Prepared By:VEETHICA SRIVASTAVA
STEGANOGRAPHY : DEFINED
Comes from the two greek words
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.
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.
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.
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
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.
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.