Symmetric Encryption uses the same key for both encryption and decryption. Both parties must possess the shared secret key before communicating securely. Symmetric algorithms are fast and efficient, making them suitable for encrypting large amounts of data. The challenge is securely distributing keys to all parties who need them.
Common symmetric algorithms include AES (current standard, 128/192/256-bit keys), 3DES (legacy, being phased out), and ChaCha20 (modern stream cipher). Modes of operation like CBC, GCM, and CTR determine how algorithms process data blocks.
CISSP Relevance
Domain 3 (Security Architecture and Engineering) covers symmetric cryptography in depth. Know major algorithms, key lengths, modes of operation, and when symmetric encryption is appropriate. Understand the key distribution problem that asymmetric cryptography solves, and how hybrid systems combine both approaches.
AES standards are defined in FIPS 197 Advanced Encryption Standard.
Related terms: Asymmetric Encryption, Encryption