On Sep 17, 2010, at 7:36 PM, Ashley Sheridan wrote: > > >>> >>> Even the stenography has its flaws. Opening the image in an image editor, >>> then doing a select all and pasting as a new image would remove any hidden >>> meta info, and saving a couple of times as a jpeg would destroy any >>> detailed information without distorting the photo (assuming it was a photo >>> and not a diagram which would look awful as a jpeg) >>> >>> I'm not sure if you ever had this at your school, but back when I was a >>> kid, once a year class photos would be taken, as well as photos by >>> yourself, even if you didn't want them. To ensure people paid for the >>> proper photo, a large watermark was sprawled across the photo. It took a >>> little while, but with a decent image editor you could pull out that >>> watermark from the scanned in photo and have a good quality photo without >>> paying for it. I'm not saying we should all do this (the photographer needs >>> to be paid somehow!) but I'm saying it's possible if you have the time, >>> inclination and means. >>> >> >> Actually Ash, properly done stenography is actually embedded it the pixels - >> not the metadata and can be placed such that only when the image is reduced >> to x degraded percent is it lost which removes the value of the full res >> image. >> >> However, the power of real stenography for copyrights (and not for spying) >> is about the fact that the real user uses the image and if it gets copies by >> someone the stenography copyright signatures remain and the copier doesn't >> know about them >> >> Tom >> >> > > > I know this is getting a little off-topic here, but surely the way a > jpeg destroys data in an image would destroy the stenography information > too? To the human eye all would appear normal, but the copyright info > would be lost? > > I don't know much about this sort of thing, so I'm making assumptions > here. >
Totally depends on the approach. Both jpeg and jpeg 2000 have their own mathematical characteristics which can be properly exploited. Nevertheless, I say again the key is to add something is that if an employee of a customer who purchases the image and resells it that you have a possibility to prove. Yes really smart bad people can defeat but 1) most of these aren't stealing your pictures and 2) the others don't know you have embedded a copyright. tom Tom -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
