Jon Callas is an American computer security expert,[1] software engineer, user experience designer, and technologist who is the co-founder and former CTO of the global encrypted communications service Silent Circle.

[2] He has held major positions at Digital Equipment Corporation, Apple, PGP, and Entrust, and is considered "one of the most respected and well-known names in the mobile security industry.

"[3] Callas is credited with creating several Internet Engineering Task Force (IETF) standards, including OpenPGP, DKIM,[4] and ZRTP, which he wrote.

"[6] He has also worked for Bruce Schneier's Counterpane Internet Security, was one of the primary authors of the DKIM method, and was Chief Scientist of the original PGP, Inc. founded by Phil Zimmermann.

[6] He was a member of the technical staff at Century Computing from 1980 to 1981, then served as principal software engineer at Digital Equipment from 1981 to 1993.

[6] Callas's security product designs have won major innovation awards from The Wall Street Journal and others.

[2] Callas lectured widely about computers and Internet security, and was scheduled to be a speaker at the Oslo Freedom Forum in 2014.

Callas is currently the founder of Zatik Security (since August 2023) and a Senior Computer Scientist at SRI International (since November 2023).

His views stem from big tech's mass pooling of personal data for advertising and the polarization within Silicon Valley.

Callas has stated that if the advertising market takes a downturn, companies that protect their users' data are the most insulated from harm.