Chaotic Map Based Steganography of Gray Scale Images in Wavelet Domain

Matlab Project

A method of hiding the stego image in cover image by using a technique called fractional fourier transform with wavelet coefficients is proposed. Application of steganography is internet/web security. To maintain higher security Arnold transform is performed on host image with key, key is only known to a receiver/sender. For embedding, perform a fractional Fourier transform of cover image and secret image. Then apply DWT on both images. Cover image and secret image will added by using a technique called alpha blending which can add foreground with background color and wavelet coefficients of both images. Stego image will be extracted by applying IDWT (Inverse Discrete Wavelet Transform). For extracting, cover image will subtracted from stego image by using alpha blending. Secret image will be produced. By considering different aspects we have investigated the results of our scheme. This proposed method provides higher security, robustness against different attacks, good feasibility.

Steganography can be classified into different categories.
Spatial domain
o    Spatial domain has less complexity but less robustness against attacks. In spatial domain pixel intensities of image is altered. LSB is defined as a technique used for embedding secret information in its pixel.
Transform domain
o    In transform domain digital media converted into frequency domain by using different transform wavelet transform, fractional fourier transform, fourier transform, wavelet transform, cosine transform, counterlet transform. Transform domain has good robustness in comparison to spatial domain. Transform domain has high computational complexity but good robustness against attacks. Wavelet based steganograhy provides a good picture quality with high resolution. Steganography in transform domain has ability to tolerate signal processing operations and noises. In this less significant coefficients of cover image are used for embedding significant coefficients of secret data. In this DCT (discrete cosine transform) and DWT (discrete wavelet transform ) techniques are frequently used.

Spatial domain steganography has drawback of LSB technique is explained as human eye is highly insensitive to edge, contrast, sharpening, texture where embedded information based on BPCS (bit plane complexity segmentation) and PVD (pixel value differencing).
These methods are basically used for embedding more and more data.
For maintaining higher security and authentication of this embedded data transform domain is used.

A new technique is proposed for embedding secret image in cover image by using Fractional wavelet transform (FRWT) with Arnold transform and alpha blending.
Algorithm proposed for gray scale images of dimension 256×256.
Proposed to use FRWT (fractional wavelet transform) for hiding stego data in cover image.
For higher security Arnold transform is used through which image can be scrambled.
To embed stego image into original image Alpha blending is used in which it is decided alpha factor.
High efficiency
Less computational complexity and
High robustness against attacks

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