Since some time, new users and users who change their profile image, get a salt added to their email address when they want to use an automatically generated Gravatar identicon. Great!

With the annual Data Privacy Day coming up on January 28th: why not send out some system wide alert (or some Inbox message, or a blog post if other notifications are truly deemed too intrusive) that day, to tell folks they can easily get a more secure identicon?

Happy Data Privacy Day! Using a generated identicon on these sites? Get a more secure avatar!

Some linked explanatory post could be something like:

When using Gravatar for your profile picture, your email address is encoded (MD5 hash) in the image URL. When using very common providers such as Gmail, this might be subject to brute force attacks, and hence a privacy concern.

If you're using an automatically generated Gravatar identicon, then you can easily get a more secure version on Stack Exchange:

  • Log in and go to your profile
  • Click "change picture" when hovering your profile picture
  • Select the new identicon
  • Optionally copy the same image to all your Stack Exchange profiles: click "edit" to edit your profile, and then click "Save And Copy Profile To All Stack Exchange Accounts"

This will change the identicon. If you want to keep using your old icon, you can still make it safer: download the old icon, and then upload it to the Stack Exchange image hosting, using the same "change picture" dialog. This will use a different URL, which does not include your encoded email address.

When you're not using an automatically generated identicon, but instead uploaded an image to Gravatar, then your email address will still be encoded the old way. Stack Exchange cannot change that. If this bothers you, then you can also upload the same picture to Stack Exchange and no longer use Gravatar URLs on these sites.

More help on How do I change my profile picture, or avatar?

and still no definitive answer to "Someone contacted me by email but my email is not public"... ;-)

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    Related feature request: a URL like stackoverflow.com/users/me to get to one's own profile ;-) – Arjan Jan 8 '14 at 22:00
  • I don't think system wide alerts should be used for this. On the next "XYZ day" there'd be as much of an outcry as when Dennis Ritchie died, and no-one wants that again. – Matt Jan 8 '14 at 22:05
  • Why does copying and pasting the existing image make it more secure? – Richard Tingle Jan 8 '14 at 22:05
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    @RichardTingle: Because the URL of the uploaded image (which is uploaded to imgur) does not contain the hash of your email (which your gravatar does). – Matt Jan 8 '14 at 22:07
  • Or some Inbox message, @Matt? As an aside: did you know your email address is really easy to guess? (Of course, in your case it helps that you posted your domain name...) And that it would also have been easy to find your Twitter handle if you'd not posted that? – Arjan Jan 8 '14 at 22:14
  • @Arjan I don't think he really cares... I mean he even posted in his about me "You can also find me on twitter. I'm mattlunn." – Doorknob Jan 8 '14 at 22:18
  • (I know, @Doorknob, that's why I wrote "if you'd not posted that?".) – Arjan Jan 8 '14 at 22:19
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    @Arjan stackoverflow.com/users/current – Flyk Jan 8 '14 at 22:22
  • @Arjan: I still don't think it's the right medium to communicate it across, and it depends what email you mean. Pfft, all of my public profiles are linked from the footer of my website, which is linked from my SE profile, and my handle is often "mattlunn" to make them connectable and discoverable, so I'm not too bothered :P. – Matt Jan 8 '14 at 22:22
  • Though @Richard has a point: using the same identicon image, still allows people to visually compare the results. Not as easy as a brute force attack though. – Arjan Jan 8 '14 at 22:26
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    I think the best we can expect is a blog post here. New blog posts get a special place in the right sidebar for a few days. Sending actual inbox message do seem wrong, it will cause more harm than good in my opinion by scaring people. "What?! I was using a non secure avatar all this time?!" – Shadow Keeps Social Distance Jan 8 '14 at 22:30
  • @Matt, as for comparing it to earlier notifications: the (silent) change in salting the hash is more directly related to Stack Exchange, I feel. I guess it's not urgent enough to send out an email, like was done when MyOpenID used Twitter to announce they would stop. Shadow's blog idea might be nice if other notifications are indeed deemed too intrusive. – Arjan Jan 8 '14 at 22:32
  • To make the internet a better place, I truly don't mind scaring people, if that wakes them up, @Shadow. – Arjan Jan 8 '14 at 22:34
  • @Arjan just saying, personally I won't mind such message. – Shadow Keeps Social Distance Jan 8 '14 at 22:34
  • +1 for the information and general idea - though an email message is a bit extreme. I like the idea of a blog post about it, though. – JDB still remembers Monica Jan 8 '14 at 22:46

Would it be significantly different than this thing I have to look at all the time?

WARNING: this facility contains chemicals known to the state of California to cause cancer, and birth defects or other reproductive harm.

Gee that notice really helps me.. uh.. er... feel a pointless, vague sense of dread everywhere I go? Thanks prop 65, you added a notice that really improved everyone's life!

I do not think it is wise to advocate messaging of this sort. "Look out! This site and all its data will be deleted in two days!" showing up as a system alert for all users. Sure, that's useful. It's urgent.

But somehow "Look out! We aren't sure but maybe something bad might happen at some unknown indeterminate point in the future but we can't say for sure!" does not have the same.. urgency. And I would argue that kind of required-by-law labeling has a cost, it adds a very real burden to businesses and society.

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    You don't think it's already happening? I feel every idea you had for SE was truly great, except for using Gravatar. The changes that are being made are great too; why not advertise those? – Arjan Jan 8 '14 at 22:46
  • shrug I still like and use gravatar everywhere I can. Options and alternatives are very good of course. – Jeff Atwood Jan 8 '14 at 22:53
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    FWIW, @Arjan, I somewhat doubt the scenario you linked to is connected to email hashes. The most plausible solution is that the email address was available to someone who copied it down and then used it later - I know that's less of a sexy technothriller, but it's the sort of privacy leak that actually happens all the time just because it's easy to be careless, particularly with other people's data. – Shog9 Jan 8 '14 at 23:05
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    Just curious: when using Gravatar for new projects, aren't you also implementing improvements that SE has been adding lately? Like Kevin wrote in August: "Basically we wanted to stop putting a user's email hash into the page, unless they explicitly want to link in their gravatar. Naturally we didn't want to change anybody's existing profile image, so it only applies to new users." (SE having the additional problem that old data dumps will never go away.) – Arjan Jan 8 '14 at 23:05
  • @Shog9, I truly consider it a viable option that someone who started a company promising recruiters "a complete view" of candidates, and was not answering the OP's email question, and did not respond on Meta but instead cleaned up his answers/comments, might have created a database of known MD5 hashes. I even consider it an option that he might even have some userscript to show email addresses next to Gravatars, as otherwise it would have been truly much easier to just leave a comment (like he did later on other posts) instead of sending an email. – Arjan Jan 8 '14 at 23:15
  • (But, @Shog9, Jarrod is investigation, so let's hope he doesn't find anything. Still then, MD5 brute forcing would much easier be done on a datadump, not on the site directly.) – Arjan Jan 8 '14 at 23:16
  • Not saying it isn't feasible, @arjan - just... A bit much to hand someone a bug report. Now, that guy offering folks $30 for undelete votes... – Shog9 Jan 8 '14 at 23:51

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