Steganography Based on Chaotic System for Random LSB Positions

— The objective of hiding text in an image is hiding text without raising suspicions that the image contains a hidden message or text, which leads to protecting and maintaining text confidentiality. The previous hiding methods have problems in capacity, randomization, and imperceptibility. This paper will be solved some of these problems; we suggested a new method for hiding text in an image. Firstly, encrypting the text by the AES-192 bit algorithm for obtaining a secret message. When the initial key of the AES-192 (bit) algorithm is generated by a chaotic system for randomness purposes, secondly, hiding the secret message is into a gray image for obtaining a stego-image. The hiding step is based on a proposed map that chooses from the last round of key expansion in the AES-192 algorithm. This map represented random positions of LSB in each byte of the gray image. The experimental result of this method proved a successful method based on metric criteria. Also, this method is the very speed for hiding ciphertext in the gray image as well as extracting ciphertext from the gray image. Also, it is very safe because it is difficult for attackers to distinguish between the original image and the stego image therefore the correlation between the original image and the stego-image is very close to 1.


Introduction
Covered Text" is a word synonymous with Steganography.The hiding texts, data and information is very important [1], [2], as it aims to hide data without raising suspicions that it contains a hidden message or file, which leads to protecting it and maintaining its confidentiality [3].The science of invisibility is completely different from the science of cryptography.To simplify the meaning, data encryption is represented as a safe that contains data, texts, and information.The safe can only be opened with a specific key, while steganography only refers to camouflaging [4], [5]- [6].In reality, steganography is an integral part of cryptography after the process of encrypting the text in one of the well-known encryption algorithms and after obtaining the ciphertext, the ciphertext is hidden under the cover and, steganography used to protect data from unauthorized persons [7].Just as the protection of information requires a great effort, some encryption and concealment algorithms have had great success in concealing information, but some algorithms suffer from delaying the encryption time, delaying the time of concealment, and the quality of concealment.In this research, we have strived to achieve a balance between the speed of the encryption process and proposing a steganography map that achieves very high quality.The chaotic system was used to generate the encryption key.Chaos is one of the conducts that connect nonlinear systems and that develops specific values of an information system [8].The discovery of this random system was considered a revolution that led to many interrelated issues, stability theory, new engineering features, and offers to distinguish signatures.The chaotic function has been used mainly to develop mathematical models for non-linear systems and has been attracted by many mathematicians because of the high sensitivity of the initial value and its applications to daily life problems [9].The chaotic functions have good features "sensitivity to initial conditions", Fractal dimensions, the Lyapunov exponent, "strangeness", and ECT [10], [11], therefore, it used in this research to generate the encryption key (Symmetric key) of the AES-192 bit algorithm to increase the confidentiality of the transmitted information and secure the transmission process.Also, the chaotic system is characterized by there are many types of chaotic functions, each of which has an advantage over the others of these types: Lorenz Equation., Rössler Equation, and Logistic Equation (this function has been used in our work) [12].In this research, the chaotic system was used to generate the encryption key, and this is one of the most prominent strengths in our work, as it helped to increase the strength of the encryption and the speed of generating the encryption key, also use the last round of key expansion such as random positions of LSB technique for hiding secret text into gray image, therefore, the chaotic system helps the process of encryption and concealment gained durability and Speed and success this the proposed method.Section 2 describes some of the related work; Section 3 describes the proposed method; section 4 describes the experiments and results.Conclusions are explained in Section 5

2
Literature Review Hussein L. Hussein [13] in this Search Steganography has done several masking methods according to the proposed maps to hide the message inside a gray image, so that the text is masked by drawing a map from ASCII that used (AMT) to create an encrypted table by mapping the text message and matching some bits with the cover image.The result is referred Low computational efficient performance to be used for multiple purposes Applications.Alaa Kadhim F and Rasha Subhi Ali [14] in this research, an advanced map was used to hide data, with which they used biotechnological methods for encryption and to improve the strength of data security while hiding messages inside an image.In this research, data hiding using LSB and DNA arithmetic were presented and they presented a new secret map to hide the data.(DNA) computing was used to encrypt data, and LSB was used to arrange the encrypted data to the least important elements of the cover, and they used a new secret map to locate locations.And Steganography.The researchers pointed out that the same equation is used for both the sender and the receiver to create a map, and this map depends on a common key.Alaa Kadhim Farhan , Nadia M.G.Al-Saidi, Abeer Tariq Mold, Fahimeh Nazarimehr and Iqtadar Hussain [15], in this research, a new and unique chaotic system has been proposed, represented by crossing inside and outside the cylinder repeatedly.As an engineering system, the efficiency of the system in encryption images was tested.The performance of the encryption method is analyzed using the histogram, correlation coefficient, Shannon entropy, and encryption quality.The results show that the encryption method using the proposed chaotic system has reliable performance.Relying on this system and the tests conducted on it, the same tests were used in the research and the proposed method for our work.Jagan Raj Jayapandiyan, Ph.D. Research Scholar, Kavita, Assistant Professor and Sakthivel and Professor [16] this proposed work improving the (LSB) method is based on the spatial domain.The proposed method is based on encrypting the text in two stages.The first stage is creating metadata and storing header information in the first few bytes of the images.The second stage is the process of including secret texts.Inside the cover image using the improved method, and in this proposed method, it results in the acquisition of space or a lesser method for the secret message in the cover image, and this leads to improving the quality of masking and obtaining standards for better results than the results obtained (eLSB).Our research presented in this paper has obtained much better results than the results obtained in this method in terms of evaluation criteria, and the consideration has been taken from several.This method will be encoded (eLSBRAISDSCSO) in our research in order to compare it with its results.Ranyiah Wazirali, Waleed Alasmary, Mohamed Mahmoud and Ahmad Alhindi [17], In the research, the researchers presented a proposal for a new information steganography that works on the basis of a genetic algorithm.The researchers confirmed that this research works to increase the embedding capacity and reduce distortion.The research showed that scanning is better for pixels for vertical and horizontal directions, circular transformation, secret bit fluctuation, and transmission of confidential information after using the genetic algorithm.The (LSB) to include the data and the evaluation criteria were applied to it.The paper for our work was compared with this work and it was proven that the work presented in our research is better in terms of evaluation metrics.This method will be encoded (AOSHCAIUGA) in our research in order to compare it with its results.
Mansoor Fateh, Mohsen Rezvani, and Yasser Iran [19], In this paper, the LSB approach has been proposed with an updated version, where the proposed matching approach works to LSB that the number of bits in the secret text is greater than 2 The work has been clarified in two steps, the first is to hide the secret text and the second is to extract the text.It has been shown that the method of the proposed approach needs to be changed less than LSBMR when the number of bits is greater than 2. The capacity in the proposed approach is higher than the F5 method when the number of the bit =3, where it was found that the number of secret text bits is greater than 2, its value = 75% this method is considered a new coding method because it reduces the change in the image.The results showed that this new method provides a 10% larger detection error for SRNet via two Steganography schemes.This method will be symbolized in our research (CFSLSB) in order to be compared with its results.
Ali Salem Ali, Mohammed Sabbih Hamoud Al-Tamimi and Alaa Ahmed Abbood [18], in this research improvement of the (Bit Inverting Map) method of narrowing the gap to obtain effective results to maintain a balance between image accuracy, protection, and security.Comparisons of this method with previous methods have proven that the method is effective and superior to the rest of the methods.This method will be symbolized in our research (SISTMS) in order to be compared with its results.

Method
In the proposed method, the chaotic system was used to generate the encryption key, and this is one of the most prominent strengths in our work, as it helped to increase the strength of the encryption and the speed of generating the encryption key, also use the last round of key expansion such as random positions of LSB technique for hiding secret text into the gray image as shown in figure 1.The proposed method consists of two phases: the hiding phase and Extracting Phase.Both phases have two parts: cryptography and steganography.The hiding phase consists of the encryption process and the hiding process.Also, extracting phase consists of the decryption process and extracting process.The AES-192 (bit) used because it is more complex than the AES-128 (bit) and less expensive than the AES-256 (bit).The initial key generated by chaotic system where a 24-digit was generated randomly each time to generate the key.The chaotic system was chosen in the generation of the key in order to achieve high protection strength and an increase in the chaos of key generation and the difficulty of predicting it.Where modern methods were used in chaotic sampling of data TOA (Time -of -arrival) in chaotic samples instead of random samples, and thus we will produce a sequence of chaotic values called (Chaotic sequences).And as we know that the chaotic system is a nonlinear system its structure is unstable and the output behaves as a random behaviour in some steps and depends on the (initial condition) and (control parameters).inorder to determine the (Localization GD) and therefore equation ( 1) is the equation of the simple chaos logistics function chosen to generate the key of the algorithm AES192 bits.[20,21]: Where, N = 0, 1………..... L= Length of Sequence  = control Parameter Table 1 shows chaotic system generated a different sequence with a different initial value.This key is distinguished by the speed of generation and the strength of the key, as it is difficult to predict the value of the key by an attacker.

Table 1. The chaotic system generated a different sequence with a different initial value
In the steganography part, the secret message hides in gray image based on a map that represented a random positions of the LSB as shown in table 2. The proposed map represented last round of key expansion in the AES-192 algorithm.In the map, when the value equal to 1, meaning hide one bit from secret message into the byte of gray image, when the value equal to 2, meaning hide two bits from secret message into the byte of gray image, when the value equal to 3, meaning hide three bits in the byte, and when the value equal to zero, meaning no hide in the current byte of the gray image.This map repeated for the length of secret message.The hiding process explains by the following example, suppose the ciphertext =" 10000111", gray sub-image (Byte1=00111010, Byte2=11100011, Byte3=00111011) and map=123.The first step, hide the first bit of cipher text "1" (a) in the LSB of the first byte of gray sub-image as shown in figure 2(a).In the second step, hide the second and third bits of ciphertext "00" in the LSB of the second byte of gray sub-image as shown in figure 2(b).The third step, hide the fourth,fifth,and sixth bits of cipher text "001" in the LSB of the third byte of gray sub-image as shown in figure 2(c

Results and Discussion
In testing the proposed system for variant data and testing many coefficients for both the cryptography part and steganography parts.Take as an example 10 plaintext with different lengths and 10 gray images (or colored image transform for gray image) for the text steganography.

Cryptography Part
This is the first part of the proposed system, applying the AES 192-bit algorithm.The initial key generated by the chaotic system, table 3 illustrated the different lengths of the plaintext that take different times for the encryption process, including the key generation time that generation chaotic system for achieving randomness.The encryption time is measured by picosecond because of the faster encryption process.From the above result in table 3, the range of the plaintext from 10 (char) to 100 (char) in the other words, the range of the plaintext from (1) Block to (7) Block when increases the plaintext length due to increase the encryption time.The positive Relationship between the encryption time and plaintext length, as shown in figure 3.

The positive Relationship between Encryption Time and Plaintext lengths.
The proposed method that used chaotic system to generate initial key of the AES-192-bit standard algorithm, when examined the security of the cipher text against attacking by using the NIST.The proposed method proved is the strongest security and its success in all testing.Table 4 explains the cipher text encrypted by using key generation of chaotic system.From the result explain in table 4 the proposed modified key generation is stronger because its very secure ciphertext against the most attacks in all different cases.

4.2
The Steganography part This is the second part of the proposed system, apply Hiding process in the LSB but with random positions Of bits (based proposed map explain in table 1) in each byte of the gray image.Table 5 on the illustrated the gray image properties that used for hiding process.
From the result in table 5, the gray images have a different size and different image resolution.The proposed work checks the image size with the ciphertext length for making decisions that image has enough capacity for hiding From the above result, the original images similar to the stego-images that any person could not show the effectiveness of the hiding process of your eye.When increases the cipher text length due to increase the hiding time.The Positive Relationship between hiding time and cipher text lengths, as shown in figure 4 The positive relationship between hiding time and cipher text lengths.
Tested 10 gray images with different properties for hiding ciphertext with different lengths.The measurements that used in this research, mean square error (MSE), Signal-To-Noise Ratio (SNR), Peak Signal to Noise Ratio (PSNR), Embedded Capacity measured (EC), Entropy, and Histogram.Table 7 illustrated the result of the previous metrics.
In the a blew table 7, the MSE that all values ranged between the highest value of 0.195816697 for gray image that has resolution (318X241)and the lowest value being very close to Zero 0.000977083 for gray image that has resolution (900 X 1600).Also, the gray image that has the lowest value of MSE that has the highest value of PSNR 75.72135129 and the highest value of the SNR 68.61384535And the gray image that has the highest value of MSE that has the lowest value of PNSR 52.70217015 and the lowest value of SNR 47.15894861These results 7BA3A6573629A46FBDF58EA1238292228E F6E9AD3CCC1622E641970214EF4557DADA D8ABFE3DFF914806CB8D4C0326ABDDA3A A636E8A49F76DBDB24C8B530F1EF5E257F9 EC7E07A14381289CF8E0E10DA3BAC4B019F 5E1F013DA331277DD27B42B58FF6F 00:00:00.0046315indicate that the proposed method is a good quality and high secret according to the specific values of MSE, PSNR, and SNR [23].
Also, EC measured is to embed and calculate the highest number of safe bits that can be hidden in the image that it is measured in units bits per pixel (bpp) [21,24].The largest value of EC in table 6 is (0.006680759) and smallest value of EC is (0.00015009).This result gives a good trace achieved through the proposed method, (EC) depends on the properties of the image as well as the length of the ciphertetxt.
Entropy is a measure of the degree of randomness between the original image and the stego image [25][26][27][28][29], the entropy values ranged between (2.820111545) and (5.160472612).From entropy values notice that the entropy ratio is an acceptable and a good ratio compared to other steganography methods, where the lower the value is more optimize.The histogram shape was drawn to the stego image that hidden a ciphertext of different lengths, in table 7, the histogram shape has a good result that depends on the properties of the image and the length of the ciphertext.In additional, the investigation Variance and correlation that calculated between original image and Steganography image, as shown in figure 5. Entropy is a measure of the degree of randomness between the original image and the stego image [25,26], the entropy values ranged between (2.820111545) and (5.160472612).From entropy values notice that the entropy ratio is an acceptable and a good ratio compared to other steganography methods, where the lower the value is more optimize.The histogram shape was drawn to the stego image that hidden a ciphertext of different lengths, in table 7, the histogram shape has a good result that depends on the properties of the image and the length of the ciphertext.In additional, the investigation Variance and correlation that calculated between original image and Steganography image, as shown in figure 5.
The investigation Variance and The Correlation.
From the above result in figure 5, it shows the variance of the images.The variance refers to how the pixel values are spread in the images, where the variance calculated for the original image and the stego-image was the result of the image (A) = 1.4981 and (B) =5.1627 and (C) = 5.9343.Figure 5 illustrated the last measurement that is the Correlation between original image and Steganography image.It shows the Correlation between the original image and the steganography image according to the graph shown the Correlation of A = (0.982) and B= (0.999) and = (0.951).The results show that the relationship between the original image and the image is very close to 1 meaning that it is difficult to distinguish between the two images and this is evidence it is difficult for attackers to distinguish and the proposed method has proven to be a successful method.
Compare the results obtained through our proposed work to hide the ciphertext in a gray-level image based on the proposed map.It is worth mentioning that each of the methods in the comparison table 8 has used different properties of the images, as well as texts of different lengths.Then Compare the results for the best value in each method.
In the blew table (8), the evaluation results between the different remaining steganography methods and the proposed method showed.According to the results, the results of the proposed method are very good results compared to the rest methods.// Generate Initial Key by using chaotic system Step 2: Key_rounds=Expansion key(Initial_key) // Generate key rounds by using expansion key of the AES algorithm Step 3: ciphertext=Encryption process (plaintext, key_rounds) Step 4:Img_binary=convert_array_of_binary(Img) Step 5:CT=Convert_CipherText_to_Binary(ciphertext) Step 6: set hidden_map=first_round (key_rounds) conclusion Because increase the attackers and intruders that theft the information, the text steganography need for achieving the confidentiality.In this paper, suggested a new method for hiding a text in an image.Firstly, encrypting the text by the AES-192 bit algorithm for obtaining a secret message.When the initial key of the AES-192 (bit) algorithm is generated by chaotic system for randomness purpose, secondly, hiding the secret message into a gray image for obtaining a stego-image.The hiding step based on a proposed map that choice from last round of key expansion in AES-192 algorithm.This map represented a random positions of LSB in each byte of gray image.This map cannot guested testing of the proposed method obtained a faster method for hiding ciphertext in the gray image as well as extracting ciphertext from gray image.Also, it is difficult to distinguish between the original image and stego-image because the correlation between the original image and the image is very close to 1 meaning that it is difficult for attackers to distinguish among two images and the proposed method has proven to be a successful method based on Mean Square Error (MSE), Signal to Noise Rate (SNR), Peak Signal Noise Rate (PSNR), Embedding Capacity (EC), Entropy, and Histogram.
Main flowchart of the proposed method: (a) hiding phase and (b) extracting phase In cryptography part, the AES-192 (bit) algorithm used for encrypting a text.The text consists of different lengths of characters.This algorithm has several advantages in terms of: • Security: AES has the ability to resist attacks better than other encryption algorithms .• Cost: This algorithm includes unlimited global domain and royalty-free.• Implementation: The AES algorithm is flexible and well suited when implemented in hardware and software.
(b) (c) Hide the secret message into gray image based on random positions of the LSB

1 :
Steganography Based on Chaotic System for Random LSB Positions Input: Plaintext, Initial value, Image as Img Output: Stego-Image Processes: Begin Step Initial_key=chaotic System (initial_value)

Table 2 .
The proposed hiding map (last Round of Key Expansion)

Table 3 .
Encryption time for different lengths of plaintext and Hiding Time for different

Table 4 .
NIST Test for The Ciphertext that Encrypted based on Chaotic System

Table 5 .
Gray images properties

Table 6 .
the hiding time for different lengths of ciphertext

Table 7 .
The result of the MSE, SNR, PSNR, EC, Entropy, and Histogram

Table 8 .
The comparison Evaluation Criteria between proposed method and other methods