Reversible Data Insertion in Encryption Domain Based on Reduced Quad Difference Expansion

A novel method for lossless extra information embedding in encrypted two-dimensional images is proposed. According to our method, reducing difference values of the quad pixels in each blocks of the encrypted host image is used. Therefore, first the encrypted carrier is divided into separated blocks of four pixels. After block partitioning, Reduced Quad Difference Expansion (RQDE) is used for data insertion reversibly. By reducing difference values as a preprocessing step and before the embedding process, less distortion is applied to the carrier signal during data insertion. Therefore, higher quality is obtained for the decrypted signal. The method is classified as a Vacating Room After the Encryption (VRAE) and separable. Obtained results indicate our method has better performance in against other related methods in the current literature for lossless data insertion.