Reversible data hiding in encrypted images based on side matching and enhanced complexity function

Cloud computing has developed to be the most promising business model in recent times owing to access business applications or infrastructure resources at a negligible cost but the issue of security still lies as a question to be answered since storing and processing of data are done by a third-party data centers. Reversible data hiding in images guaranties security to data accumulated at a third-party center. Zhang proposed a complexity function that neglects borders of the image block. Hong et al. worked on the side matching technique and evaluated complexity function considering two adjacent pixels of the image block. Liao et al. organize image block of three different groups containing two, three and four neighborhoods for the computation of complexity function. In our proposed method, instead of utilizing the whole image block for data embedding, selection of pixels are based on the unencrypted fourth least significant bit (LSB) layer because it is nearly random. Further, a new complexity function is proposed considering every pixels of the image. The proposed method decreases the error rate during bit extraction when compared with existing approaches.