Steganography Lab Lecture Outline Introducing Steganography Steganography Lab CSCI 415 Computer and Network Security Dr Nazli Hardy Steganography Lab Introduction Nothing new Romans and Greeks and Egyptians wax tablets War efforts messages knit There are many ways in which messages can be hidden in digital media some examples are in unused portion of file headers within digital images within art in text files within video audio files pinpricks in maps Carrier files give no indication of what is hidden within Good and bad uses CSCI 415 Computer and Network Security Dr Nazli Hardy Steganography Lab Example 1 Null Cipher One common almost obvious form of steganography is called a null cipher the hidden message is formed by taking the first or other fixed letter of each word in the carrier cover message Imagine the following during wartime in a newspaper read by all 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 The first letters of each word form the character string PERSHING SAILS FROM NYJUNE I CSCI 415 Computer and Network Security Dr Nazli Hardy Steganography Lab Example 2 the exposed message may not be encrypted Memo to the Director Subject Letter of Recommendation Jane S a chief sub editor and editor can always be found hard at work in her cubicle Jane works independently without wasting company time talking to colleagues She never thinks twice about assisting fellow employees and she always finishes given assignments on time Often Jane takes extended measures to complete her work sometimes skipping coffee breaks She is a dedicated individual who has absolutely no vanity in spite of her high accomplishments and profound knowledge in her field I firmly believe that Jane can be classed as a high caliber employee the type which cannot be dispensed with Consequently I duly recommend that Jane be promoted to executive management and a proposal will be sent away as soon as possible Project Leader CSCI 415 Computer and Network Security Dr Nazli Hardy Steganography Lab Example 2 the exposed message may not be encrypted Later another memo was sent Memo to the Director Sorry about the earlier memo Jane was looking over my shoulder as I wrote it Kindly read every other line i e 1 3 5 7 for my true assessment of her Regards Project Leader CSCI 415 Computer and Network Security Dr Nazli Hardy 1 Jane S a chief sub editor and editor can always be found 2 hard at work in her cubicle Jane works independently without 3 wasting company time talking to colleagues She never 4 thinks twice about assisting fellow employees and she always 5 finishes given assignments on time Often Jane takes extended 6 measures to complete her work sometimes skipping 7 coffee breaks She is a dedicated individual who has absolutely no 8 vanity in spite of her high accomplishments and profound 9 knowledge in her field I firmly believe that Jane can be 10 classed as a high caliber employee the type which cannot be 11 dispensed with Consequently I duly recommend that Jane be 12 promoted to executive management and a proposal will be 13 sent away as soon as possible Steganography Lab Example 3 using images CSCI 415 Computer and Network Security Dr Nazli Hardy Steganography Lab Least Significant Bit Insertion One approach to hiding data within an image file is called least significant bit LSB insertion take the binary representation of the hidden data and overwrite the LSB of each byte within the carrier image Using 24 bit color the amount of change will be minimal and indiscernible to the human eye As an example suppose that we have three adjacent pixels nine bytes with the following RGB encoding 10010101 00001101 11001001 10010110 00001111 11001010 10011111 00010000 11001011 10010101 00001100 11001001 10010111 00001110 11001011 10011111 00010000 11001011 CSCI 415 Computer and Network Security for the Computer Dr Nazli Hardy source An Overview of Steganography Forensics Examiner Gary Kessler Forensic Science Communication July 2004 Steganography Lab Carrier and Hidden Images hidden image carrier image CSCI 415 Computer and Network Security for the Computer Dr Nazli Hardy source An Overview of Steganography Forensics Examiner Gary Kessler Forensic Science Communication July 2004 Steganography Lab Carrier and Hidden Images palette before hidden image palette after hidden image CSCI 415 Computer and Network Security for the Computer Dr Nazli Hardy source An Overview of Steganography Forensics Examiner Gary Kessler Forensic Science Communication July 2004