Public key infrastructure (PKI) is the system used to create and manage public keys for encryption, which is a process used to secure online data exchange. “That little lock icon means your browser verified the website’s certificate and then used key pairs to create a secure, encrypted connection. How Public and Private Keys Work Together to Protect DataIn public-private key pairs, the public key can be shared freely while the private key is kept secret. Fleck shares this classic example: Bob can encrypt data using Alice’s public key but only Alice can decrypt it using her private key. “A certificate links a public key to a real person, business or device and is issued by a trusted authority.