Cipher
A cipher is an algorithm that transforms readable data into protected data and back when the correct key is available.
- Format
- Security & Encryption
- Updated
- Updated
Definition
A cipher is an algorithm that transforms readable data into protected data and back when the correct key is available.
How it works
TLS never relies on a single algorithm. When a connection starts, both ends agree on a cipher suite — a bundle of cryptographic choices covering encryption and integrity — and modern TLS versions keep that menu deliberately short, retiring weak options as attacks against them improve.
Example: A TLS connection might use AES-GCM to encrypt application data and detect tampering in one pass.
Often confused: The cipher is the recipe; encryption is what happens when you apply it with a key.
Related terms
Sources
- IETF RFC 8446: The Transport Layer Security Protocol Version 1.3
- NIST Computer Security Resource Center Glossary
Last reviewed 2026-07-19.