Caeser Cipher – the Shift Cipher

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Network Security / e-Business Security


1. Introduction
2. History & Development
3. How It Works
4. C++ Source Code [Encryption]
5. C++ Source Code [Decryption]
6. Step By Step Explanation [Decryption]
7. Step By Step Explanation [Decryption]
8. Pros & Cons
9. Conclusion
10. Reference


In cryptography, a Caesar cipher, also known as Caesar's cipher, the shift cipher, Caesar's code or Caesar shift, is one of the simplest and most widely known encryption techniques. It is a type of substitution cipher in which each letter in the plaintext is replaced by a letter some fixed number of positions down the alphabet. For example, with a left shift of 3, D would be replaced by A, E would become B, and so on. The method is named after Julius Caesar, who used it in his private correspondence.

The encryption step performed by a Caesar cipher is often incorporated as part of more complex schemes, such as the Vigenère cipher, and still has modern application in the ROT13 system. As with all single alphabet substitution ciphers, the Caesar cipher is easily broken and in modern practice offers essentially no communication security.


The cipher was named after Julius Caesar. It was used during 50BC by notable Romans including Julius Caesar. In cryptography, the Caesar cipher is also known as Caesar’s shift or the Shirt Cipher. Julius Caesar used the Caesar cipher to communicate with his generals during military campaigns to protect and encrypt messages that were important to the military and the government.

The Caesar Cipher is a type of substitution cipher. Each letter in the plaintext is replaced by a letter some fixed number of positions further down the alphabet. The Caesar cipher is a “monoalphabetic substitution cipher”, meaning only one letter is assigned to the alphabet it is supposed to represent.

According to Suetonius, who wrote...
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