An authentication scheme for color images with grayscale invariance and recoverability using image demosaicing

This paper proposes a novel recoverable authentication scheme for color images that ensures the consistency of grayscale values after embedment. In the proposed scheme, the color image is sub-sampled based on the Bayer pattern, and the most significant bits (MSBs) of the sub-sampled image are used as the recovery codes. Image blocks are divided into two categories, feasible and infeasible. Feasible blocks are utilized for embedding both authentication and recovery codes, whereas infeasible ones are only used for embedding authentication codes. In case of tampering, the authentication codes are employed to detect the tampered regions, and the undamaged recovery codes can be utilized to reconstruct the sub-sampled image. The demosaicing algorithm is applied to the sub-sampled image to obtain the demosaicked image, which is then used to recover the tampered regions. Experiments demonstrate that the proposed scheme yields an acceptable image quality even when the tampering rate is as high as 40 %.