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 



PHP General Mailing List (http://www.php.net/)
To unsubscribe, visit: http://www.php.net/unsub.php

Reply via email to