content: THIS ENTIRE TOPIC WAS DISCUSSED LIVE IN CONGRESS IN C-SPAN in 1986 It was even telecasted across to NPR FM radio channels (the floor discussion in congress) ITS NOT VERY SECRET if you paid attention since 1986, and it had to do mainly with color copiers in canada first, then color scanner/copiers in USA (stocks, bonds, currency, etc), and finally many years later appeared also in INK JET PRINTERS. I myself wrote about it in 2000 and 2001 and "broke" the story years before anyone when I was amazed that people forgot the laws and statutes and debates.  Broke the story? Yes... because even slashdot.org in 2004 was STILL CLUELESS and ignorant of the yellow data hidden under black ink :  proof :    https://it.slashdot.org/story/04/10/14/1742224/new-technique-could-trace-documents-by-printer hah! thats 2004! And remember its was public info in congress CSPAN revelation from 1986 (albeit for hi rez color document scanner law).