Quality Of Decrypted Images Research Articles

A crosstalk-free multiple-image encryption scheme based on computational ghost imaging with binarized detection

Crosstalk noise is a main problem limiting the performance of multiple-image encryption (MIE) scheme. In this work, we proposed a crosstalk-free MIE scheme based on computational ghost imaging (CGI) with binarized detection. In the encryption process, the plaintext images are encrypted into intensity sequences by the CGI system and quantified into two levels to obtain binary ciphertext sequences, which does not cause severe degradation in decrypted image quality compared to traditional CGI. Then, for the binary ciphertext sequences, we can combine them into a decimal grayscale ciphertext. To enhance security, a pixel bit layer scrambling (PBLS) algorithm is designed to scramble the grayscale ciphertext to obtain the final ciphertext. In the decryption process, anyone of the plaintext images can be decrypted without being affected by other plaintext images after performing inverse PBLS algorithm on the ciphertext and extracting the binary ciphertext sequence. The effectiveness, robustness, encryption capacity and security of the proposed scheme are demonstrated by numerical simulations and theoretical analysis.

Research on Variable Parameter Color Image Encryption Based on Five-Dimensional Tri-Valued Memristor Chaotic System.

To construct a chaotic system with complex characteristics and to improve the security of image data, a five-dimensional tri-valued memristor chaotic system with high complexity is innovatively constructed. Firstly, a pressure-controlled tri-valued memristor on Liu's pseudo-four-wing chaotic system is introduced. Through analytical methods, such as Lyapunov exponential map, bifurcation map and attractor phase diagram, it is demonstrated that the new system has rich dynamical behaviors with periodic limit rings varying with the coupling parameter of the system, variable airfoil phenomenon as well as transient chaotic phenomenon of chaos-periodic depending on the system parameter and chaos-quasi-periodic depending on the memristor parameter. The system is simulated with dynamic circuits based on Simulink. Secondly, the differently structured synchronous controls of chaotic systems are realized using a nonlinear feedback control method. Finally, based on the newly constructed five-dimensional chaotic system, a variable parameter color image encryption scheme is proposed to iteratively generate varying chaotic pseudo-random sequences by varying the system parameters, which will be used for repetition-free disambiguation, additive modulo left-shift diffusion and DNA encryption for the three components of RGB of the color image after chunking. The simulation results are analyzed by histogram, information entropy, adjacent pixel correlation, etc., and the images are tested using differential attack, noise attack and geometric attack, as well as analyzing the PSNR and SSIM of the decrypted image quality. The results show that the encryption method has a certain degree of security and can be applied to medical, military and financial fields with more complex environmental requirements.

Multilayer Convolutional Processing Network Based Cryptography Mechanism for Digital Images Infosecurity

Digital images can be easily shared or stored using different imaging devices, storage tools, and computer networks or wireless communication systems. However, these digital images, such as headshots or medical images, may contain private information. Hence, to protect the confidentiality, reliability, and availability of digital images on online processing applications, it is crucial to increase the infosecurity of these images. Therefore, an authorization encryption scheme should ensure a high security level of digital images. The present study aimed to establish a multilayer convolutional processing network (MCPN)-based cryptography mechanism for performing two-round image encryption and decryption processes. In the MCPN layer, two-dimensional (2D) spatial convolutional operations were used to extract the image features and perform scramble operations from grayscale to gray gradient values for the first-image encryption and second-image decryption processes, respectively. In the MCPN weighted network, a sine-power chaotic map (SPCM)-based key generator was used to dynamically produce the non-ordered pseudorandom numbers to set the network-weighted values as secret keys in a sufficiently large key space. It performs the second and first encryption processes using the diffusion method, modifying the image pixel values. Children’s headshots and medical images were used to evaluate the security level by comparing the plain and cipher images using the information entropy, number of pixel change rate, and unified averaged changed intensity indices. Moreover, the plain and decrypted images were compared to verify the decrypted image quality using the structural similarity index measurement and peak signal-to-noise ratio.

IoT based medical image encryption using linear feedback shift register – Towards ensuring security for teleradiology applications

Telemedicine gains prominence in today’s scenario and image security plays a vital role in the healthcare sector for authenticating data transfer. Medical data, when transferred through a cloud network should be encrypted to ensure security, this research work proposes a medical image encryption scheme using a linear feedback shift register (LFSR). The LFSR generates pseudo-random numbers and shuffles the pixel position. The encrypted image was transferred through a cloud platform, receiver side node decrypts the data to recover the original image. The Digital Imaging and Communications in Medicine (DICOM) computed tomography images are utilized in this research work and for IoT implementation, a Raspberry Pi B+ processor was used. The IoT implementation facilitates data transfer through the cloud network. The performance validation was done by metrics and the results reveal the proficiency of the encryption/decryption model. The decrypted image quality was evaluated in terms of the Peak to Signal Noise Ratio (PSNR) and Means Square Error (MSE), low value of the correlation coefficient proves the robustness of the encryption. The outcome of the research work paves the way for the researchers in the secure transfer of medical data through the cloud platform.

Separable Reversible Data Hiding in Encrypted VQ-Encoded Images

In this paper, a reversible data-hiding scheme in encrypted, vector quantization (VQ) encoded images is proposed. During image encryption, VQ-encoded image, including codebook and index table, is encrypted by content owner with stream-cipher and permutation to protect the privacy of image contents. As for additional-data embedding, a baseline method is first proposed and its corresponding optimized method is then given. By grouping one high-occurrence index with one or multiple low-occurrence indices, a series of index groups are constructed. Thus, by modifying the high-occurrence index to the corresponding index within the same group according to the current to-be-embedded bits, data embedding can be realized. The optimal hiding capacity is obtained by optimizing the coefficient vector for different types of index groups. Separable operations of data extraction, image decryption, and recovery can be achieved on the receiver side based on the availability of the encryption and data-hiding keys. Experimental results show that our scheme can achieve high hiding capacity and satisfactory directly decrypted image quality and guarantee security and reversibility simultaneously.

Application of compressive sensing based on multimode fiber specklegram in optical image encryption

In order to ensure the secure and effective transmission of image information, a new method of optical image encryption using the multimode fiber (MMF) specklegram based compressive sensing combined with the double random phase encoding (DRPE) is proposed in this paper. The specklegrams obtained from the facet of the multimode fiber are used as the measurement matrix of compressive sensing (CS), and the compression and the first-stage encryption of the image are completed by compressive sensing, in which the specklegram also functions as the first secret key. Then, the second-stage encryption is implemented by using the double random phase encoding technology, in which the random phase mask acts as the second secret key. All of the specklegrams used in this paper are obtained from the facet of a 5 m-long and 105-μm-diameter-MMF and offset launching technique. Then the fiber specklegrams are proposed in several steps to provide the measurement matrix in CS. By performing an encryption and decryption test on a standard Lena image of 256 × 256 size, it is found that the decrypted image and the original image are visually consistent, and the encryption is also realized in the process of compression, which indicates the method proposed in this paper is feasible. Furthermore, the comparison studies of the performances of specklegram based measurement matrix and some classic measurement matrices show that the decrypted image quality using the specklegram matrix is better. And at the same time, comparing with the high hardware implementation complexity and high cost of other measurement matrices, specklegram based matrix can be easily realized by simple optical device, and the corresponding secret key can be easily changed by the working wavelength, which is helpful for enlarging the secret key space. It is further proved that the encryption method be able to effectively resist the statistical analysis attacks, cropping attacks and noise interference, and also have high sensitivity to the secret key, which shows good robustness and high security. Therefore, the image encryption method combined with the specklegram matrix based compression sensing with the optical DRPE can obtain good encryption effect and has a great secret key space, which may provide a good candidate scheme for the pure optical realization of image encryption.

Intelligent Tunicate Swarm-Optimization-Algorithm-Based Lightweight Security Mechanism in Internet of Health Things

Fog computing in the Internet of Health Things (IoHT) is promising owing to the increasing need for energy- and latency-optimized health sector provisioning. Additionally, clinical data (particularly, medical image data) are a delicate, highly protected resource that should be utilized in an effective and responsible manner to fulfil consumer needs. Herein, we propose an energy-effi- cient fog-based IoHT with a tunicate swarm-optimization-(TSO)-based lightweight Simon cipher to enhance the energy efficiency at the fog layer and the security of data stored at the cloud server. The proposed Simon cipher uses the TSO algorithm to select the optimal keys that will minimize the deterioration of quality between the original and reconstructed (decrypted) images. In this study, the decrypted image quality is preserved by the peak signal-to-noise ratio (PSNR) such that consumers can generate precise medical reports from IoHT devices at the application level. Moreover, a lightweight encryption step is implemented in the fog to improve energy efficiency and reduce additional computations at the cloud server. Experimental results indicate that the TSO-Simon model achieved a high PSNR of 61.37 dB and a pixel change rate of 95.31.

Experimental research on optical image encryption system based on joint Fresnel transform correlator

Optical image encryption system based on joint Fresnel transform correlator is experimentally researched. Factors affecting decrypted image quality are analyzed, and measures of improving decrypted image quality are taken. Firstly, after a few denoising operations are performed, noise in decrypted image is effectively reduced. Secondly, effects of experimental device parameters on decrypted image quality are also analyzed. After random phase mask in object window and key mask are both optimized by an iteration algorithm, space bandwidth of joint image can match with that of experimental system. Through above-mentioned methods, quality of decrypted image is remarkably improved. Correlation coefficient (0.8346) between experimental decrypted image and original image is close to that (0.8686) between simulational decrypted image and original image. Experimental error-bit rate in decrypted image is also analyzed.

Reversible data hiding in encrypted images based on multi-level encryption and block histogram modification

In recent years there has been significant interest in reversible data hiding, and also in particular, reversible data hiding in encrypted images (RDH-EI). This means that additional data can be embedded into a previously encrypted image with no knowledge of the original image content. According to the held keys, legal receivers can get the embedded data or an image very similar to the original one, or, both the embedded data and an image exactly as the original one. In this paper, we propose and evaluate a RDH-EI framework. Firstly, we propose a multi-level encryption (MLE) scheme using both Josephus traversal based multi-granular encryption and a stream cipher. To reduce the quantity of side information required to embed into images together with additional data, we also present a block histogram modification (BHM) approach with self-hidden peak pixels to perform reversible data embedding and a location map marking scheme to perform histogram contraction and recovery. The experimental results demonstrate that, in comparison with other similar methods, the proposed framework achieves improvements in terms of the embedding payload, the decrypted image quality and the accuracy of image restoration.

Double-image encryption using chaotic maps and nonlinear non-DC joint fractional Fourier transform correlator

A double-image encryption method is reported using chaotic maps, nonlinear non-DC joint transform correlator (JTC), and fractional Fourier transform (FrFT). The double images are converted into the amplitude and phase of a synthesized function through the application of chaotic pixel scrambling. The synthesized function bonded with a chaotic random phase mask (CRPM) and another different CRPM serve as the input signal of the JTC architecture in the fractional Fourier domain to obtain a real-valued encrypted image. The nonlinear and non-DC operation is also done to improve the security and decrypted image quality. The parameters in joint FrFT correlator and chaotic map serve as the encrypted keys. Numerical simulations have been done to demonstrate the feasibility and validity of this algorithm.

Application of input amplitude masks in scheme of optical image encryption with spatially-incoherent illumination

Optical encryption with spatially incoherent illumination does not have drawbacks of coherent encryption techniques. In this case however, one of the factors affecting decrypted image quality is original image spectrum. In most cases, majority of image energy is concentrated in area of low spatial frequencies. Therefore, only this area in spectrum of encrypted image contains information about original image, while other areas contain only noise. Additional amplitude encoding of input scene can be used for increase of the size of the area of spatial frequencies containing useful information. Numerical simulation demonstrates reduction of decryption error up to 2.7 times.

Steganographic optical image encryption system based on reversible data hiding and double random phase encoding

This study presents a steganographic optical image encryption system based on reversible data hiding and double random phase encoding (DRPE) techniques. Conventional optical image encryption systems can securely transmit valuable images using an encryption method for possible application in optical transmission systems. The steganographic optical image encryption system based on the DRPE technique has been investigated to hide secret data in encrypted images. However, the DRPE techniques vulnerable to attacks and many of the data hiding methods in the DRPE system can distort the decrypted images. The proposed system, based on reversible data hiding, uses a JBIG2 compression scheme to achieve lossless decrypted image quality and perform a prior encryption process. Thus, the DRPE technique enables a more secured optical encryption process. The proposed method extracts and compresses the bit planes of the original image using the lossless JBIG2 technique. The secret data are embedded in the remaining storage space. The RSA algorithm can cipher the compressed binary bits and secret data for advanced security. Experimental results show that the proposed system achieves a high data embedding capacity and lossless reconstruction of the original images.

Multiple-image encryption based on position multiplexing of Fresnel phase

A multiple-image encryption approach based on the position multiplexing of Fresnel phase is proposed. Encryption keys are generated according to different distances' propagation of Fresnel phase and used as filters in typical 4f system. The proposed method can achieve multiple-image encryption by an analytical algorithm without iteration. Basic theories are described and corresponding formulas are derived. Single image and multiple-image encryption are numerically simulated while the encrypted security and the decrypted image quality are investigated as well. Numerical results are presented to demonstrate the validity of the proposed multiple-image encryption method.