One of the symmetric ciphers I will be explaining now is Blowfish. Blowfish is a technique for securing information-when readable data is transformed to scrambled code that only a person with the secret key can unlock. Suppose you have a notebook into which you write messages, but prior to sending it to your friend, you use a special pen that jumbles the letters in a very special way. Only your friend, having the same pen or knowing the secret method, is able to read the message.

Blowfish works such that it takes small portions of your message and mixes them through a series of steps using the secret key. If somebody intercepts the message without the key, it just seems to be random letters and numbers. Blowfish is fast and flexible; hence, it has found applications in the protection of files, emails, and even some kinds of internet connections. What happens is that one secret code locks and unlocks the information, and both sender and receiver need to know it. That makes Blowfish a very good example of a symmetric cipher when it comes to everyday digital security.