To create the secure tunnel, a VPN uses a variety of technologies that support encryption, authentication, and/or data integrity. Encryption is the process of making information unreadable to unauthorized users by converting it to cipher text. Authentication ensures that users attempting to access your network are who they say they are. Authentication methods include passwords, usernames, and PKI (public-key infrastructure; a means of verifying users and network devices). Data integrity guarantees that the transmitted information is not altered or tampered with.