10-01-2011, 04:52 PM
Khan, Mohammed Minhajuddin
What is Steganography?
Greek Words:
STEGANOS – “Covered”
GRAPHIE – “Writing”
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.
This can be achieve by concealing the existence of information within seemingly harmless carriers or cover
Carrier: text, image, video, audio, etc.
Steganography, Cryptography, and Watermarking
There are two major branches of information hiding, Steganography and Watermarking
Watermarking:
Communication in watermarking is the host signal, with the embedded data providing copyright protection.
The existence of a watermark is often declared openly.
Any attempt to remove or invalidate the embedded content renders the host useless.
Cryptography:
Doesn’t conceal the communication.
Scrambles the data to prevent eavesdroppers understanding the content.
Cryptography involves various methods and implementations.
May be considered complementary and orthogonal (unrelated).
Once the presence of hidden information is revealed or even suspected, the purpose of steganography is defeated.
History of Steganography
Steganography ancient origins can be traced back to 440 BC, from the Histories of Herodotus
Demeratus sent a warning about a forthcoming attack to Greece by writing it on a wooden panel and covering it in wax.
Histiaeus, who shaved the head of his most trusted slave and tattooed a message on it. After his hair had grown the message was hidden. The purpose was to instigate a revolt against the Persians.
World War II
Invincible inks
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.
Modern Steganography Techniques
Masking and Filtering: Is where information is hidden inside of a image using digital watermarks that include information such as copyright, ownership, or licenses. The purpose is different from traditional steganography since it is adding an attribute to the cover image thus extending the amount of information presented.
Algorithms and Transformations: This technique hides data in mathematical functions that are often used in compression algorithms. The idea of this method is to hide the secret message in the data bits in the least significant coefficients.
Least Significant Bit Insertion: The most common and popular method of modern day steganography is to make use of the LSB of a picture’s pixel information. Thus the overall image distortion is kept to a minimum while the message is spaced out over the pixels in the images. This technique works best when the image file is larger then the message file and if the image is grayscale.
Important Requirement for Steganographic System
Security of the hidden communication
size of the payload
Robustness against malicious and unintentional attacks
Detection of Steganographic Content/Countermeasures
The detection of steganographically encoded packages is called Steganalysis.
Visual Analysis tries to reveal the presence of secret communication through inspection, either with the naked eye or with the assistance of a computer.
Statistical (Algorithmic) Analysis reveals tiny alterations in an image's statistical behavior caused by steganographic embedding.
The nominally universal methods developed to detect embedded stego-data are generally less effective than the steganalytic methods aimed at specific types of embedding.
for more:
http://docs.googleviewer?a=v&q=cache:Eyg...WJs6xIWV2w
