Separable reversible data hiding in an encrypted image using unaltered adjacent pixels to enhance information security

The demand for secure handling and confidentiality of information has heightened immensely in the contemporary era, particularly due to high volumes of data exchanged through the Internet. Steganography and cryptography are two widely used techniques for safeguarding data, each with its inherent strengths and limitations. Cryptography protects information by converting it into an unreadable form, guaranteeing confidentiality. However, it does not hide the fact that a communication is present, which can draw unwanted attention. Steganography conceals information within digital media to render its presence less noticeable. Nevertheless, this approach can diminish the quality of the cover media and faces challenges in achieving lossless recovery of the cover. Reversible Data Hiding in Encrypted Images (RDHEI) has been proposed to transcend these limitations, enhancing security and recoverability. RDHEI provides a robust method for extracting and embedding data while maintaining the integrity of the original image. Separable Reversible Data Hiding in Encrypted Images (SRDHEI) takes it a step further by enabling data to be decrypted and extracted separately, without requiring access to or modification of the original image. This paper presents a novel SRDHEI solution with a high embedding capacity of 0.691 bits per pixel (bpp), which is achieved by combining Wang’s “multiple-bit RDH scheme without histogram shifting” with additive homomorphic encryption concepts. Experimental comparisons demonstrate that the new solution outperforms other methods in terms of embedding capacity, visual quality, and overall security.