Block ciphers are symmetric cryptographic algorithms. They are faster algorithms than public key cryptographic algorithms. It uses only one key, that is, the same key is used when encrypting a message or decrypting a ciphertext. However, for block ciphers, sender requires securely transferring the key to the receivers.

There are different types of symmetric key cryptography. It is mainly classified as block ciphers and stream cipher. A stream cipher generally adds the plaintext digits with a pseudorandom cipher stream that is called key stream.