### 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

### Sample input and output to check the program

You might also be interested in

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

### Infix to Prefix conversion using Stack

This post is about conversion of Infix expression to Prefix conversion. For this conversion we take help of stack data structure, we need to push and pop the operators in and out of the stack.

Infix expressions are the expressions that we normally use,eg. 5+6-7; a+b*c etc. Prefix expressions are the expressions in which the 2 operands are preceded by the operator eg. -+567 , +a*bc etc.

This method is very similar to the method that we used to convert Infix to Postfix but the only difference is that here we need to reverse the input string before conversion and then reverse the final output string before displaying it.

NOTE: This changes one thing that is instead of encountering the opening bracket we now first encounter the closing bracket and we make changes accordingly in our code.

So, to convert an infix expression to a prefix expression we follow the below steps
(we have 2 string, 1st is the input infix expression string 2nd is the output string which is empty initially)

We first revers…

Hashing is a technique used for storing , searching and removing elements in almost constant time. Hashing is done with help of a hash function that generates index for a given input, then this index can be used to search the elements, store an element, or remove that element from that index.

A hash function is a function that is used to map the data elements to their position in the data structure used. For example if we use an array to store the integer elements then the hash function will generate position for each element so that searching, storing and removing operation on the array can be done in constant time that is independent of the number of elements in the array. For better look at the example below.

now we face a problem if for 2 numbers same position is generated example consider elements 1 and 14

1 % 13 = 1

14 % 13 = 1

so when we get 1 we store it at the first position, but when we get 14 we see that the position 1 is already taken, this is a case of collision.

Inorder…