Capacity-raising reversible data hiding scheme using quinary secrets square in dual-images

In recent years, reversible data hiding has become one of the most commonly used techniques. In this paper, a novel dual image reversible data hiding (RDH) technique based on a quinary secret square is proposed. In this technique, the imperceptibility and data hiding capacity are improved while maintaining good image quality in a lossless manner. The information overhead sent to the receiver for extraction and recovery is also reduced. A secret square is used during the embedding and extraction processes. In addition, the use of 5-ary numbers rather than binary numbers is proposed to ensure that all secret messages are embedded from the symbols. This technique uses two pixels as a block (2 × 2) and a maximum of 25 symbols to embed the secret message. In the experiments, 25 symbols and 16 symbols were used to embed a 512 × 512 image. Two hiding capacities were achieved by using two different numbers of symbols, as previously mentioned. Using 16 symbols, the technique achieved good average PSNR values for both PSNR1 and PSNR2 with an average PSNR of 51.60 dB for the same data hiding capacity of 524,288 bits. With 25 symbols and the exact same technique, the embedding capacity was increased to 608,174 bits, which is greater than the hiding capacity of other existing techniques.