Update README.md

Author: harshildarji

README.md

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 ## Ciphers
 
 ### Caesar
-Add comments here
+![alt text][caesar]
+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.<br>
+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. <br>
+The method is named after **Julius Caesar**, who used it in his private correspondence.<br>
+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.
+###### Source: [Wikipedia](https://en.wikipedia.org/wiki/Caesar_cipher)
 
 [bubble-toptal]: https://www.toptal.com/developers/sorting-algorithms/bubble-sort
 [bubble-wiki]: https://en.wikipedia.org/wiki/Bubble_sort
@@ -103,3 +108,4 @@ Add comments here
 [selection-toptal]: https://www.toptal.com/developers/sorting-algorithms/selection-sort
 [selection-wiki]: https://en.wikipedia.org/wiki/Selection_sort
 [selection-image]: https://upload.wikimedia.org/wikipedia/commons/thumb/b/b0/Selection_sort_animation.gif/250px-Selection_sort_animation.gif "Selection Sort Sort"
+[caesar]: https://upload.wikimedia.org/wikipedia/commons/4/4a/Caesar_cipher_left_shift_of_3.svg