the art and science of writing hidden messages

SteganographyDr. Frank Li

Steganographycoveredwritingthe art and science of writing hidden messages in such a way that no one, apart from the sender and intended recipient, suspects the existence of the message

Steganography in Ancient Greece -- Tattoo message on head An ancient Greek historian Herodotus reports that messages were tattooed onto the shaved heads of slaves. Once the hair grew back, the slaves were sent to the recipient, with the message hidden in plain sight.

Steganography in World War I -- Null CipherThe message below was sent by the Germanembassy in World War I.

PRESIDENT'S EMBARGO RULING SHOULD HAVE IMMEDIATE NOTICE. GRAVE SITUATION AFFECTING INTERNATIONAL LAW. STATEMENT FORESHADOWS RUIN OF MANY NEUTRALS. YELLOW JOURNALS UNIFYING NATIONAL EXCITEMENT IMMENSELY. Taking the first letter in each word of message reveals thehidden text: PERSHING SAILS FROM NY JUNE 1.

Steganography in Espionage -- Invisible inkSpies use milk, fruit juice or urine as invisible inks,which darken when heated.

An FBI agent is shown using ultraviolet light to read secret writing on a paper from a suspected spy case

Steganography in Modern Days Digital media lend themselves to steganography because of the large amount of information in certain file types

Steganography Carrier Files:bmpjpeggifwavmp3Amongst others

Steganography Terminology

Some Steganography ToolsSteganosS-Tools (GIF, JPEG)StegHide (WAV, BMP)Invisible Secrets (JPEG)JPHideCamouflageHidermanAnd many others (We will try it today )

RGB Color Model in Image Filesred, green, and blue light are added together in various ways to reproduce a broad array of colors.(0, 0, 0) is black (255, 255, 255) is white (255, 0, 0) is red (0, 255, 0) is green (0, 0, 255) is blue (255, 255, 0) is yellow (0, 255, 255) is cyan (255, 0, 255) is magenta

The simplest and most common type of steganography is LSB (least significant bit). The ones bit of a byte is used to encode the hidden information.

Suppose we want to encode the letter A (ASCII 65 or binary 01000001) in the following 8 bytes of a carrier file.

01011101 11010000 00011100 1010110011100111 10000111 01101011 11100011

becomes

01011100 11010001 00011100 1010110011100110 10000110 01101010 11100011

A Common Technique of Steganography -- LSB

Left image is original JPEG fileRight image is with hidden message

Steganography Application-- UV Watermarking

Steganography ToolsA list of over 100 steganography tools:http://www.jjtc.com/Steganography/toolmatrix.htm

Some of them run in Linux platformJPHS (JPHide JPSeek, JP hide and seek)http://linux01.gwdg.de/~alatham/stego.htmlSteghideOutguessBlindsideGifshuffleGzStegEtc.

SteganalysisSteganalysis is the counter-measure against steganography.

Attempts to analyze a data stream to determine whether or not it contains hidden messages.

In Conclusion Steganography is really coolIts fun to play with Easy to implement but fairly effective.Obviously has a lot of good and bad applications, as with an technology.

*Typical .wav file uses 16 bit sampling.Is the difference between level 37,243 and 37,242 detectable by the human ear? Probably not.

***Some images are much better than others when used a host file - plenty of fine detail is good. A image of cloudless blue sky not good for hiding message.A waterfall in a forest is probably ideal*tar zcvf jphs-0.3.tgz *