Steganography (Hiding the Message)
Steganography is the practice of concealing secret communication by hiding a message inside an innocuous-looking file, known as the cover medium (such as an image or audio file). Its primary goal is total secrecy, ensuring that outside observers don't even suspect the very existence of the message being exchanged. It differs from cryptography in that it focuses on concealing the message rather than encrypting the content. The technique often involves making minute, imperceptible changes to the cover medium's data.
Goal: To establish an undetectable covert communication channel.
Mechanism: It works by making subtle, often imperceptible modifications to the least significant bits of the cover medium's data (e.g., changing the color of a few pixels).
Output: A stego-object (the cover medium with the hidden message inside) that is visually or audibly identical to the original file.
Example: Hiding a secret text document within a high-resolution JPEG image.
Steganalysis (Finding the Message)
Steganalysis is the set of techniques used to detect the presence of steganography, determine the location of the hidden data, and, if possible, extract the secret message. It is the countermeasure to steganography and is a vital tool in digital forensics.
Goal: To detect and prove the existence of a hidden message.
Mechanism: It relies on specialized statistical analysis (e.g., histogram analysis, Chi-Square attacks) and machine learning to find microscopic, non-random anomalies created by the embedding process.
Output: A classification indicating whether the file is clean or stego-infected, often followed by the recovery of the payload.
Example: Analyzing the statistical distribution of color values in an image to see if it deviates from a natural photo.
Steganography vs Steganalysis