Quantum Steganography Embedded Any Secret Text without Changing the Content of Cover Data

Steganography is a technique hiding secret information within innocent-looking information (e.g., text, audio, image, video, and so on). In this paper, we propose a quantum steganography protocol using plain text as innocent-looking information called cover data. Our steganograpy protocol has three features. First, we can use any plain text that is independent of any secret message sent between parties. When we make stego data, we do not need to change the content of plain text at all. Second, embedded messages are not included in opened information (innocent-looking messages), but are included as phases of the entangled states. Finally, in quantum states shared between parties in advance, i.e., as quantum keys used when the parties recover secret messages from stego data, neither innocent-looking information nor the information of any secret message is included.