1. Lawrence Snyder University of Washington, Seattle © Lawrence Snyder 2004 Computing Is Pretty Strange

2.  The process of hiding information  Two Greek roots meaning: “stego” == “roof” “stega” == “cover” 2/6/2016© 2011-2013 Larry Snyder2

3.  Most common reason to hide information is to avoid being caught with it  Military and spy documents  Repressive governments restricting news/info  Avoid others “snooping” – privacy  Hiding is different than encryption … uses the fact that the searcher doesn’t know it’s there 2/6/2016© 2011-2013 Larry Snyder3

4.  The Plan …  hide “subversive” protest photo in “calendar art” 2/6/2016© 2011-2013 Larry Snyder4 Guest Image Host Image

5.  We don’t need all of the bits in RGB to get a decent picture 2/6/2016© 2011-2013 Larry Snyder5 1011 0100 1101 0011 0001 1100 All bitsLeft 2 bits of each color only 1000 0000 1100 0000 0000 0000

6.  Put guest bits into right 2 bits of host 2/6/2016© 2011-2013 Larry Snyder6 1111 0100 1101 0011 1011 11011011 0100 1101 0011 0001 1100 1111 0110 1101 0011 1011 1100

7.  2/6/2016© 2011-2013 Larry Snyder7 foglg.jpg stegFog.png Really? Just Do It! Really? Just Do It!

8. Each of the colors is shifted left 1 bit at a time … and then we’ll see the details 2/6/2016© 2011-2013 Larry Snyder8 10110100 11010011 00011100 01101000 10100110 00111000 11010000 01001100 01110000 10100000 10011000 11100000 01000000 00110000 11000000 10000000 01100000 10000000 00000000 11000000 00000000 Original Hidden Picture

9.  2/6/2016© 2011-2013 Larry Snyder9 Encoding Code Code To Save Result on Click

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12.  After the pictures are loaded Clear right 2 bits of host Extract left 2 bits of guest New combined color 2/6/2016© 2011-2013 Larry Snyder12 10110100 11010011 00011100 101101xx 110100xx 000111xx 10110100 11010011 00011100

13.  2/6/2016© 2011-2013 Larry Snyder13

14.  Read in the file, and then on key press, shift the bits left one position 2/6/2016© 2011-2013 Larry Snyder14 Just Do It! Again Just Do It! Again

15.  Run A Test … www.tineye.com 2/6/2016© 2011-2013 Larry Snyder15 The Original

16. 2/6/2016© 2011-2013 Larry Snyder16 Steganized

17.  Steganography can be used extensively – there are many places to hide information  Tomorrow, you’ll hide a picture, too. 2/6/2016© 2011-2013 Larry Snyder17