Two Families of Encryption
Encryption hides data so that only an authorized party can read it. There are two broad families, and good systems use both together.
Symmetric encryption uses a single shared secret key for both encrypting and decrypting. It is fast and well suited to bulk data. The hard part is key distribution, because both sides must already share the same secret without leaking it.
Asymmetric encryption uses a key pair: a public key that anyone may hold and a private key kept secret. Data encrypted with the public key can only be decrypted with the matching private key. This solves key distribution, but it is much slower and limited to small payloads.
How They Combine
Real protocols pair them. Asymmetric crypto safely exchanges a fresh symmetric key, then the fast symmetric cipher protects the actual traffic.
- Use symmetric ciphers for bulk data and storage.
- Use asymmetric keys to exchange secrets and verify identity.
- Never reuse one long lived symmetric key across many unrelated sessions.
Key idea
Symmetric encryption is fast but needs a shared secret, asymmetric encryption solves distribution but is slow, so combine them by exchanging a symmetric key with public key crypto.