Posted on 01/28/2011 10:15:15 AM PST by butterdezillion
I need to know how to make sure there is no question that jpegs or pdf's I post on my blog have not been tampered with in any way. If I simply upload them in my Wordpress blog would they be certifiably genuine? If I took a photo and scanned it to be a jpeg would it show that there had been no tampering?
Thanks for any advice on how to document authenticity.
http://getmd5checker.com/download/
An identical file will have an identical checksum.
Send it to Dan Rather for verification.
If you blow it up (zoom) to well over 300%, you should be able to see editing anomalies.
Thats one of the ways they showed that Obama’s COLB was fake.
I believe that programs like photoshop leave some kind if tag in the data that you can see if you look at the code.
You cannot prove that a jpeg originally came from a photo if that is what you’re asking.
Ping.
Yes. Also, a photo from many digital cameras will also have EXIF data.
So if I scanned a document without editing it in any way, saved it as a jpeg or pdf, and posted it to my blog, could somebody who doubted its genuineness use MD5 to find that it has not been manipulated or edited in any way?
Of course, if I got a PDF from somebody else and they edited it in any way that would show, right?
So if I figured out how to upload an image from my digital camera could people be able to find out that it was genuine, when the photo was taken, etc?
For instance, I posted some photos my husband took with his digital camera, at http://butterdezillion.wordpress.com/2011/01/28/spring-will-come/ . Can a person look at those and determine that they are genuine and when they were taken?
There’s a PDF I uploaded there also, in which I took an image from the web, added words, saved as a PDF, and uploaded it as a PDF. Is there any way for people to know whether I altered the web image before I saved the PDF?
I want to make sure that what I post can be verified as genuine and unedited. If putting things in a PDF obscures the genuineness then I need to avoid PDF’s.
No.
Of course, if I got a PDF from somebody else and they edited it in any way that would show, right?
No, unless you were the one who scanned the original PDF.
You can perform a checksum on your original scanned file and post the image and the checksum on your site.
A person who downloaded the file could run a checksum on it. If his checksum matches the sum you posted, he has a genuine, unaltered copy of your file.
If the checksums differ, the files are not identical.
The EXIF data will include the date (assuming that the date and time were entered correctly in the camera’s internal calendar), time, exposure setting, file type, aperature setting, dpi, etc.
One can easily take a photograph with digital camera, download it, edit it, and upload it back in the camera with fake dates. Ye old polaroid instant camera pictures happen to be the most resistant to tampering.
I could read data on image dimensions, bit depth, and dpi, but all the other data was gone.
I wonder how I could get an image onto my blog with authentication still possible. Would that take having it certified by somebody like VeriSign (sp?)?
Do you think most people would consider a document authentic if there weren’t anomalies that showed up at high magnification? If I posted a genuine document could I trust that most people would be able to satisfy themselves that it was genuine, or are there other steps I should take to make sure it can be proven?
I am a total moron when it comes to graphics and computers, but I have important documents whose provenance and genuineness I need to be beyond question.
btt
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