Secure Data Hiding in Binary Images Using Run-Length Pairs

The popularity of digital media is on the rise today. Besides multilevel images, video, and audio, binary document images are also digitized in many applications. These include legal documents, digital books, maps, pictures, and architectural drawings. Security and confidentiality of information transmitted through digital media are the primary concerns. Employing cryptography is an imperfect solution because doing so can expose sensitive information to intruders. Information hiding is more promising as it focuses on imperceptibility. However, hiding information in binary media is more difficult than in color and greyscale media, as it causes more visual distortion due to two-shade limitations. Apart from this, the hiding technique one uses needs to take into account the requisite hiding capacity and the security of hidden information. This chapter presents an approach for hiding information in binary images which tries to address these issues. The message to be hidden is initially encrypted by a key known to both transmitter and receiver. This encrypted message is then represented as a two-dimensional sparse matrix and then transformed to a one-dimensional matrix where only information about locations of black pixels ‘1’ in the sparse matrix is preserved. An arithmetic compression algorithm is used to compress the sparse matrix. Black and white pixel run length (RL) pairs are utilized for hiding information which satisfy the threshold set for RL pair length. On the receiver side, a reverse process is applied to extract secret messages. The encryption, sparse matrix representation and arithmetic data compression secures the information and enhances hiding capacity. Utilization of run length pairs minimizes visual distortion. The results show that-high capacity information is hidden with less distortion. As digital multimedia sources become more specialized, the information hidden within them is used for steganography and watermarking.