Detailed Explanation of Steganography
- Introduction to Steganography Steganography is the practice of concealing information within another medium, such as images, audio, video, or even text, to ensure secrecy. Unlike cryptography, which focuses on encrypting data to make it unreadable without a decryption key, steganography hides the very existence of the message.
The word steganography comes from the Greek words "steganos" (covered or hidden) and "graphia" (writing), meaning "hidden writing."
- Key Concepts in Steganography Steganography relies on several principles and techniques to embed secret messages in various media. The fundamental concepts include:
a) Carrier (Cover Medium) The file or medium in which the secret message is hidden. Examples include:
Images (JPEG, PNG, BMP) Audio files (MP3, WAV) Video files (MP4, AVI) Text files (Unicode manipulation, spaces, invisible characters) b) Payload (Hidden Message) The actual secret message that needs to be embedded, which can be:
Text Image Audio Encrypted files c) Stego-Object The final output after embedding the secret message into the cover medium. The goal is to make it indistinguishable from the original cover medium.
d) Stego-Key A secret key used for additional security in embedding or extracting the hidden message. This ensures that only authorized parties can access the secret data.
- Types of Steganography There are different methods of hiding information depending on the medium used.
a) Image Steganography Hiding messages within images is one of the most common forms of steganography. Techniques include:
Least Significant Bit (LSB) Substitution:
The least significant bit of image pixels is modified to store secret data. Since the human eye is not sensitive to small color variations, these modifications go unnoticed. Palette-Based Steganography:
Works with indexed images (GIF, PNG) by modifying the color index to store data. Discrete Cosine Transform (DCT) Steganography:
Used in JPEG images where message bits are embedded in the frequency domain instead of pixel values. b) Audio Steganography Secret data is hidden within audio files using:
LSB Modification: Changing the least significant bit of audio samples. Echo Hiding: Introducing subtle echoes to encode secret data. Phase Encoding: Encoding data in the phase of the audio signal. c) Video Steganography Since videos contain multiple frames, data can be hidden in:
Individual frames using LSB modification Motion vectors in compressed formats like MP4 Audio tracks of the video d) Text Steganography This involves hiding messages in text using:
Whitespace Steganography: Adding extra spaces or tabs in a pattern. Font-Based Steganography: Using invisible characters like zero-width spaces. Contextual Steganography: Replacing words with synonyms or restructuring sentences. e) Network Steganography Hiding data in network protocols (TCP, UDP, ICMP) by manipulating:
Packet headers Unused fields Timing between packets