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Data encryption using Caesar Cipher

In this post we will discuss what is cryptography and how can we encrypt our files using Caesar Cipher. First Things first let us first understand the what is cryptography, according to wikipedia,

"Cryptography is the practice and study of techniques for secure communication in the presence of third parties called adversaries"

Simply stated it is passing messages between 2 user using a channel that is not secure yet the intruders trying to get steal information will not be able to understand messages directly as the messages are encrypted.

In order to encrypt a message, we change the contents of message such that only the intended receiver of the message is able to decode it. Let us now discuss Caesar Cipher, sometime also called as shift cipher is a ciphering technique that is one of the most simple and widely known techniques of encryption. This technique uses a substitution technique in which for each letter in our message we have a letter that substitutes it. In Caesar Cipher we use a shift value to decide the substitution value. 
For example if our shift value is 3 then we replace each letter in our message with the letter that is three places to the right of it in alphabetical order.

So for shift value of 3 we have,
Plaintext :       ABCDEFGHIJKLMNOPQRSTUVWXYZ 
Ciphertext :     DEFGHIJKLMNOPQRSTUVWXYZABC

Hence every 'a' in our message is replaced by 'd' if the shift value is 3.

consider, Plaintext :  "HELLO, WELCOME TO MY BLOG" will be changed to 
             Ciphertext: "KHOOR, ZHOFRPH WR PB EORJ"


In the above sentence is completely changed and most people won't guess it, but still it is known that caesar cipher encryption can be broken easily as there are only 26 shift values to try and also simple analysis of letter occurrences can give up the shift value, so lets make it a bit complex.

For my code, along with the letters I also chose to encrypt spaces, punctuation's and numbers. this increases the size of the key space hence makes it a bit complex and secure.

The following is my keyspace,
"0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ!"#$%&'( )*+,-./"

The above key space includes almost all the printable characters. 

Lets get to the coding part, first I created a string that contained the above characters, then I have created a function that accepts a string and a shift value to encrypt the string, then iterating over each character we simple replace it with the character with it's substitution character.
I have also made a function the receives the path of a file and stores the encrypted file on the desktop, you can change the destination path to wherever you want.

The following is the code for Caesar cipher encryption in c++, Python and Java 


C++ Program

Sample input and output to check the program


You might also be interested in 

LCM of 2 numbersAnagram Strings
Double Linked List
Finding Middle node in a Linked List
Infix to Prefix Conversion
Infix to Postfix Conversion
Binary Search Tree

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