Images are widely used in communication all over the world. Images are used in many applications, including medical images, remote sensing, education images, electronic commerce, etc. Through the convenience of the Internet, we can share images and information at any time and any place.

However, some images may refer to private personal or other commercial information. Image security should be paid much attention in order to combat illegal access, revision, and other attacks. In recent years, many image encryption algorithms have been proposed and published, for example, chaos-based methods, compressive sensing-based schemes, quantum map-based algorithms, etc. Under the information era and the arrival of big data, we need a higher level of security protection for our images. Our images are transferred and opened over public networks, so applying cryptography to the image is a direct way to hiding image information and implementing data protection. There are two cipher structures: symmetric cipher and asymmetric cipher. Symmetric ciphers use the same keys to encrypt and decrypt the image, while in asymmetric ciphers the sender and receiver have different keys. However, quantum computers within the environment of 5G networks will present a challenge to the current image encryption algorithms. The design of new encryption algorithms needs further investigation.

This Special Issue welcomes all experts and scholars to submit their new methods or algorithms written in research papers, aiming to offer image security and image privacy protection. Original research and review articles are welcome.

Potential topics include but are not limited to the following:

• Image encryption
• Image watermarking
• Visual image encryption
• Image information hiding
• Quantum image encryption
• Blockchain with its applications in image encryption
• Compressive sensing with its applications in image encryption
• Chaos with its applications in image encryption
• Optical image security
• Other encryption methods for images