Jon Callas is an American cryptographer, inventor, and entrepreneur. He is the co-founder and CTO of Silent Circle, an encrypted communications firm that provides secure communication services for mobile devices. Callas is also the co-founder of PGP Corporation, a computer software company that has received numerous innovation awards for its encryption technologies. He is the creator of Apple’s Whole Disk Encryption System. Callas is considered one of the top security software engineers in the world and is currently an adjunct professor at Indiana University. In 2023, he founded Hand-Craft Software.