SteganographyPPT教學課件

1、Some History 1665 - Steganographica, Gaspari Schotti 400 B.C. - writings of Herodotus1870 - The Pigeon Post into Paris1499 - “Steganographia”, Trithemius - steganography and magic2001 - A Beautiful Mind第1頁/共9頁Low-tech Methods of Steganography Message hidden Message hidden as Message hidden as Messag

2、e written in invisible ink ID# etched into第2頁/共9頁The cover provides a host for transporting the hidden embed -file extractinfo第3頁/共9頁Digital Steganography HTML message as cover? computer program as cover? network protocol headers white space in text unused space in buffer least significant

3、 bits of image slight distortion in sound file “Easter eggs”第4頁/共9頁Easter egg from the SimpsonsIn episode 7F19, Dustin Hoffman supplied the voice for Lisas substitute teacher, but was not credited on screen. Instead, they used the phony name Sam Etic. In the next season (episode 7F24), Michael Jacks

4、on 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 doesnt exist. The egg lies in episode 9F09 when Lisa says, It was t

5、he greatest movie Ive ever seen in my life! And you wouldnt believe the celebrities who did cameos. Dustin Hoffman, Michael Jackson.of course they didnt use their real names, but you could tell it was them.第5頁/共9頁Steganography in ImagesTwo types of compression: lossless (gif) lossy (jpeg)Sometimes c

6、oncealed message inserted as a comment.Sometimes the accuracy of the image is sacrificed slightly.Common ToolsStegoDOSWhite Noise StormS-toolsoutguesssteghide第6頁/共9頁Three Types of Steganography1) Covert Channelconceal message so only sender and recipient knowWatermarkingconcealed message contains its source ID 2) _ Watermarkingdesigned for concealed message to survive 3) (Semi-)_ Watermarkingdesigned so concealment is corrupted wheneverstego-file is modified. 第7頁/共9頁Applications of SteganographyCovert exchange of informationEstablish identityCombat illegal copyingSte