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Cryptography · Module 2 of 10

Symmetric encryption

Encrypt with one shared secret key.

📖 Key ideas

  1. Symmetric encryption uses the same key to encrypt and decrypt.
  2. AES is the standard (128, 192, 256-bit keys).
  3. Fast, suitable for large data.
  4. Challenge: sharing the key securely.
  5. Modes: GCM provides encryption plus integrity; avoid ECB.
💡 Real-life example: Symmetric encryption is a house key: everyone who should enter needs a copy of the same key.
Symmetric keySame key for both directions
AESAdvanced Encryption Standard
Block cipherEncrypts fixed-size blocks
GCMAuthenticated encryption mode