II. Steganography in Wave files
Wave file format
The WAVE file format is a subset of Microsoft's RIFF spec, which can include lots of different kinds of data. It was originally intended for multimedia files, but the spec is open enough to allow pretty much anything to be placed in such a file, and ignored by programs that read the format correctly.This description is not meant to be exhaustive, but to suggest simple ways of doing common tasks with waveform audio, and give some pointers to other sources of information.
WAVE audio files are one of the common formats used to store and play audio data. They support variables sampling frequencies, multiple channels, and a number of compression algorithms.
Hide algorithm
v Extract wave file size from header.
v Copy header as it is.
v Get message or secret file size after encryption.
v Store this in the first 32 bytes (data part).
v Calculate displacement =Wave file size / (message/secret file size).
v Convert encrypted message / secret file to bit representation.
v Hide each bit to the LSB of left and right channel byte.
v Move forward by the displacement.
v Continue the above process until the end of the wave file.
The ‘displacement and hide’ technique is used to improve the quality of the output file. Data is hidden only at the LSB of those bytes encountered by moving forward according to the displacement.
Unhide algorithm.
v Extract wave file size from header.
v Extract Message/Secret file size from the first 32 bytes of left & right channel data.
v Calculate displacement = Wave file size/(message / secret file size)
v Extract Encrypted Message/File From LSB of Left & Right Channel data.
v Move Forward By the displacement.
v Do the above until the end of the file.
v Pass the file / message to the decryption module.