" Data format changed using a secret key and can be decrypted only with this secret key receiver must have the secret key for decrypt message. Symmetric Encryption. "
Symmetric encryption is the oldest and best-known technique. A secret key, which can be a number, a word, or just a string of random letters, is applied to the text of a message to change the content in a particular way. This might be as simple as shifting each letter by a number of places in the alphabet. As long as both sender and recipient know the secret key,
they can encrypt and decrypt all messages that use this key.