Symmetric Key Cryptography
Symmetric key algorithms use the same key to encrypt (scramble the information into ciphertext) and decrypt (recover the plaintext from the ciphertext). There are many well-known algorithms, such as IDEA, AES, Serpent, Camellia and TwoFish. These are good at bulk encryption, but poor at key management (securely sharing keys between sender and recipient) and authentication (establishing someone’s identity). Modern symmetric key algorithms use keys from 128 to 256 bits in length.