Caesar cipher

In cryptography, a Caesar cipher is an ancient form of substitution cipher. It is named in the honor of the Roman emperor, Julius Caesar.

 Method 
To encrypt a message with a Caesar cipher, each letter in the message is changed using a simple rule: shift by three. Each letter is replaced by the letter three letters later in the alphabet. A becomes D, B becomes E, and so on. For the last letters, we can think of the alphabet as a circle and "wrap around". W becomes Z, X becomes A, Y becomes B, and Z becomes C. To change a message back, each letter is replaced by the one three before it.

 Weakness 
However, it is very easy to break a Caesar cipher, even if you change the "key number" to a different number. Using a more modern form of encryption would be better.
240px|thumb|left|The Caesar cipher rule

Changing by three is the rule that the well known Julius Caesar used, but the same idea works for any number. ROT13 can be seen as a modern version of the Caesar cipher, with the same weaknesses.

The Caesar cipher is a substitution cipher: each letter is replaced by another. No substitution cipher is safe for sensitive information.

 References 

Category:Cryptography