Hybrid encryption and decryption method based on chaotic system and optical key

Abstract

The invention discloses a hybrid encryption and decryption method based on a chaotic system and an optical key, and the encryption method comprises the steps: generating a chaotic key through the initial information of a to-be-encrypted object and an initial key, and generating a chaotic sequence for the chaotic key through employing a five-dimensional Hamiltonian conservative chaotic system (FHCCS); scrambling and grouping the initial information according to the chaotic sequence, and selecting a corresponding diffraction distance as an optical key; generating a computer-generated hologram by adopting a layered angular spectrum method according to the diffraction distance; encrypting the computer-generated hologram by adopting the chaos sequence to obtain an optical password book; and encrypting a ciphertext of the optical password book by using the chaotic sequence to obtain a ciphertext of a final encrypted object. According to the method, an encryption mode of combining the optical key and the chaotic key is adopted, and the optical password book inherits the advantages of efficient information storage, high decryption speed, high parallelism and the like of optical encryption, and has the advantages of high shear resistance, high security and the like which are not possessed by a traditional password book.

Description

Technical Field

[0001] The invention relates to the field of information security, and more specifically to a hybrid encryption and decryption method based on a chaotic system and an optical key. Background Art

[0002] With the rapid development of information technology, the importance of data security and privacy protection has become increasingly prominent, and various encryption methods have emerged one after another. However, as a data encryption technology with a long history and wide application, the traditional codebook has difficult key management and low security, which has gradually shown its limitations in the modern information security system.

[0003] Therefore, the information capacity and security of traditional codebook technology face severe challenges. Traditional codebooks carry little information and are difficult to resist increasingly advanced brute force attacks. Summary of the invention

[0004] In view of this, the present invention provides a hybrid encryption and decryption method based on a chaotic system and an optical key, which can solve the problem that the traditional code book carries a small amount of information and is difficult to resist increasingly advanced brute force attacks, and can improve data security.

[0005] In order to achieve the above object, the present invention adopts the following technical solution:

[0006] In a first aspect, an embodiment of the present invention provides a hybrid encryption method based on a chaotic system and an optical key, comprising the following steps:

[0007] S1. Generate a chaotic key from the initial information and initial key of the encrypted object, and use a five-dimensional Hamiltonian conservative chaotic system (FHCCS) to generate a chaotic sequence for the chaotic key;

[0008] S2, scrambling and grouping the initial information according to the chaotic sequence, selecting the chaotic scrambling diffraction distance as the optical key; and generating a computer-generated hologram using a layered angular spectrum method according to the diffraction distance;

[0009] S3, using the chaotic sequence to encrypt the computer generated hologram to obtain an optical code book;

[0010] S4. Encrypt the ciphertext of the optical code book using the chaotic sequence to obtain the ciphertext of the final encrypted object.

[0011] In a second aspect, an embodiment of the present invention further provides a hybrid decryption method based on a chaotic system and an optical key, comprising the following steps:

[0012] S100, obtaining a chaotic key corresponding to the object to be decrypted; the chaotic key includes: K_1, K_2, K_3, K_4, K_5; using the chaotic key to generate a corresponding chaotic sequence through FHCCS; the chaotic sequence includes: R_1, R_2, D_1, S_1, R_3;

[0013] S200, decrypting the ciphertext of the object to be decrypted according to R_3 to obtain the ciphertext of the optical code book;

[0014] S300, decrypting the optical codebook according to the chaotic sequences S_1 and D_1 to obtain a computer generated hologram;

[0015] S400, placing the computer generated hologram in an optical experimental system, using the computer generated hologram and an optical key to decrypt the ciphertext to obtain a final decrypted plaintext.

[0016] It can be seen from the above technical solution that compared with the prior art, the present invention has the following advantages:

[0017] The present invention uses the chaotic sequence generated by FHCCS to scramble and group the initial information and initial key of the object to be encrypted, uses the diffraction distance of chaotic encryption as the optical key, and then uses the layer-based hybrid iterative angular spectrum method to make a computer-generated hologram. Finally, the chaotic sequence generated by FHCCS is used to encrypt the computer-generated hologram, and at the same time, the transmitted plaintext information is encrypted using the chaotic sequence. The generated optical code book realizes high-density information storage and encryption. Multi-dimensional chaotic keys and optical keys are required for decryption, as well as a computer-generated holographic three-dimensional display experimental system, which can realize the rapid reconstruction and extraction of decrypted information. The encryption and decryption method provided by the present invention has high security, and the optical code book generated during encryption carries a large amount of information; the decryption speed is fast during decryption, and it can effectively resist shear damage and current violent attack methods, and has a very reliable practical application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0019] Figure 1 A flow chart of a hybrid encryption method based on a chaotic system and an optical key provided by the present invention;

[0020] Figure 2 A codebook generation flow chart provided by the present invention;

[0021] Figure 3A schematic diagram of the encryption process of a computer generated hologram (CGH image) provided by the present invention;

[0022] Figure 4 A flow chart of a hybrid decryption method based on a chaotic system and an optical key provided by the present invention;

[0023] Figure 5 A schematic diagram of an optical experiment for reconstructing an image provided by the present invention;

[0024] Figure 6 The ciphertext decryption flow chart provided by the present invention;

[0025] Figure 7 A schematic diagram showing the effect of a single key deviation on a reconstructed image provided by the present invention;

[0026] Figure 8 This is a schematic diagram of the impact of the cropping attack provided by the present invention on the reconstructed image. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] In related technologies, chaotic systems have the characteristics of pseudo-randomness, initial value sensitivity, parameter sensitivity and unpredictability compared to traditional encryption methods. Therefore, chaos theory has enabled more encryption methods to be obtained in the field of information security. For example, Kamal et al. introduced image segmentation technology, achieved image block scrambling through zigzag scanning, rotation and random arrangement, and then used the chaotic system to generate keys for image diffusion encryption. Gao et al. achieved scrambling through row and column shifts, and achieved diffusion encryption through forward and backward propagation operations. Kong et al. proposed a 2n+1-dimensional simplest Hamiltonian conservative chaotic system, and used the system to perform fractal scrambling and batch diffusion encryption on images. Cao et al. used a chaotic sequence technology based on logical mapping to encrypt CGH hierarchical scrambling, realizing the encryption of three-dimensional scene hierarchical information. With the rapid development of chaos theory, chaotic encryption methods used in the field of image encryption have become more and more mature, especially the encryption method combining chaos theory with computational holography technology, which provides a new way for information protection.

[0029] In addition, in related technologies, with the development of optoelectronic modulation technology and computational optics, holographic technology has made great progress. For example, Gerchberg and Saxton proposed the famous Gerchberg-Saxton (GS) algorithm, which reconstructs high-quality images by using constraints. In order to speed up the iteration speed, some improved weighted GS (WGS) methods have been proposed. For example, Wu et al. proposed an adaptive weighted GS algorithm, which uses an optimized GS algorithm to generate a pure phase CGH image. In order to increase the generation speed of holograms, Zhao et al. proposed a layer-oriented angular spectrum propagation computational holography algorithm, which layers 3D information according to depth information, and uses an angular spectrum algorithm to simulate the light transmission process between parallel layers to holograms. The quality and speed of optical reconstruction have been greatly improved. In order to further improve the reconstruction performance, various optimization algorithms such as the intermediate angular spectrum method, the scaled angular spectrum method, and the time-division multiplexing angular spectrum method have been proposed. Zhai et al. proposed a novel layer-based CGH algorithm, which uses hybrid iterative angular spectrum propagation to reduce the noise caused by inter-layer crosstalk. In short, the information capacity and reconstruction quality of CGH are greatly improved, and optical keys such as phase, wavelength, and diffraction distance can be introduced in the encoding process.

[0030] Therefore, the present invention proposes a hybrid encryption and decryption method based on chaotic system and optical key. The core of the method is to generate chaotic sequence through five-dimensional Hamiltonian conservative chaotic system (FHCCS), combine it with computer generated hologram (CGH) based on layered hybrid iterative angular spectrum method, and introduce diffraction distance and wavelength as optical key to construct an optical codebook with high security and large information capacity.

[0031] Embodiment 1:

[0032] Reference Figure 1 As shown, the embodiment of the present invention discloses a hybrid encryption method based on a chaotic system and an optical key, comprising the following steps:

[0033] S1. Generate a chaotic key from the initial information and initial key of the object to be encrypted, and use FHCCS to generate a chaotic sequence for the chaotic key; the object to be encrypted can be data, text, etc., such as a piece of text information, a group of data, etc.

[0034] In this step, the SHA-256 hash algorithm can be used to generate an initial information hash value, which is combined with multiple initial keys K1, K2, K3, K4, K5 to generate multiple chaotic keys K_1, K_2, K_3, K_4, K_5; and then FHCCS is used to generate the corresponding chaotic sequences R_1, R_2, D_1, S_1, R_3.

[0035] S2, scrambling and grouping the initial information according to the chaotic sequence, selecting the chaotic scrambling diffraction distance as the optical key; and generating a computer-generated hologram using a layered angular spectrum method according to the diffraction distance;

[0036] In this step, the original information is scrambled and grouped using R_1, encrypted using R_2, and the diffraction distance is selected as the optical key, and the pure phase CGH is generated using the layered angular spectrum method.

[0037] S3, using the chaotic sequence to encrypt the CGH to obtain an optical code book. D_1 can be used to perform diffusion encryption on the CGH, S_1 can be used to scramble the CGH, and then D_1 can be used to perform secondary diffusion encryption on the CGH.

[0038] S4, encrypt the ciphertext of the optical code book using the chaotic sequence to obtain the ciphertext of the final encrypted object. This step is to encrypt the ciphertext using R_3.

[0039] In this embodiment, the initial information is scrambled and grouped using a chaotic sequence generated by FHCCS, and then a layered angular spectrum iteration method is used to make a computer-generated hologram, and the wavelength and the diffraction distance of the chaotic encryption are used as the optical key. Finally, the chaotic sequence generated by FHCCS is used to encrypt the computer-generated hologram, and at the same time, the transmitted plaintext information is encrypted using the chaotic sequence. The generated optical code book realizes high-density information storage and encryption. The present invention can be widely used in the field of information security, such as data encryption, information hiding, identity authentication, etc.

[0040] The above steps of the present invention are described in detail below through specific embodiments:

[0041] Step S1: Chaotic sequence generation

[0042] In order to verify the feasibility and security of the proposed invention, the original message is arranged in the order of 26 letters and two punctuation marks "," and "." as an example, and the generation process and performance analysis are described, where "," represents the interval between messages and "." represents the end of message delivery. In order to improve the sensitivity of the chaotic key and the ability of the optical code book to resist brute force attacks, a chaotic key related to the initial message is designed and used.

[0043] First, the hash value of the initial information is calculated using the SHA-256 hash algorithm to obtain a 32-byte binary sequence, which is divided into 8 groups of binary sequences and recorded as Digest. Then, the initial keys K1, K2, K3, K4, and K5 are set. Each initial key is 8 32-bit unsigned integers. The value of the initial key must make the SE complexity of the generated chaotic sequence greater than 0.5. If it is less than 0.5, the value of K1 needs to be readjusted. Among them, SE complexity refers to: the larger the SE value of Spectral Entropy Complexity (SE complexity), the more random the random sequence is. For example, multiplying Digest and K1 to obtain a vector of 8 64-bit unsigned integers, recorded as Key. The discrete space chaotic map is used to evenly map the Key to the entire 64-bit space. The iterative mapping process is shown in formula (1), where i = 1, 2, ..., 8.

[0044]

[0045] In the formula, i = 1, 2, 3, 4, 5, 6, 7, 8; x represents the intermediate variable for calculating the Key; key represents the intermediate variable obtained by multiplying the Digest and the initial key.

[0046] Finally, the Key is mapped to a suitable floating point space through formula (2) to generate the chaotic key K_1. Among them, Si and Li are related to the dynamic behavior of the FHCCS system. In order to ensure that the system does not have a periodic window, it is necessary to set appropriate values ​​to ensure that the system generates chaos stably. In addition, the same method can be used to generate chaotic keys K_2, K_3, K_4, and K_5 in sequence. The process is as follows: Figure 2 As shown in part (a).

[0047]

[0048] Compared with ordinary chaotic systems, high-dimensional hyperchaotic systems have larger key spaces, more control parameters and more complex dynamic behaviors. Therefore, a new five-dimensional HCCS (FHCCS) is used to generate chaotic sequences for use in our optical codebook, which contains as few elements as possible and exhibits hyperchaotic characteristics in a wide range of parameters. The expression of FHCCS is shown in formula (3).

[0049]

[0050] Among them, a, b, c, x1, x2, x3, x4, x5 are the 8 values ​​of the key K_1. Then input the keys K_1, K_2, K_3, K_4, K_5 into FHCCS respectively to obtain the chaotic sequences R_1, R_2, D_1, S_1, R_3. The process is as follows: Figure 2 As shown in part (b).

[0051] R_1, R_2, D_1, S_1, R_3, i.e., the chaotic sequence generated by the chaotic keys K_1, K_2, K_3, K_4, K_5 through FHCCS; R_1 is used to scramble the initial information of the group; R_2 is used to generate seven chaotically encrypted diffraction distances; D_1 is used for diffusion encryption CGH; S_1 is used for scrambling encryption CGH; R_3 is used for ciphertext chaotic encryption.

[0052] When chaotic sequences are applied to the codebook, they are modified into chaotic sequences with the same size as the information to be encrypted and without repeated elements, where R_1, R_3, S_1 are the same size as the information to be encrypted, R_2 is the same size as the diffraction distance range used as the optical key, and D_1 is mapped to the range of [0,255] and meets the required size to be diffused.

[0053] Step S2: Chaotic encryption and optical key

[0054] The spatial distribution characteristics of three-dimensional computer holography provide huge capacity for the storage and display of information. Therefore, this embodiment adopts the layered iterative angular spectrum method to produce a computer hologram. The encrypted hologram is used as a code book. The original information is a sequence of 26 letters and two punctuation marks "," and ".". Assume that the transmitted plaintext information is "BRB,TTYL.", "BRB" and "TTYL" are common English abbreviations, respectively representing "Be Right Back" and "Talk to you later". The plaintext is the corresponding symbol position, which can be expressed as "02, 18, 02, 27, 20, 20, 25, 12, 28".

[0055] First, the original information is scrambled and divided into seven groups using the chaotic sequence R_1 to make it random and free from human intervention. This is the first step of the optical codebook chaotic encryption. Next, each group is used as a layer in the hologram to make Figure 2 The seven-layer image shown in part (c) of the figure. The plaintext information can be encrypted into "32, 23, 32, 64, 31, 31, 63, 34, 24" according to the information after scrambling grouping by R_1, corresponding to the number of layers and the sequence number within the layer. The ciphertext after chaotic encryption can effectively resist known plaintext attacks.

[0056] The following is the introduction of optical key and the generation of CGH. First, the chaotic sequence R_2 is used to encrypt and select the diffraction distance corresponding to the seven sets of encrypted data. It must meet the diffraction spacing and be arranged in sequence to reduce inter-layer interference. The obtained diffraction distance is recorded as Figure 2 Then, the diffraction distances assigned according to the seven-layer information correspond to Figure 2 The seven-layer image shown in part (c) uses the GS algorithm of the layered angular spectrum method to generate a phase-only CGH.

[0057] The ciphertext after the introduction of the optical key can be expressed as "143212531432191414311431191314341254", where the layer number is replaced by the diffraction distance. The diffraction distance as the optical key can be expressed using other bases, group replacement or compression coding technology to make the ciphertext shorter.

[0058] Step S3, CGH code book

[0059] CGH is encrypted into an optical codebook through chaos to improve security and maintain the generality of its transmission. The CGH encryption process is diffusion-scrambling-diffusion. First, in the diffusion process, the M×N size CGH is expanded to M×M size by zero padding, and then the chaotic sequence D_1 is used to perform forward or backward row and column diffusion on the zero-padded expanded CGH. The first step is forward row diffusion, and the diffusion process is shown in formula (4), where i = 2, 3, ..., M.

[0060]

[0061] In the formula, P is the object to be encrypted (CGH image), C represents the object after diffusion encryption, such as an image; 257 is used to keep the grayscale value of the encrypted image between 0 and 256. i, j, and l are used to calculate the intermediate variables of the diffusion encrypted image C.

[0062] The second step is forward column diffusion. The diffusion process is shown in formula (5), where j = 2, 3, ..., M.

[0063]

[0064] The forward diffusion diffuses the image information from the upper left to the lower right. The third step is the backward row diffusion, and the diffusion process is shown in formula (6), where q = M-1, M-2, ..., 1.

[0065]

[0066] The fourth step is back column diffusion. The diffusion process is shown in formula (7), where l = M-1, M-2, ..., 1.

[0067]

[0068] Backward diffusion makes the image information diffuse from the lower right to the upper left. After multiple rounds of diffusion in the above process, the image reaches the full diffusion fusion of CGH and chaotic sequence D_1. This process is as follows Figure 3 As shown in part (a), Diffusion1 represents the process of diffusion using chaotic sequence D_1, and Scrambling represents the process of scrambling.

[0069] The scrambling process is Figure 3 As shown in part (b), the chaotic sequence S_1 is used to scramble the diffused CGH, where Shuffle means dividing the CGH into blocks and scrambling it, and Merge means merging the blocks into a maximum block. The last step is the secondary diffusion process, as shown in Figure 3 As shown in Diffusion2 in part (a), the chaotic sequence D_1 is used to perform secondary diffusion on the scrambled CGH.

[0070] After the diffusion-scrambling-diffusion chaotic encryption process, CGH encryption becomes an optical code book, such as Figure 2 As shown in part (e), its pixel values ​​and positions have changed significantly, effectively hiding all the information of the original data.

[0071] For the optical codebook, the initial information is encrypted using two chaotic keys, and the CGH encoding is encrypted using the optical key of the diffraction distance. Finally, the CGH is encrypted twice after diffusion and scrambling of the two chaotic keys to obtain the optical codebook.

[0072] The hybrid encryption method of chaotic key and optical key significantly improves the security of information transmission, ensuring that the ciphertext is not easily cracked or tampered with during transmission. At the same time, the three-dimensional CGH code book can encrypt and store unlimited data in principle, and can be combined with chaotic cryptography for optical implementation, solving the problems of low security, small amount of information carried, slow information extraction speed of traditional code books, and can effectively resist violent destruction such as cropping or occlusion.

[0073] Step S4: Chaotic encryption of ciphertext

[0074] In order to prevent attackers from using frequency characteristics to analyze ciphertext, hide CGH parameter information and optical keys, and further improve security, a chaotic sequence of the same length as the ciphertext is used to further encrypt the ciphertext. First, each element in the ciphertext corresponds to the element position of the chaotic sequence R_3, then the chaotic sequence R_3 is sorted, the ciphertext at the corresponding position is mapped, and then each digit in the ciphertext is XORed with the last binary digit of each digit in the chaotic sequence R_3, thereby obtaining the ciphertext "540251213809014040321225024224050340". The process is as follows: Figure 2 As shown in part (f).

[0075] The ciphertext encrypted by the chaotic sequence R_3 can better resist ciphertext attacks. Only by generating the information of the chaotic sequence R_3 with the correct chaotic key can the ciphertext with the correct value and order be restored. To further resist frequency analysis attacks, the same plaintext can be added to the optical codebook, and different diffraction distances and positions within the layer can be used. This method can average the ciphertext frequency distribution, making frequency analysis more difficult.

[0076] Embodiment 2:

[0077] Reference Figure 4 As shown, the embodiment of the present invention further discloses a hybrid decryption method based on a chaotic system and an optical key. The decryption process performed by the encryption method of embodiment 1 includes the following steps:

[0078] S100, obtaining a chaotic key corresponding to the object to be decrypted; the chaotic key includes: K_1, K_2, K_3, K_4, K_5; using the chaotic key to generate a corresponding chaotic sequence through FHCCS; the chaotic sequence includes: R_1, R_2, D_1, S_1, R_3;

[0079] S200, decrypting the ciphertext of the object to be decrypted according to R_3 to obtain the ciphertext of the optical code book;

[0080] S300, decrypting the optical codebook according to the chaotic sequences S_1 and D_1 to obtain a computer generated hologram;

[0081] S400, placing the computer generated hologram in an optical experimental system, using the computer generated hologram and an optical key to decrypt the ciphertext to obtain a final decrypted plaintext.

[0082] In this embodiment, multi-dimensional chaotic keys and optical keys are required for decryption, as well as a computer-generated holographic three-dimensional display experimental system, which can achieve rapid reconstruction and extraction of decrypted information. Theoretical and experimental research results show that this scheme has superior security and feasibility.

[0083] The decryption process of the encrypted object in the above-mentioned embodiment 1 of the present invention is described below through a specific embodiment:

[0084] Step S100: Chaotic sequence generation

[0085] The chaotic keys K_3, K_4 and K_5 are input into FHCCS to generate chaotic sequences S_1, D_1 and R_3 respectively.

[0086] Step S200: Chaotic decryption of ciphertext

[0087] XOR each number in the ciphertext with the last binary digit of each number in the chaotic sequence R_3. Then correspond the sorted chaotic sequence R_3 to the position of the ciphertext "540251213809014040321225024224050340", obtain the position index of the original chaotic sequence R_3 according to the order sequence R_3, and obtain the ciphertext "143212531432191414311431191314341254" according to the position index ciphertext. The process is as follows: Figure 6 As shown in part (a).

[0088] Step S300: Decryption of the codebook

[0089] The chaotic decryption of the codebook is the reverse process of the CGH chaotic encryption. The CGH is reverse diffused by the chaotic sequence D_1 generated by the key K_3, and the chaotic sequence S_1 generated by the key K_4 is reverse scrambled. The chaotic sequence D_1 is reverse diffused again to obtain the CGH after chaotic decryption, as shown in Figure 5 As shown in part (d).

[0090] Step S400: Extracting codebook information

[0091] First, the original information is restored in the optical path. The schematic diagram of the experimental device is shown in Figure 5 As shown in part (a), the optical experimental system is as follows Figure 5 As shown in part (b) of the figure. The laser (LWRL633-20mW) is used as the light source, the pinhole filter and the double convex lens are used for beam expansion and collimation, and the polarizer modulates the polarization state of the incident spatial light modulator (LETO-3-CFS-127). The chaotic decrypted CGH is loaded onto the SIM, and the reflective SLM reflects the light containing the hologram information to the 4f system through the BS. The SCMOS camera (BeamOn U3-VIS NIR) records the reconstruction information. The reconstruction results are shown in Figure 5 As shown in part (d), when the optical key such as wavelength and diffraction distance is correct, the clear codebook storage information is obtained. When the chaotic key is wrong, the reconstruction result is as follows Figure 5 As shown in part (c), the attacker cannot obtain any valid information of the codebook from the reconstruction result.

[0092] The process of extracting codebook information using decrypted ciphertext is as follows: Figure 6 The first group of information in the ciphertext is 1432. According to the diffraction distance d = 143 mm and the position in the layer r = 2, the extraction result in the optical code book is B. According to this rule, the code book information of all ciphertext transmissions is extracted, and the following is obtained: Figure 6The plain text information shown in part (c) is: "BRB, TTYL.", and then we get: "Be Right Back, Talk to you later.".

[0093] The hybrid encryption and decryption method based on chaotic system and optical key provided by the present invention has high security, which can be analyzed and explained from three aspects:

[0094] 1 Key space analysis

[0095] The key space is the set of all possible keys, which directly affects the security and strength of the encryption algorithm. The larger the key space, the stronger the ability to resist brute force attacks. The chaotic key used in the present invention is composed of 8 double-precision floating-point numbers, 5 of which are used as initial values ​​and 3 as system parameters. Chaotic encryption uses 5 chaotic keys, K_1, K_2, K_3, K_4 and K_5, so the chaotic keys used are 40 double-precision floating-point numbers. A double-precision floating-point number is represented by a 64-bit binary number, so the chaotic key space of the code book is 2 2560 , which is much larger than the key space that can be cracked under the computing power of current computers. In addition, the key space of the optical codebook adds optical keys such as diffraction distance, position in the layer, and wavelength combined with chaotic keys. The combination of optical keys and chaotic keys makes the key space of the optical codebook huge, the key form is changeable, and it can completely and effectively resist brute force cracking attacks.

[0096] 2 Key sensitivity analysis

[0097] The five chaotic keys of the present invention, K_1, K_2 and K_5, are used for text data encryption, and the Hamming distance is used for sensitivity evaluation, because text data is discrete and reflects changes at the bit level. On the other hand, K_3 and K_4 are used for image data, and the sensitivity is evaluated by the correlation coefficient (CC), because image data has spatial correlation, and the correlation coefficient better captures the impact of key changes on the overall image structure.

[0098] Taking the code book of the present invention as an example, if one of the digits of the key K_1 changes by 2 -30 Deviation, the Hamming distance between the correct 28-character group and the group obtained with the wrong key K_1 is 26. If one of the digits in the key K_2 changes by 2 -30 Deviation, the Hamming distance between the correct 7 diffraction distances and the diffraction distance obtained by the wrong key K_2 is 7. The results show that when the key has a slight deviation, the result obtained is very different from the original value, and the attacker cannot infer other plaintext ciphertext pairs from the known plaintext ciphertext pairs.

[0099] The quality of information reconstruction after decryption is closely related to the key. When the key deviates, the quality of information reconstruction will drop rapidly, resulting in failure in extracting the transmitted information. Figure 7 Part (a) is the CC value of information reconstruction when a single key K_3 changes. Figure 7 Part (b) is the information reconstruction CC value when a single key K_4 changes, from Figure 7 (a) and Figure 7 From the reconstructed image in (b), it can be seen that when the keys K_3 and K_4 are correct, the valid information can be completely extracted, but when the key has a slight deviation, the CC value drops rapidly and no valid information can be extracted.

[0100] Decrypting the ciphertext requires the correct chaotic key K_5 to generate the chaotic sequence R_3. -30 The chaotic sequence R_3 will also deviate, and the decrypted transmission ciphertext result is "204312528345934355020040114251113021". After combining with the optical key, no valid information can be extracted from the optical code book according to "2043". The experimental results are as follows Figure 7 As shown in part (c).

[0101] In addition, the chaotic key generation of the present invention adopts the SHA-256 algorithm, which has good plaintext sensitivity. Even if the initial information changes slightly, the generated key will be completely different, resulting in completely different encryption results, which greatly improves the security of the optical code book.

[0102] 3 Analysis of Anti-cropping Attack

[0103] The codebook is prone to clipping or information loss during transmission. The optical codebook of the present invention can effectively overcome such problems. We perform middle clipping and upper left corner clipping attacks on the optical codebook to evaluate the information recovery ability of the codebook when part of the data is damaged. The CC value of the reconstructed result of the clipped codebook is as follows: Figure 8 As shown in the figure, part (a) represents the middle cropped reconstruction result, and the upper left corner of part (b) is the cropped reconstruction result; in the relationship curve between the cropping ratio and the CC value of the reconstruction result, the red, green and yellow points correspond to the cropping ratio on the left and the reconstruction result after decryption.

[0104] Experimental results show that the optical codebook proposed in the present invention can effectively resist clipping attacks or information loss. When the codebook data loss or damage ratio exceeds 50%, the reconstruction effect is still good. Therefore, the optical codebook has excellent anti-clip ability, ensuring the security and effectiveness of the codebook in practical applications.

[0105] The chaotic sequence generated by the FHCCS used in the present invention is extremely sensitive to the key, and the obtained codebook has high security and strong randomness, and can effectively resist violent attacks. By adopting an encryption method combining optical keys with chaotic keys, the light field codebook inherits the advantages of optical encryption such as efficient information storage, fast decryption speed and high parallelism, and has advantages that traditional codebooks do not have, such as high shear resistance and high security. Experiments and analysis show that, in addition, the codebook proposed by the present invention has the advantages of large information storage capacity, high security, fast decryption speed, etc., and has great practical application potential.

[0106] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0107] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A hybrid encryption method based on chaotic system and optical key, characterized in that: The steps include: S1. Generate a chaotic key from the initial information and initial key of the encrypted object, and use a five-dimensional Hamiltonian conservative chaotic system to generate a chaotic sequence for the chaotic key; S2, scrambling and grouping the initial information according to the chaotic sequence, and selecting the diffraction distance of the chaotic scrambling as the optical key; and generating a computer-generated hologram using a layered angular spectrum method according to the diffraction distance; S3, using the chaotic sequence to encrypt the computer generated hologram to obtain an optical code book; S4. Encrypt the ciphertext of the optical code book using the chaotic sequence to obtain the ciphertext of the final encrypted object.

2. A hybrid encryption method based on chaotic system and optical key according to claim 1, characterized in that: The step S1 comprises: S11. Calculate the hash value of the initial information of the object to be encrypted using the SHA-256 hash algorithm to obtain a 32-byte binary sequence; S12, dividing the binary sequence into 8 equal groups and recording them as Digest; S13, set initial keys K1, K2, K3, K4, K5, each of which is 8 32-bit unsigned integers; S14, multiply Digest by K1, K2, K3, K4, and K5 respectively, to obtain five groups of eight 64-bit unsigned integer vectors, recorded as Key; S15, using discrete space chaotic mapping to evenly map each group of keys to the entire 64-bit space; S16, mapping the five groups of Key to the corresponding floating point space, thereby generating chaotic keys K_1, K_2, K_3, K_4, K_5; S17. Input the chaotic keys K_1, K_2, K_3, K_4, and K_5 into the five-dimensional Hamiltonian conservative chaotic system respectively to obtain chaotic sequences R_1, R_2, D_1, S_1, and R_3.

3. A hybrid encryption method based on chaotic system and optical key according to claim 2, characterized in that: In step S15, the formula (1) of the mapping process is as follows: In the formula, i = 1, 2, 3, 4, 5, 6, 7, 8; x represents the intermediate variable for calculating the Key; key represents the intermediate variable obtained by multiplying the Digest and the initial key.

4. A hybrid encryption method based on chaotic system and optical key according to claim 3, characterized in that: In step S16, the Key is mapped to the corresponding floating point space by the following formula: In the formula, S i , L i Indicates the value set to adjust the Key value to ensure that the system does not have a periodic window.

5. A hybrid encryption method based on chaotic system and optical key according to claim 4, characterized in that: In step S17, the formula of the five-dimensional Hamiltonian conservative chaotic system is as follows: In the formula, a, b, c, x1, x2, x3, x4, and x5 are used to represent the eight values ​​of the chaotic key, among which a, b, and c are used as system parameters.

6. A hybrid encryption method based on chaotic system and optical key according to claim 5, characterized in that: The step S2 comprises: S21, using the chaotic sequence R_1 to scramble and group the initial information; S22, using the chaotic sequence R_2 to select the diffraction distance corresponding to the grouping information, and ensuring the diffraction spacing, and arranging them in sequence to reduce inter-layer interference; the diffraction distance is used as an optical key; S23. Generate a computational hologram using a layer-based hybrid iterative angular spectrum method according to the grouping information and the corresponding diffraction distance.

7. A hybrid encryption method based on chaotic system and optical key according to claim 6, characterized in that: The step S3 comprises: S31, expanding the CGH into a larger matrix by zero padding; S32, using the chaotic sequence D_1 to perform forward or backward row and column diffusion on the expanded matrix; S33, using the chaotic sequence S_1 to scramble the diffused matrix; S34. Use the chaotic sequence D_1 to perform secondary diffusion on the scrambled matrix to obtain an optical codebook.

8. A hybrid encryption method based on chaotic system and optical key according to claim 7, characterized in that: The step S4 comprises: S41, corresponding each element in the ciphertext of the optical code book to the element position of the chaotic sequence R_3, sorting the chaotic sequence R_3, and performing ciphertext mapping at the corresponding position; S42, XOR each digit in the ciphertext with the last binary digit of each digit in the chaotic sequence R_3, so as to obtain the ciphertext of the final encrypted object.

9. A hybrid decryption method based on chaotic system and optical key, characterized in that: Decrypting an encrypted object using a hybrid encryption method based on a chaotic system and an optical key according to any one of claims 1 to 8, the decryption method comprising: S100, obtaining a chaotic key corresponding to the object to be decrypted; the chaotic key includes: K_1, K_2, K_3, K_4, K_5; using the chaotic key to generate a corresponding chaotic sequence through FHCCS; the chaotic sequence includes: R_1, R_2, D_1, S_1, R_3; S200, decrypting the ciphertext of the object to be decrypted according to R_3 to obtain the ciphertext of the optical code book; S300, decrypting the optical codebook according to the chaotic sequences S_1 and D_1 to obtain a computer generated hologram; S400, placing the computer generated hologram in an optical experimental system, using the computer generated hologram and an optical key to decrypt the ciphertext to obtain a final decrypted plaintext.

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