What is Steganography? def’n: the art and science of hiding information by embedding it in some other data.

cryptography - render message unintelligible

steganography - conceal the existence of the message

Some History

1665 - Steganographica, Gaspari Schotti

400 B.C. - writings of Herodotus

1870 - The Pigeon Post into Paris

1499 - “Steganographia”, Trithemius - steganography and magic

2001 - A Beautiful Mind

Low-tech Methods of Steganography• Message hidden

• Message hidden as

• Message hidden as

• Message written in invisible ink

• ID# etched into

The cover provides a host for transporting the hidden info.

info

embed

-file

extract

info

Digital Steganography• HTML message as cover?

• computer program as cover?

• network protocol headers

• white space in text

• unused space in buffer

• least significant bits of image

• slight distortion in sound file

• “Easter eggs”

Easter egg from the SimpsonsIn episode 7F19, Dustin Hoffman supplied the voice for Lisa's substitute teacher, but was not credited on screen. Instead, they used the phony name Sam Etic. In the next season (episode 7F24), Michael Jackson supplied the voice for a man in an insane asylum that thought he was Michael Jackson. Due to contractualobligations, they were unable to give Jacksonon-screen credit. Instead, the show credited John Jay Smith, another person that doesn't exist. The egg lies in episode 9F09 when Lisa says, "It was the greatest movie I've ever seen in my life! And you wouldn't believe the celebrities who did cameos. Dustin Hoffman, Michael Jackson...of course they didn't use their real names, but you could tell it was them."

Steganography in ImagesTwo types of compression: • lossless (gif) • lossy (jpeg)

Sometimes concealed message inserted as a comment.

Sometimes the accuracy of the image is sacrificed slightly.

Common ToolsSteghide (GNU open source_

OpenPuffS-toolsstegaMailSilentEye

Three Types of Steganography1) Covert Channelconceal message so only sender and recipient know

Watermarkingconcealed message contains its source ID

2) ___________ Watermarkingdesigned for concealed message to survive

3) (Semi-)___________ Watermarkingdesigned so concealment is corrupted wheneverstego-file is modified.

Applications of SteganographyCovert exchange of information

Establish identity

Combat illegal copying

Steg____________How would you?

Comparison of files for statistical differences

What files are available?