CSCI 415: Computer and Network Security Dr. Nazli HardySteganography LabLecture Outline Introducing Steganography Steganography LabCSCI 415: Computer and Network Security Dr. Nazli HardySteganography LabIntroduction 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 HardySteganography LabExample 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 ICSCI 415: Computer and Network Security Dr. Nazli HardySteganography LabExample 2 – the exposed message may not be encryptedMemo to the DirectorSubject: Letter of Recommendation—————————————————————-Jane S., a chief sub editor and editor, can always be foundhard at work in her cubicle. Jane works independently, withoutwasting company time talking to colleagues. She neverthinks twice about assisting fellow employees, and she alwaysfinishes given assignments on time. Often Jane takes extendedmeasures to complete her work, sometimes skippingcoffee breaks. She is a dedicated individual who has absolutely novanity in spite of her high accomplishments and profoundknowledge in her field. I firmly believe that Jane can beclassed as a high-caliber employee, the type which cannot bedispensed with. Consequently, I duly recommend that Jane bepromoted to executive management, and a proposal will besent away as soon as possible.Project LeaderCSCI 415: Computer and Network Security Dr. Nazli HardySteganography LabExample 2 – the exposed message may not be encryptedLater another memo was sent…)Memo to the Director:Sorry about the earlier memo. Jane was looking over my shoulderas I wrote it. Kindly read every other line (i.e. 1, 3, 5, 7…) for my trueassessment of her.Regards,Project Leader1. Jane S., a chief sub editor and editor, can always be found2. hard at work in her cubicle. Jane works independently, without3. wasting company time talking to colleagues. She never4. thinks twice about assisting fellow employees, and she always5. finishes given assignments on time. Often Jane takes extended6. measures to complete her work, sometimes skipping7. coffee breaks. She is a dedicated individual who has absolutely no8. vanity in spite of her high accomplishments and profound9. knowledge in her field. I firmly believe that Jane can be10. classed as a high-caliber employee, the type which cannot be11. dispensed with. Consequently, I duly recommend that Jane be12. promoted to executive management, and a proposal will be13. sent away as soon as possible.CSCI 415: Computer and Network Security Dr. Nazli HardySteganography LabExample 3 – using imagesCSCI 415: Computer and Network Security Dr. Nazli HardySteganography LabLeast 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 1100101110011111 00010000 11001011source: An Overview of Steganography for the Computer Forensics Examiner, Gary Kessler, Forensic Science Communication, July 2004CSCI 415: Computer and Network Security Dr. Nazli HardySteganography LabCarrier and Hidden Imagescarrier image“hidden” imagesource: An Overview of Steganography for the Computer Forensics Examiner, Gary Kessler, Forensic Science Communication, July 2004CSCI 415: Computer and Network Security Dr. Nazli HardySteganography LabCarrier and Hidden Imagespalette before hidden image palette after hidden imagesource: An Overview of Steganography for the Computer Forensics Examiner, Gary Kessler, Forensic Science Communication, July