Originally posted by Gools
None of the articles that I found mentioned how to see this pale yellow print and it's only 0.1 millimeter high.
Maybe a UV lamp (blacklight)?
Here is your answer
The dots are yellow, less than one millimeter in diameter, and are typically repeated over each page of a document. In order to see the
pattern, you need a blue light, a magnifying glass, or a microscope
Source
eff.org
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Originally posted by invader_chris
Woah, thats weird. I have a Canon printer. I was wondering if that applies to home printers and if so, is it possible to read the invisible serial in
any way.
Source
www.eff.org...
The DocuColor series prints a rectangular grid of 15 by 8 miniscule yellow dots on every color page. The same grid is printed repeatedly over the
entire page, but the repetitions of the grid are offset slightly from one another so that each grid is separated from the others. The grid is printed
parallel to the edges of the page, and the offset of the grid from the edges of the page seems to vary. These dots encode up to 14 7-bit bytes of
tracking information, plus row and column parity for error correction. Typically, about four of these bytes were unused (depending on printer model),
giving 10 bytes of useful data. Below, we explain how to extract serial number, date, and time from these dots. Following the explanation, we
implement the decoding process in an interactive computer program.
This is an image of the dot grid produced by a Xerox DocuColor 12, magnified 10x and photographed by a Digital Blue QX5 computer microscope under
white light. While yellow dots are visible, they are very hard to see. We will need to use a different technique in order to get a better view.
This is an image of a portion of the dot grid under 60x magnification. Now the dots are easy to see, but their overall structure is hard to discern
because the microscope field only includes a few dots at a time.
This is an image of one repetition of the dot grid from the same Xerox DocuColor 12 page, magnified 10x and photographed by the QX5 microscope under
illumination from a Photon blue LED flashlight. Note that the increased contrast under blue light allows us to see the entire dot pattern clearly.
Here, we use computer graphics software to overlay the black dots in the microscope image with larger yellow dots for greater visibility. (Because
these computer-generated dots are significantly larger than the original dots, this image is no longer to scale and is now a schematic representation
of the relative position of the dots.)
Finally, we add explanatory text to show the significance of the dots.
The topmost row and leftmost column are a parity row and column for error correction. They help verify that the forensic information has been read
accurately (and, if a single dot has been read incorrectly, to identify the location of the error). The rows and columns all have odd parity: that is,
every column contains an odd number of dots, and every row (except the topmost row) contains an odd number of dots. If any row or column appears to
contain an even number of dots, it has been read incorrectly.
Each column is read top-to-bottom as a single byte of seven bits (omitting the first parity bit); the bytes are then read right-to-left. The columns
(which we have chosen to number from left to right) have the following meanings:
* 15: unknown (often zero; constant for each individual printer; may convey some non-user-visible fact about the printer's model or
configuration)
* 14, 13, 12, 11: printer serial number in binary-coded-decimal, two digits per byte (constant for each individual printer; see below)
* 10: separator (typically all ones; does not appear to code information)
* 9: unused
* 8: year that page was printed (without century; 2005 is coded as 5)
* 7: month that page was printed
* 6: day that page was printed
* 5: hour that page was printed (may be UTC time zone, or may be set inaccurately within printer)
* 4, 3: unused
* 2: minute that page was printed
* 1: row parity bit (set to guarantee an odd number of dots present per row)
The printer serial number is a decimal number of six or eight digits; these digits are coded two at a time in columns 14, 13, 12, and 11 (or possibly
just 13, 12, and 11); for instance, the serial number 00654321 would be coded with column values 00, 65, 43, and 21.
This site also has a computer program on it that lets you punch in your own yellow dots to conclude what the dots you find mean.
Link to download this program is
here
To use this program on the site... go here to the bottom
www.eff.org...
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Someone was also asking about a list of printers? Here you go. This is also taken from eff.org but from another page
www.eff.org...
Remember that a "no" simply means that we couldn't see yellow dots; it does not prove that there is no forensic watermarking present. (For example,
the HP Color LaserJET 8500 series does not include any yellow tracking dots that we can see, but it may still include some kind of forensic marking,
since the majority of earlier CLJ models did.)
Remember that a "yes" simply means that we (or another source, as noted) saw yellow dots that appeared anomalous to us. Until we decipher the
marking schemes or receive other confirmation, this does not constitute proof that any particular kind of information is represented by these dots. In
a very few cases, for example, they might be the result of a poor dithering technique, rather than a forensic mark.
Brother yes
* HL-4200CN [exp]
Canon yes
* CLC 1000 [exp]
* CLC 2400 [exp]
* CLC 4000 [exp]
* Color imageRUNNER C3100CN [exp]
* Color imageRUNNER C3200 [exp]
* Color imageRUNNER C3220 [exp]
Dell yes
* 3000cn [exp]
* 3100cn [exp]
* 5100cn [exp]
Epson AcuLaser yes
* C900 [exp]
* C1100 [exp]
* C1100 [press]
* C1500 [exp]
* C1900 [exp]
HP Color LaserJet no
* 2250ln [exp (??)]
* 4500 [exp]
* 4500dn [exp]
* 4500n [exp]
* 4550 [exp]
* 4550n [exp]
* 5M [exp]
* 8500 [exp]
* 8550 [exp]
* 8550dn [exp]
* 8550gn [exp]
HP Color LaserJet yes
* 1500l [exp]
* 2500 [exp]
* 2500n [exp]
* 2550l [exp]
* 2550n [exp]
* 2600n [exp]
* 2680 [exp]
* 2840 [exp]
* 3500 [exp]
* 3500n [exp]
* 3600dn [exp]
* 3700 [exp]
* 3700dn [exp]
* 3700n [exp]
* 4600 [exp]
* 4600dn [exp]
* 4600hdn [exp]
* 4600n [exp]
* 4650 [exp]
* 4650dn [exp]
* 4650dtn [exp]
* 5100cn [exp]
* 5500 [exp]
* 5500atn [exp]
* 5500dn [exp]
* 5500hdn [exp]
* 5550 [exp]
* 5550dtn [exp]
* 9500 [exp]
* 9500hdn [exp]
IBM unclear
* Infoprint Color 1454 [exp] [dithering algorithm?]
Konica/Minolta unclear
* DialtaColor CF 2001 [exp] [dithering algorithm?]
Konica/Minolta yes
* Bizhub C350 [exp]
* CF1501 [exp]
* Colorforce 8050 [exp]
* Desklaser 2200 [exp]
* DialtaColor CF 2001 [exp]
* Ikon CPP500E [exp]
* Magicolor 2210 [exp]
* Magicolor 2300 DL [exp]
* Magicolor 2430 DL [exp]
* Magicolor 3300 [exp]
* Magicolor 7300 [exp]
Kyocera yes
* FS-C5016N [exp]
Lanier yes
* LD238C [exp]
* LP125cx/LP126cn [exp]
Lexmark no
* C720 [exp (??)]
Lexmark yes
* C510 [exp]
* C720 [exp]
* C912 [exp]
Minolta: see Konica/Minolta Oki/OkiDATA no
* C5150 [exp]
* C5150n [exp]
* C5300 [exp]
* C7200 [exp]
* C7350 [exp]
* C9300 [exp]
Ricoh: see also Savin Ricoh yes
* Aficio CL 3000 [exp]
* Aficio CL 6010 [exp]
* Aficio CL 7000 [exp]
* AP 206 [exp]
Samsung no
* CLP-510 [exp]
* CLP-500 [exp]
* CLP-550 [exp]
Savin yes
* C3210 [exp]
* CLP35 [exp]
Tektronix: see Xerox/Tektronix Toshiba yes
* eStudio 210c [mfr]
* eStudio 310c [mfr]
* eStudio 311c [mfr]
* eStudio 211c [mfr]
* eStudio 2100c [mfr]
* eStudio 3100c [mfr]
* eStudio 3511 [exp]
* FC15i [mfr]
* FC15 [mfr]
* FC22i [mfr]
* FC22 [mfr]
* FC25Pi [mfr]
* FC25P [mfr]
* FC70 [mfr]
Xerox yes
* DocuColor 12 [exp]
* DocuColor 40 [exp]
* DocuColor 2045 [exp]
* DocuColor 2000 [mfr]
* DocuColor 6060 [mfr]
* DocuColor 6060 [exp]
* WorkCentre M24 [exp]
* WorkCentre Pro all models [press]
* WorkCenter Pro 40 [exp]
* WorkCenter Pro C2636 [exp]
Xerox/Tektronix Phaser no
* 560 [exp]
* 740 [exp]
* 750 (Z750V) [exp]
* 750P [exp]
* 780 [exp]
* 850DP [exp]
* 860DP [exp]
* 6100 [exp]
* 6200 [exp]
* 6200DP [exp]
* 6250DP [exp]
* 7700 [exp]
* 8200DP [exp]
* 8200DX [exp]
Xerox/Tektronix Phaser unclear
* 8400B [exp?] [dithering algorithm?]
* 8400DP [exp]
* 8440DP [exp?] [dithering algorithm?]
* 8400DX [exp]
* 8400N [exp]
[edit on 19-10-2005 by noslenwerd]