What Are Public and Private Keys?

Public and private keys are the core components of public-key cryptography, a method used to secure data and verify identities over untrusted networks.

A public key is shared openly and is used to encrypt data or verify digital signatures. A private key is kept secret and is used to decrypt data or create signatures. Together, they form a cryptographic key pair.

When a secure connection is established, a public key protects a temporary session key that is later used for fast, symmetric encryption. Only the corresponding private key can decrypt this session key, ensuring confidentiality.

Because private keys act as proof of identity, their protection is critical. If a private key is compromised, attackers can impersonate systems, decrypt sensitive data, or sign malicious content. Proper key management is therefore essential to maintaining trust in any PKI-based system.