Speculation as to why printer manufacturers have forensic tracking dots

[grarpamp]

On Sat, Nov 18, 2017 at 5:58 PM, Ryan Carboni <ryacko at gmail.com> wrote:
> https://www.eff.org/pages/list-printers-which-do-or-do-not-display-tracking-dots
>
>> (Added 2017) REMINDER: IT APPEARS LIKELY THAT ALL RECENT COMMERCIAL COLOR
>> LASER PRINTERS PRINT SOME KIND OF FORENSIC TRACKING CODES, NOT NECESSARILY
>> USING YELLOW DOTS. THIS IS TRUE WHETHER OR NOT THOSE CODES ARE VISIBLE TO
>> THE EYE AND WHETHER OR NOT THE PRINTER MODELS ARE LISTED HERE. THIS ALSO
>> INCLUDES THE PRINTERS THAT ARE LISTED HERE AS NOT PRODUCING YELLOW DOTS.
>
> I have a theory as to why. CALEA allows the government to compel "a
> manufacturer of telecommunications transmission or switching equipment" to
> modify the equipment. Under that or a similar law, printing manufacturers
> are compelled to put tracking information onto paper.

Don't take a lack of happy yellow dots to mean safety.
Even a single DPI print shift applied to a physical bitmap
of the page area could transmit a lot of stego data.
Assume all consumer devices contain some such marking
mechanism, perhaps even some blockchain of hashes of
all the previous digital job input to the device.
And analogue classifiers as well.