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Now Available: Lookup by Email MD5 Hash

Looking back on 2012, the one tech story that stands out in my mind isn’t Facebook’s rocky IPO. Nor is it the much-derided launch of Apple Maps. Nor is it even Felix Baumgartner’s jump from the edge of space (although I’ve gotta be honest – that one’s pretty high on my list).

As a marketer who cares about privacy, for me, the top tech story was the number of times an email list was stolen. It seemed like every other week we saw another headline reading “Hackers Publish More Than 900,000 Emails and Passwords….” Given how many times it happened (and for how many high-profile sites), I’d venture to say that most people with an email address found themselves on at least one of those lists.

From a data security standpoint, it was a bad year.

At FullContact, we’re big on keeping our users’ data protected. And a lot of our API users feel the same way.

That’s why today we’re announcing a small (but big) change to our Person API: in addition to being able to look up by email, Facebook ID, Twitter handle, and vCard, you can now query the Person API via an MD5-hashed email address.

Performing an Email MD5 Lookup

Don’t have a list of hashed email addresses? Start by using the MD5 Hash Generator to hash a sample email address and test it out.

If you’re already using the FullContact Person API, this’ll be simple. Looking up social profiles by email MD5 hash is as easy as querying the Person API – just replace the email parameter with the new emailMD5 parameter, along with a hashed email address.

You can test out the new functionality in your browser using the URL below. (If you don’t already have one, you’ll need to sign up for a free FullContact API key first).

https://api.fullcontact.com/v2/person.json?emailMD5=79d083b578589d5809922254639f6d99&apiKey=xxxx

The request above will return social media profile links for the email MD5 hash 79d083b578589d5809922254639f6d99. (Told you it was simple. Only one thing to be aware of: when you use MD5 to hash the email addresses in your list, be sure that each email address is in lowercase letters, and trim any whitespace on either side.)

Response Data

Querying the Person API via the emailMD5 parameter will return social media profile links and contact data in the same format as the standard email lookup. Just as with the email lookup, you can change the response format by replacing .json with .html or .xml.

PLEASE NOTE: match rates for email MD5’s will generally be slightly lower than using the standard email lookup to request social profiles – if we haven’t seen the email MD5 before, we are unable to search for social profiles based on the email address.

Example Email MD5 Lookup Response (truncated)

{
  "status": 200,
   "contactInfo": {
    "familyName": "Chambers",
    "fullName": "Kipp Chambers",
    "givenName": "Kipp"
  },
  "demographics": {
    "locationGeneral": "Denver, CO",
    "gender": "Male"
    "ageRange": "25-34"
  },
  "socialProfiles": 
  [
    {
      "type": "facebook",
      "typeId": "facebook",
      "typeName": "Facebook",

For those of you already using hashed email addresses internally, this new parameter should give you a quick way to add an extra layer of protection to your email lists. And if you’re not using MD5 email hashes, there are several libraries online for you to get set up.

MD5 hashes alone can’t solve the problem of stolen user lists…but they can help make it one step harder to accomplish.


To learn more about the new emailMD5 parameter, check out the Person API docs.

(And if you’re not yet a FullContact API user, sign up for a free API key, give it a test drive, and let us know what you think!)

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