14-10-2016, 03:56 PM
CSE steganography ppt.pptx (Size: 234.74 KB / Downloads: 9)
WHAT IS STEGANOGRAPHY
The word steganography literally means covered writing as derived from Greek. Steganography is the art of concealing the existence of information within seemingly innocuous carriers. In broad sense, term Steganography is used for hiding message within an image.
Steganography is the art and science of communicating in a way which hides the existence of the communication. In contrast to cryptography, where the "enemy" is allowed to detect, intercept and modify messages without being able to violate certain security premises guaranteed by a cryptosystem, the goal of steganography is to hide messages inside other "harmless" messages in a way that does not allow any "enemy" to even detect that there is a second secret message present. Steganography is in the (especially military) literature also referred to as transmission security or short TRANSEC.
STEGANOGRAPHY VS CRYPTOGRAPHY
Steganography can be viewed as akin to cryptography. Both have been used throughout recorded history as means to protect information. At times these two technologies seem to converge while the objectives of the two differ.
Cryptographic techniques "scramble" messages so if intercepted, the messages cannot be understood. Steganography, an essence, "camouflages" a message to hide its existence and make it seem "invisible" thus concealing the fact that a message is being sent altogether. An encrypted message may draw suspicion while an invisible message will not.
Steganography cannot be detected. Therefore, it is used when encryption is not permitted. Or, more commonly, steganography is used to supplement encryption. An encrypted file may still hide information using steganography, so even if the encrypted file is deciphered, the hidden message is not seen.
EVOLUTION OF STEGANOGRAPHY
CODE BREAKERS : David Kahn's The Code breakers and Bruce Norman’s Secret Warfare: The Battle of Codes and Ciphers recounts numerous tales of steganography .
INVISIBLE INK : An innocent letter may contain a very different message written between the lines with invisible ink. Common sources for invisible inks are milk, vinegar, fruit juices and urine. All of these darken when heated. Later on, more sophisticated inks were developed which react to various chemicals.
MICRODOTS: The Germans developed microdot technology. Microdots are photographs the size of a printed period having the clarity of standard-sized typewritten pages. The first microdots were discovered masquerading as a period on a typed envelope carried by a German agent in 1941. The message was not hidden, nor encrypted. It was just so small as to not draw attention to itself (for a while). Besides being so small, microdots permitted the transmission of large amounts of data including drawings and photographs