Nearly all of cryptography builds on two families of encryption that solve different problems — and modern systems use both together.
Symmetric — one shared key
The same secret key encrypts and decrypts. Fast and strong, but both parties must already share the key — and getting it to them securely is the hard part.
| Algorithm | AES (the standard) |
| Speed | Very fast |
| Problem | Key distribution |
Asymmetric — a key pair
Each party has a public key (shareable) and a private key (secret). What one encrypts, only the other decrypts.
encrypt with someone's PUBLIC key → only their PRIVATE key opens it (confidentiality)
sign with your PRIVATE key → anyone verifies with your PUBLIC key (authenticity)| Algorithms | RSA, Elliptic Curve (ECC) |
| Speed | Slow |
| Solves | Key distribution, signatures |
They work together
Asymmetric is slow, so real systems use it only to exchange a symmetric key, then switch to fast symmetric encryption for the data — exactly what happens in The TLS Handshake.
Symmetric is the fast workhorse; asymmetric is the clever handshake that lets strangers agree on a secret in the open.
Related: The TLS Handshake · Digital Signatures · Public Key Infrastructure