMARY OF THE INVENTION [0008] Accordingly, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a real- And to provide a novel holographic image encryption and decoding system and method.

1 is a block diagram of a holographic image encryption and decryption system in accordance with a preferred embodiment of the present invention.

2 is a block diagram of a joint Fourier transform system for encryption of a holographic image encryption and decryption system in accordance with another embodiment of the present invention.

3 is a block diagram of a decoding system for decrypting a holographic image encoding and decoding system in accordance with a preferred embodiment of the present invention.

Fig. 4 (a) shows an original image to be encrypted, and Fig. 4 (b) shows an amplitude distribution of an encryption key image.

Fig. 5 (a) is an image encrypted with a positive real value, and Fig. 5 (b) is an example of an image encrypted with a phase type.

6 is an exemplary view showing an image reconstructed using a phase-type cryptographic image and an encryption key.

FIG. 7 is an exemplary view showing a coded image of a positive real number and an original image restored by a phase-type cryptographic key. FIG.

8 is an exemplary view showing a phase-type cryptographic image and an original image restored with a positive real-valued cryptographic key.

FIG. 9 is an exemplary view showing a reconstructed image using a cipher key and a cipher key in the form of a positive real number; FIG.

10 is an exemplary view showing a reconstructed image when the alignment is not made correctly.

Description of the Related Art

100: Processor 110: Memory

200, 300: primary, secondary input plane

210, 310: primary and secondary Fourier transform lens

220, 340: primary and secondary photodetectors 320: encryption card

330: inverted Fourier transform lens

According to an aspect of the present invention, there is provided a method of encrypting and digitally encrypting personal information and optically reconstructing an encrypted image, the method comprising: A digital encryption step of generating a real image by using a cryptographic key image of a real image type by using a digital processing device, a decryption step of decrypting the real image by an optical device And an optical decryption step of extracting a decrypted image corresponding to the original image through a process of decrypting the original image and an optical decryption step of decrypting the decrypted image corresponding to the original image, Calculating a product of the original image and the cipher key image, A may include the step of storing in a storage device coupled to the Fourier transform step, wherein the Fourier transformation of the real form of the encrypted image generated by the digital processing apparatus. The optical decryption step may include Fourier transforming the real key cryptographic key image using a lens included in the optical device, calculating a product of the Fourier transformed real key cryptographic key image and the real key cryptographic key Transforming the Fourier-transformed real-valued cryptographic key image and the real-valued cryptographic image to inverse Fourier transform, and extracting the decoded image corresponding to the original image using the inverse Fourier transformed result According to another aspect of the present invention, there is provided a holographic image encrypting method comprising: a digital processing device for digitally encrypting an original image corresponding to personal information; and an optical device for optically decrypting the encrypted image, And a decoding device, wherein the digital device has a program stored therein And a processor coupled to the memory and executing the program, wherein the processor is configured to extract, by the program, a real key cryptographic key image corresponding to the original image, Performing a Fourier transform on the product of the calculated original image and the cryptographic key image, and a step of storing the encrypted image of the real number generated by the Fourier transform in the memory, The optical device includes an input plane for outputting the real-key cryptographic key image, a Fourier transform lens for Fourier transforming the real cryptographic key image output from the input plane, A real-valued cryptographic key image in the form of a Fourier transform and an encrypted image in the real- An inverse Fourier transform lens for inverse Fourier transforming a product of the Fourier-transformed real-valued cryptographic key image and the real-valued cryptographic image, and an inverse Fourier transform The input plane may include a spatial light modulator that arranges the original image in correspondence with the real cryptographic key image. In another aspect of the present invention, A digital processing device for digitally encrypting an original image corresponding to personal information, the digital processing device comprising: means for extracting a real key cryptographic key image corresponding to the original image; Means for Fourier transforming the multiplication of the calculated original image and the cryptographic key image, The convolution of the conjugate cryptographic key image of the cryptographic key image and the cryptographic key image may be a function of an impulse function . ≪ / RTI > Preferably, the cryptographic key image is white noise. At least one of the real key cryptographic key image and the real cryptographic key image is at least one of a positive type and a phase type. There is provided a holographic image encrypting method in a digital processing apparatus for digitally encrypting an original image corresponding to personal information, the method comprising: extracting a real key cryptographic key image corresponding to the original image; A step of calculating a product of a cryptographic key image of a real number type, a step of Fourier transforming a product of the calculated original image and a cryptographic key image, and a step of storing the encrypted real image generated by the Fourier transform The method comprising the steps of: Standing, the convolution of the conjugated image encryption key of the encryption key image and the encryption key image can be approximated by an impulse function. Preferably, the cryptographic key image is white noise. Preferably, at least one of the real-valued cryptographic key image and the real-valued encrypted image is at least one of a positive type and a phase type.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 shows a block diagram of a holographic image encoding and decoding system according to a preferred embodiment of the present invention.

Referring to FIG. 1, a processor 100 for processing an original image or an encryption key image to calculate encrypted data, and a memory 110 for recording the original image.

First, a system (referred to as a digital encryption system or a digital processing device) for encrypting an original image will be described.

The digital encryption system includes a calculation unit that calculates a product of the original image and the cryptographic key image by generating an original image cryptographic key image corresponding to the original image, a Fourier transform unit that multiplies the product of the calculated original image and the cryptographic key image An output means for outputting a joint power spectrum, and a recording means for recording the outputted joint power spectrum in the memory 110. [

Here, it is preferable that the cryptographic key image is a cryptographic key.

More preferably, the cryptographic key image is white noise.

The decoding system for restoring (decoding) the encrypted image through the digital system may further include the steps of Fourier transforming the cipher key image by the processor 100, converting the cipher key image into the memory 110, And outputting the decoded original image to the memory 110. The step of outputting the decoded original image to the memory 110 may be performed by performing the inverse Fourier transform on the product.

On the other hand, the encryption system according to the present invention may be optically realized as shown in FIG.

2 shows a block diagram of a joint Fourier transform system for encryption of a holographic image encoding and decoding system according to another embodiment of the present invention.

The joint Fourier transform system includes a primary input plane 200, a primary Fourier transform lens 210, and a primary photodetector 220.

The primary input plane 200 contains an original image to be encrypted, and a cryptographic key image is arranged corresponding to the original image. Also, a spatial light modulator is used to generate an encryption key image corresponding to the original image, and an original image And is located at a predetermined position on the primary input plane 200. Accordingly, a cryptographic key image corresponding to the original image is generated in the lower portion of the cryptographic key image through the spatial light modulator.

The primary Fourier transform lens 210 is a lens including a general convex lens and performs Fourier transform on the original image and the cryptographic key image of the primary input plane 200. [

The primary photodetector 220 detects a value Fourier transformed by the primary Fourier transform lens 210, and typically uses a charge-coupled device (CCD).

Therefore, the joint power spectral value, which is the encrypted image detected by the primary optical detector 220 by encrypting the original image using the joint Fourier transform system, is expressed by Equation (1).

here, and Is a constant that can be arbitrarily selected as representing coordinates on the spatial frequency, * denotes a conjugate complex number, Represents a spatial frequency, Wow The Wow Respectively, and < RTI ID = 0.0 > Wow Is an input function, Wow Represents an output function. Also, Is an encrypted image, and since the right side binomial of Equation 1 is a conjugate relation, it is a real number. In the present invention, This is to make it easier to manufacture the encrypted image to be attached to the ID card or the like.

First, when light (for example, laser light) is incident on the front end of the primary input plane 200, the original image included in the primary input plane 200 is multiplied by the cryptographic key image and output, The joint power spectral value thus output is detected by the primary optical detector 220 and recorded on various cards.

Here, Is a function used to camouflage the original image. By encrypting the original image with the encryption key image, it is possible to prevent another card user from acquiring the information of the original image. In a preferred embodiment of the present invention, Is a mistake. In the present invention, Is limited to a real number, To be more easily represented in the SLM.

Although the optical system and the digital system can be used for encrypting the original image as described above, it is preferable to use a digital system because a random mask is used because an optical system must be multiplied by a random phase function.

3 shows a block diagram of a decoding system for decrypting a holographic image encoding and decoding system according to a preferred embodiment of the present invention.

The decoding system includes a secondary input plane 300, a secondary Fourier transform lens 310, an encryption card 320, an inverse Fourier transform lens 330, and a secondary photodetector 340.

The secondary input plane 300 may be the same as the primary input plane 200 of FIG. 1 and may be another plane for convenience. The secondary input plane 300 is provided with a cryptographic key Video function .

The second Fourier transform lens 310 is a lens for Fourier transforming the cryptographic key image of the secondary input plane 300. The cryptographic key image is Fourier transformed by the second Fourier transform lens 310 It is output in the form of an exponential function.

The encryption card 320 is a card in which a cipher is stored. The joint power spectrum of Equation (1) encrypted by the joint Fourier transform system is stored.

The inverse Fourier transform lens 330 transforms the cryptographic key image in the secondary input plane 300 and the cryptographic function in the cryptographic card 320 into an inverse Fourier transform to decode the cryptogram to restore the original image.

The secondary Fourier transform lens 310 and the inverse Fourier transform lens 330 may use the same lens as the primary Fourier transform lens 210 of FIG. 1 or another lens.

The secondary photodetector 340 detects the original image reconstructed by inverse Fourier transform by the inverse Fourier transform lens 330.

The secondary photodetector 340 is the same as the primary photodetector 220 of FIG. 1, and a charge coupled device can be used.

Accordingly, the expression for recovering the original image by removing the cryptographic key image from the image encrypted by the decoding system appears as a convolution form as shown in Equation (2) below.

Here, * denotes a convolution, The inverse Fourier transform of or (*) Is omitted because it is a real function, Is an input function, Represents an output function for restoring the original image.

Referring to Equation (2) above, The most ideal pattern for Is an impulse function , And if the autocorrelation function is < RTI ID = 0.0 > , The first term to the right of equation (2) .

First, the encryption key image function included in the secondary input plane 300 The cryptographic key image function output from the secondary input plane 300 is Fourier transformed by the secondary Fourier transform lens 310 and output in an exponential form, and the secondary Fourier transform lens The Fourier transformed value is multiplied by the joint power spectral value of Equation 1 included in the encrypted card, and the output value is inverse Fourier transformed by the inverse Fourier transform lens 330, ).

Therefore, the function < RTI ID = 0.0 > Is output from the secondary optical detector 340, and the cryptographic key image function Is closer to the impulse function.

Also, the encryption key image function Is preferably white noise.

If the encryption key image function Is white noise, any two sampled values at different positions are completely uncorrelated, and thus are most preferable as a cryptographic key function.

As a result, Is white noise, in the second term on the right side of Equation (2) Resulting in another white noise that is uniformly distributed, and the output function serves as a baseband filter And becomes smooth.

Also, Considering a finite aperture of the function, the noise component spreads relatively uniformly centered on (0, -d ₁ + 2d ₂ ), and the noise is obtained from the original image by appropriately selecting the values of d ₁ and d ₂ Can be separated.

Therefore, when the noise components are separated, the original image can be detected from the center of the photodetector located at the coordinates (0, d ₁ ) on the output plane.

As described above, a method for restoring the encrypted original image can be performed using optical and digital systems, but an optical system capable of realizing real time on a plane is more preferable.

A method of encrypting an original image by random phase coding will be described.

The original image Is a real-valued function and a real-valued cryptographic key image function Is given as a uniformly distributed white noise, Partial information about the Is information about the individual identity, partial amplitude information can be predicted by chance.

First, it will be examined whether a cryptographic key can be decrypted from the partial amplitude information using a heterogeneous loop (Hetero-Associative Loop) or the like and furthermore, the ID card can be duplicated.

Is a partial amplitude pattern, and in the decoding system the cryptographic key image Instead of (2) using Equation (3). &Quot; (3) "

here, Represents an inverse Fourier transform, Input function Lt; RTI ID = 0.0 > Fourier < / RTI & Is a partial amplitude function Is an output function representing the Fourier transform value of the input signal.

In Equation (3), the first term represents a noise component, the second term represents a partial amplitude function Accidental original image function Ramen .

At this time, the partial amplitude function Represents the fractional function of the original image, the original image can be expressed by the following equation (4).

Here, Is a partial residual function in the original image.

The second term of Equation (3) can be summarized as Equation (5) below using Equation (4).

The first term of Equation (5) And the second term has a noise form.

Finally, the partial amplitude function , The original image Cryptographic keys that are not even enough Can be inferred.

That is, the partial amplitude function Using the output function By adjusting the amplitude of the output function appropriately to a threshold value Similar to Can be obtained, and the above Through the decoding system More original video Another partial amplitude pattern close to < RTI ID = 0.0 >

In order to solve the above problem, a random phase function Can be used.

That is, the partial function of the original image In this case, The .

Therefore, the encrypted image output is expressed by Equation (6) below.

here, Input function ≪ / RTI > Represents the output function. By coding the random phase function as above, the original image can never be predicted or estimated.

On the other hand, the output function Is a real number function, it is not necessarily a positive real number function.

In the present invention, two methods are used to solve this problem.

The first method is expressed by Equation (7) below.

here, Is an encrypted joint power spectrum, Constant To the output function.

As shown in Equation (7), the output function of the joint Fourier transform system Positive integer So that the output function can always be derived as a positive value.

If the original image is reconstructed by the decoding system based on Equation (7), it can be expressed as Equation (8).

here, Represents the output function of the reconstructed original image, Represents an output function including a noise component in the output function of the reconstructed original image.

Referring to Equation (8), since the noise due to the bias of the second term on the right side is positioned at (0, -d ₂ ) Lt; / RTI > can be separated in the area where it is restored.

Next, the second method uses the output function Is transformed into a phase type, when in, when Respectively.

Also, the output function and instead Wow Lt; / RTI >

More preferably, Wow Lt; / RTI >

if Wow , Then the decoder output function, in the absence of quantization noise, The light intensity function The two methods described above have an advantage in that the original image to be included in the ID card can be more easily produced. May take a positive form or a phase form by the above two methods.

Hereinafter, a preferred embodiment of the present invention will be verified through simulation.

In the present invention, the encryption process and the optical decoding process using the digital calculation of the original image are simulated.

4 (a) and 4 (b), the original image is "YHG" having a size of 128 × 128.

4 (a) shows the amplitude distribution when the original image function is located in a 512 × 512 null array.

The cryptographic key image shown in Fig. 4 (b) has a size of 128 x 128, and 1 and -1 are randomly distributed.

Here, the amplitude values of the cryptographic key image are all equal to 1, but for display, 1 and -1 are shown as gray levels 0 and 255 in Fig. 4 (b), respectively.

Dimensional FFT (Fast Fourier Transform) for a 512 × 512 array. Also, Can also be calculated similarly, Using two two-dimensional functions on a plane Respectively.

In this simulation Is assumed to be a distance corresponding to 64 sample intervals in the array, The Respectively.

remind Transformed the data to positive real and topological form for practical implementation.

5 (a) and 5 (b) are graphs respectively showing positive real values and phase values .

The data in phase form is represented by two gray levels 0 and 255 as shown in FIG. 4 (b).

Cryptographic key image function Is a binary phase function consisting of +1 and -1, and thus takes a phase form.

Data modification to positive real numbers can be obtained simply by adding +1 to all data.

FIG. 6 shows a decoded restored image when the image and cryptographic keys are coded with phase-type data.

Here, the original image component is reconstructed at (0, -d ₁ ), and the interference noise caused by the second term of Equation ( ₂ ) is centered at a position coincident with (0, -d ₁ + 2d ₂ ).

FIG. 7 shows a decoded result when a picture is encoded with a positive real number and the cryptographic key is data of a phase type.

As expected from Equation (8), it is shown that a square-shaped interference noise occurs around (0, d ₂ ). The reason why the noise is black in FIG. 7 The amplitude is uniformly 1.

Fig. 8 is a positive real function of the encryption key consisting of 0 and 2, and is a reconstructed image when the image is encoded in the phase type.

Here, In addition, there are two interference components, one of which is centered at (0, d ₁ ) where the original image component is reconstructed and the other is located at (0, -d ₁ + 2d ₂ ) Respectively.

FIG. 9 shows an image of a reconstructed result when both the image and the encryption key are coded in a positive real form.

As shown in Fig. 9, two interference components can be identified.

In this case, since most of the energy is consumed to output the noise component, The intensity of the light is very low.

In Fig. 10, the coded image and the encryption key are coded in phase type, and the spatial light modulator is in the original position And the result is decoded.

As shown in FIG. 10, although the sharpness of the restored image is the same, .

If the card is at (0, d1) If the input The original image is not reconstructed but becomes blurred. This is because the cryptographic card and the cryptographic key are multiplied in the frequency plane, and thus the motion invariant restoration characteristic between the cryptographic image and the cryptographic key can not be guaranteed.

According to the present invention as described above, an original image can be reconstructed in real time using a white noise type encryption key used for encrypting an image digitally using an FFT routine.

In addition, when digital encryption is used, the interference noise can be separated from the original image by appropriately selecting two parameter values. Also, by using the real key cryptographic key image, Can be expressed. Further, by transforming the cryptographic key image into a positive number or a phase value, the cryptographic key image can be more easily represented in the SLM. Further, an encrypted image obtained by multiplying the real number cryptographic key image by the original image, Since it is a real number format, an ID card including an encrypted image can be easily produced. Furthermore, by transforming the encrypted image into a positive form or a phase form, an encrypted image included in the ID card can be produced more easily.

In addition, the reconstruction image obtained by using the phase type data in the cryptographic image and the encryption key through simulation can be used as the ideal image for the cryptographic image and the cryptographic key by multiplying the original image by the random phase function. .

Further, by encrypting the original image with the encryption key image, it is possible for another card user to prevent the information of the original image from being acquired.

Claims (25)

A holographic image encryption and decryption method for digitally encrypting personal information and optically restoring an encrypted image, A digital encryption step of generating an encrypted image in the form of a real number by using a digital processing device using a cipher key image of a real number corresponding to the original image corresponding to the personal information; An optical decryption step of extracting a decrypted image corresponding to the original image through a process of decrypting the real image by using an optical device using the real key cryptographic key image The method comprising the steps of: The method according to claim 1, The digital encryption step Calculating a product of the original image and the real-valued cryptographic key image; Performing a Fourier transform on the product of the original image and the cipher key image; Storing the real image encrypted image generated by the Fourier transform in a storage device coupled to the digital processing device The method comprising the steps of: The method according to claim 1, The optical decoding step Performing a Fourier transform on the real key cryptographic key image using a lens included in the optical device; Calculating a product of the Fourier-transformed real-valued cryptographic key image and the real-valued cryptographic image; Transforming the product of the Fourier-transformed real-valued cryptographic key image and the real-valued cryptographic image computed by the Fourier transform; Extracting a decoded image corresponding to the original image using the inverse Fourier transformed result The method comprising the steps of: A holographic image encrypting and decrypting apparatus comprising a digital processing apparatus for digitally encrypting an original image corresponding to personal information and an optical apparatus for optically decrypting the encrypted image, The digital device A memory in which a program is stored; And A processor coupled to the memory and executing the program, , ≪ / RTI & The processor, by means of the program, Extracting a real key cryptographic key image corresponding to the original image; Calculating a product of the original image and the real-valued cryptographic key image; Performing a Fourier transform on the product of the original image and the cipher key image; And Storing the real image of the encrypted image generated by the Fourier transform in the memory The holographic image encrypting and decrypting apparatus. 5. The method of claim 4, The optical device An input plane for outputting the real key cryptographic key image; A Fourier transform lens for Fourier transforming the output coded real key image; An encryption key for outputting the Fourier-transformed real-valued encryption key image and the real-valued encrypted image as a product; An inverse Fourier transform lens for inverse Fourier transforming a product of the Fourier-transformed real-valued cryptographic key image and the real-valued cryptographic image; And A photodetector for extracting a decoded image corresponding to the original image using the inverse Fourier transformed result; And decrypting the encrypted image. 6. The method of claim 5, Wherein the input plane is a spatial light modulator for arranging the original image in correspondence with the real- And decrypting the encrypted image. A digital processing apparatus for digitally encrypting an original image corresponding to personal information, Means for extracting a real key cryptographic key image corresponding to the original image; Means for calculating a product of the original image and the real-valued cryptographic key image; Means for Fourier transforming the product of the original image and the cryptographic key image; And Means for storing the real image of the encrypted image generated by the Fourier transform The holographic image encrypting device comprising: 8. The method of claim 7, The convolution of the conjugate cryptographic key image of the cryptographic key image and the cryptographic key image is approximated by an impulse function And the holographic image encrypting device. 8. The method of claim 7, The encryption key image is a white noise And the holographic image encrypting device. 8. The method of claim 7, The original image is obtained by multiplying the random phase function And the holographic image encrypting device. 8. The method of claim 7, Wherein at least one of the real-valued encryption key image and the real-valued encrypted image is at least one of a positive type and a phase type And the holographic image encrypting device. A holographic image encrypting method in a digital processing apparatus for digitally encrypting an original image corresponding to personal information, Extracting a real key cryptographic key image corresponding to the original image; Calculating a product of the original image and the real-valued cryptographic key image; Performing a Fourier transform on the product of the original image and the cipher key image; And Storing the real image of the encrypted image generated by the Fourier transform in a storage device coupled to the digital processing device The holographic image encrypting method comprising: 13. The method of claim 12, The convolution of the conjugate cryptographic key image of the cryptographic key image and the cryptographic key image is approximated by an impulse function And encrypting the holographic image. 13. The method of claim 12, The encryption key image is a white noise And encrypting the holographic image. 13. The method of claim 12, The original image is obtained by multiplying the random phase function And encrypting the holographic image. 13. The method of claim 12, Wherein at least one of the real-valued encryption key image and the real-valued encrypted image is at least one of a positive type and a phase type And encrypting the holographic image. delete delete delete delete delete delete delete delete delete