Modern Symmetric Ciphers

At the outset, let’s have a general overview on the following figure, which shows the cryptography side; along with its types and sub-types.



Symmetric ciphers are known when the key is private from everyone, but the sender and the receiver (only known by the sender and the receiver). So, the key is kept secret only to the people who encrypt and decrypt the message. Therefore, it is known as a “private key” or “secret key”. Symmetric ciphers are old method of encryption and they are the most used ciphers. It can be divided into two main parts: Block ciphers and Stream ciphers.

Note: Plaintext = x, Ciphertext = y & key = k.


  • Stream ciphers:
    • This cipher encrypts bit by bit.
    • Since it encrypts bits individually, it is smaller and faster; and common in embedded devices.



  • Block ciphers:
    • encrypts a full block in one go (Several bits and usually 128).
    • It is bigger, but slower. However, it is common Internet applications.





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