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Possible Duplicates:
Is using Gravatar a security risk?
Is Gravatar a privacy risk?

Since the Gravatar is generated based on the email address. Is it possible to determine a user's email address based on their Gravatar?

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marked as duplicate by Adam Davis, Arjan, The Unhandled Exception, Michael Mrozek, Josh K Feb 18 '11 at 20:22

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

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where is the duplicate question? – rubo77 Jun 19 '12 at 16:01
up vote 3 down vote accepted

The email addresses in Gravatar are stored as MD5 hashes. It's the same kind of one-way protection used in password storage.

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But for avatars, the "password" might be much more easily guessed, and then validated against the hash. Like when assuming a display name might also be the user name at one of the main email providers. – Arjan Feb 18 '11 at 19:59
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@chrisay It's only used for passwords by incompetent programmers, because brute-forcing md5 is fast. And for the same reason it sucks when hiding email addresses too. – CodesInChaos Jan 28 '12 at 16:54

No, fortunately not, it would have been a huge security hole. It's basically an one-way hash like SHA.

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According to Gravatars: why publishing your email's hash is not a good idea, about 10% of the SO users have a display name that relates to a (discoverable) email address at one of the major email providers. – Arjan Feb 18 '11 at 19:56
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And >20% have an easily guessable address. – CodesInChaos Feb 5 '12 at 23:20

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