Public and private key pairs are the foundation of asymmetric encryption, also called public key cryptography. In this model, each entity has two mathematically related keys: a public key that can be shared widely and a private key that must be kept secret. The keys are designed so that what one key does, only the other key can undo. This enables two core security functions used throughout cybersecurity architectures.

First, confidentiality: data encrypted with a recipient's public key can only be decrypted with the recipient's private key. This allows secure communication without having to share a secret key in advance, which is especially important on untrusted networks like the internet. Second, digital signatures: a sender can sign data with their private key, and anyone can verify the signature using the sender's public key. This provides authenticity (proof the sender possessed the private key), integrity (the data was not altered), and supports non-repudiation when combined with proper key custody and audit practices.

These mechanisms underpin widely used security controls such as TLS for secure web connections, secure email standards, code signing, and certificate-based authentication. A VPN may use public key cryptography during key exchange, but the key pair itself is specifically an encryption technology. IoT and network segregation are unrelated categories.