Privacy, GPS, and Image Metadata
Transparency is cool, but since Steem is a block chain, that transparency works out to be a permanent record that's easily accessible to anyone that cares to read it. I realize that some people don't care about privacy or how much private information they share in their posts, but some people may be unwittingly sharing a little more than they intended.
This post is a warning that the data you publish as media might contain more information than you intended to publish. There's very little new information in this post that's not already widespread on the Internet, but I wanted to write something up about it, because hey, the block chain.
JPEG, TIFFs, PNGs
Many image file formats let you include all sorts of cool tags that really do add value to the format. But the value they add might not be as valuable to you, the creator of the image, as it is to others. You should consider that when you publish an image in JPEG format, chances are you may be posting your GPS location, your user name, your real name, the phone or camera type, the software you used to create the image, evidence that you were in a particular location on a particular date at a particular time, and these are just a few things off the top of my head. You might not care, but it's the sort of stuff cyber stalkers like. So I just wanted you to know it's there.
Avatars on Steemit.com
The steemit.com avatars are stripped of metadata. You wont find very much of interest in them, or at least I didn't in the few that I fetched.
Pictures posted to Steemit.com
If you're using a web browser, you can just right click on the image you care to see or manually type in the url, but I like the command-line, so I use stuff like wget. If you swing that way, you could use curl, too.
Anyway here's how I can fetch my profile image that I use for steemit.com:
wget https://steemitimages.com/u/not-a-bird/avatar
In a web browser you can view some of the metadata if you're viewing an image by right clicking and choosing something like "View Image info". Or you could use something like the inspector in Photoshop, or Preview on a Mac. If you are in windows, you can view properties on the file, go to the Details tab, and see the tags there.
Unlike the avatar thumbnails, images posted to steemit.com in articles are not stripped of metadata. So use the aforementioned technique on images within posts.
I'm on Linux and I like the command-line, so I'd use exiftool.
exiftool -a avatar
Not just Steemit, but Steemit.chat, too...
Steemit.chat is great for networking! But did you know that in addition to fetching the images people post in the chat, you can also fetch avatar images? Did you know you don't even need to be logged in to do that? Did you know that some people don't bother to remove any of the tags from their images, so you can just go ahead and see where the picture was taken, and when, and occasionally fetch other interesting data from the image?
Images and avatars both on Steemit.chat are not stripped of metadata by the upload process.
For example, you can fetch an image for any given user just by using a particular URL. For example, my user name is not.a.bird on Steemit.Chat (On a side note: I didn't know hyphens wouldn't work in user names... Definitely would have chosen a name for Steem that could match on there, too, but I'm getting distracted...)
Here's how I can fetch my profile image that I use for steemit.chat:
wget 'https://steemit.chat/avatar/not.a.bird'
And this might look a little confusing, but as I sort of alluded to earlier, as my steemit.chat account name is not.a.bird and my steemit.com account is not-a-bird. For most people, it's the same thing.
And here's how I can view the metadata in it:
exiftool -a not.a.bird
My avatar was created using a command-line tool and it doesn't have any particularly useful metadata in it, but I didn't feel comfortable posting any of the examples I found that did contain GPS coordinates.
How to fix it?
One easy way is to pick a better image host, like imgur.com which strips the tags from any content that's uploaded.
In windows, the same properties dialog that lets you view the tags will also let you selectively erase tags. On Mac, I think the inspector will let you, but I don't have any way of checking and I'm too lazy to google it. I imagine Photoshop or Preview would both let you since the Gimp has an option to not preserve the tags when you export an image.
There are a few command-line tools that let you edit metadata. Two quick ones I can think of for Linux are exiftool and jpegtrans.
This strips the tags, no backups:
exiftool -all= yourimage
Strip all tags:
jpegtran -copy none yourimage.jpg > outputimage.jpg
I've also been told that some Camera apps on mobile phones let you disable embedding exif tags all together, so that's worth looking into for your own because a majority of the GPS-embedded images are from mobile phones.
Summary
In summary, lots of images posted to Steemit.com and Steemit.chat have stuff like GPS location embedded in them and you don't even need to log in to fetch them as it's all publicly available.
Image from Pixabay