Text visualization encryption based on coordinate substitution and chaotic system

The text may contain information such as personal privacy and national security, and it is vital to protect these sensitive information. The traditional text encryption methods only encrypt text into the garbled code. Although the encrypted text appears to be garbled, there may be text length exposure and semantic preservation. Attackers can use these information leakages to analyze and attack. Therefore, in order to confuse the attackers, we propose a technique to encrypt the text into the image in which it can hide the information that may be exposed in the ciphertext such as text length, language structure, frequency distribution, etc. It mainly uses coordinate substitution encryption and image encryption to encrypt text into image. First, the text is encrypted using coordinate substitution to initially disrupt the correlation between characters. Second, the encrypted text is converted to ASCII values and presented as the image. It is then multiplied with the Hankel matrix to adjust its elements values close to the true range of pixel values. Finally, the two-dimensional polynomial chaotic system and the image encryption algorithm are combined to obfuscate and diffusion encrypt images. It is experimentally verified that the scheme has good security and robustness for protecting text data.