Talk:Printer steganography

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Microdots?[edit]

My impression from the EFF materials is that we are dealing with microdots. Did I get it wrong? (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).Joaquin Murietta 07:39, 2 November 2005 (UTC)

Not at all. A microdot is a miniaturized photograph downscaled to the size of a dot. This is a pattern of individual dots without finer internal structure. --Shaddack 02:45, 22 January 2007 (UTC)

Timestamps?[edit]

I understand how the printers can do serial numbers, since these are obviously embedded in the firmware or some other ROM/Flash IC. But how do they do timestamps? Do their timestamps depend on the administrator having correctly configured the time in the HTTP setup interface? Or do they try to access NTP servers via the network or something? Would be interesting to know how that works... Moxfyre 05:08, 7 February 2007 (UTC)

When the equipment is setup for the first time or rebuilt, the date and time is configured. Jeffz1 (talk) 00:32, 25 May 2009 (UTC)

Additional Manufacturer[edit]

Today I observed the pattern on a Ricoh Aficio MP C4500. LorenzoB (talk) 05:35, 21 October 2010 (UTC)

Only in color prints[edit]

My HP Color LaserJet 1600 produces there microdots only when I print something in color. When I print black only there are no microdots. So when you write threatening letters, dont use color :-)) —Preceding unsigned comment added by 90.176.57.105 (talk) 12:26, 13 November 2010 (UTC)