This paper presents a new blind watermarking system based on the Discrete Cosine Transform (DCT). The system’s security is increased by encrypting the watermark image using the fractional-order Lorenz system. After converting the cover image to the YCbCr color domain, DCT is applied on the Y channel and embedding of the encrypted watermark is performed in the frequency domain. The fractional-order Lorenz system has more parameters than the integer order system, which increase the length of the system key and make it secure against brute-force attacks. Although blind detection of the watermark is not easy, the proposed algorithm successfully detects the hidden watermark by using statistical properties of the DCT coefficients. Standard imperceptibility and robustness measures are used to evaluate the proposed system, and the results are good. © 2022 IEEE.
Progressive Multi-Secret Sharing of Color Images Using Lorenz Chaotic System
Multi-Secret Image Sharing (MSIS) systems share multiple images to multiple participants in unintelligible forms that can be recovered using all the shares. This paper employs the concept of progressive secret sharing with MSIS to introduce a new system, where the number of used shares in the recovery process defines the quality of the recovered secrets. The proposed system works for any number of secret color images, and is lossless when all the shares are present. The Lorenz chaotic system, which is numerically solved using Euler method, is used as source of randomness to encrypt the secret images. Image encryption utilizes a long system key to perform the substitution and permutation stages. The system passes all security tests, including statistical analysis and key sensitivity, and it is also robust to noise and crop attacks. The analysis results are within the required ranges for a good encryption system, and they are better than those of the compared MSIS systems. © 2023 IEEE.
A Unified System for Encryption and Multi-Secret Image Sharing Using S-box and CRT
Multi-Secret Image Sharing (MSIS) is used when multiple images need to be shared to multiple participants, but the images can not be recovered without the presence of all shares. In this paper, a unified system for performing encryption and (n,n)-MSIS is proposed. While MSIS is based on the XOR operation, encryption combines the utilization of Chinese Remainder Theorem (CRT), SHA-256, and S-box for improved security. The same designed system is used for the generation of secret shares and the recovery of secret images. In addition, a sensitive system key is designed where three pairwise relatively prime subkeys are automatically generated for utilization in the CRT. The resulting secret shares pass statistical evaluation criteria such as RMSE, correlation, and entropy, and give good results for differential attack measures, and runtime. In addition, the proposed system succeeds in passing the NIST SP-800-22 statistical test suite and key sensitivity measures. © 2022 IEEE.
PRNG Using Primitive Roots of Primes and its Utilization in Chess-based Image Encryption
Recently, number theory has proved its importance in cryptography because of its well-known hard problems. For instance, a primitive root for a prime number shows a special property of uniqueness when raised to different powers mod the prime number. In this paper, a Pseudorandom Number Generator (PRNG) is designed based on this property using a prime number and some of its primitive roots. The PRNG is, first, validated for utilization in cryptography applications using histograms, correlation coefficients, and the National Institute of Standards and Technology (NIST) statistical test suite. Then, the PRNG is utilized in an image encryption system and the system security is tested using statistical measures, differential attack measures, and sensitivity to one-bit change. The results are promising and in the expected good ranges. © 2022 IEEE.
Registerless Multiplierless YCoCg-R and YCoCg Color Space Converters Hardware Implementation
Multimedia data, e.g., images and videos, are widely used over the internet and on computers. Image processing applications require color space conversion to be able to deal with these types of data more efficiently. This paper investigates three color space conversions and proposes simplified combinational hardware designs and FPGA realizations for RGB to YCoCg-R and YCoCg color spaces encoders and decoders and compares them to their sequential counterparts. The proposed hardware design for the encoders and decoders uses only adders and subtractors without any registers or multipliers. The proposed YCoCg-R converter exhibits better resources utilization compared to implementing the design using shift registers, where it uses 56.3% and 72.1% less LUTs and FFs, respectively. Similarly for the YCoCg color space, the combinational design used 48.1% less LUTs and 67.8% less FFs than its sequential counterpart. © 2022 IEEE.
Image encryption in the fractional-order domain
This paper presents a new image encryption scheme based on the fractional-order Lorenz system which gives more degrees of freedom in key generation. In the modified fractional-order system, the key length is doubled using the three fractional-orde r parameters beside the three initial conditions, which makes it invulnerable to brute-force attacks. In addition, using a very simple algorithm, based on pixel confusion only, strongly encrypted images are produced. Such an algorithm can be used in real time applications. To evaluate the algorithm and analyze the encryption results, a standard image is used. A comparison of the colored correlation coefficients (horizontal, vertical, diagonal) for different cases with respect to a fractional-order parameter and another system parameter are introduced. Moreover, the encrypted image shows high sensitivity to the fractional-order key, which appears from the wrong decryption with 0.1% change of the fractional-order parameter. © 2012 IEEE.
Image encryption using generalized tent map
This paper introduces two generalized tent maps where the conventional map is a special case. Although the output of the conventional tent map shows different responses, it has only one control parameter that limits its behavior and applications. The proposed generalized tent maps increase the degrees of freedom and produce a versatile response that can fit many applications. The characteristics of each generalization are discussed such as: fixed points, bifurcation diagrams, and Lyapunov exponents. Finally, a simple image encryption application, based on the generalized tent maps, is presented for the design of long encryption key using the added parameters. Moreover, statistical and sensitivity analysis are presented to demonstrate the benefits of the generalized maps. © 2013 IEEE.
Design of pseudo random keystream generator using fractals
This paper presents a novel method for designing a pseudo random keystream generator (PRKG) based on fractal images. Although a fractal image has high correlation between its pixels, the proposed technique succeeds in almost eliminating this correlation and the output stream passes the NIST statistical test suite. The post-processing on the fractals is based only on a confusion process and uses a nonlinear network with a delay block to randomize the output stream. Many statistical measures and the NIST suite have been used to evaluate the processed fractals and the results are promising. As an example to validate the PRKG, the output stream is used in a simple image encryption system. The encrypted image is tested by calculating pixel correlations, differential attack measures, entropy and it also passes the NIST test suite. © 2013 IEEE.
Hardware Speech Encryption Using a Chaotic Generator, Dynamic Shift and Bit Permutation
This paper proposes a speech encryption and decryption system, its hardware architecture design and FPGA implementation. The system utilizes Nosé Hoover chaotic generator and/or dynamic shift and bit permutation. The effect of different blocks in the proposed encryption scheme is studied and the security of the system is validated through perceptual and statistical tests. The complete encryption scheme is simulated using Xilinx ISE 14.5 and realized on FPGA Xilinx Kintex 7, presenting the experimental results on the oscilloscope. The efficiency is also validated through hardware resources utilization compared to previous works based on maximum frequency and throughput. © 2018 IEEE.
Pixel-based Visual Secret Sharing Using Lorenz System
(n, n)-Visual Secret Sharing (VSS) allows a user to send an image in the form of shares to different participants. Every share can not reveal the secret alone, and only all shares together can reveal the secret with fast recovery. This paper proposes a pixel-based (n, n)-VSS system, where to share a pixel from the secret image, (n – 1) random pixels are generated from the Lorenz chaotic system for a varying set of (n – 1) shares. Then, the nth pixel is calculated for a random share using the secret pixel and the generated (n – 1) random pixels. The system is efficient, lossless, implemented for grayscale and color images, and has a simple XOR-based recovery scheme. It passed several security analysis tests and is robust against noise attacks. Moreover, performance analysis and comparisons with other VSS systems are presented, showing good results. © 2023 ACM.