13-04-2012, 11:06 AM
Steganography
2004-01-21-presentation-steganography.pdf (Size: 235.19 KB / Downloads: 75)
What is steganography
The art of hiding information inside information
Since everyone can read, encoding text
in neutral sentences is doubtfully effective
What is it used for?
● Hiding the fact that you are sending messages
● Hiding several messages inside data
● Digital watermarking
Kerckhoffs' principle
● Secure with knowlegde of the system
● Message can only be read with secret key
Digital watermarking
● Not really hiding information
● Important: not modificable
● Uses the hiding-property of steganography
● Recent: MPAA hides watermarks in movies
implementation
Text / Webpages
● Use of a codebook
● Layout of texts
● Every Nth character
● Use of whitespaces and newlines
● Can be difficult to detect and decode
Defeating steganography
Images
● Compress with lossy compression
● Convert to different format
● Resize the image
● Modify colors
Conclusion
Hide data practically everywhere
● Detection of steganography
− Possible, but can be difficult
− Hard when valid to Kerckhoffs' principle
● Defeating steganography is not hard