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The word Steganography literally means ?covered writing? as derived from Greek. It encompasses all methods of secret communication that conceal the very existence of the message.

Digital technology gives us new ways to apply Steganographic techniques including one of the most intriguing that of hiding information in the digital images. A popular method is the LSB encoding, so encoding and detection of LSB Steganography is discussed in detail. Steganography goes well beyond simply embedding text in an image.

It also pertains to other media, including voice, text, binary files and communication channels. The importance of techniques that can reliably detect the presence of secret message in images is increasing. Research has been pursued in the study of estimating the initial bias from stego images to improve the sensitivity of the RS detection method to short messages in digital images.
Prepared By:VEETHICA SRIVASTAVA

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STEGANOGRAPHY : DEFINED
Comes from the two greek words
steganos -”covered”
graphie –”writing”
Steganography is the art & science of writing hidden messages in such a way that no one apart from the intended recipient knows of the existence of the message.
This can be achieve by concealing the existence of information within seemingly harmless carrier or cover.
Carrier- text,image,audio,video
HISTORY
Null ciphers (unencrypted messages):

Apparently neutral's protest is thoroughly discounted and ignored. Isman hard hit. Blockade issue affects pretext for embargo on by products, ejecting suets and vegetable oils.

Sent by a German Spy in WWII, by taking the second letter in each word the following message emerges:

Pershing sails from NY June 1.

Microdot Technology

Shrinking messages down to the size of a dot became a popular method. Since the microdot could be placed at the end of a sentence or above a j or an i.

BASIC DEFINITIONS
Cover medium: This is the medium in which we want to hide data, it can be an innocent looking piece of information for steganography, or some important medium that must be protected for copyright or integrity reasons.
Embedded message: This is the hidden message we want to put in the cover. It can be some data for steganography and some copyright information or added content for digital watermarking.
Stegokey: This is represented by some secret information, which is needed in order to extract the embedded message from the stegomedium.
Stego-medium: This is the final piece of information that the casual observer can see.
Cover-medium + embedded-message = stego-message
BASIC METHOD BEHIND STEGANOGRAPHY
IMAGES
Is an array of numbers that represent light intensities at various points or pixels.

Digital images are typically stored in either 24-bit or 8-bit per pixel files.

IMAGE COMPRESSION
LOSSY(JPEG)-Discards excess image data, removes details that are too small for human eye to differentiate. Lossy compression is frequently used on true-colour images, as it offers high compression rates.

LOSSLESS(BMP,GIF)-Lossless compression maintains the original image data exactly; hence it is preferred when the original information must remain intact. It is thus more favored by steganographic techniques.
TYPES OF STEG EXPLORED
Least significant bit (LSB) insertion

Spread spectrum image steganography

Masking and filtering.

Algorithms and transformations.