Navyashree K M, IJRIT-129 International Journal of Research in Information Technology
(IJRIT)
www.ijrit.com ISSN 2001-5569
A Novel Technique for Concealed Communication Using Dwt
Navyashree K M 1, Vijayalakshmi Y2
1PG Final year Department of ECE Sir MVIT, Bangalore, India [email protected]
2Associate Professor Department of ECE Sir MVIT, Bangalore, India [email protected]
Abstract
Image steganography is an engineering term describing a diverse and significant discipline for information concealing. This method is defined as concealing of undisclosed information behind an image. DWT is the identified methods used in steganography. The proposed work is on decreasing the complexity in image concealing through DWT technique while providing better undetectability and lesser distortion in the stego image. This algorithm is for embedding and extractingtwo secret image embedded behind the cover color image. Also, the analysis of quality measurement approaches such as Peak signal to noise ratio and Mean square error are calculated.
Keywords:
Image steganography, DWT, cover image, Stego image, MSE, PSNR1. Introduction
Data sharing and data transfer are a part of internet technology. Intruders will try to access the secretdata which is communicated. So security of information is to be modified exponentially.
Data security can be provided by two methods namely cryptography and steganography. In this
Navyashree K M, IJRIT-130 paper, steganography technique is used to protect the data. The purpose of steganography is to hide the data not only content but also its existence. Object which is used to embed information is known as cover object.The cover object along with the secret information is known as Stego- object. Image is the media which is used in image steganography.
The object which is used in this paper is image hence it is called cover image and stego- image respectively.In this paper image steganography is used for data security.
Image steganography is classified into:
1.1 Spatial domain based method
Spatial domain mainly includes least significant bit steganography. LSB insertion is a common technique and also a simple approach for embedding secret information in a cover image.
The least significant bitof some or all of the bytes inside animage is changed to a bit of the secret message,
1.2 Transform domain based method
Basically there are many kinds of transforms that exist to transform the signal or data or image from spatial domain to its frequency domain, some of which are Discrete Cosine Transform (DCT), Discrete Wavelet Transform, Discrete Fourier transformation technique (DFT). In this paper, DWT is used to implement image steganography.
1.2.1Discrete Wavelet Transform
Discrete Wavelet transform (DWT) is mathematical technique for pyramidal decomposition of an image. The transform is based on small waves called wavelets. For 2-D images, apply DWT which corresponds to processing the image by 2-D filters in each dimension. The filters divide the input into four non-overlapping and multi-resolution sub-bands
1. A (LL) - Approximation area.
2. H (HL) - Horizontal area.
3. V (LH) - Vertical area.
4. D (HH) - Diagonal area
Since Human eyes are more sensitive to the low frequency components i.e. LL sub band, hence payload information is hidden in other 3 parts i.e. in high frequency parts without making any alteration in LL sub band. High frequency sub-band (HL,LH,HH) they contain
Navyashree K M, IJRIT-131 insignificant information. Hiding payload information in these sub-bands does not change image quality that much. DWT used in this work is Haar-DWT, the simplest type of DWT.
Figure:2-level DWT of an original image
2. Proposed Method
Proposed steganography approach consists of two parts namely transmitter and receiver. In the transmitter part, two secret images are hidden in single cover image usingDWT. At the receiver part, secrete imagesare extracted from the cover image using the inverse DWT method. Secret image is also called as payload image. Below figure shows the complete block of proposed image steganography model
Figure: Complete block of proposed image steganography.
2.1 Algorithm
2.1.1 Encoding
1. Consider two payload images and cover image as input
Navyashree K M, IJRIT-132 2. Each Payload image is applied to DWT, this decomposes image into four sub bands namely
LL, LH, HL, HH.
3. Redundant values of two payload images are made as zero. Then max value in each sub band is selected. Normalized values are foundby dividing it with max value.
4. Normalized values of image are saved as DEC.
5. Apply DWT to carrier image.
6. Normalized values of undisclosed image DEC is stored in LH and HHcomponent of carrier image.
7. Obtained image is the stego image
2.1.2 Decoding
1. Consider the output of an encoding algorithm as input for decoding.
2.
The payload data can be obtained from the HL component of cover image.3.
Obtained values are de-normalized.4.
Obtain DEC values from combined values of diagonal and vertical component.5.
Then de-normalize the values.6.
ApplyIDWT on stego image sub bands respectively and save it as Rec.7.
The secrete images are recovered.2.2 Image Quality Measures
2.2.1 Mean Square Error
MSE is the cumulative squared error between the compressed image and the cover image.
Where, M and N are the number of rows and columns in the original matrix.
Where, fij - pixel value of cover Image gij -pixel value from the stegoimage
2.2.2Peak Signal to Noise Ratio
Navyashree K M, IJRIT-133 This ratio measures the quality between the original and a stegoimage. The higher value of PSNR represents the better quality of the stegoimage. PSNR is usually expressed in terms of thedB scale.
3. Result
Software which is used for this proposed method is Matlab. Cover image and two payload images are shown below. PSNR value obtained is 42.
Cover image Payload 1 Payload 2
4. Conclusion
In this paper, a technique called image steganography is used for hiding twosecrete image in the cover image, in this paper DWT is used to hide the two secrete images. Secret images can be protected safely using DWT. This approach helps in hiding two payload color images in a single cover image. Better PSNR value is gained by using this approach.
References
[1] Prabakaran. G and Bhavani. R, “A Modified Secure Digital Image Steganography Based on Discrete Wavelet Transform”.
[2] Prajanto Wahyu Adi, Farah Zakiyah Rahmanti and Nur Azman Abu “High Quality Image Steganography on Integer Haar Wavelet Transform using Modulus Function”.
[3] Prabakaran. G, Dr. Bhavani. R and Sankaran S, “Dual Wavelet Transform Used in Color Image Steganography Method”.
Navyashree K M, IJRIT-134 [4] Hamad A. Al-Korbi, Ali Al-Ataby, Majid A. Al-Taee and Waleed Al-Nuaimy, “High-
Capacity Image Steganography Based on Haar DWT for Hiding Miscellaneous Data”.
[5] Tanmay Bhattacharya, Nilanjan Dey and S. R. Bhadra Chaudhuri, “A Session based Multiple Image Hiding Technique using DWT and DCT”.
[6] Mohammad Reza Dastjani Farahani and Ali Pourmohammad“A DWT Based Perfect Secure and High Capacity Image Steganography Method”.
