Concepts
Steganography vs cryptography
Hiding the existence of a message
How it works
Cryptography makes a message unreadable but obvious; steganography hides the fact that a message exists. A common technique changes the least significant bits of pixels in an image or samples in an audio file, which is invisible to a casual observer. The two are often combined: encrypt first, then hide.
Strengths
- Conceals communication from casual inspection
- Used legitimately for watermarking
Weaknesses and known attacks
- Provides no confidentiality on its own once the hiding method is known.
- Statistical steganalysis can detect altered files, and re-compressing or resizing an image often destroys the hidden data.
- Attackers use it to exfiltrate data and hide malware payloads or command-and-control instructions in images.
Use it for
- Watermarking and covert channels in authorised testing
Don't use it for
- Protecting confidential data instead of encryption
Exam tip
Steganography = concealment (security through obscurity), not encryption. Data loss prevention tools may miss data hidden in images.