Error-free reversible data hiding with high capacity in encrypted image

Data hiding in encrypted image is a hot topic of data security in recent years. In this paper, we propose a reversible data hiding algorithm with high capacity in encrypted domain by exploiting alpha channel of portable network graphics (PNG) image. Specifically, our algorithm divides secret data into some segments. For each segment, one bit is embedded into the LSB of encrypted pixel and other bits are hidden in the corresponding element of the alpha channel, which is finally encrypted by two chaotic maps. With the use of alpha channel, our algorithm can perfectly recover secret data and reach high embedding capacity and good visual quality. Many experiments with standard benchmark images are carried out to validate efficiency of our algorithm. Comparison shows that our algorithm outperforms Zhang's algorithm (IEEE SPL 18(2011) 255-258).