An image encryption scheme based on an improved Hilbert curve and a novel 4D hyper-chaotic system

The present scenario of the medical field is that sending the healthcare images through the internet is so far exposed to security threats. Hence, there is a need for an efficient and secure procedure to exchange healthcare images over the Internet. The Digital Image and Communication in Medicine (DICOM) provides security features for image header information but not for the pixel information. Hence to send the pixel information in a highly secured manner, the pixels need to be encrypted by using a suitable encryption algorithm. The number of pixel changing rate (NPCR) and the unified averaged changed intensity (UACI) are well-known encryption evaluation metrics to analyse the differential attack in image encryption. These two values are used to calculate the average number of pixel changes and intensity changes between two encrypted images before and after modifying any one pixel in a plaintext image respectively. If these two values are high, then the image encryption can resist the differential attacks. In this paper, a theoretical value of NPCR and UACI are computed for DICOM image encryption concerning different significant levels. An encryption algorithm with Gould transform, RC5, logistic map and DNA Diffusion is proposed for DICOM image to increase the NPCR, and UACI value and this method offered an efficient security strategy for DICOM pixel information. Finally, the computed theoretical value of NPCR and UACI are compared with the existing and proposed algorithm.

In the 6G era, where ultra-fast and reliable communication is expected to be ubiquitous, encryption shall continue to play a crucial role in ensuring the security and privacy of data. Encryption and decryption of medical images and 3D printed models using 6D hyperchaotic function is proposed in this research work for ensuring security in data transfer. Here we envisage using a six-dimensional hyperchaotic system for encryption purposes which shall offer a high level of security due to its complex and unpredictable dynamics with multiple positive Lyapunov exponents. This system can potentially enhance the encryption process for 3D objects and medical images, ensuring the protection of sensitive data and preventing unauthorized access. A hyperchaotic system is a type of dynamical system characterized by exhibiting more than one positive Lyapunov exponent, which indicates strong sensitivity to initial conditions. These systems have more degrees of freedom and complex and intricate dynamics compared to standard chaotic systems. The security of the encryption scheme depends on the complexity of the hyperchaotic system and the randomness of the secret key. The parameters of a 6D hyperchaotic system shall be used as an encryption key with six dimensions, each with its range of values, and shall provide many possible keys. In this work, we implemented a 6D hyperchaotic system for the encryption of the 3D printed model and medical images. The performance evaluation was done by metrics entropy, correlation, Number of Pixels Change Rate (NPCR), and Unified Averaged Changed Intensity (UACI) which revealed the robustness of the encryption model in ensuring security. Hyperchaotic systems can be efficiently implemented in parallel computing architectures, which allow faster encryption and decryption processes.

The security of information and digital images has become a major issue during the last three decades. A large number of algorithms for data and image encryptions are reported in the literature. However, many of the proposed algorithms are not suitable in the fields of application, because they are cryptographically weak. In the present work, a novel algorithm for encoding digital images by using a circle map with 3 parameters has been proposed. In this article different images are used for testing the validity of the proposed algorithm. The algorithm has increased the strength of security of the image encryption against cipher-text-only, chosen-plaintext and chosen-cipher-text attacks. The analysis of cryptographic strength has also been performed to confirm the fact. The results of several experimental tests, such as, key space analysis, key sensitivity analysis and statistical analysis show that the proposed algorithm for image cryptosystems provides an efficient and secure way for image encryption. A comparison in terms of correlation between the initial and transformed images, number of pixels change rate (NPCR) and unified average changing intensity (UACI) is also done. Keywords: Circle map, Chaos, Lyapunov exponent, anti-differential attack, NPCR, UACI.

Image encryption is an evolving technique in the arena of data communication. In the last decade, many encryption schemes have been suggested. Unfortunately, most of the current schemes are unable to maintain a balance between security and computational complexity. To overcome this challenge, this paper introduces a novel encryption scheme that effectively maintains the trade-off between security and computational complexity. Initially, the plain image is randomized and scrambled by the Logistic map and Arnold’s scrambling technique. The intermediate image found above, is then encrypted by the special word-oriented feedback shift register (wfsr) to get the final cipher image. Wfsr is inherently suitable for high-quality pseudorandom number generation with good statistical properties. It usually posses high throughput. Further, the elliptic curve Diffie-Hellman (ECDH) is used for sharing the keys required for encryption and decryption process. The performance of the proposed cryptosystem is evaluated based on several statistical properties of the cipher image, the resistance of the cipher image to various attacks, and time required for encryption and key sharing process. The statistical properties of the encrypted image are found out through histogram analysis, correlation and entropy finding, key sensitivity analysis, chi-square test, and NIST randomness test. The resistance of the encrypted image to various attacks is either found out experimentally or indirectly by using metrics like Unified Average Changing Intensity (UACI), Number of Pixel Changing Rate (NPCR). The proposed encryption method compares favorably with similar image encryption schemes.

A wrist-based photoplethysmography (PPG) tool offers a simple and non-invasive approach for applications in vital sign monitoring and healthcare. However, in a telecare network, these physiological signals ensure the authorisation demands for the domain of medical applications. Hence, this study proposes an intelligent method for PPG signal encryption and decryption. This method combines chaotic map and radial basis function network (RBFN) into symmetric cryptography with an adaptive scheme. The sine-power chaotic map is used as a key generator of 256 non-ordered numbers (key space) to set the private cipher codes. Two RBFNs are used to train an encryptor and a decryptor with the authorised cipher codes. Its substitution-based infosecurity scheme can change the numerical values of PPG raw data for each encrypted communication, and the decrypted PPG data are further applied for time- and frequency-domain analyses in clinical applications, such as heart and respiration rate analysis and arterial stiffness and upper extremity vascular disease evaluations. Through experimental results, the security levels are validated using the number of pixel change rate (NPCR), unified averaged changed intensity (UACI), and correlation analysis. The average NPCR, UACI, and correlation coefficient (CC) are 96.57%, 35.43%, and 0.005, respectively, between the plain PPG and the encrypted PPG data against hacker attacks. The larger-the-better of NPCR and UACI indexes and the smaller-the-better of CC index are obtained to evaluate the efficiency of the proposed cryptography method. The encrypted PPG also guarantees physiological signals of good quality in clinical applications. In addition, the performance of RBFN-based method is superior in adaptive learning capability than that of the traditional learning method in real-time applications.

Secure image transmission is one of the most challenging problems in the age of communication technology. Millions of people use and transfer images for either personal or commercial purposes over the internet. One way of achieving secure image transmission over the network is encryption techniques that convert the original image into a non-understandable or scrambled form, called a cipher image, so that even if the attacker gets access to the cipher they would not be able to retrieve the original image. In this study, chaos-based image encryption and block cipher techniques are implemented and analyzed for image encryption. Arnold cat map in combination with a logistic map are used as native chaotic and hybrid chaotic approaches respectively whereas advanced encryption standard (AES) is used as a block cipher approach. The chaotic and AES methods are applied to encrypt images and are subjected to measures of different performance parameters such as peak signal to noise ratio (PSNR), number of pixels change rate (NPCR), unified average changing intensity (UACI), and histogram and computation time analysis to measure the strength of each algorithm. The results show that the hybrid chaotic map has better NPCR and UACI values which makes it more robust to differential attacks or chosen plain text attacks. The Arnold cat map is computationally efficient in comparison to the other two approaches. However, AES has a lower PSNR value (7.53 to 11.93) and has more variation between histograms of original and cipher images, thereby indicating that it is more resistant to statistical attacks than the other two approaches.

In the last decade, the communication of images through the internet has increased. Due to the growing demands for data transfer through images, protection of data and safe communication is very important. For this purpose, many encryption techniques have been designed and developed. New and secured encryption schemes based on chaos theory have introduced methods for secure as well as fast communication. A modified image encryption process is proposed in this work with chaotic maps and orthogonal matrix in Hill cipher. Image encryption involves three phases. In the first phase, a chaotic Henon map is used for permuting the digital image. In the second phase, a Hill cipher is used whose encryption key is generated by an orthogonal matrix which further is produced from the equation of the plane. In the third phase, a sequence is generated by a chaotic tent map which is later XORed. Chaotic maps play an important role in the encryption process. To deal with the issues of fast and highly secured image processing, the prominent properties of non-periodical movement and non-convergence of chaotic theory play an important role. The proposed scheme is resistant to different attacks on the cipher image. Different tests have been applied to evaluate the proposed technique. The results of the tests such as key space analysis, key sensitivity analysis, and information entropy, histogram correlation of the adjacent pixels, number of pixel change rate (NPCR), peak signal to noise ratio (PSNR), and unified average changing intensity (UCAI) showed that our proposed scheme is an efficient encryption technique. The proposed approach is also compared with some state-of-the-art image encryption techniques. In the view of statistical analysis, we claim that our proposed encryption algorithm is secured.

The widespread use of images, especially color images and rapid advancement of computer science, have led to an emphasis on securing these images and defending them against intruders. One of the most popular ways to protect images is to use encryption algorithms that convert data in a way that is not recognized by someone other than the intended user. The Advanced Encryption Standard algorithm (AES) is one of the most protected encryption algorithms. However, due to various types of theoretical and practical assaults, like a statistical attack, differential analysis, and brute force attack, its security is under attack.
 In this paper, a modified AES coined as (M-AES) is proposed to improve the efficiency of the AES algorithm by increasing the algorithm's security to make the algorithm more suitable for color image encryption, and make it more resistant to many attacks. The modification is conducted on ShiftRows transformation of the original AES algorithm. To test the efficiency of the proposed M-AES algorithm, several images are drawn from the Signal and Image Processing Institute's (SIPI) image dataset. Moreover, the Mean Square Error (MSE), Peak Signal-to-Noise Ratio (PSNR), Entropy (H), Correlation Coefficient (CC), visual evaluation of histogram, Number of Pixels Change Rate (NPCR) and Unified Average Changing Intensity (UACI) are used as an evaluation metric. The results show that proposed modification to the AES algorithm makes the algorithm more appropriate to image and surpasses the original AES. 
 The modification is conducted on ShiftRows step of the original AES algorithm. To test the efficiency of the proposed M-AES algorithm, several images are drawn from the signal and image processing institute's (SIPI) image dataset. Moreover, the mean square error (MSE), peak signal-to-noise ratio (PSNR), entropy (H), correlation coefficient (CC), visual evaluation of histogram, number of pixels change rate (NPCR) and unified average changing intensity (UACI) are used as an evaluation metrics. The results show that the suggested modification to AES makes it's more appropriate to the image and surpasses the original AES.

Differential evolution (DE) is a powerful evolutionary algorithms, widely applied in different fields of science and engineering for solving the problem of optimization. Since image encryption has been viewed as an interesting research topic by many experts and innumerable methods to encrypt images have emerged, currently, the focus is on obtaining optimized images. The paper presents a novel image encryption scheme that uses intertwining logistic map (ILM), DNA encoding and DE optimization. The proposed approach is based on three phases: permutation involving ILM, diffusion engaging DNA and optimization using DE. Parameters like entropy, key sensitivity, secret key space, unified average change in intensity (UACI), correlation coefficient —vertical, horizontal and diagonal, and number of pixel change rate have been evaluated to test the efficiency of the proposed method. The paper also compares this performance with that of the genetic algorithms (GA), used previously for optimization. The significance of this approach is enhancing entropy, the essential characteristic of randomness, resisting against numerous statistical and differential attacks and generating good experimental results. The main contribution of this paper is to present the efficiency of DE in image optimization and exhibit how DE is better than GA.

In this paper, an efficient and low‐cost cryptographic system for highly secure image encryption is presented. The proposed image encryption structure is implemented based on the key processing (KP) stage, the processing of the input image (PII) stage, and the round function (KPPII‐RF). The key processing stage and the processing of the input image stage are used to increase key sensitivity and plain‐image sensitivity, respectively. The method is independent of the input image and the bit pattern of the main key, and no information is affected by the main key and the original image. In the proposed method, three parameters, the main key, the counter value, and the previously generated ciphertext, are utilized within the encryption process to produce each subsequent ciphertext. Because this method uses the previous ciphertext to generate the next ciphertext, it increases the confusion of the final result and provides better security against differential attacks. The most important innovations of this work include the simultaneous use of various techniques such as shuffling key bits by the key processing unit, shuffling pixels of the original image by the original image processing unit, utilizing a parameter known as a seed as a unique parameter for an image, and employing an appropriate round function to apply complexity to the data. The performance of the proposed structure is evaluated based on different security analyses. The information entropy values of the encrypted images based on the proposed scheme are higher than 7.995, while correlation values are very close to zero. Furthermore, the number of pixel change rate (NPCR) and unified average change intensity (UACI) for the proposed KPPII‐RF image encryption are higher than 99.5% and 33.3, respectively. The KPPII‐RF image encryption is verified for randomness through 16 NIST benchmark statistical tests from the NIST SP 800‐22 suite. The proposed structure provides an acceptable security level for image encryption.

In this paper, a cryptosystem is proposed to encrypt 16-bit monochrome DICOM image using enhanced chaotic economic map. A new enhanced chaotic economic map (ECEM) is designed from the chaotic economic map which has better bifurcation nature and positive Lyapunov exponent values. In order to improve the sternness of the encryption algorithm, the enhanced chaotic map is employed to generate the pixel permutation, masking, and swapping sequences. The substitution operation is introduced in-between the standard permutation and diffusion operations. The robustness of the proposed image encryption algorithm is measured by various analyses such as histogram, key sensitivity, key space, number of pixel change rate (NPCR), unified average change intensity (UACI), information entropy and correlation coefficient. The results of the security analyses are compared with existing algorithms to validate that the proposed algorithm is better in terms of larger key space to resist brute force attacks and other common attacks on encryption.

Aiming at the problem of digital image encryption, an image encryption algorithm is proposed. The algorithm is divided into preparation stage and permutation diffusion stage. In the preparation stage, Arnold algorithm is improved and combined with Logistic chaotic map to generate the necessary sequence for the next stage. In the permutation diffusion stage, the final encrypted image is obtained by permutation, positive XOR operation, shift operation, S-box substitution and reverse XOR operation. The experimental results show that the algorithm can effectively resist the common attacks. For the 128 × 128 Lena gray image, the resistance performance number of pixel change rate (NPCR) is 99.6090, unified average changing intensity (UACI) is 33.4316. In addition, the time consumption of the algorithm is about 0.0055 s, and the experiments show that the algorithm has high security and real-time performance.

In this paper, the quality of image encryption using filter bank with lifting scheme has been studied and evaluated. Many extensive techniques have been applied to examine the security of the image encryption using the filter bank cipher with one or two rounds. To analyze and evaluate the proposed scheme, many parameters have been employed, such as, histogram analysis, correlation coefficient, global entropy, block entropy, avalanche effect, number of pixel change rate (NPCR), unified average change intensity (UACI), compression friendliness, exhaustive key analysis, and key sensitivity test. The simulation results showed that, the quality of the image encryption passes all these tests. Moreover, it reaches or excels the current state-of-the-arts. So that, the proposed image encryption process produces random-like output from the statistical point of views.

ABSTRACTRecently, in chaotic cryptography several new techniques have been suggested to develop efficient and secure image encryption algorithm for communication of image over insecure/public channels. Some of these techniques are computationally less complex but fails to provide sufficient security, and some techniques are though highly secured but increases computational overhead for encryption and decryption. This paper presents an efficient bit-plane encryption algorithm using chaotic, quadratic, and cubic maps. The proposed algorithm is based on the confusion, diffusion, and pixel randomisation processes. The encryption security of this technique for different bit-plane has been tested through key space analysis, statistical analysis, entropy analysis, and sensitivity analysis for real time image encryption and transmission. The presented algorithm shows the strength of security in terms of information entropy, peak signal-to-noise ratio (PSNR), number of pixels change rate (NPCR), unified average changing intensity (UACI), and correlation coefficient with the number of encrypted bit planes. It is clear that the strength of security increases with the number of encrypted bit planes, but the presented results demand that the level of security reached to the requirements (expected theoretically according to [C. Fu, et al., Optic Express, 20, 2363–78, Jan. 2012]) after encryption of four to six bit planes with reasonable small encryption/decryption time. This features proved the novelty of the proposed work. The algorithm is tested by the random and pseudo-random sequence of test standard SP 8000-22 released by National Institute of Standard and Technology Commission (NIST).

This study introduces a cutting-edge image encryption algorithm aimed at elevating security standards. The Pan-Tompkins Algorithm (PTA) for key generation is proposed for the first time in this study. Additionally, employing steganography through the Least Significant Bit (LSB) method for embedding keys within the encrypted image enhances secure key distribution, thereby fortifying the encryption process. On the other hand, the integration of advanced algorithms, such as Zigzag scanning, the Affine Image Encryption Algorithm (AA), and the Vigenere Image Encryption Algorithm (VA), constitutes the fundamental innovation of the proposed image encryption algorithm. The proposed algorithm is named PanAAVA:Affine Algorithm and Vigenere Algorithm Encryption with PTA-Based Key Generation. The PanAAVA algorithm ensures unparalleled security by encrypting the positions and values of pixels using AA and VA. Notably, using PTA for key generation marks a distinctive and new key generation method feature of the algorithm. To assess the effectiveness of the PanAAVA, a comprehensive comparative analysis is conducted against well-established encryption methodologies, including Lena, Baboon, Airplane, and Pepper.The PanAAVA demonstrates exceptional proficiency in histogram analysis. The PanAAVA demonstrates a Unified Average Changing Intensity (UACI) of 33.4044%. Additionally, the Number of Pixels Change Rate (NPCR) is measured at 99.7442%, showcasing the algorithm’s effectiveness in inducing significant pixel changes. The proposed algorithm’s Mean Square Error (MSE) is calculated at 3.20679E5%. The proposed algorithm’s Peak Signal to Noise Ratio (PSNR) is recorded at 9.512475. The Key Space Size of the proposed algorithm is measured at 2209. Regarding correlation analysis, the PanAAVA achieves a high correlation score of 7.9996. The proposed algorithm successfully passes the National Institute of Standards and Technology (NIST) analysis, demonstrating a remarkably strong correlation close to 0 and a Structural Similarity Index Measure (SSIM) of 0.9977. Furthermore, regarding quantum communication, the proposed algorithm maintains stable key rates of 47.5 ± 0.8 kHz during the day and 50.9 ± 0.7 kHz at night. Additionally, PanAAVA achieves low Quantum Bit Error Rate (QBER) values of 4.77 ± 0.02, ensuring reliable and secure communication. The PanAAVA also demonstrates robust asymmetries at 49.81 ± 0.02 and 50.14 ± 0.03 for a crystal length of 20 mm. highlighting PanAAVA’s adaptability and effectiveness in different scenarios. PanAAVA outperforms other encryption algorithms concerning performance measurements and comparisons. In conclusion, the PanAAVA emerges as a beacon of superior security capabilities and innovation in image encryption, showcasing the potential to redefine standards in the field.