New methods and apparatuses for information security have evolved as a result of the rapid expansion of optical information processing. Security is one of the major issues in digital image transmission because it can deliver very secret information to any corresponding agency such as the military, biomedical, and security agencies. Previously, various techniques are proposed to perform optical image encryption techniques using different transformation and pixel-level techniques. Each work has its advantages and disadvantages in terms of computational complexity, security level, flexibility, quality, and so on. To overcome the security issues present in the previous works, a novel optical image encryption standard is proposed in this paper. This work uses information hiding followed by image encryption using Gyrator Transform (GT) using mean gradient key-based block swapping techniques. The main advantage of this work is that the key generation is dynamic and it depends upon the pixel intensity of 8 × 8 blocks. Secret information hiding is performed in the Discrete Cosine Transform (DCT) domain to protect the data against noise attacks. To analyze the performance, various evaluation metrics are used to measure the quality of the decrypted image under various distortions such as cropping and rotation. The robustness of information hiding is analyzed using a noise attack on the received image. This work achieved 45.6 dB of Peak Signal-to-Noise Ratio (PSNR) and 0.965 of Structural Similarity Index (SSIM), which is the best when compared to the conventional image encryption standards.

Recent development in the digital system shows that data security is most important and that optical encryption can be used not only to keep signals confidential but also to authenticate information. By integrating sparsity constraint with optical encryption, the reconstructed decoder image is not always visually recognizable, but can be authenticated using optical correlation means methods. Traditional optical encryption methods can add an extra layer of security to this design as it authenticates without leaking primary signal information. This paper discusses advances in optical authentication and includes theoretical principles and implementation examples to demonstrate the workings of typical authentication systems. Benchmarking and upcoming possibilities are discussed and it is hoped that this review work useful in advancing the field of optical safety.

In recent years a huge attention is given to the technique called Reversible Data Hiding In Encrypted Images (RDHEI) due to the demand for high security requirement. RDHEI is a type of data hiding that supports the lossless recovery of the host image following the extraction of secret hidden data. Since the technique is lossless, it is suitable for applications like medical imaging, scientific investigation, military applications, cloud services, law enforcement etc. Based on the method of implementation RDHEI can be classified into different categories. Existing RDHEI are mainly classified as with or without preprocessing of the host image before image encryption. Here different existing RDHEI techniques and its basic procedures is discussed.

This paper proposes a new algorithm for encrypting secret data to be communicated over internet. This method combines the advantage of normal encryption and visual cryptography. The secret image is encrypted using a new encryption algorithm producing multiple encrypted images. Images are same as the cover images thus become easy to handle. Then meaningful images are embedded on each share using embedding algorithm. At the receiver side after de embedding these meaningful encrypted images are decoded to form the secret image back. This method can be used for multiple meaningful encrypted images with perfect reconstruction of secret image.

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