The story
GeoTrust was the first certificate authority to use the domain-validated certificate method US Granted 8028162, Douglas D. Beattie & Christopher T. M. Bailey, "Methods and systems for automated authentication, processing and issuance of digital certificates", published September 27, 2011, assigned to GeoTrust
which is now widely accepted and used by all certificate authorities including Let's Encrypt.
GeoTrust was a restarted company in 2001 that acquired the security business of Equifax. The Equifax business was the basis of its fast growth. The founders of the restarted company were CEO Neal Creighton, CTO Chris Bailey and Principal Engineer Kefeng Chen. Having no previous fund raising experience Creighton, Bailey and Chen used an existing company as the vehicle to acquire the business they had started at Equifax. The buyout of the Equifax certificate business was inexpensive given the final exit price in 2006.
VeriSign acquired GeoTrust on 5 September 2006 for $125 million. The main investor was St. Paul Venture Capital/VesBridge. ACG/ Mass High tech named VeriSign's acquisition of GeoTrust as the sell side deal of the year for 2006.
Symantec acquired the GeoTrust brand in 2010 as part of its $1.28 billion acquisition of Verisign security business.
Symantec announced the sale of its entire certificate business in August 2017 to Thoma Bravo LLC for $1 billion with the intention of merging it with DigiCert. Thoma Bravo merged GeoTrust into DigiCert and GeoTrust is now owned by DigiCert.
From Wikipedia’s article on GeoTrust, shared under CC BY-SA 4.0.4