# US 11,451,395 B2 · Methods for optical image encryption and decryption based on biological information

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- Number: US 11,451,395 B2
- Document ID: US11451395B2
- Status: Granted
- Kind: B2
- Application number: 17/215,792
- Filed: 2021-03-29
- Published: 2022-02-17
- Granted: 2022-09-20
- Earliest claimed: 2020-08-12
- Assignees: Zhejiang Normal University
- Applicants: Zhejiang Normal University
- Inventors: Weimin Jin; Xueru Sun; Lihong Ma
- Web page: https://patentgrep.com/patent/US11451395B2

## CPC

- H04L 9/3231: {Biological data, e.g. fingerprint, voice or retina (network architectures or network communication protocols for supporting authentication of entities using biometrical features in a packet data network H04L63/0861)}
- G06F 21/602: {Providing cryptographic facilities or services}
- H04L 9/001: {using chaotic signals}
- H04L 9/0866: {involving user or device identifiers, e.g. serial number, physical or biometrical information, DNA, hand-signature or measurable physical characteristics}
- H04L 9/0894: {Escrow, recovery or storing of secret information, e.g. secret key escrow or cryptographic key storage}
- H04L 9/3013: {involving the discrete logarithm problem, e.g. ElGamal or Diffie-Hellman systems}
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)
- G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N)

## Abstract

Image encryption and decryption methods based on biological information. The encryption method includes: obtaining the biological information; using the chaotic mapping method to preprocess the biological information to construct the first chaotic biological phase plate and the second chaotic biological phase plate; obtaining the original image to be encrypted and use the first chaotic biological phase plate and the second chaotic biological phase plate to determine the reconstructed optical encrypted image based on the discrete cosine transform method, and Fresnel transform method; and inputting reference light that interferes with the encrypted image of the reproduction light to determine the encrypted image. The invention can reduce the information amount of the key, improve the efficiency of storage and transmission, and improve security.

## Claims

### Claim 1

An image encryption method based on biological information, comprising:
acquiring biological information that comprises fingerprint, iris, face, palm print, and voiceprint;
preprocessing the biological information by using a chaotic mapping method, to construct a first chaotic biological phase plate and a second chaotic biological phase plate;
acquiring an original image to be encrypted, performing discrete cosine transform on the original image to be encrypted to obtain an encrypted image after discrete cosine transform;
multiplying the first chaotic biological phase plate with the encrypted image after discrete cosine transform to obtain an encrypted image modulated by the first chaotic biological phase plate;
performing a first Fresnel transformation on the encrypted image modulated by the first chaotic biological phase plate to obtain an encrypted image after the first Fresnel transformation;
performing a first phase truncation and phase preservation on the encrypted image after the first Fresnel transform, to obtain an encrypted image after the first phase truncation and phase preservation;
multiplying the second chaotic biological phase plate with the encrypted image after the first phase truncation and phase preservation, to obtain an encrypted image modulated by the second chaotic biological phase plate;
performing a second Fresnel transform on the encrypted image modulated by the second chaotic biological phase plate to obtain an encrypted image after the second Fresnel transform;
performing a second phase truncation and phase preservation on the encrypted image after the second Fresnel transform to obtain an encrypted image after the second phase truncation and phase preservation;
causing the encrypted image after the second phase truncation and phase preservation to undergo Fresnel diffraction, and an interference with an introduced reference light, to output a light intensity distribution of a plane hologram, as a final encrypted image.

### Claim 2 (depends on 1)

The image encryption method based on biological information according to claim 1, wherein the performing a first Fresnel transformation on the encrypted image modulated by the first chaotic biological phase plate to obtain an encrypted image after the first Fresnel transformation, comprises:
performing, according to a formula f(x1,y1)=FrTz1{f′(x0,y0)exp[j2πϕ(x0, y0)]}, the first Fresnel transform on the encrypted image modulated by the first chaotic biological phase plate to obtain the encrypted image after the first Fresnel transform;
wherein f(x1,y1) is the encrypted image after the first Fresnel transform; FrT is a Fresnel transform; z1 is a first transform distance; f′(x0,y0) is the encrypted image after discrete cosine transform; ϕ(x0,y0) is a phase distribution function in x0,y0 domain; and j is an imaginary number.

### Claim 3 (depends on 2)

The image encryption method based on biological information according to claim 2, wherein the performing a first phase truncation and phase preservation on the encrypted image after the first Fresnel transform, to obtain an encrypted image after the first phase truncation and phase preservation, comprises:
performing, according to formulas PT{f(x1,y1)}=|f(x1,y1)| and PR{f(x1,y1)}=exp[j2πϕ(x1,y1)]=RPM1, the first phase truncation and phase preservation on the encrypted image after the first Fresnel transform to obtain the encrypted image after the first phase truncation and phase preservation;
wherein PT{f(x1,y1)} is a phase truncation in x1,y1 domain; PR{f(x1,y1)} is a phase reservation in x1,y1 domain; ϕ(x1,y1) is a phase distribution function in x1,y1 domain; and RPM1 is a first key.

### Claim 4 (depends on 3)

The image encryption method based on biological information according to claim 3, wherein the performing a second phase truncation and phase preservation on the encrypted image after the second Fresnel transforms to obtain an encrypted image after the second phase truncation and phase preservation, comprises:
performing according to formulas PT{f(x2,y2)}|f(x2,y2)| and PR{f(x2,y2)}=exp[j2πϕ(x2,y2)]=RPM2, the second phase truncation and phase preservation on the encrypted image after the second Fresnel transform to obtain the encrypted image after the second phase truncation and phase preservation;
wherein f(x2,y2) is the encrypted image after the second Fresnel transform; PT{f(x2,y2)} is a phase truncation in x2,y2 domain; PR{f(x2,y2)} is a phase reservation in x2,y2 domain; ϕ(x2,y2) is a phase distribution function in x2,y2 domain; and RPM2 is a second key.

### Claim 5 (depends on 1)

The image decryption method based on biological information according to claim 1, further comprising:
obtaining users' biological information;
judging whether the user is a legal user according to the biological information of the user;
if so, acquiring the first key and the second key, and irradiating the final encrypted image with reference light;
decrypting the final encrypted image after irradiation according to the first key and the second key by using a Fresnel inverse transform method and the chaotic mapping method, to obtain the original image;
if not, stopping decryption.

### Claim 6 (depends on 5)

The image decryption method based on biological information according to claim 5, wherein performing a first Fresnel transformation on the encrypted image modulated by the first chaotic biological phase plate to obtain an encrypted image after the first Fresnel transformation, comprises:
performing, according to a formula f(x1,y1)=FrTz1{f′(x0,y0)exp[j2πϕ(x0,y0)]}, the first Fresnel transform on the encrypted image modulated by the first chaotic biological phase plate to obtain the encrypted image after the first Fresnel transform;
wherein f(x1,y1) is the encrypted image after the first Fresnel transform; FrT is a Fresnel transform; z1 is a first transform distance; f′(x0,y0) is an encrypted image after discrete cosine transform; ϕ(x0,y0) is a phase distribution function in x0,y0 domain; and j is an imaginary number.

### Claim 7 (depends on 6)

The image decryption method based on biological information according to claim 6, wherein performing a first phase truncation and phase preservation on the encrypted image after the first Fresnel transform, to obtain an encrypted image after the first phase truncation and phase preservation, comprises:
performing, according to formulas PT{f(x1,y1)}=|f(x1,y1)| and PR{f(x1,y1)}=exp[j2πϕ(x1,y1)]=RPM1, the first phase truncation and phase preservation on the encrypted image after the first Fresnel transform to obtain the encrypted image after the first phase truncation and phase preservation;
wherein PT{f(x1,y1)} is a phase truncation in x1,y1 domain; PR{f(x1,y1)} is a phase reservation in x1,y1 domain; ϕ(x1,y1) is a phase distribution function in x1, y1 domain; and RPM1 is a first key.

### Claim 8 (depends on 7)

The image decryption method based on biological information according to claim 7, wherein performing a second phase truncation and phase preservation on the encrypted image after the second Fresnel transforms to obtain an encrypted image after the second phase truncation and phase preservation, comprises:
performing, according to formulas PT{f(x2,y2)}=|f(x2,y2)| and PR{f(x2,y2)}=exp[j2πϕ(x2,y2)]=RPM2, the second phase truncation and phase preservation on the encrypted image after the second Fresnel transform to obtain the encrypted image after the second phase truncation and phase preservation;
wherein f(x2,y2) is the encrypted image after the second Fresnel transform; PT{f(x2,y2)} is a phase truncation in x2,y2 domain; PR{f(x2,y2)} is a phase reservation in x2,y2 domain; ϕ(x2,y2) is a phase distribution function in x2,y2 domain; and RPM2 is a second key.

### Claim 9 (depends on 5)

The image decryption method based on biological information according to claim 5, wherein decrypting the final encrypted image after irradiation according to the first key and the second key by using a Fresnel inverse transform method and the chaotic mapping method, to obtain the original image, comprises:
illuminating the final encrypted image by using the reference light to obtain a reconstructed optical encrypted image;
performing a first inverse Fresnel transform on the reconstructed optical encrypted image to obtain a decrypted image after the first inverse Fresnel transform;
multiplying the decrypted image after the first inverse Fresnel transform with the second key to obtain a first decrypted image;
performing a second inverse Fresnel transform on the first decrypted image to obtain a decrypted image after the second inverse Fresnel transform;
multiplying the decrypted image after the second inverse Fresnel transform by a conjugate of the first chaotic biological phase plate to obtain a second decrypted image;
performing a third inverse Fresnel transform on the second decrypted image to obtain a decrypted image after the third inverse Fresnel transform;
multiplying the decrypted image after the third inverse Fresnel transform with a conjugate of the second chaotic biological phase plate to obtain a third decrypted image;
performing an inverse discrete cosine transform on the third decrypted image to obtain the original image.

### Claim 10 (depends on 6)

The image decryption method based on biological information according to claim 6, wherein decrypting the final encrypted image after irradiation according to the first key and the second key by using a Fresnel inverse transform method and the chaotic mapping method, to obtain the original image, comprises:
illuminating the final encrypted image by using the reference light to obtain a reconstructed optical encrypted image;
performing a first inverse Fresnel transform on the reconstructed optical encrypted image to obtain a decrypted image after the first inverse Fresnel transform;
multiplying the decrypted image after the first inverse Fresnel transform with the second key to obtain a first decrypted image;
performing a second inverse Fresnel transform on the first decrypted image to obtain a decrypted image after the second inverse Fresnel transform;
multiplying the decrypted image after the second inverse Fresnel transform by a conjugate of the first chaotic biological phase plate to obtain a second decrypted image;
performing a third inverse Fresnel transform on the second decrypted image to obtain a decrypted image after the third inverse Fresnel transform;
multiplying the decrypted image after the third inverse Fresnel transform with a conjugate of the second chaotic biological phase plate to obtain a third decrypted image;
performing an inverse discrete cosine transform on the third decrypted images to obtain the original image.

### Claim 11 (depends on 7)

The image decryption method based on biological information according to claim 7, wherein decrypting the final encrypted image after irradiation according to the first key and the second key by using a Fresnel inverse transform method and the chaotic mapping method, to obtain the original image, comprises:
illuminating the final encrypted image by using the reference light to obtain a reconstructed optical encrypted image;
performing a first inverse Fresnel transform on the reconstructed optical encrypted image to obtain a decrypted image after the first inverse Fresnel transform;
multiplying the decrypted image after the first inverse Fresnel transform with the second key to obtain a first decrypted image;
performing a second inverse Fresnel transform on the first decrypted image to obtain a decrypted image after the second inverse Fresnel transform;
multiplying the decrypted image after the second inverse Fresnel transform by a conjugate of the first chaotic biological phase plate to obtain a second decrypted image;
performing a third inverse Fresnel transform on the second decrypted image to obtain a decrypted image after the third inverse Fresnel transform;
multiplying the decrypted image after the third inverse Fresnel transform with a conjugate of the second chaotic biological phase plate to obtain a third decrypted image;
performing an inverse discrete cosine transform on the third decrypted images to obtain the original image.

### Claim 12 (depends on 8)

The image decryption method based on biological information according to claim 8, wherein decrypting the final encrypted image after irradiation according to the first key and the second key by using a Fresnel inverse transform method and the chaotic mapping method, to obtain the original image, comprises:
illuminating the final encrypted image by using the reference light to obtain a reconstructed optical encrypted image;
performing a first inverse Fresnel transform on the reconstructed optical encrypted image to obtain a decrypted image after the first inverse Fresnel transform;
multiplying the decrypted image after the first inverse Fresnel transform with the second key to obtain a first decrypted image;
performing a second inverse Fresnel transform on the first decrypted image to obtain a decrypted image after the second inverse Fresnel transform;
multiplying the decrypted image after the second inverse Fresnel transform by a conjugate of the first chaotic biological phase plate to obtain a second decrypted image;
performing a third inverse Fresnel transform on the second decrypted image to obtain a decrypted image after the third inverse Fresnel transform;
multiplying the decrypted image after the third inverse Fresnel transform with a conjugate of the second chaotic biological phase plate to obtain a third decrypted image;
performing an inverse discrete cosine transform on the third decrypted images to obtain the original image.

### Claim 13 (depends on 9)

The image decryption method based on biological information according to claim 9, wherein performing a first inverse Fresnel transform on the reconstructed optical encrypted image to obtain a decrypted image after the first inverse Fresnel transform, comprises:
using a formula f′(x2,y2)=FrT−z3{f(x3,y3)} to perform the first inverse Fresnel transform on the reconstructed optical encrypted image, and obtaining an absolute value of f′(x2,y2) to obtain the decrypted image after the first inverse Fresnel transform;
wherein f′(x2,y2) is the decrypted image after the first inverse Fresnel transform; f(x3,y3) is the reconstructed optical encrypted image; FrT is a Fresnel transform; and z3 is a third transform distance.

### Claim 14 (depends on 10)

The image decryption method based on biological information according to claim 10, wherein performing a first inverse Fresnel transform on the reconstructed optical encrypted image to obtain a decrypted image after the first inverse Fresnel transform, comprises:
using a formula f′(x2,y2)=FrT−z3{f(x3,y3)} to perform the first inverse Fresnel transform on the reconstructed optical encrypted image, and obtaining an absolute value of f′(x2,y2) to determine obtain the decrypted image after the first inverse Fresnel transform;
wherein f′(x2,y2) is the decrypted image after the first inverse Fresnel transform; f(x3,y3) is the reconstructed optical encrypted image; FrT is a Fresnel transform; and z3 is a third transform distance.

### Claim 15 (depends on 11)

The image decryption method based on biological information according to claim 11, wherein performing a first inverse Fresnel transform on the reconstructed optical encrypted image to obtain a decrypted image after the first inverse Fresnel transform, comprises:
using a formula f′(x2,y2)=FrT−z3{f(x3,y3)} to perform the first inverse Fresnel transform on the reconstructed optical encrypted image, and obtaining an absolute value of f′(x2,y2) to obtain the decrypted image after the first inverse Fresnel transform;
wherein f′(x2,y2) is the decrypted image after the first inverse Fresnel transform; f(x3,y3) is the reconstructed optical encrypted image; FrT is a Fresnel transform; and z3 is a third transform distance.

### Claim 16 (depends on 12)

The image decryption method based on biological information according to claim 12, wherein performing a first inverse Fresnel transform on the reconstructed optical encrypted image to obtain the decrypted image after the first inverse Fresnel transform, comprises:
using a formula f′(x2,y2)=FrT−z3{f(x3,y3)} to perform the first inverse Fresnel transform on the reconstructed optical encrypted image, and obtaining an absolute value of f′(x2,y2) to obtain the decrypted image after the first inverse Fresnel transform;
wherein f′(x2,y2) is the decrypted image after the first inverse Fresnel transform; f(x3,y3) is the reconstructed optical encrypted image; FrT is a Fresnel transform; and z3 is a third transform distance.

### Claim 17 (depends on 13)

The image decryption method based on biological information according to claim 13, wherein performing a second inverse Fresnel transform on the first decrypted image to obtain a decrypted image after the second inverse Fresnel transform, comprises:
using a formula |f(x1,y1)|exp[j2πφ(x1,y1)]=FrT−z3{f′(x2,y2)|exp[j2πφ(x2,y2)]} to perform the second inverse Fresnel transform on the first decrypted image to obtain the decrypted image after the second inverse Fresnel transform;
wherein f′(x1,y1) is the decrypted image after the second inverse Fresnel transform; ϕ(x1,y1) is a phase distribution function in a domain x1,y1; z2 is a second transform distance; j is an imaginary number, and ϕ(x2,y2) is phase distribution function in a domain x2,y2.

### Claim 18 (depends on 14)

The image decryption method based on biological information according to claim 14, wherein performing a second inverse Fresnel transform on the first decrypted image to obtain a decrypted image after the second inverse Fresnel transform, comprises:
using a formula |f′(x1,y1)|exp[j2πφ(x1,y1)]=FrT−z2{f′(x2,y2)|exp[j2πφ(x2,y2)]} to perform the second inverse Fresnel transform on the first decrypted image to obtain the decrypted image after the second inverse Fresnel transform;
wherein f′(x1,y1) is the decrypted image after the quadratic second inverse Fresnel transform; ϕ(x1,y1) is a phase distribution function in a domain x1,y1; z2 is a second transform distance; j is an imaginary number; and ϕ(x2,y2) is a phase distribution function in a domain x2,y2.

### Claim 19 (depends on 17)

The image decryption method based on biological information according to claim 17, wherein performing a third inverse Fresnel transform on the second decrypted image to obtain a decrypted image after the third inverse Fresnel transform, comprises:
using a formula |f′1(x0,y0)|exp[j7πφ(x0,y0)]=FrT−z1{f′(x1,y1)|exp[j2πφ(x1,y1)]} to perform the third inverse Fresnel transform on the second decrypted image to obtain the decrypted image after the third inverse Fresnel transform; wherein f′1(x0,y0) is the decrypted image after the third inverse Fresnel transform; ϕ(x0,y0) is a phase distribution function in x0,y0 domain.

### Claim 20

A method for encrypting and decrypting biological information based on a biological image, comprising:
acquiring biological information that comprises fingerprint, iris, face, palm print, and voiceprint;
preprocessing the biological information using a chaotic mapping method to construct a first chaotic biological phase plate and a second chaotic biological phase plate;
acquiring an original image to be encrypted, and performing discrete cosine transform on the original image to be encrypted, to obtain an encrypted image after discrete cosine transform;
multiplying the first chaotic biological phase plate with the encrypted image after discrete cosine transform to obtain an encrypted image modulated by the first chaotic biological phase plate;
performing a first Fresnel transformation on the encrypted image modulated by the first chaotic biological phase plate to obtain an encrypted image after the first Fresnel transformation;
performing a first phase truncation and phase preservation on the encrypted image after the first Fresnel transform to obtain an encrypted image after the first phase truncation and phase preservation;
multiplying the second chaotic biological phase plate with the encrypted image after the first phase truncation and phase preservation to obtain an encrypted image modulated by the second chaotic biological phase plate;
performing a second Fresnel transform on the encrypted image modulated by the second chaotic biological phase plate to obtain an encrypted image after the second Fresnel transform;
performing a second phase truncation and phase preservation on the encrypted image after the second Fresnel transform to obtain an encrypted image after the second phase truncation and phase preservation;
causing the encrypted image after the second phase truncation and phase preservation to undergo Fresnel diffraction, and an interference with an introduced reference light to output a light intensity distribution of a plane hologram as a final encrypted image; and;
obtaining users' biological information;
judging whether the user is a legal user according to the biological information of the user;
if so, acquiring a first key and a second key, and irradiating the final encrypted image with reference light;
decrypting the final encrypted image after irradiation according to the first key and the second key; by using a Fresnel inverse transform method and the chaotic mapping method to obtain the original image;
if not, stopping decryption.