Reversible Data Hiding in Encrypted Images Based on Hybrid Cryptosystem

Abstract

ABSTRACT As an important branch of reversible data hiding, reversible data hiding in encrypted images (RDH-EI) can embed secret message into images, but also effectively protect the privacy of the images in an open environment. Most of the recently proposed RDH-EI methods are based on the public-key cryptosystem. However, the expansion rate of the public-key cryptosystem is too high to make the information transmission more difficult. In this paper, to achieve a low expansion rate, a hybrid encryption combined with Paillier cryptosystem and stream cipher is proposed. The original image is partitioned into non-overlapping blocks, which are selected as two categories of blocks and encrypted by a hybird encryption with a low expansion rate. The embedding capacity of these two types of blocks is determined by the adaptive optimization algorithm. Hidden data are embedded into images by modifying ciphertexts according to the data hiding key. In the decoding phase, the embedded data can be extracted, and the original image can be recovered with the encryption key and data hiding key. Experimental results show that the low expansion rate can be obtained with a relatively high PSNR compared with some state-of-the-art methods.