A zero-watermark scheme with geometrical invariants using SVM and PSO against geometrical attacks for image protection

► A zero-watermark scheme is proposed using RST invariant features, the SVM and the PSO algorithm against RST attacks for image authentication. ► The SVM-based zero-watermark scheme makes no changes to original images after embedding the owner signature of images. ► The SVM-based zero-watermark scheme requires no original image while retrieving watermarks. ► The particle swarm optimization algorithm is employed to search for a set of nearly optimal parameters of the SVM. ► In average, the SVM-based zero-watermark scheme outperforms other existing methods against RST attacks.