What is Cryptography? - A Very Brief Explanation

The art of writing and solving codes

Okay , let's start with a simple example so that is's easy to understand. 

let's say you have a got a letter that you want to send to your friend. Let's pretend that your friend is very far from you and the message you want to send is very secret. You just can't send it around the world because there is going to be many people who will be handling your letter . So there is a risk that somewhere along the way the letter may be intercepted by untrusted person. And that person can read your secret information and pass the message to your friend and nobody knows he has your message. So , here one solution can be using cryptography so that no one on the middle uncover your secret information. 

So what is cryptography then ?

Well, the you send your message first then probably you might send in language that anyone can understand, say for example English, Spanish, Chinese and so on. So, when you send your message you need to encrypt your message. So, what does it mean to encrypt the message? 

Let's say you want to send the message "We are planning to comeback". This message is considered as plain text because anyone can read this message. So first you convert this message to numerical value according to the position of English alphabet. Then you add a key, for example 30, in your numerical value then you end up with another numerical value which is known as cipher text. So, if anyone somewhere on the way reads your message, what he gets is those numerical value known as cipher text. So he can't get what you want to say to your friend without a key. Once, your friend have your message he will then convert it into numerical value and we will need a decryption key to again convert it to plain text. Once, he converts it into plain text he can easily read your message. And, the key is something only you and your friend share in between. 

So , in this way, you can prevent your message from being stolen anywhere in the middle. There are different techniques of encryption and different tools for this purpose but the primary concern of cryptography is to make sure that our valuable information is secure. 

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