Pramatha Nath Basu School of Education Technology Jadavpur University Abstract A steganographic method of embedding textual information in an audio file is presented in this paper. In the proposed technique, first the audio file is sampled and then an appropriate bit of each alternate sample is altered to embed the textual information. As a steganographic approach the perceptual quality of the host audio signal was not to be degraded. Keywords: Steganography, Human Auditory System (HAS), Cover object, Covert data, Stego-object, Embed, Extraction. I. INTRODUCTION Steganography is an art of sending hidden data or secret messages over a public channel so that a third party cannot detect the presence of the secret messages. The goal of steganography is different from classical encryption, which seeks to conceal the content of secret messages; steganography is about hiding the very existence of the secret messages. Modern steganography is generally understood to deal with electronic media rather than physical objects. There have been numerous proposals for protocols to hide data in channels containing pictures [1, 2, 3], video [3, 4], audio [1, 3] and even typeset text [1, 3]. This makes sense for a number of reasons. First of all, because the size of the information is generally quite small compared to the size of the data in which it must be hidden (the cover text), electronic media is much easier to manipulate in order to hide data and extract messages. Secondly, extraction itself can be automated when the data is electronic, since computers can efficiently manipulate the data and execute the algorithms necessary to retrieve the messages. Electronic data also often includes redundant, unnecessary and unnoticed data spaces which can be manipulated in order to hide messages. The main goal of this paper was to find a way so that an audio file can be used as a host media to hide textual message without affecting the file structure and content of the audio file. Because degradation in the perceptual quality of the cover object may leads to a noticeable change in the cover object which may leads to the failure of objective of steganography. Tanmay Bhowmik Dept. of Information Technology Murshidabad College of Engineering & Technology II. ASSUMPTION AND SCOPE Modern steganography based on embedding of secret data into electronic media like image [1, 2, 3], audio [1, 3], video [3, 4] and text [1, 3]. For example, to a computer, an image is an array of numbers that represent light intensities at various pixels. A common image size is 640 × 480 pixels and 256 colors (or 8 bits per pixel). Such an image could contain about 300 kilobits of data [5]. Digital images are typically stored in either 24 bit or 8 bit files. A 24 bit image provides the most space for hiding information. A data – embedding technique into an audio file can be based on frequency masking [6], temporal masking [7], bit modification [8], LSB based method based on lifting wavelet transform [9] etc. It has been already proved that modification of the least significant bit creates a minimal change in the audio file format [1]. So while embedding text into an audio file LSB modification creates an imperceptible change in the host audio file. A steganography system, in general, is expected to meet three key requirements, namely, imperceptibility of embedding, accurate recovery of embedded information, and large payload (payload is the bits that get delivered to the end user at the destination) [1]. In a pure steganography framework, the technique for embedding the message is unknown to anyone other than the sender and the receiver. An effective steganographic scheme should posses the following desired characteristics [10-11]: Secrecy: a person should not be able to extract the covert data from the host medium without the knowledge of the proper secret key used in the extracting procedure. Imperceptibility: the medium after being embedded with the covert data should be indiscernible from the original medium. One should not become suspicious of the existence of the covert data within the medium. High capacity: the maximum length of the covert message that can be embedded should be as long as possible. Resistance: the covert data should be able to survive when the host medium has been manipulated, for example by some lossy compression scheme [12]. Accurate extraction: the extraction of the covert data from the medium should be accurate and reliable. On Embedding of Text in Audio – A case of Steganography 2010 International Conference on Recent Trends in Information, Telecommunication and Computing 978-0-7695-3975-1/10 $25.00 © 2010 IEEE DOI 10.1109/ITC.2010.16 203