Abstract With the omnipresence of digital interaction, the need to secure sensitive information has increased tremendously. Hence, crypto-steganography has become an integral part of secret communication in various applications, ranging from image confidentiality in medical informatics to secured data transfer in sensor-based wireless networks. The challenge for researchers in IoT and embedded systems is to work under resource-constrained environments while preserving image quality and achieving computational efficiency. However, most of the current approaches consider cryptography and steganography as independent techniques, which often leads to higher computation overhead, reduced imperceptibility with increased payload, and low cryptographic security. Addressing these limitations, this work proposes a lightweight and unified crypto-steganographic approach whereby encryption is integrated into the embedding operation. A dual Piecewise Linear Chaotic Map (PWLCM) randomizes the reading order of payload and pixel embedding positions, while an in-place XOR transformation combines each payload bit with selected bits of pixels prior to embedding. The integration of Huffman compression effectively increases payload capacity, and multi-format support for lossless cover images (, , ) and input file formats (, , ) extends practical applicability. Experimental evaluation with both grayscale and color images shows very high imperceptibility, with peak PSNR values reaching $$\varvec{77.42dB}$$ and SSIM of approximately $$\varvec{1.0}$$ for smaller payloads, while sustaining the PSNR above $$\varvec{51dB}$$ even for a full capacity of $$\varvec{166,336}$$ characters. Also, embedding and extraction remain less than $$\varvec{1.6}$$ seconds. Further, the robust statistical undetectability allows RS Analysis, Sample Pairs Analysis, and Chi-Square tests to be evaded even at high payload capacities. A key space of more than $$\varvec{1.2483 \times 2}^{\varvec{199}}$$ ensures high cryptographic strength. All these observations together establish that the proposed approach is a lightweight embedding technique that can be used for big data, provides high cryptographic security and maintains image quality, hence is appropriate for low-resource situations.

Abstract Images are a crucial component in contemporary data transmission. Numerous images are transmitted daily through the open-source network. This paper presents a multi-image encryption scheme that utilises flip-shift-rotate synchronous-permutation-diffusion (FSR-SPD) processes to ensure the security of multiple images in a single encryption operation. The proposed encryption technique distinguishes itself from current multi-image encryption methods by utilising SPD operation and rapid FSR-based pixel-shuffling and diffusion operation. The SPD is a cryptographic technique that involves the simultaneous application of permutation and diffusion methods. The FSR-based process involves the manipulation of pixels through three different operations, namely flipping, shifting, and rotating. In the process of encryption, the image components of red, green, and blue colours are merged into a single composite image. The large image is partitioned into non-overlapping blocks of uniform size. The SPD technique is employed to tackle each specific block. The encryption method is efficient and expeditious as it exhibits high performance with both FSR and SPD procedures. The method employs a single, fixed-type, one-dimensional, piecewise linear chaotic map (PWLCM) for both the permutation and diffusion phases, resulting in high efficiency in both software and hardware. The proposed method is assessed using key space, histogram variance, neighbouring pixel correlation, information entropy, and computational complexity. The proposed method has a much bigger key space than the comparative method. Compared to comparison approaches, the suggested solution reduces encrypted picture histogram variance by 6.22% and neighbouring pixel correlations by 77.78%. Compared to the comparison technique, the proposed scheme has a slightly higher information entropy of 0.0025%. Other multiple-color image encryption methods are more computationally intensive than the suggested method. Computer simulations, security analysis, and comparison analysis evaluated the proposed methodology. The results show it outperforms multiple images encrypting methods.

This paper proposes an image securing technique that aims to provide two-level security on two images in terms of encryption at the same time. In this technique, both bit and pixel-level encryptions are carried out; first, the pixel-level-shuffling is performed using the piece-wise linear chaotic map (PWLCM); then, the diffusion in bit-level is performed using the key-image. The bit-level diffusion using chaos not just to confuse the pixels, but is also diffuses them intensely. In addition, the bit and pixel-level processes improve that algorithm's security. Additionally, the parallel bit-plane diffusion process reduces the method's computational complexity. This technique uses one type of one-dimensional chaotic map in both permutation and diffusion, thereby increasing the algorithm's hardware and software efficiency. The results of the security analysis and simulation show that the suggested method is more effective in encoding and improves the security of the encrypted images.

Medical images such as brain MRI, ultrasound, and X-ray images are currently used by doctors to treat many serious diseases in most hospitals and clinics. These images play a major role in medical diagnosis. Diagnostic images with sensitive patient data are recorded and exchanged owing to the advancement of public networks. As a result, maintaining the privacy of sensitive patient data is becoming increasingly important. In medical imaging, the pixels are highly correlated. To reduce pixel correlation, a variety of complex encryption methods have been used in recent years, increasing the algorithm's computational complexity. This paper proposes an image encryption method based on chaos-based shifting operations. Security, convenience, and speed are all advantages of shifting activities. This method initially executes bit-plane flipping and permutation operations, then block-based flipping and diffusion operations to obtain the cipher images. The simulation and security analysis findings show that the proposed approach performs better.