A public key is one half of an asymmetric cryptographic key pair used for encryption, signature verification, and secure communication. Public keys can be openly shared, while private keys must remain secret. Data encrypted with a public key can only be decrypted with the corresponding private key. Public keys also verify digital signatures to confirm authenticity.
Why it matters
Public-key cryptography enables secure communication across the internet without pre-shared secrets. It powers HTTPS, SSH, JWT signatures, and many authentication protocols.
Examples
Sharing an SSH public key to grant access to a server or distributing a TLS certificate containing a public key. Lessons on SSL/TLS and SHA provide foundational security context.