of two Greek words: Steganos (στεγᾰνός) : concealed Graphe (γραφή) : writing • It is the practice of concealing a file, message, image, or video within another file, message, image, audio, or video. • Steganography, relies on the imperfection of the human auditory and visual systems. • Data hidden in plain sight!
write the message, wait till the servant’s hair has regrown and then send him to the destination. Ancient Greece Send a warning about a forthcoming attack to Greece by writing it directly on the wooden backing of a wax tablet before applying its beeswax surface. Sparta Using invisible ink (vinegar, fruit juice, milk, …). The receiver used heat to view what was what hidden on the paper. Europe Ave Maria cipher. 384 columns of letters of the alphabet, each with a corresponding code w ord Germany 440 BC 510-491 BC World war II Renaissance
data that is being transmitted. • However, the attacker will know that some sort of secret communication is taking place between the 2 parties. • On the other hand, Steganography allows the sender and receiver to exchange secret data hidden inside ordinary data without rising suspicions.
the law. • Some of the countries that restrict importing cryptography technology: Belarus, Iraq, Mongolia, Myanmar, Russia, Turkmenistan, Uzbekistan. • Cybercriminals and terrorists are using steganography to avoid being caught with cryptography technologies.
amount of data that can be hidden without significantly changing the cover medium Capacity The resistance for possible modification or destruction in unseen data Robustness Does not raise any suspicion of eavesdroppers Invisibility
bit with the lowest arithmetic value. - The least significant bits of the R G B colors of a pixel of a visible image are replaced by bits of the hidden image. RED: 233 => 11101001 Green: 205 => 11001101 Blue: 166 => 10100110
bits. - Let’s say we want to hide the letter M inside an image. - We need to explain first ASCII code: - It is a code for representing 128 English characters as numbers, with each letter assigned a number from 0 to 127. - For example, the ASCII code for uppercase M is 77. - Most computers use ASCII codes to represent text, which makes it possible to transfer data from one computer to another. - M => 77 => 0100 1101 - We have 8 bits to hide => we need 3 pixels (as each pixel can hide 3 bits)
each pixel for a specific color channel or for all color channels is replaced with a bit from the secret data. • The probability of detecting the hidden data is high. • Algorithms were developed to make detection of hidden data harder.
an image using LSB Steganography? • The answer depends on the algorithm we are using and the total change to the image that is acceptable. • Let’s say we have an image composed of 1024*768 pixels = 786432 pixels • Each pixel can hide 3 bits (if we are using the last bit of R, G, and B). • Total = 2359296 bits = 288 Kbytes
presence of a strong tone in its temporal or spectral neighborhood. • The human ear cannot perceive frequencies at lower power level if these frequencies are present in the vicinity of tone-or noise-like frequencies at higher level. • Audio steganography consists of embedding a secret message into a digital audio signal. • The differences in the resulting audio file are not noticeable for the human ear.
the same coin. • Art of detecting Steganography. • Challenge: the suspected images, audio, or video may or may not have secret data. • Some of the techniques include: • Difference in file size between cover image and stego images • Increase or decrease of unique colors in stego images