Presented by:
CH.SAHITHI
K.BHAGYA SAHITYA

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ABSTRACT:
Steganography is the art of hiding the fact that communication is taking place, by hiding information in other information. In image steganography the information is hidden exclusively in images. Many different carrier file formats can be used, but digital images are the most popular because of their frequency on the Internet. Generation of stego images containing hidden messages using LSB is a very common and most primitive method of steganography. In this method, the least significant bit of some or all of the bytes inside an image is changed. With a well-chosen image, one can even hide the message in the least as well as second to least significant bit and still not see the difference. The present paper compares these two schemes. Good conclusions are drawn from the experimental results.
1.INTRODUCTION:
Steganography is the art and science of writing hidden messages in such a way that no one apart from the intended recipient knows of the existence of the message. Unlike cryptography, where the existence of the message is clear, but the meaning is obscured, the steganographic technique
strives to hide the very presence of the message itself from an observer.
The word steganography is derived from the Greek words “stegos” meaning “cover” and “grafia” meaning “writing” defining it as “covered writing”.
Steganography simply takes one piece of information and hides it within another. Computer files (images, sounds recordings, even disks) contain unused or insignificant areas of data. Steganography takes advantage of these areas, replacing them with information. One can replace the least significance bit of the original file (audio/image) with the secret bits and the resultant cover will not be distorted. It is not to keep others from knowing the hidden information, but it is to keep others from thinking that the information even exists. If a steganography method causes someone to suspect that there is secret information in the carrier medium, then this method fails. The noise or any modulation induced by the message should not change the characteristics of the cover and should not produce any kind of distortion. The paper is organized as follows. The II section gives methodology. The III section gives the types of LSB techniques. IV section gives the experimental results followed by conclusions.
2. METHODOLOGY:
LSB is a simple approach for embedding information in an image. In this scheme the hidden message will be inserted in LSB’s of the image.
When using a 24-bit image, a bit of each of the red, green and blue colour components can be used, since they are each represented by a byte. In other words, one can store 3 bits in each pixel. An 800 × 600 pixel image, can thus store a total amount of 1,440,000 bits or 180,000 bytes of embedded data.
For example a grid for 3 pixels of a 24-bit image can be as follows:
(00101101 00011100 11011100)
(10100110 11000100 00001100)
(11010010 10101101 01100011)
When the number 200, which binary representation is 11001000, is embedded into the least significant bits of this part of the image, the resulting grid is as follows:
(00101101 00011101 11011100)
(10100110 11000101 00001100)
(11010010 10101100 01100011)
Although the number was embedded into the first 8 bytes of the grid, only the 3 underlined bits needed to be changed according to the embedded message. On average, only half of the bits in an image will need to be modified to hide a secret message using the maximum cover size. Since there are 256 possible intensities of each primary colour, changing the LSB of a pixel results in small changes in the intensity of the colours. These changes cannot be perceived by the human eye -thus the message is successfully hidden.
With a well-chosen image, one can even hide the message in the least as well as second to least significant bit and still not see the difference.