An optimal hidden dual protection text method

Abstract

This invention discloses an optimal method for dual-protection text hiding, comprising the following steps: Step 1: Encrypting the carrier text using the SHA256 algorithm to generate a hash digest 'a'; Step 2: Embedding the secret information and hash digest 'a' into the three components of the carrier text's color pixel values ​​R, G, and B using an information hiding algorithm to form steganographic text; Step 3: Sending the steganographic text to a receiver; Step 4: The receiver receives the file, which is either steganographic text, legally modified steganographic text, or illegally tampered steganographic text; Step 5: The receiver extracts a hash digest 'b' from the file using the SHA256 hash algorithm; Step 6: Checking if hash digest 'b' is equal to hash digest 'a'. If they are not equal, it indicates that the secret information has been illegally tampered with; if they are equal, the receiver extracts the secret information. This invention combines hash encryption technology with text information hiding technology that minimizes pixel modification, thereby ensuring the integrity and security of the file during transmission to a greater extent.

Description

Technical Field

[0001] This invention relates to the field of encrypted information technology, and in particular to an optimal method for hiding double-protected text. Background Technology

[0002] With the rapid development of multimedia technology and the widespread adoption of internet applications, the trend towards digitization and networking of information is inevitable, greatly promoting changes in social production, daily life, and information dissemination. The internet provides a more convenient and rapid transmission channel for information interaction, enabling people to exchange and share information anytime, anywhere. A large amount of digital information is transmitted through the internet, including important and sensitive data such as military intelligence, e-commerce information, and personal privacy. Due to the openness of the internet environment and the vulnerability of digital information, information security risks are becoming increasingly complex, with problems such as the illegal copying and dissemination of digital works, the leakage of personal privacy, and the tampering of confidential information emerging one after another. How to ensure data security during transmission has become one of the most pressing problems to be solved in the field of information security.

[0003] Encryption technology [8,15] is an important support for the field of information security. The numbers in parentheses refer to the reference numbers in the following references. Encryption technology refers to the method of using a key and encryption algorithm to convert plaintext to be transmitted into ciphertext that is difficult for ordinary people to understand, thereby protecting data security. Its essence is data transformation under specific mapping rules. Encryption technology is mainly divided into three categories: symmetric-key algorithm

[16] , asymmetric-key algorithm [5], and digest algorithm [6]. Symmetric algorithm refers to a cryptographic algorithm in which the encryption key and decryption key are the same. It includes AES, SM1, SM4, DES, 3DES, IDEA, and RC2. Asymmetric algorithm refers to a cryptographic algorithm in which the encryption key and decryption key are different. Common asymmetric algorithms include RSA, SM2, DH, DSA, ECDSA, and ECC. Digest algorithm is a cryptographic algorithm that converts any input message data of arbitrary length into output data of fixed length. It is also called a hash function. Digest algorithms are commonly used to determine data integrity; that is, they perform hash calculations on data and then compare the digest values ​​to see if they match. Digest algorithms are mainly divided into three categories: MD (Message Digest) series, SHA (Secure Hash Algorithm) series, and MAC (Message Authentication Code) series.

[0004] Encryption technology can effectively hide the semantic content of secret information, but the ciphertext usually appears as a bunch of meaningless gibberish, clearly indicating the existence of the secret information, which can easily entice attackers to decipher it. Even if attackers cannot reverse engineer the plaintext information, they can still track, tamper with, or destroy it, preventing the recipient from successfully extracting the original plaintext information, thereby interfering with covert communication. It is clear that relying solely on encryption algorithms cannot conceal the communication itself, and it is difficult to ensure data security under open channel conditions.

[0005] To reduce the possibility of secret information being attacked, information hiding technology [9,11,18] embeds secret information into a selected carrier in an imperceptible manner, achieving covert communication through the public transmission of the carrier. Information hiding can effectively conceal the existence of secret information, making it "imperceptible" instead of "incomprehensible," thereby avoiding attracting the attention of attackers and achieving the effect of preventing theft or destruction. Information hiding utilizes the redundancy characteristic that is common in multimedia information to secretly hide meaningful secret information, such as software serial numbers, ciphertext, or copyright information, within multimedia information using a certain algorithm. Typically, the carrier can be text, images, audio, and video, etc. Currently, the most extensive and in-depth research focuses on information hiding using images as carriers. This is mainly because images contain a large amount of redundant information, allowing for a large hiding capacity. On the other hand, it is also due to the intuitiveness of image processing. Based on these advantages of image carriers, some secret information can be hidden within them without arousing suspicion. However, text files are the most popular and convenient mass-market information media tool, and using text for secure communication is the most convenient method. However, text files are directly encoded text data, with almost no data redundancy. Therefore, it's impossible to hide information by modifying the original file's valid data. Thus, hiding information using text is quite difficult, but text containing secret information is often less likely to be suspected, offering relatively good security. Therefore, text-based information hiding has significant practical implications and application prospects. Encryption technology aims to encrypt communication content, generating a bunch of meaningless gibberish. Information hiding technology, on the other hand, focuses more on hiding the communication behavior itself. In the field of covert communication, information hiding technology offers more ideal security.

[0006] Related technical introduction

[0007] 1. Character feature methods[7] can hide text information by changing a certain feature of the text, such as font size or font style. For example, secret information can be hidden by changing the font style, or by changing the dots of i and j, or by lengthening or shortening the ends of h, d, and b. This method is visually more concealed because readers may not notice individual letter changes. However, since there are few objects in the carrier that can be used for format modification, the amount of secret information embedded in the imported carrier text is small, resulting in low hiding capacity. Furthermore, the secret information will be lost if the text format is modified or the text is re-entered during transmission. Moreover, this method may require the creation of a new font, which is quite difficult.

[0008] 2. Syntactic Methods [1] aim to transform the text structure to embed secret information, such as moving the position of adverbs, adding formal subjects, or changing active to passive. By changing the text structure to embed secret information, for example, using different syntaxes to represent the same meaning, the sender sets rules to first convert the secret information into a binary stream. One syntax represents the embedded data "0", and another syntax embeds the data "1". If there are multiple syntaxes, more than two binary bits can be embedded at the same time, which can increase the embedding capacity of the hiding method. Although more than two binary bits can be embedded, there are relatively few places where different syntax structures can be used to express the same meaning. Perhaps there are only a few in a few thousand words of text bytes, so its usage opportunities are very limited. Therefore, the embedding capacity of this method is not high, but the concealment is good. The syntax results are diverse, and even if the reader sees the difference in syntax structure, they will not notice that there is secret information hidden inside.

[0009] 3. Semantic Methods

[23] aim to modify text content to insert secret information. The following describes a method for embedding secret information by modifying text content. Specifically, two synonyms are designated as primary or secondary values. The sender sets a rule that one word represents embedded data "1" and one data represents embedded data "0". When there are many synonyms, a group of synonyms can embed two or more secret information. This method is used relatively infrequently and has a small embedding capacity. Furthermore, the use of too many synonyms may be noticed by the reader. However, this method has good robustness and is not easily modified.

[0010] 4. Double Space Methods (DS96), Open Space method [1,23] hides secret information by manipulating whitespace, concealing it within the cover text using blank spaces. For example... Figure 2The image shows an example of text content using sentence-space steganography. This method hides information by controlling the spaces between sentences in the carrier text. The secret information is converted into a binary bit stream, and one or two spaces are placed after the terminating character of each sentence. The sender sets rules, such as one space hiding a binary '0' and two spaces hiding a binary '1'. When the receiver receives the carrier text, it extracts the secret information according to the rules. This method suffers from low efficiency; the amount of text that can be hidden depends on the number of sentences. Even so, a large amount of text is needed to hide a small amount of secret information. Furthermore, many word processors automatically set inter-sentence spaces, which can completely destroy the hidden secret information. Also, different spaces are visible to the human eye, making this method relatively undetectable.

[0011] 5. Regular Space with Unicode Space (RSUS15), Kumar et al.

[10] proposed the USC15 text steganography method, which uses Unicode space characters to hide secret data information in Microsoft Word files. By reducing the font size, the width of Unicode characters is standardized so that their width is equal to the width of hair or Six-Per-Em Unicode characters. This method can hide 4 bits of secret data in the space between words and sentences, and 3 bits of secret information in the space between paragraphs or at the end of lines.

[0012] 6. Steganography and encryption techniques, Color Coding Approach (CC17), Malik et al.

[14] proposed the CC17 text steganography method, which uses Move To Front (MTF) encoding, Huffman compression and color encoding, and hides secret data by forwarding email platforms. The method can cover more than 1 bit / character of text. Input: confidential information, cover text; output: steganographic text, a set of email addresses. Extract the binary bits of the secret information according to the color encoding table, extract the email addresses, decompress using Huffman, and then use Move To Front (MTF) encoding to obtain the original secret information.

[0013] 7. Hybrid text steganography (HT17), Aman et al.[2] proposed the HT text steganography method, which performs a series of operations such as permutation, padding, and compression on secret information, and then uses minimum width Unicode to encode the spaces in the cover text to achieve the purpose of information hiding.

[0014] 8. The Minimum Pixel Modification (MPM2022)

[21] method embeds secret information into the cover image carrier. This method modifies the image pixels and uses an optimization function to minimize the modification of the image pixels, thus maintaining good image quality while having a large capacity for hiding. Input: A cover pixel group G = (g0, g1, ..., g n-1 ) and 2k+1 bits of secret information; Output: a group of steganalytic pixels G′=(g′0,g1′,…,g′ n-1 Step 1: Use the formula to find a cover pixel with a specified index;

[0015] g h =q Mod n (4);

[0016] Step 2: Convert the binary secret information into a decimal number d, and group the secret information into blocks, such as (b... k b k-1 …b1b0)2 is converted to decimal d0, and (b yk …b yk+2 b yk+1 )2 converted to decimal d y y∈[1,n-1]; Step 3: Find x in the optimization problem h and x i ;

[0017]

[0018]

[0019]

[0020]

[0021] Embed information g′ in the stegpixel h =x h +g h g i ′=x i +g i Step 4: Merge g′ h and g i We get G′=(g′0,g1′,…,g′) h ,…,g′ n-1 ). via d h =g′ h mod m0 and d i =g i 'mod m1 get d h and d i , merged dh and d i Obtain the secret information.

[0022] References

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[0046] Therefore, the drawback of existing technologies is that while current encryption techniques can effectively hide the semantic content of secret information, the ciphertext usually appears as a bunch of meaningless gibberish, clearly indicating the existence of the secret information and making it vulnerable to tracking, tampering, and destruction. Existing text hiding technologies suffer from low secret information hiding capacity; susceptibility to modification and corruption during transmission; and relatively low concealment. Summary of the Invention

[0047] In view of at least one deficiency of the prior art, the purpose of this invention is to provide an optimal hidden dual-protection text method that combines hash encryption technology with text information hiding technology that minimizes the modification of pixels, thereby ensuring the integrity and security of files during transmission to a greater extent and realizing dual covert communication; it is the first to propose a text information hiding technology that uses the RGB three-channel pixels of the modified text font to greatly increase the embedding capacity and improve the undetectability of the text, and it is innovative.

[0048] To achieve the above objectives, the present invention adopts the following technical solution: an optimal hidden double-protected text method, comprising the following steps: Step 1: Encrypting the carrier text using the SHA256 hash algorithm to generate a hash digest a; Step 2: Embedding the secret information and hash digest a into the R, G, and B components of the color pixel values ​​of the carrier text using an information hiding algorithm to form steganographic text; Step 3: Sending the steganographic text to the receiver; Step 4: The receiver receives the file, which is steganographic text, legally modified steganographic text, or illegally tampered steganographic text; Step 5: The receiver uses the SHA256 hash algorithm to extract hash digest b from the file; Step 6: Determining whether the regenerated hash digest b is equal to the extracted hash digest a. If they are not equal, it indicates that the secret information has been illegally tampered with by an attacker, and the receiver discards the file; if they are equal, it indicates that the file is steganographic text or legally modified steganographic text, proceeding to Step 7; Step 7: The receiver extracts the secret information.

[0049] Step two employs the following information hiding algorithm to embed the secret information and hash digest a into the R, G, and B components of the color pixel values ​​of the carrier text;

[0050] Input: Carrier text, font color, RGB three-channel G1, G2, G3 and 3nk+3 bits of secret information;

[0051] Output: Steganographic text G1′, G2′, G3′;

[0052] The embedding process includes the following steps:

[0053] Step 21: Process the carrier text information; Step 21 further includes:

[0054] Step 211: Obtain the pixel value of each letter in the carrier text, and use P(i,1), P(i,2), P(i,3) to represent the pixel values ​​of the R, G, and B components of the i-th letter; denoted as P(i,a), a = 1, 2, 3;

[0055] Step 212: Obtain the pixel values ​​of the R, G, and B channels of each letter in the carrier text, and represent them as G1, G2, and G3 respectively; merge G1, G2, and G3 into G; G is the total number of pixel values ​​of the carrier text.

[0056] Step 213: Group the total number of obtained pixel values ​​into groups of n pixels;

[0057] Step 22: Processing secret information; Step 22 further includes:

[0058] Step 221: Divide the 3nk+3 bit secret information into 3 groups, each group having nk+1 bits, as follows:

[0059] B3=(b 3nk+3 b 3nk+2 …b 2nk+3 b 2nk+2 )2;

[0060] B2=(b 2nk+1 b 2nk …b nk+2 b nk+1 )2;

[0061] B1=(b nk b nk-1 …b1b0)2;

[0062] Where n represents a group of pixels containing n pixels, and k is the embedding degree. The larger k is, the more secret information is embedded.

[0063] Step 222: Convert the binary confidential information B1, B2, and B3 of each group into decimal numbers D;

[0064] D3 = 2 nk b 3nk+3 +2 nk-1 b 3nk2 +…+2 1 b 2nk+3 +2 0 b 2nk+2 D2 = 2 nk b 2nk+1 +2 nk-1 b 2nk +…+2 1 b nk+2 +2 0 b nk+1 ;

[0065] D1 = 2 nk b nk +2 nk-1 b nk-1 +…+2 1 b1+2 0 b0;

[0066] Step 223: Divide B1 into n groups, the first group includes k+1 bits, (b k b k-1 …b1b0)2 is converted to decimal number d0, and the remaining n-1 groups are: (b (y+1)k …b yk+2 b yk+1 )2 converted to decimal number d y ,y∈[1,n-1]; similarly, perform these operations on B2 and B3 as well;

[0067] Step 23: Embed secret information; Step 23 further includes:

[0068] The decimal numbers of each group (B1, B2, B3) are embedded into the pixel value of each group. The embedding process for B1 is as follows:

[0069] Step 231: q represents the index of the carrier text color pixel value, and formula (6) is used to index the hidden k+1 bit pixel value, g i g represents the pixel value of the original carrier text font. h This refers to the h-th pixel in a set of carrier text font pixels; using g i ' represents the pixel value of the embedded steganographic text font, g' h This refers to the h-th pixel value in a group of steganographic text font pixels;

[0070] g h =q mod n (6);

[0071] Step 232: Find x in the optimization problem h x h This represents the optimized value found for the h-th pixel value;

[0072]

[0073]

[0074] Using g′ h =x h +g h Embedding secret information;

[0075] Step 233: Simultaneously, in the optimization problem, find x. i x i This represents the optimized value found for the i-th pixel value;

[0076]

[0077]

[0078] Using g′ i =x i +g i Embedding secret information;

[0079] Step 234: Similarly, perform steps 231-233 of step 23 on B2 and B3; Step 235: Set g′ h and g′ i The merging process yields the three-channel pixels G′1, G′2, and G′3 of the steganographic text font (R, G, and B channels).

[0080] Step seven, where the receiver extracts the secret information, includes: obtaining inputs G′1, G′2, G′3, and outputting 3nk+3 bits of secret information; step seven includes the following steps: Step 71: using index g′ i =q mod n, find the pixel value that hides the (k+1)th bit of binary secret information; Step 72: Restore d0 = g′ h mod 2 k+1 ;

[0081] Step 73: Restore d i =g′ i mod2 k Step 74: Set d0, d i Combine the data to obtain the secret information d, and convert it into binary bits.

[0082] Significant effects: This invention provides an optimal method for hiding dual-protected text, combining hash encryption technology with text information hiding technology that minimizes pixel modification, thereby ensuring the integrity and security of files during transmission to a greater extent and achieving dual covert communication; it is the first to propose a text information hiding technology that uses the RGB three-channel pixels of the text font to modify the text information, which greatly increases the embedding capacity and improves the undetectability of the text, and is innovative. Attached Figure Description

[0083] Figure 1 This is the overall flowchart of the present invention;

[0084] Figure 2 This is a diagram illustrating text content using sentence spacing steganography.

[0085] Figure 3 This is a diagram illustrating the process of encrypting data using the SHA256 algorithm to generate a digest.

[0086] Figure 4 These are the eight initial hash values ​​in the SHA256 algorithm;

[0087] Figure 5 It is a 64-bit hash constant in the SHA256 algorithm;

[0088] Figure 6 A schematic diagram illustrating the generation of hash digests in the SHA256 algorithm;

[0089] Figure 7 A text example used for the SHA256 algorithm.

[0090] Figure 8 This is the secret digest obtained using the SHA256 algorithm;

[0091] Figure 9 A binary stream converted from a 256-bit secret digest;

[0092] Figure 10 The original cover text file and the generated summary value are: (a) the content of the original cover text file; and (b) the generated summary value of the cover text file.

[0093] Figure 11 This refers to the legal modification of a text file and the generated digest value; where (a) represents the legally modified content of the text file; and (b) represents the digest value generated by the legally modified text file.

[0094] Figure 12 The text file was illegally modified and the resulting digest value was generated; where (a) is the content of the illegally modified text file; and (b) is the digest value generated by the illegally modified text file.

[0095] Figure 13 This is a comparison chart of the security levels of this invention and other algorithms;

[0096] Figure 14 This is a diagram comparing the original cover text and the steganographic text; where (a) is the content of the original cover text file; and (b) is the content of the cover text file containing the steganographic text.

[0097] Figure 15 The images show an RGB comparison of the original cover text and the steganographic text; where (a) is the RGB image of the original cover text and (b) is the RGB image of the cover text containing the steganographic text.

[0098] Figure 16 This is a comparison chart of the data hiding capabilities of this invention and other algorithms;

[0099] Figure 17 This is a comparison chart showing the number of characters required to hide the same data using this invention and other algorithms. Detailed Implementation

[0100] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0101] like Figure 2 As shown, the Open Space method hides secret information by manipulating whitespace, concealing it within the cover text. An example of text content using sentence-space steganography is provided. This method hides information by controlling the spaces between sentences in the carrier text. The secret information is converted into a binary bitstream, and one or two spaces are placed after the terminating character of each sentence. The sender sets rules, such as one space hiding a binary 0 and two spaces hiding a binary 1. When the receiver receives the carrier text, it extracts the secret information according to these rules. This method suffers from inefficiency; the amount of text that can be hidden depends on the number of sentences.

[0102] Information hiding technology is a technique that embeds secret information into multimedia carriers such as text, images, audio, and video. In recent years, researchers have proposed many image hiding schemes, but research on text information hiding technology is still insufficient. This invention proposes a dual-protection text method (TPM) based on the idea of ​​combining encryption algorithms and text information hiding algorithms, thereby improving the text hiding ability and anti-tampering ability. The main idea of ​​TPM is to generate 256-bit binary data from a text file using the Sha256 hash algorithm, group the pixel values ​​of the R, G, and B channels of the n+1 text fonts into a group, perform a specific modulo operation on each group, and embed the 256-bit binary data and secret information into it. This embodiment compares the performance of TPM with text information hiding algorithms proposed in recent years. TPM shows excellent embedding ability (bits per pixel (bpp)), security, imperceptibility, and resistance to visual attacks, with the highest overall performance. To achieve more secure information communication, this invention proposes to combine encryption technology with text information hiding to achieve dual-coverage communication. This invention proposes a secure contract protection scheme for formatted text files (such as WordPad or .doc files generated from Word documents). This scheme organically combines encryption and information hiding techniques. First, the contract file is encrypted using a hash function to obtain a fixed digest value. Then, text information hiding technology is used to hide the digest value within the contract file before sending it to the intended recipient, thus achieving double-coverage communication. In this embodiment, it has been proven that using the pixel values ​​of text color to carry secret information is a feasible solution. Therefore, a text information hiding method by modifying the pixels of the text font is proposed for file protection. When the intended recipient receives the file, they only need to generate a digest using the same hash function. If the digest matches the extracted secret information, it indicates that the file has not been tampered with or destroyed. Simultaneously, more confidential information can also be hidden within the text file to prevent the leakage of secret data. The innovations and contributions of this invention are as follows:

[0103] 1. By combining hash encryption technology with text information hiding technology that minimizes pixel modification, the integrity and security of files during transmission can be guaranteed to a greater extent, achieving double covert communication.

[0104] 2. This paper proposes for the first time a text information hiding technique using the RGB three-channel pixels of the text font to greatly increase the embedding capacity and improve the undetectability of the text, which is innovative.

[0105] 3. Use text hiding technology to conceal confidential secret data and protect the privacy of files.

[0106] like Figures 1-17As shown, an optimal method for hiding hidden text using dual protection, namely TPM (Text Pixels Modification), is proposed in this invention. This method combines cryptography and steganography to hide text information, and it is divided into two stages. The first stage uses a hash function to encrypt the carrier text and generate a digest. When the digest is transmitted to the receiver, the receiver uses the hash function to generate a digest, thereby verifying the integrity of the transmission process. The second stage involves embedding the encrypted information and the information to be hidden into the R, G, and B components of the color pixel values ​​of the carrier text. Figure 1 The overall flowchart of the proposed algorithm is shown.

[0107] Encryption Process: The basic process of data encryption is to process the original plaintext file or data according to an algorithm, making it an unreadable ciphertext. This method protects data from being stolen or read by unauthorized individuals. The encryption technology used in this paper is the SHA256 (Secure Hash Algorithm 256) algorithm, a cryptographic hash function algorithm. This algorithm includes three stages: constant initialization, information preprocessing, and digest value calculation. The process of generating the digest is as follows... Figure 3 As shown.

[0108] 1. Constant initialization: Take the first 8 prime numbers from the natural numbers, calculate their square roots, extract the 32 bits of the decimal part of the result, convert it to a hexadecimal number, and generate the initial hash value. For example, The 32 bits of the decimal part are converted to hexadecimal numbers using formula (71). The initial value corresponding to the prime number 2 is 6a09e667.

[0109] 0.41421356237309504880168872420970≈6*16 -1 +a*16 -2 +0*16 -3 +…(1);

[0110] Therefore, the 8 initial hash values ​​are as follows: Figure 4 As shown. Next, take the first 64 prime numbers of natural numbers, calculate their cube roots, and convert the 32 bits of their fractional part into hexadecimal numbers to generate a hash constant K. Similar to the initial hash value above, the 64-bit hash constant is as follows: Figure 5 As shown.

[0111] 2. Information preprocessing: Preprocessing refers to adding necessary information after the message for hash calculation, so that the message meets the required structure. Information preprocessing consists of two steps.

[0112] Step 1: Add padding bits.

[0113] Let the number of bits in the binary code of the message be l. Add a "1" after the code bits, and then add k "0" bits, where k is the smallest non-negative integer that satisfies the following equation.

[0114] l+1+k≡448mod512 (2);

[0115] Step 2: Append the length value. Encode the length l of the original message into a 64-bit binary form and append it to the padded message, making the length of the entire message 512 bits or a multiple of 512 bits.

[0116] 3. Calculate the summary value.

[0117] Step 1: Divide the preprocessed message into 512-bit blocks. Assume that message M can be decomposed into n blocks, i.e., M1 to M2. n .

[0118] Step 2: Construct block M1 into 64 words. The first 16 words are directly decomposed into 16 32-bit words, denoted as w[0], w[1], ..., w

[15] . The last 48 words are w t It is generated by iterative calculation using equation (3).

[0119] w t =σ1(w t-2 )+w t-7 +σ0(w t-15 )+w t-16 (3);

[0120] Where σ0 and σ1 are bitwise operations related to logic:

[0121]

[0122]

[0123] Step 3: Calculate the M1 block, and encrypt each word in the M1 block in a loop. The encryption process for h0 to h7 is as follows: Figure 6 As shown: Ch, ∑1, Ma, and ∑0 are nonlinear logic functions, and their representations are shown in formulas (61) to (64). The "+" squares indicate that the numbers are added together and then modulo 2. 32 , for 2 32 Modulo operation. The initial values ​​of h0 to h7 are the previously calculated initial hash values. K0 represents the first hash constant, also known as the hash key. From... Figure 6 As can be seen, adding the first block w[0] of M1 to K0 mod 2 32 The operation is performed, and the resulting value is added to h7 again modulo 2. 32The calculated value is added modulo 2 to the values ​​of h4 to h6 obtained by the Ch nonlinear logic function. 32 The result of the operation is then added to the value obtained by applying the ∑1 nonlinear logic function to h4, modulo 2. 32 The operation is performed, and the resulting value is added to h3 modulo 2. 32 The operation is performed, and the resulting value is assigned to h4, according to... Figure 6 The new h0 to h7 are obtained sequentially.

[0124]

[0125]

[0126]

[0127]

[0128] Step 4: Calculate each block repeatedly until M is calculated. n Finally, a 256-bit hash digest is obtained.

[0129] 4. Encryption example: An example text used by the SHA256 algorithm is shown below. Figure 7 As shown.

[0130] The secret digest obtained using the SHA256 encryption algorithm is as follows: Figure 8 As shown. The text is converted into a 256-bit digest, and then the digest is converted into binary bits. Figure 9 A binary stream converted from a 256-bit digest.

[0131] 5. Embedding process: Input: Carrier text, font color, RGB three-channel G1, G2, G3 and 3nk+3 bits of secret information; Output: Steganographic text G′1, G′2, G′3;

[0132] Step 1: Process carrier information.

[0133] 1. Obtain the pixel value of each letter in the carrier text, and use P(i,1), P(i,2), and P(i,3) to represent the pixel values ​​of the R, G, and B components of the i-th letter. Let P(i,a), where a = 1, 2, 3.

[0134] 2. Obtain the pixel values ​​of the R, G, and B channels for the color of each letter in the carrier text, denoted as G1, G2, and G3 respectively. Merge G1, G2, and G3 into G. G represents the total number of pixel values ​​for the cover text.

[0135] 2. Group the obtained pixel values ​​into groups of n pixels.

[0136] Step 2: Processing secret information.

[0137] 1. Divide the 3nk+3 bit secret information into 3 groups, each group having nk+1 bits, as follows:

[0138] B3=(b 3nk+3 b 3nk+2 …b 2nk+3 b 2nk+2 )2;

[0139] B2=(b 2nk+1 b 2nk …b nk+2 b nk+1 )2;

[0140] B1=(b nk b nk-1 …b1b0)2;

[0141] Where n represents a group of pixels containing n pixels, and k is the embedding degree. The larger k is, the more secret information is embedded.

[0142] 2. Convert the binary confidential information B1, B2, B3 of each group into a decimal number D, where D3 = 2. nk b 3nk+3 +2 nk-1 b 3nk+2 +…+2 1 b 2nk+3 +2 0 b 2nk+2 D2 = 2 nk b 2nk+1 +2 nk-1 b 2nk +…+2 1 b nk+2 +2 0 b nk+1 D1 = 2 nk b nk +2 nk-1 b nk-1 +…+2 1 b1+2 0 b0.

[0143] 3. Divide B1 into n groups, the first group includes k+1 bits, (b k b k-1 …b1b0)2 is converted to decimal number d0, and the remaining n-1 groups are: (b (y+1)k …b yk+2 b yk+1 )2 converted to decimal number d y y∈[1,n-1]. The same operations are performed on B2 and B3.

[0144] Step 3: Embed secret information. Embed the decimal numbers of each group in B1 into each group of pixel values. The embedding process is as follows:

[0145] 1. q represents the index of the pixel value of the carrier text color. Equation 6 is used to index the hidden pixel value at position k+1, where g is used. i To represent the pixel values ​​of the original carrier text font, g h This refers to the h-th pixel value in a set of original carrier text font pixel groups. Using g... i The pixel value of the embedded steganographic text font is represented by 'g'. h This refers to the h-th pixel value in a set of steganographic text font pixels.

[0146] g h =q mod n (6);

[0147] 2. Finding x in the optimization problem h :

[0148]

[0149]

[0150] Using g′ h =x h +g h Embed secret information.

[0151] 3. Simultaneously, in the optimization problem, find x. i :

[0152]

[0153]

[0154] Using g′ i =x i +g i Embed secret information.

[0155] 4. Perform the same steps 1-3 on B2 and B3.

[0156] 5. [The following is a separate, unrelated sentence:] Place g′ h and g i The pixels in the three channels G1′, G2′, and G3′ of the stegtext font are obtained by merging them.

[0157] Extraction process: Input: G1′, G2′, G3′; Output: 3nk + 3 bits of secret information.

[0158] 1. Using index g′ h =q mod n, find the pixel value that hides the k+1 bits of binary secret information.

[0159] 2. Restore d0 = g′ h mod 2 k+1 3. Restore d i =g i 'mod2 k ;

[0160] 4. Set d0, d i Combine the data to obtain the secret information d, and convert it into binary bits.

[0161] Experimental analysis was conducted in this embodiment to evaluate the performance of the proposed method. The experiments were implemented in Python and run on a computer equipped with an Intel(R) Core(TM) i7-10700 CPU @ 2.90GHz and 16GB of RAM. The operating system was Windows 10 Professional 64-bit. The performance evaluation metrics of this scheme included embedding capability, protection index, and text quality.

[0162] 1. Security Analysis: The security of information hiding refers to the characteristic that information is guaranteed to be unmodified, undamaged, and unlost during transmission, exchange, storage, and processing. In this invention, the secret information is hidden in the letter color pixels of the transmitted cover text. Only a designated recipient can extract the secret information using a specific extraction method. The text after embedding the secret information is very similar to the original cover text, so much so that it is not noticeable to the naked eye. Furthermore, the method uses the SHA256 function to encode the entire text file, generating a 256-bit digest, which is embedded in the cover text along with the secret information. The recipient only needs to perform a single SHA256 operation on the received text and then compare it with the extracted original digest. If the two digest values ​​are not completely identical, it indicates that the information has been illegally tampered with by an attacker, and the recipient should discard the file immediately and report back to the sender. This process ensures the integrity and security of the text transmission.

[0163] Figure 10 The original cover text file and the generated summary value are: (a) the content of the original cover text file; and (b) the generated summary value of the cover text file.

[0164] This embodiment considers two types of tampering: legal modification and illegal modification. Legal modification includes changing font format, font size, and color. These modifications do not affect the understanding and transmission of the file content, so they do not need to be detected, and the generated digest value remains unchanged. Illegal modification includes adding or deleting a character, replacing a character with a visually different character, or replacing a character with a visually similar character. This type of tampering affects the interpretation of the text content, so it needs to be detected, and therefore the generated text digest value is different from the original text digest value. Figure 11 This refers to the legal modification of a text file and the generated digest value; where (a) represents the legally modified content of the text file; and (b) represents the digest value generated by the legally modified text file.

[0165] exist Figure 11 In section (a), the color of the letter "a" in the original cover text was changed, which is a legal modification. The resulting summary is:

[0166] bacdbd027c5660eb068790920aef11de6d127bf9888264fc71c6ce077801dbdc, consistent with the summary generated from the original text, such as Figure 11 As shown in (b) of the diagram. Figure 12 The text file was illegally modified, and the resulting digest value was generated; where (a) is the content of the illegally modified text file; and (b) is the digest value generated by the illegally modified text file. Figure 12 In (a), change one character "a" in the original cover text to "e", and then... Figure 12 The illegally modified digest value obtained in (b) is:

[0167] The value 6fa5a61685228a82cc19222733ffe774a8b578f75f901967b9208ab9354b5302 is completely different from the previous original digest value. In DS96, RSUS15, and HT17 schemes, once it is suspected that a file contains hidden secret information, it is easily detected. In the CC17 scheme, the rich colors also make it easy to detect. Therefore, compared to the TPM method, these methods have a lower level of security. The method proposed in this invention is highly sensitive to illegal tampering. Figure 13 The paper presents a comparative analysis of the security level of the present invention compared to other algorithms, demonstrating that the method proposed in this invention has a higher security level than other encryption technologies.

[0168] 2. Imperceptibility Analysis: Because the method proposed in this invention uses Sha256 cryptography, the integrity of the transmitted text file is guaranteed, but others are unaware that we have hidden the text digest within the text, thus ensuring the imperceptibility of the transmission process. Even if a malicious actor believes they have unknowingly tampered with the text file and then transmits it to the recipient, we can actually detect the tampering. Furthermore, the steganographic text obtained using the method proposed in this invention is not significantly different from the cover text (e.g., ...). Figure 14 As shown in the image, it is difficult to detect with the naked eye. Figure 15 The image shows the difference between a letter before and after steganography; the RGB difference is small and not easily noticeable. Figure 14 This is a diagram comparing the original cover text and the steganographic text; where (a) is the content of the original cover text file; and (b) is the content of the cover text file containing the steganographic text. Figure 15 The images show an RGB comparison of the original cover text and the steganographic text; where (a) is the RGB image of the original cover text and (b) is the RGB image of the cover text containing the steganographic text.

[0169] 3. Data hiding capability analysis: Data hiding capability refers to the number of secret data bits (bpc) that each character can hide. The following formula represents the data hiding capability HC of the cover text.

[0170]

[0171] A higher bpc indicates that more secret data can be embedded in a single character, while a lower bpc indicates lower embedding efficiency. The method proposed in this invention can achieve a data hiding capability of 6-9 bpc, successfully realizing the goal of enhancing text data hiding capabilities. Figure 16 The data hiding capabilities of this method are demonstrated for n=1, 2, 3, 4 and k=3, 4, 5, respectively, and compared with methods proposed in previous related works. The method proposed in this invention has a higher data hiding capability. Table 1 summarizes the characteristics of the proposed text steganography methods, including the number of carrier text characters in a group, the number of embedding bits in each group, and the data hiding capability. We set 5 characters as one word and 10 words as one sentence. In this table, n is the number of text characters in a group, and k is used to adjust the degree of secret data embedding.

[0172] Table 1 Comparison of Data Hiding Capabilities

[0173]

[0174] To conduct the experiment, the above method was applied to secret information of the same size. The embedded secret information was 16 bits, and the cover text was: "Akbar said, 'How many crows are there in this city?' Without even a moment's thought, Birbal replied, 'There are fifty thousand five hundred and eighty-nine crows, my lord.' 'How can you be so sure?' asked Akbar. Birbal said, 'Make your men count, my lord. If you find more crows, it means some have come to visit their relatives here. If you find less number of crows, it means some have gone to visit their relatives elsewhere.' Akbar was very pleased by Birbal's wit." The experimental results were presented on... Figure 17 In the context of hiding 16-bit secret information, the DS96 method requires 77 cover text characters, the RSUS15 method requires 18 cover text characters, the CC17 method requires 16 cover text characters, the HT17 method requires 18 cover text characters, the UC19 method requires 8 text characters, while our proposed method only requires 2 cover text characters. Figure 17 This is a comparison chart showing the number of characters required to hide identical data using this invention and other algorithms. This invention requires the fewest characters to hide identical data.

[0175] 4. Visual similarity and resistance to visual attacks. The method proposed in this invention modifies the R, G, and B channels of the RGB of the text font. The changes to each channel are very small, so the difference is imperceptible to the naked eye. Figure 14The cover text and steganographic text are almost indistinguishable. The Open Space method hides secret information by varying the size of whitespace, resulting in inconsistent spacing between words or sentences. Careful readers will notice these differences, making this method vulnerable to visual attacks. The USC15 text steganography method uses the width of Unicode characters in the Unicode space character specification, which is also visible to the naked eye, thus also vulnerable to visual attacks. The CC17 method uses rich color variations in the steganographic text, making the cover text distinct from the steganographic text, thus failing to resist visual attacks. The HT17 method performs a series of operations such as permutation, padding, and compression on the secret information, then uses the minimum width Unicode to encode the spaces in the cover text to achieve information hiding. This concealment is also difficult to detect with the naked eye, thus resisting visual attacks. The UC19 method performs three levels of encryption on the confidential data, then uses Unicode characters to embed the generated binary data into the cover text, which is also difficult to detect with the naked eye, thus resisting visual attacks. As shown in Table 2, we have compared the ability to resist visual attacks.

[0176] Table 2 Comparison of resistance to visual attacks

[0177]

[0178] Conclusion: This invention combines encryption and information hiding techniques to protect text files and secret data. The information hiding method utilizes an optimization function to minimize changes to the cover text while maximizing the amount of secret information hidden. This method not only increases the security of transmitted files but also improves the ability to embed secret information. Experimental results show that, because each character's pixels can be divided into R, G, and B channels, and each channel of a character can hide 3 bits of secret information, and because an optimization algorithm is used to minimize the number of pixels modified, the method outperforms other techniques in terms of payload and visual attack resistance. Most importantly, the proposed method ensures the integrity of transmitted files; if malicious actors illegally tamper with the file, the recipient can readily observe and discard it.

[0179] Finally, it should be noted that the above are only specific embodiments of the present invention. Of course, those skilled in the art can make modifications and variations to the present invention. If these modifications and variations fall within the scope of the claims of the present invention and their equivalents, they should be considered as being within the protection scope of the present invention.

Claims

1. A method for optimally hiding dual-protected text, characterized in that, Includes the following steps: Step 1: Use the SHA256 hash algorithm to encrypt the carrier text and generate a hash digest a; Step 2: Use an information hiding algorithm to embed the secret information and hash digest 'a' into the R, G, and B components of the color pixel values ​​of the carrier text to form steganographic text; Step 3: Send the steganographic text to the recipient; Step 4: The recipient receives the file, which is either steganographic text, legally modified steganographic text, or illegally tampered steganographic text. Step 5: The recipient uses the SHA256 hash algorithm to extract the hash digest b from the file; Step 6: Determine if the regenerated hash digest b is equal to the extracted hash digest a. If they are not equal; This indicates that the confidential information has been illegally altered by an attacker, and the recipient has discarded the file. If they are equal, it means that the file is steganography or legally modified steganography, proceed to step seven; Step 7: The recipient retrieves the secret information.

2. The optimal hidden dual-protection text method according to claim 1, characterized in that: Step two employs the following information hiding algorithm to embed the secret information and hash digest a into the R, G, and B components of the color pixel values ​​of the carrier text; Input: Carrier text, font color, RGB three-channel G1, G2, G3 and 3nk+3 bits of secret information; Output: Steganographic text G′1, G′2, G′3; The embedding process includes the following steps: Step 21: Process the carrier text information; Step 21 further includes: Step 211: Obtain the pixel value of each letter in the carrier text, and use P(i,1), P(i,2), P(i,3) to represent the pixel values ​​of the R, G, and B components of the i-th letter; denoted as P(i,a), a = 1, 2, 3; Step 212: Obtain the pixel values ​​of the R, G, and B channels of each letter in the carrier text, and represent them as G1, G2, and G3 respectively; merge G1, G2, and G3 into G; G is the total number of pixel values ​​of the carrier text. Step 213: Group the total number of obtained pixel values ​​into groups of n pixels; Step 22: Processing secret information; Step 22 further includes: Step 221: Divide the 3nk+3 bit secret information into 3 groups, each group having nk+1 bits, as follows: B3=(b 3nk+3 b 3nk+2 …b 2nk+3 b 2nk+2 )2; B2=(b 2nk+1 b 2nk …b nk+2 b nk+1 )2; B1=(b nk b nk-1 …b1b0)2; Where n represents a group of pixels containing n pixels, and k is the embedding degree. The larger k is, the more secret information is embedded. Step 222: Convert the binary confidential information B1, B2, and B3 of each group into decimal numbers; D3=2 nk b 3nk+3 +2 nk-1 b 3nk+2 +…+2 1 b 2nk+3 +2 0 b 2nk+2 ; D2=2 nk b 2nk+1 +2 nk-1 b 2nk +…+2 1 b nk+2 +2 0 b nk+1 ; D1=2 nk b nk +2 nk-1 b nk-1 +…+2 1 b1+2 0 b0; Step 223: Divide B1 into n groups, the first group includes k+1 bits, (b k b k-1 …b1b0)2 is converted to decimal number d0, and the remaining n-1 groups are: (b (y+1)k …b yk+2 b yk+1 )2 converted to decimal number d y ,y∈[1,n-1]; similarly, perform these operations on B2 and B3 as well; Step 23: Embed secret information; Step 23 further includes: The decimal numbers of each group (B1, B2, B3) are embedded into the pixel value of each group. The embedding process is as follows: Step 231: q represents the index of the carrier text color pixel value, and formula (6) is used to index the hidden k+1 bit pixel value, g i g represents the pixel values ​​of the original carrier image. h This refers to the h-th pixel in a group of pixels; using g′ i g′ represents the pixel value of the embedded steganographic image. h This refers to the pixel value of the h-th steganographic image in a group of pixels; g h =q mod n (6); Step 232: Find x in the optimization problem h x h This represents the optimized value found for the h-th pixel value; Using g′ h =x h +g h Embedding secret information; Step 233: Simultaneously, in the optimization problem, find x. i x i This represents the optimized value found for the i-th pixel value; Using g′ i =x i +g i Embedding secret information; Step 234: Similarly, perform steps 231-233 of step 23 on B2 and B3; Step 235: Place g′ h and g′ i The merging process yields the three-channel pixels G′1, G′2, and G′3 of the steganographic text font (R, G, and B channels).

3. The optimal hidden dual-protection text method according to claim 2, characterized in that, Step seven, where the receiver extracts the secret information, includes: acquiring inputs G′1, G′2, G′3, and outputting 3nk+3 bits of secret information; Step seven includes the following steps: Step 71: Use index g′ i =q mod n, find the pixel value that hides the k+1 bits of binary secret information; Step 72: Restore d0 = g′ h mod 2 k+1 ; Step 73: Restore d i =g′ i mod2 k ; Step 74: Set d0, d i Combine the data to obtain the secret information d, and convert it into binary bits.

4. The optimal hidden dual-protection text method according to claim 1, characterized in that, Legitimate modifications include changing the font format, font size, and color of the steganographic text; illegal modifications include adding a character, deleting a character, replacing a character with a visually different character, or replacing a character with a visually similar character to tamper with the steganographic text.

5. The optimal hidden dual-protection text method according to claim 1, characterized in that, The SHA256 hash algorithm consists of three stages: constant initialization, information preprocessing, and digest value calculation.

6. The optimal hidden dual-protection text method according to claim 5, characterized in that, The constant initialization includes: taking the first 8 prime numbers from the natural numbers, calculating the square root of them, taking the 32 bits of the decimal part of the result and converting it into a hexadecimal number to generate the initial hash value; Next, take the first 64 prime numbers of natural numbers, calculate their cube roots, take the 32 bits of the fractional part and convert them into hexadecimal numbers to generate a hash constant K; Information preprocessing refers to appending necessary information to the hashed message to achieve the required structure. Information preprocessing involves two steps: Step 11: Add padding bits; Let the number of bits in the binary code of the information be l. After the code bits, add one "1" bit, and then add k "0" bits, where k is the smallest non-negative integer that satisfies the following equation; l+1+k≡448mod512(2); Step 12: Append length value; The length l of the original information is encoded into a 64-bit binary form and appended to the padded message, making the length of the entire message 512 bits or a multiple of 512 bits. Step 13: Calculate the digest value to obtain a 256-bit hash digest.

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