Multiple image watermarking using LWT, DCT and arnold transformation

Abstract

In this paper, a new algorithm for multiple digital watermarking is proposed that is based on the combination of lifting wavelet transform (LWT) and discrete cosine transform (DCT) then Arnold transformation for encryption purpose is used. Multiple watermarks are embedded to avoid the chances of identity theft. The algorithm comprises of two parts, watermark embedding and watermark extraction. In embedding part, the cover image is decomposed into four sub bands by applying second level LWT. Low frequency sub bands LL2 and LH2 are then transformed by DCT. Two image watermarks are also transformed using DCT then one of the transformed watermark is again transformed using Arnold and its resultant is known as encrypted watermark. Encrypted watermark is embedded to LL2 sub band and normal DCT transformed to LH2 sub band. Extraction of watermark is performed using extraction algorithm. Watermarked image is subjected to various attacks to check the robustness of the algorithm. Experimental results are provided to demonstrate that the algorithm provides good results.