Steganography Paul Krzyzanowski [email_address] [email_address] Distributed Systems Except as otherwise noted, the content...
cryptography κρυπό   ς hidden γραφία writing A secret manner of writing, … Generally, the art of writing or solving cipher...
cryptology κρυπός hidden λογια speaking 1967  D. Kahn,  Codebreakers  p. xvi, Cryptology is the science that embraces cryp...
steganography στεγανός covered γραφία writing The art of secret (hidden) writing
Steganography <ul><li>Art and science of communicating in a way that hides the existence of a message </li></ul><ul><li>si...
Classic techniques <ul><li>Invisible ink (1st century AD - WW II) </li></ul><ul><li>Tatoo message on head </li></ul><ul><l...
Motivation <ul><li>Steganography received little attention in computing </li></ul><ul><li>Renewed interest because of indu...
Null Cipher <ul><li>Hide message among irrelevant data </li></ul><ul><li>Confuse the cryptoanalyst </li></ul>
Null Cipher <ul><li>Hide message among irrelevant data </li></ul><ul><li>Confuse the cryptoanalyst </li></ul>Big rumble in...
Null Cipher <ul><li>Hide message among irrelevant data </li></ul><ul><li>Confuse the cryptoanalyst </li></ul>B ig  r umble...
BBC News 27 April 2006 Judge creates own Da Vinci code  The judge who presided over the failed Da Vinci Code plagiarism ca...
Chaffing & Winnowing <ul><li>Separate good messages from the bad ones </li></ul><ul><li>Stream of unencoded messages with ...
Image watermarking <ul><li>Spatial domain watermarking </li></ul><ul><ul><li>bit flipping </li></ul></ul><ul><ul><li>color...
UV Watermarking
Machine ID codes in laser printers See http://www.eff.org/Privacy/printers/
Machine ID codes in laser printers
Machine ID codes in laser printers
Machine ID codes in laser printers
Text <ul><li>Text lines shifted up/down (40 lines text    2 40  codes) </li></ul><ul><li>word space coding </li></ul><ul>...
Text <ul><li>Text lines shifted up/down (40 lines text    2 40  codes) </li></ul><ul><li>word space coding </li></ul><ul>...
Audio <ul><li>Perceptual coding </li></ul><ul><ul><li>inject signal into areas that will not be detected by humans </li></...
Video <ul><li>Coding still frames - spatial or frequency </li></ul><ul><li>data encoded during refresh </li></ul><ul><ul><...
Watermarking vs. Steganography <ul><li>Goal of steganography </li></ul><ul><ul><li>Intruder cannot detect a message </li><...
The end.
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Steganography (Distributed computing)

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Steganography (Distributed computing)

  1. 1. Steganography Paul Krzyzanowski [email_address] [email_address] Distributed Systems Except as otherwise noted, the content of this presentation is licensed under the Creative Commons Attribution 2.5 License.
  2. 2. cryptography κρυπό ς hidden γραφία writing A secret manner of writing, … Generally, the art of writing or solving ciphers. — Oxford English Dictionary
  3. 3. cryptology κρυπός hidden λογια speaking 1967 D. Kahn, Codebreakers p. xvi, Cryptology is the science that embraces cryptography and cryptanalysis, but the term ‘cryptology’ sometimes loosely designates the entire dual field of both rendering signals secure and extracting information from them. — Oxford English Dictionary
  4. 4. steganography στεγανός covered γραφία writing The art of secret (hidden) writing
  5. 5. Steganography <ul><li>Art and science of communicating in a way that hides the existence of a message </li></ul><ul><li>signal or pattern imposed on content </li></ul><ul><ul><li>persistent under transmission </li></ul></ul><ul><ul><li>not encryption </li></ul></ul><ul><ul><ul><li>original image/file is intact </li></ul></ul></ul><ul><ul><li>not fingerprinting </li></ul></ul><ul><ul><ul><li>fingerprinting leaves separate file describing contents </li></ul></ul></ul>
  6. 6. Classic techniques <ul><li>Invisible ink (1st century AD - WW II) </li></ul><ul><li>Tatoo message on head </li></ul><ul><li>Overwrite select characters in printed type in pencil </li></ul><ul><ul><li>look for the gloss </li></ul></ul><ul><li>Pin punctures in type </li></ul><ul><li>Microdots (WW II) </li></ul><ul><li>Newspaper clippings, knitting instructions, XOXO signatures, report cards, … </li></ul>
  7. 7. Motivation <ul><li>Steganography received little attention in computing </li></ul><ul><li>Renewed interest because of industry desire to protect copyrighted digital work </li></ul><ul><ul><li>audio </li></ul></ul><ul><ul><li>images </li></ul></ul><ul><ul><li>video </li></ul></ul><ul><ul><li>Text </li></ul></ul><ul><li>Detect counterfeiter, unauthorized presentation, embed key, embed author ID </li></ul><ul><li>Steganography ≠ Copy protection </li></ul>
  8. 8. Null Cipher <ul><li>Hide message among irrelevant data </li></ul><ul><li>Confuse the cryptoanalyst </li></ul>
  9. 9. Null Cipher <ul><li>Hide message among irrelevant data </li></ul><ul><li>Confuse the cryptoanalyst </li></ul>Big rumble in New Guinea. The war on celebrity acts should end soon. Over four big ecstatic elephants replicated.
  10. 10. Null Cipher <ul><li>Hide message among irrelevant data </li></ul><ul><li>Confuse the cryptoanalyst </li></ul>B ig r umble i n N ew G uinea. T he w ar o n c elebrity a cts s hould e nd s oon. O ver f our b ig e cstatic e lephants r eplicated. Bring two cases of beer.
  11. 11. BBC News 27 April 2006 Judge creates own Da Vinci code The judge who presided over the failed Da Vinci Code plagiarism case at London's High Court hid his own secret code in his written judgement. Seemingly random italicised letters were included in the 71-page judgement given by Mr Justice Peter Smith, which apparently spell out a message. Mr Justice Smith said he would confirm the code if someone broke it. &quot;I can't discuss the judgement, but I don't see why a judgement should not be a matter of fun,&quot; he said. Italicised letters in the first few pages spell out &quot;Smithy Code&quot;, while the following pages also contain marked out letters. http://news.bbc.co.uk/go/pr/fr/-/1/hi/entertainment/4949488.stm
  12. 12. Chaffing & Winnowing <ul><li>Separate good messages from the bad ones </li></ul><ul><li>Stream of unencoded messages with signatures </li></ul><ul><ul><li>Some signatures are bogus </li></ul></ul><ul><ul><li>Need key to test </li></ul></ul>Alice Bob Irene ? ? ? ? × × × OK M 0 M 3 M 1 M 2 M 0 M 3 M 1 M 2 M 0 M 3 M 1 M 2
  13. 13. Image watermarking <ul><li>Spatial domain watermarking </li></ul><ul><ul><li>bit flipping </li></ul></ul><ul><ul><li>color separation </li></ul></ul><ul><li>Frequency domain watermarking </li></ul><ul><ul><li>embed signal in select frequency bands (e.g. high frequency areas) </li></ul></ul><ul><ul><li>apply FFT/DCT transform first </li></ul></ul><ul><ul><li>e.g. Digimarc </li></ul></ul><ul><ul><li>watermark should alter the least perceptible bits </li></ul></ul><ul><ul><ul><li>these are the same bits targeted by lossy image compression software </li></ul></ul></ul>
  14. 14. UV Watermarking
  15. 15. Machine ID codes in laser printers See http://www.eff.org/Privacy/printers/
  16. 16. Machine ID codes in laser printers
  17. 17. Machine ID codes in laser printers
  18. 18. Machine ID codes in laser printers
  19. 19. Text <ul><li>Text lines shifted up/down (40 lines text  2 40 codes) </li></ul><ul><li>word space coding </li></ul><ul><li>character encoding - minor changes to shapes of characters </li></ul>
  20. 20. Text <ul><li>Text lines shifted up/down (40 lines text  2 40 codes) </li></ul><ul><li>word space coding </li></ul><ul><li>character encoding - minor changes to shapes of characters </li></ul><ul><li>works only on “images” of text e.g., PDF , postscript </li></ul>
  21. 21. Audio <ul><li>Perceptual coding </li></ul><ul><ul><li>inject signal into areas that will not be detected by humans </li></ul></ul><ul><ul><li>may be obliterated by compression </li></ul></ul><ul><li>Hardware with copy-protection </li></ul><ul><ul><li>not true watermarking - metadata present on media </li></ul></ul><ul><ul><li>DAT </li></ul></ul><ul><ul><li>minidisc </li></ul></ul><ul><ul><li>presence of copy protection mechanisms often failed to give the media wide-spread acceptance </li></ul></ul>
  22. 22. Video <ul><li>Coding still frames - spatial or frequency </li></ul><ul><li>data encoded during refresh </li></ul><ul><ul><li>closed captioning </li></ul></ul><ul><li>visible watermarking </li></ul><ul><ul><li>used by most networks (logo at bottom-right) </li></ul></ul>
  23. 23. Watermarking vs. Steganography <ul><li>Goal of steganography </li></ul><ul><ul><li>Intruder cannot detect a message </li></ul></ul><ul><ul><li>Primarily 1:1 communication </li></ul></ul><ul><li>Goal of watermarking </li></ul><ul><ul><li>Intruder cannot remove or replace the message </li></ul></ul><ul><ul><li>Primarily 1:many communication </li></ul></ul>
  24. 24. The end.

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