Transcript
STEGANOGRAPHY
Project Guide: Dr. Jyoti Bharti
Project Members:
Lovely Mandal Vriti Mathur Dipesh Agrawal Ankur Malik
AbstractThis project introduces a new methodology for hiding a text data into an rgb image. The proposed technique can encode any color image files in order to protect confidential text data from unauthorized access. It can be applied to a very small images (24 × 24) as well as large images (1024 × 1024). We use Image quality parameters: Peak Signal to Noise Ratio, Mean Square Error and Entropy. This method comprises of three steps: one for scanning the image, second for message hiding and third for decrypting the message from the image.
Steganography is the art of hiding a message or data
in the form of text, image or multimedia into an image such that it can’t be detectable by naked eyes.
Q. How it is different from Cryptography?
In cryptography, the original message is converted into meaningless text, which can draw suspicion.Compared to this, Steganography is more secure, as the very existence of the message embedded in the image is concealed.
What is Steganography?
Payload: Original message is called payload. Carrier Image: The image in which the message
is embedded is called Carrier Image. Stego-image: The image formed after hiding the
payload into Carrier Image is called Stego-image. Encryption technique or hiding technique:
The methodology used to hide the message into the image is called encryption technique.
Steganographic Terms
Scanning Technique:
Processing the image such that each pixel of the image is traversed once is called Scanning Technique.
Decryption: The retrieval of original message from the Stego-image is called Decryption and the technique used is known as Decryption technique.
Image is divided into blocks of 50 X 50 pixels. Blocks are traversed by Snake traversal. And within a block, pixels are traversed by Spiral
traversal.
Traverse red plane with Scanning technique to search for pixel intensity equal to that of ascii value.
If found ,then convert the corresponding LSB of blue plane to 1
and at corresponding position of auxiliary matrix write index of the letter.
traverse auxiliary matrix with scanning technique
and produce a random order of indices.
convert indices into binary.
Decryption
Divide Stego-image in red, green and blue planes.
LSB of blue plane is extracted.
LSB of green plane is extracted.
LSB of blue plane traversed using Scanning technique.
If value is found 1 then corresponding value in red plane is taken.
Generates a random order of intensity value list.
69 80 76 72
Traverse boundary of LSB of green plane, 4 pixels at a time.
0001= 1
0010= 2
0100= 4
0011= 3
Extract 4 bits at a time and convert it into decimal.
Generate random order of decimal digits.
These digits are indices.
Arrange random intensity values extracted earlier according to the order of extracted
indices.
69 80 76 72
72 69 76 80
Convert ASCII values into charactersH E L P
This is the decrypted message
This technique results in less modification of
bits resulting in less randomness in the image. The image quality metrics i.e. higher Peak Signal to Noise Ratio (PSNR) and lower Mean Square errors itself prove that the proposed technique has good quality of the Stego-image.
Conclusion
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