Adaptive Pixel Pair Matching based Steganography for audio files

Steganography is the art of concealing secret information inside cover media. Initially, Steganography, originated with the method called LSB Substitution. This is one of the oldest and simplest methods of hiding information, where, only the least significant bits of the cover image are altered. However, it faced its own disadvantages of higher distortion and lower embedding efficiency. These problems were then overcome by the method called Optimum Pixel Adjustment Process (OPAP). In this process, the substitution was adjusted depending upon the error condition. These two methods are based on single pixel processing. Later on, a method called Pixel Pair Matching (PPM) was proposed which worked with two pixel adjustment. Here, a pixel pair (x,y) and (x´,y´) is chosen. One pixel is used as the reference coordinate and the other pixel is used as the search coordinate. Depending upon the incoming secret message, the searched coordinate is concealed into the reference coordinate. Exploiting Modification Direction (EMD) and Diamond Encoding (DE) are the two variations of this kind. Adaptive Pixel Pair Matching (APPM) is another variation of the kind PPM. This method offers better embedding capacity than all other methods. This paper, proposes a method for hiding audio file inside images using APPM.