Revolutionary Privacy Protection: Developments of Visual Cryptography for Secure Image Sharing

With the development of smart devices and networks, security and privacy protection have become significantly important. Numerous encryption algorithms have been invented to transmit confidential data or to protect user privacy. However, as most of them need complicated computing, sometimes they may not be the best way to encrypt certain types of data. Visual cryptography is a unique approach that is different from other kinds of cryptography as it does not need any mathematical calculation, but only relies on human vision for decryption. It was first proposed by Naor and Shamir. This paper selects two methods of visual cryptography, black-and-white image secret sharing and color image secret sharing. The paper first introduces the concept of the two methods, then summarizes the disadvantages of the two original algorithms and gives several improvements. Finally, provide examples of applications. The simple operations and decryption conditions make visual cryptography quite promising for future applications.