If you've logged in through a box like this, you've probably used Janrain's engine.

Janrain, the Portland, OR-based company that provides those boxes with “Sign in using your account with Facebook, Google, Paypal, Twitter, Account” etc., has closed $15.5 million in financing. Emergence Capital Partners led the round, and is joined by previous investors Anthem Venture Partners, DFJ Frontier, RPM Ventures, Tim Draper, and founder Larry Drebes with participation from Square 1 Bank.

The investment will be used to add resources and employees across all existing functional teams and further support the accelerated growth the company is experiencing.

Janrain provides SaaS solutions that help organizations increase acquisition and engagement with online users by leveraging the user’s social profile.

These solutions, including social login, sharing to social networks and the analytics required to measure and monitor social activities, as well as turnkey registration and social profile storage, are being rapidly adopted by leading brands across many vertical markets.

Organizations rely on Janrain to access and store detailed user profiles that can then be utilized to better serve their online customers, personalize campaigns and inform future marketing strategies.

Janrain received financing of $3.25 million in December 2009. Since that time, the company has grown 300 percent year over year, and signed customers such as MTV, Tribune, Meredith, AMC Networks, Rodale, HarperCollins, Dr. Pepper Snapple Group, Sears, Free People, Avis and Citysearch. The company employs 60 people.

See also: Janrain logs $15.5M to help you log in through social networks