Entrust explained its product with one image: digital certificates work like electronic passports. Its software proved who sent an email or signed a transaction, and kept the contents private. Entrust began in 1994 as the Secure Networks group inside Nortel, the Canadian telecom giant. When it went public in August 1998, it was based in Richardson, Texas, with its research lab in Ottawa. Nortel still owned about 55.3 percent once the shares sold.

Born Inside Nortel

Nortel's team built public key infrastructure, or PKI, the system that creates and tracks digital certificates. In December 1996 Nortel set the group up as its own company, Entrust Technologies, and moved the business into it. The bet was that companies moving email, forms and commerce onto networks would need one trusted way to manage keys and identities. Entrust sold a software framework that ran across many platforms, browsers and applications.

From $16 to $1.85

Entrust priced its IPO at $16 a share in August 1998 and listed on Nasdaq as ENTU. Later it dropped Technologies from its name and moved its headquarters to Plano, Texas. Its shares ended up far below the IPO price. In 2009 a company controlled by a Thoma Bravo fund bought Entrust for $1.85 a share in cash. Shareholders voted that June, and the stock left Nasdaq in July 2009.

Cover: The Guard Gate, Gatun Lock, Panama, Joseph Pennell. Art Institute of Chicago, public domain. Chosen for a guard gate (trusted passage).