How to understand symmetric vs asymmetric encryption

Short answer

Symmetric encryption uses one shared key and is fast. Asymmetric encryption uses a key pair (public and private) and enables secure key exchange and digital signatures.

Key differences

• Speed: Symmetric algorithms like AES are orders of magnitude faster than asymmetric algorithms like RSA.
• Key distribution: Symmetric requires a secure channel to share the key. Asymmetric allows public keys to be distributed openly.
• Use cases: Symmetric encrypts bulk data. Asymmetric encrypts small data like session keys and verifies identities via signatures.

When to use each

• Use symmetric encryption for file encryption, database encryption, and VPN tunnels after key establishment.
• Use asymmetric encryption for TLS handshakes, email encryption (PGP), and code signing.

Why it matters

Most secure protocols combine both. TLS uses asymmetric encryption to establish a session, then switches to symmetric encryption for the actual data transfer, balancing security and performance.