This block cipher supports 128-, 192-, or 256-bit keys. One of the most popular block ciphers is the Advanced Encryption Standard (AES). The second illustration shows the same secret key and symmetric algorithm being used to turn ciphertext back into plaintext. In the first illustration, a symmetric key and algorithm are used to convert a plaintext message into ciphertext. The following illustrations show how encryption and decryption work with symmetric keys and algorithms, assuming that all parties share the same key. Symmetric encryption requires that all intended message recipients have access to a shared key.
Symmetric-key cryptographic algorithms use the same cryptographic keys for both the encryption of the plaintext and the decryption of the ciphertext.
