CN110278074B - A Visual Secret Sharing Method for Image Encryption - Google Patents

Abstract

The present invention relates to a visual secret sharing scheme for image encryption. It makes full use of the local contrastive features of LBP to hide the secret image data in different image sharing, which can easily and accurately recover the secret. By converting the image into LBP code, and then dividing it, the divided part can be handed over to different holders to achieve the effect of shared encryption. The original image can be restored by combining the divided parts. This scheme can not only ensure the sharing of image data in the network, but also ensure the security of image data in the network, and has better randomness, lower pixel expansion, and lower computational cost.

Description

A Visual Secret Sharing Method for Image Encryption

technical field

The invention relates to the technical field of image processing and information encryption, and relates to a visual secret sharing method for image sharing encryption.

Background technique

With the rapid development of multimedia technology, multimedia services such as online games, video surveillance, and video conferencing are also emerging. These services are often highly dynamic and require significant resources to host. As a technology that meets resource requirements and provides cost-effective services, cloud infrastructure is used by more and more service providers to process multimedia services. Visual secret sharing technology is a method of sharing secret information to avoid potential disruption and modification, including malicious attacks and inappropriate management of individuals.

Contents of the invention

The purpose of the present invention is to provide a method of shared encryption, which divides the encrypted pattern to achieve the sharing effect, and restores the original pattern by combining the divided pattern with decryption, so as to achieve the effect of secret sharing and ensure security . In order to achieve the above effects, three schemes are proposed for different image types, binary image VSS scheme (BVSS); grayscale image VSS scheme (GVSS); multi-image VSS scheme (MIVSS), and adopt the following techniques.

Include the following steps:

Image encrypted sharing:

Step 1, encrypting the original image by ILBP algorithm to generate ILBP code;

Step 2, randomly generating the control factor α and the gray value L of the center pixel;

Step 3, randomly generate the gray value of the central pixel neighborhood by controlling the factor α, and make it meet the requirements of ILBP;

Step 4: Divide the image. There are many ways to divide the image to generate multiple shadow blocks, and the multiple shadow blocks can be distributed to different holders to achieve the effect of image encryption and sharing.

Image decryption:

Step 1, combining multiple shared shadow blocks into M×N shadow blocks;

Step 2: Calculate the ILBP code for each shadow block of M×N through the ILBP algorithm to restore the original image.

In one embodiment of the present invention, the ILBP algorithm is

是邻域的平均值，控制因子α∈[0,1]，灰度L∈[0,255]。where the parameter P controls the quantization of the angular space, and R controls the spatial resolution. L represents the gray level of the central pixel, g _p represents the gray value of the adjacent pixel p, S(x) represents the sign function,

is the average value of the neighborhood, the control factor α∈[0,1], and the gray level L∈[0,255].

In an embodiment of the present invention, the shadow block gray value must meet the following requirements in the ILBP algorithm:

In the BVSS scheme: for images

当B[i，j]＝0时，S₁[i,j]∈(0，S₁[i,j])，并保证S₂[i,j]∈(0，S₁[i,j])且满足

B={B[i,j]|B[i,j]∈[0,1], 0≤i≤M-1, 0≤j≤N-1}, assuming there are 2 shared blocks S ₁ [i ,j], S ₂ [i,j]. When B[i,j]=1, S ₁ [i,j]∈(0,L), S ₂ [i,j]∈(S ₁ [i,j]+1,L) and satisfy

When B[i,j]=0, S ₁ [i,j]∈(0,S ₁ [i,j]), and ensure that S ₂ [i,j]∈(0,S ₁ [i,j] ]) and satisfy

邻域像素为

当

保证

且满足

当

保证

且满足

In the GVSS scheme: for image G, the central pixel is

Neighborhood pixels are

when

ensure

and satisfied

when

ensure

and satisfied

假设有n+1个共享块，

其中随机生成的中心像素

当

时，S_k[i,j]＝random(S_k-1[i,j]+1,L)，且满足

当

时，S_k[i,j]＝random(0，S_k-1[i,j])，且满足

MIVSS scheme: for multiple images

Suppose there are n+1 shared blocks,

where the randomly generated central pixel

when

When , S _k [i,j]=random(S _k-1 [i,j]+1,L), and satisfy

when

, S _k [i,j]=random(0, S _k-1 [i,j]), and satisfy

Compared with existing image sharing methods, this scheme has the following advantages:

(1) Lossless secret reconstruction;

(2) There is no restriction on the image format;

(3) Easy to align;

(4) No codebook is required;

(5) Sharing of different sizes;

(6) The expansion calculation efficiency of pixels is high.

Description of drawings

Figure 1 is the 3×3 image encryption scheme, Figure 2 is the practical application of 3×3 image encryption, Figure 3 is the multiple image encryption and sharing method, Figure 4 is the practical application of multiple image encryption and sharing, and Figure 5 is two shared images S1, S2, Fig. 6 is the pixel value range of the shared image S1, Fig. 7 is the pixel value range of the shared image S1 when the shared information is 0, and Fig. 8 is the pixel value range of the shared image S2 when the shared information is 0, FIG. 9 shows the value conditions that the pixel values corresponding to the kth shared image should satisfy.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some of the embodiments of the present invention, but not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

The present invention provides a visual secret sharing method for image sharing encryption comprising the following steps:

Image encryption sharing:

Step 1, encrypting the original image by ILBP algorithm to generate ILBP code;

Step 2, randomly generating the control factor α and the gray value L of the center pixel;

Step 3, randomly generate the gray value of the central pixel neighborhood by controlling the factor α, and make it meet the requirements of ILBP;

Step 4: Divide the image. There are many ways to divide the image to generate multiple shadow blocks, and the multiple shadow blocks can be distributed to different holders to achieve the effect of image encryption and sharing.

Image decryption:

Step 1, combining multiple shared shadow blocks into M×N shadow blocks;

Step 2: Calculate the ILBP code for each shadow block of M×N through the ILBP algorithm to restore the original image.

Taking the grayscale image of 3×3 in Fig. 1 further as an example, the following steps are included:

Image encryption sharing:

Step 1, distributing the ILBP codes in 3×3 image blocks;

Step 2, randomly generate the control factor α and the gray value L of the central pixel, where α=

0.24, the center pixel value is 83;

Step 3, by controlling the factor α to randomly generate the gray value of the central pixel neighborhood, here (87, 40, 210, 68, 35, 96, 71, 180), these values meet the requirements of the GVSS scheme in ILBP;

In step 4, the image is divided into three shared blocks, Sharel, Share2 and Share3, but the division method is not limited to this one.

Image decryption:

Step 1: Combine the three shared shadow blocks Sharel, Share2 and Share3 into a 3×3 shadow block;

Step 2: Inversely calculate the ILBP code for each shadow block of 3×3 through the ILBP algorithm to restore the original image.

Further, the image decryption is described in detail in combination with the example of image 2:

In the example shown in image 2, a=0.15 is randomly generated. Among them, (a) is the original image Barbara; (e) divides image a into three shared shadow blocks; (b) is the restored image after decryption. (c) is the original image Lena; in (f) the c image is divided into 3 shared shadow blocks, and (d) is the restored image after decryption.

The present invention can be applied to images of different formats or different gray scales to realize visual cryptography. The proposed method has many advantages, including lossless secret reconstruction, not limited to image format, easy alignment, etc. Based on different ILBP extensions or variants, various VSS schemes are designed to share secret or hidden information. Experimental results show that the method is effective compared to traditional image sharing methods. It provides better sharing flexibility and low computational complexity.

Claims (1)

1. A visual secret sharing method for image sharing encryption, characterized by the steps of:

image encryption sharing:

encrypting an original image through an ILBP algorithm to generate an ILBP code;

randomly generating a control factor alpha and a gray value L of a central pixel;

step three, randomly generating a gray value of a central pixel neighborhood by controlling a factor alpha, and enabling the gray value to meet the requirements of ILBP; the method comprises the following specific steps:

in the BVSS protocol: for images

B＝{B[i,j]|B[i,j]∈[0,1]I is more than or equal to 0 and less than or equal to M-1, j is more than or equal to 0 and less than or equal to N-1, and 2 shared blocks S are assumed ₁ [i,j]，S ₂ [i,j](ii) a When B [ i, j ]]＝1，S ₁ [i,j]∈(0，L)，S ₂ [i,j]∈(S ₁ [i,j]+1, L) and satisfy

When B [ i, j ]]When =0, S ₁ [i,j]∈(0，S ₁ [i,j]) And guarantee S ₂ [i,j]∈(0，S ₁ [i,j]) And satisfy

In the GVSS protocol: for image G, the center pixel is

The neighborhood pixels are

When in use

Guarantee

And satisfy

When in use

Guarantee

And satisfy

In the MIVSS scheme: for multiple images

Assuming that there are n +1 shared blocks,

in which the central pixel is randomly generated

When in use

When S is present _k [i,j]＝random(S _k-1 [i,j]+1, L), and satisfies

When in use

When, S _k [i,j]＝random(0，S _k-1 [i,j]) And satisfy

Step four, the image is divided to generate a plurality of shadow blocks, and the shadow blocks can be distributed to different holders to achieve the image encryption sharing effect;

image decryption:

combining a plurality of shared shadow blocks into an MxN shadow block;

calculating ILBP codes for each shadow block of the MxN through an ILBP algorithm to restore an original image;

the ILBP algorithm is

Where the parameter P controls the quantization of the angular space, R controls the spatial resolution, L denotes the grey scale of the central pixel, g _p Representing the gray value of the neighboring pixel p, S (x) represents a sign function,

is the average of the neighborhood, with the control factor α ∈ [0,1 ]]The gray level L belongs to [0,255 ]]。

Images