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Security Fundamentals & Crypto · Foundational

Public Key

The shareable half of an asymmetric key pair, used to encrypt data for the owner or verify the owner's signatures.

Definition

A public key can be freely distributed, usually inside a digital certificate that binds it to an identity. Others use it to encrypt messages that only the private key holder can decrypt and to verify signatures made with the private key. Its authenticity must be established, typically through PKI or a web of trust.

Example

A browser uses the public key in a server's certificate to verify the server's TLS handshake signature.

Exam tip

Encrypt to someone with their public key; verify their signature with their public key.

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