Steganography - Color Laser Copier Dot Codes
Steganography - Color Laser Copier Dot
Codes
Duke Library: Sharp Color Copiers, disabled:
Duke University, Perkin Librarys: Sharp, DCP 7395 MX 3100N, SN ?:
Duke University, Bostok Library: Sharp, DCP 7395 MX 3100N, SN 05013496
Duke University, Bostok Library: Sharp, DCP 7395 MX 3100N, SN 05072817
Canon: Fedex, 601 Ninth Street, Durham: Canon, C5045, SN 827184319428, #1 clockwise from the doorway." |
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 Fedex: Canon CS5045 |
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 SN 827184319428, #1 |
 SN 818986449313, #2 |
 SN 819386509316, #3 |
 SN 819786549321, #4 |
 SN 818886449312, #5 |
 We consistently have 18 dots representing each machine. The boundary of each pattern seems reasonable, but it is arbitrary. Three other reasonable boundaries are shown above. There could be others... |
 Patterns of all five machines superimposed. Dots of a single color represent a single machine. The dots definitely suggest a diagonal configuration. The fact that there is so much error in dot positions suggests that these patterns are sumed over the entire document to counteract noise. |
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Ricoh: Duke University, Perkins Library: Ricoh Aficio ARDF DF 3040, MP C4501, SN W2008404434 |
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 BLUE CHANNEL (Perkins: Ricoh Aficio MPC 4501 / Code: D540-94 / SN: W2008404434 / 18 October 2011 / 2:42 p.m.) |
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 BLUE CHANNEL ENHANCED (Perkins: Ricoh Aficio MPC 4501 / Code: D540-94 / SN: W2008404434 / 18 October 2011 / 2:42 p.m.) |
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"Automatic Counterfeit Protection System Code Classification." The time and date could be represented as decimals: The time and date could be represented as a Time-Since-Epoch stamp. 1 January 2000, 00:00:00 = 0 946 684 800 |
 Perkins Ricoh e-printer: This coding block is an array of 7x8 dots, totalling 56. As 56 bits, it could represent a decimal number 17 digits long, not exceeding 72,057,594,037,927,935. Use the Windows calculator, programmer's view. It could represent 8, 7-bit ASCII characters. It could represent 14, 4-bit Binary Coded Decimal (BCD) characters. How do you pack the make/model number and date/time into this block? |
As ASCII this reads (top to bottom, left to right): As a 56-bit decimal this reads (top to bottom, left to right): |
As a 56-bit decimal this reads (top to bottom, left to right): |
As ASCII this reads (top to bottom, left to right): As a 56-bit decimal this reads (top to bottom, left to right): |
As a 56-bit decimal this reads (top to bottom, left to right): |
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Wanted: The more white space the better. The yellow dots cover the entire width and height of the paper. Please write the following information in the margin:
This is the information that is
encoded in the pattern of dots.
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Electronic Frontier Foundation: "Is
Your Printer Spying On You? Part I" |
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The yellow dots are barely visible under magnification in daylight, and much less visible under incandescent light. It is best to illuminate the document with blue light (using a blue filter or blue LED flashlight) under a microscope to confirm the presence of the yellow dots. The images below were photographed with a Nikon D100 digital camera and 105mm Nikon AF Micro Nikkor lens in fine .jpg mode in daylight. The images were opened in PhotoShop and enhancements made using the following procedure: Turn "off" the red and green channels. Highlight the blue channel. Convert the image to grayscale mode to loose the red and green channels. Adjust image levels to bring out the dots. Convert the image back to RGB mode which allows you to do markups in color. A brief review of color theory is at the bottom of this page... |
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Unknown
Printer Kinkos, Sepulveda & Jefferson, Culver City, CA - 27 May 2006 |
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Sample #1 Printer: unknown |
 The full 8.5 x 11 sheet with one repeating pattern of yellow code dots inked in black. |
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 Closeup of area inked in black. The photograph was taken in bright sunlight to maximize blue light. |
 Closeup of inked-in area in bright sunlight. The red and green channels have been deleted. The blue channel has been enhanced. |
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 An enlargement of the enhanced blue channel image with red lines superimposed to show the repititions of the pattern. The red block measures 14mm high and 11mm wide. |
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 An enlargement of the bright sunlight image without enhancement. The yellow dots are just barely visible. To enhance the image yourself, save it and then open it in PhotoShop. Select "channels" and turn off the red and green channels. The area represented above includes one full block, the same coded block that is shown below with the blue-channel enhanced. |
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 An enlargement of the enhanced blue channel image shown above with red lines inserted to outline one coded block of dots. White lines have been inserted to show the alignment of dots. The rows and columns have been arbitrarily labeled with upper and lower-case letters for reference. This sample has NOT been decoded. The dot spacing is 1mm, except for the dots in half-columns "x" and "y." These may represent start and stop delimiters. In that case the data field is likely 9 wide by 10 high (90 bits). It is not clear whether the words are arranged horizontally or vertically or whether they are to be read from left-to-right or right-to-left. Nevertheless, this is a binary code of some type. |
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Xerox
DocuColor 12 Kinkos, Westwood, Westwood, CA - 30 May 2006 - S/N FU 2-051912 |
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 Color photograph in daylight. |
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 The blue channel enhanced. |
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 Closeup of one block in daylight. |
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 Closeup of one block with the blue channel enhanced. |
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Thanks
for looking... Please email me your decodings: gessler@ucla.edu |
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A Brief Review of Color Theory
The yellow dots on paper are made of red and green light (not red and green ink or toner). On paper, the yellow toner is transparent and absorbs blue light, letting red and green pass through it. On your computer screen, the yellow you see is made up of red and green light. The additive color primaries are red, green and blue (hence "RGB"). They are the primaries used to "paint with light" like the color on your computer monitor or TV screen. You can see these if you look closely at your screen with a magnifier. The subtractive color primaries are cyan, magenta and yellow, with black thrown in for good measure (hence "CMYK"). These are the transparent inks and toners that most printers use, not just color copiers, but magazines and boxed paper products. You can often see the CMYK color swatches used for alignment if you open the hidden flaps on your grocery items. The yellow dots on paper look yellow because that transparent ink or toner absorbs the blue light from sunlight and reflects both red and green. Red and green light make yellow. (Red and green paints or inks do not.) So if you illuminate a yellow dot on paper with blue light it will absorb the blue and look dark. And if you take a digital photograph of the yellow dots, the yellow that you see on the computer screen is actually red and green. Consequently, if you only display the blue color channel in PhotoShop the dots will show up dark. |
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