Gary Kessler, a computer networking professor at Champlain College, is the author of this online introduction to cryptography. The material covers three main types of encryption and their applications, trust models, cryptographic algorithms, and much more. One of the most common areas that employs encryption techniques is the Internet, where it allows users to safely transmit private information (e.g, credit card numbers, financial information). These concepts are discussed in detail, with specific attention given to trust models and public key certificates. Kessler also mentions specific industry architectures used for authentication.