Abstract—Stegnography is a new way of secret communication the most widely used mechanism on account of its simplicity is the use of the least significant bit. We have used the least significant bit (2 LSB and 4 LSB) substitution method. Depending upon the characteristics of the individual portions of cover image we decide whether to use 2 LSB or 4 LSB thus it is an adaptive stegnography technique. We used one of the three channels to behave as indicator to indicate the presence of hidden data in other two channels. The module showed impressive results in terms of capacity to hide the data. In proposed method, instead of using RGB color space directly, YCbCr color space is used to make use of human visual system characteristic. Keywords—Stegoimage, steganography, Pixel indicator, segmentation, YCbCr.. I. INTRODUCTION TEGANOGRAPHY deals with embedding information in a given media (called cover media)without making any visible changes to it [4].cryptography is about screening the matter or the material of the message while stegnography is about concealing the presence of the message. For many years Information Hiding has captured the imagination of researchers. Digital watermarking and steganography techniques are used to address digital rights management, protect information, and conceal secrets. Information hiding techniques provide an interesting challenge for digital forensic investigations. Information can easily traverse through firewalls undetected. We can use digital images, videos, sound files, and other computer files that contain redundant information as covers or carriers to hide secret messages. After embedding a secret message into the cover images, we obtain a so-called stego-image. It’s important that the stego- images don’t contain any detectable artifacts due to messages embedding. A third party could use such artifacts as an indication that a secret message is present. Once a third party can reliably identify which images contain secret messages, the steganographic tool becomes useless. Obviously, the less information we embed into the cover. Parvinder S. Sandhu and Alka Handa are associated with the Rayat & Bahra Institute of Engineering & Bio-Technology, Mohali-Sahauran14004. E- Mail: parvinder.sandhu@gmail.com, Surbhi Gupta is working as a Assistant Professor with the Rayat & Bahra Institute of Engineering Technology, Railmajra-140001. cover_medium + hidden_data + stego_key = stego_medium Message embedding is performed in spatial or frequency domain. One of the representative data hiding methods in spatial domain is to use the least significant bit (LSB), such as LSB replacement or LSB matching. Transform domain steganographic methods employ the well-known transformation techniques such as Discrete Cosine Transform (DCT), Fourier Transform (FT), or Discrete Wavelet Transform (DWT). Spatial domain methods are simpler and have a large capacity while transform domain methods are more robust compared to spatial domain method. Fig. 1 General Model of Steganography Images typically use either 8-bit or 24-bit color. When using 8-bit color, there is a definition of up to 256 colors forming a palette for this image, each color denoted by an 8- bit value. A 24-bit color scheme, as the term suggests, uses 24 bits per pixel and provides a much better set of colors. In this case, each pixel is represented by three bytes, each byte representing three channels Y (luminance)Cb and Cr (croma). A. Constraints for concealing information Many different protocols and methods are available that enables us to enclose data in a given object. However, all of the protocols and techniques must satisfy a number of constraints so that steganography can be applied correctly. The following is a list of main constraints or requirements that steganography methods must satisfy: • In case of images, after hiding the data in the cover image we get stego image and this stego image must remain unchanged. If there is significant amount of change in the stego image then it will become noticeable, thus third party can detect the existence of hidden data and can corrupt or destroy it. Implementing Adaptive Steganography by Exploring the Ycbcr Color Model Characteristics Surbhi Gupta, Alka Handa, Parvinder S.Sandhu S World Academy of Science, Engineering and Technology International Journal of Electronics and Communication Engineering Vol:4, No:10, 2010 1530 International Scholarly and Scientific Research & Innovation 4(10) 2010 scholar.waset.org/1307-6892/15200 International Science Index, Electronics and Communication Engineering Vol:4, No:10, 2010 waset.org/Publication/15200