Symmetric encryption
Encryption using same key for both encryption and decryption. Fast and efficient for bulk data. Requires secure key distribution.
Formula
C = E(K, P); P = D(K, C)
Real World
WhatsApp uses AES-256 symmetric encryption to scramble each message on your phone before sending it, so even WhatsApp's own servers cannot read the content — only the recipient's device, which holds the same key, can decrypt it.
Exam Focus
State that the same key encrypts and decrypts, and always name the key-distribution problem as the main drawback.
How well did you know this?