Digital steganography refers to secret communication. It aims at providing secure, undetectable and imperceptible ways to conceal data into digital medium. On the other hand, digital steganalysis is the science of detecting such secret communication. This book is devoted to digital audio steganography and steganalysis. It presents a state-of-the-art review of the existing methods along with an evaluation and a performance study of the reviewed techniques. To meet the requirements of steganographic systems, we provide a new algorithm that exploits the Human Auditory System and the energy of the frequency components of digital audio signal spectra in data hiding. Finally, we present a new and effective yet simple to implement audio steganalysis method based on the principle of signal maximum entropy methods and active speech level.