TA Associates, a middle-market growth private equity firm, has acquired a majority stake in DigiCert. The company provides online authentication and encryption services primarily through Secure Socket Layer (SSL) certificates to companies, government agencies, financial institutions, and educational and medical institutions worldwide. Headquartered in Lindon, UT, DigiCert counts more than 60,000 customers in 176 countries as clients. VC firm Polaris Venture Partners found its exit in the deal after financing a round of equity funding in July 2011. Boston-based TA Associates leads buyouts and minority recapitalizations of profitable growth companies in the healthcare, technology, financial services, business services and consumer industries.