Introduction to Cryptography

ACM Roorkee
5 min readMar 25, 2020


From ancient times, the transfer of the information from one place to another securely was a great challenge. Cryptography is not a new term. The concepts of cryptography had also been used earlier for the secret conversation. These days the use of cryptography has been expanded. It is used for online shopping, cryptocurrency and many more. The knowledge of cryptography will help you to see all the activities done on the internet from a very different perspective than the others. Many people are interested in learning about cryptography but to find the right resource is a problem. I promise reading this blog will help you guys to tackle some of these problems.

What is Cryptography

Cryptography is the practice and study of secure communication between the two parties in the presence of the third one. But in modern cryptography, we will have mostly the intersection of mathematics and computer science. Before we understand it properly, we need to get familiar with some of the basic terminology used in cryptography very often.

  • Plaintext:- The information which the sender wants to protect from the third party.
  • Ciphertext:- The unintelligible text(impossible to understand) converted from the plaintext.
  • Encryption:- The process of conversion of plaintext into ciphertext using the key.
  • Decryption:- The process of reverting back the plaintext from the ciphertext using the key.
  • Key:- It is a variable that is applied using an algorithm to convert the plaintext into the ciphertext or the vice-versa.
  • Algorithm:- In cryptography, the algorithm is also called a cipher. An algorithm is a series of well-defined steps used for the encryption and the decryption.

There are many more terms you will face as you read more about cryptography. But these terms will help you understand the following simple example in cryptography.

Suppose you are playing an online game and you are hiding in a house. You want help but you can’t risk disclosing your position. In this situation, you can use the concept of cryptography. You and your friend have discussed that you guys are going to use Caesar Cipher and the Key will be 2.

Caesar Cipher:- An algorithm in which we shift each alphabet in the right direction with the value of the key.

So here the Plaintext will be “HOUSE” and the ciphertext will become “JQWUG”.

First, you need to encrypt the information “HOUSE” using the key=2 and deliver it to your friend. Then your friend will decrypt it using the key to get your message that you are in the house. All the other participants will also hear you saying “JQWUG” but none of them will understand it except your friend, and hurrah you will be saved.

The above example is a simple one to get a glimpse of how the cryptography works.

There are two words “Cryptology” and “Cryptanalysis” which sound similar to cryptography but they are different in meaning. Both Cryptography and Cryptanalysis are the branch of Cryptology. In Cryptanalysis, we study about breaking the ciphertext without having any knowledge about the plaintext, algorithm, and the key.

Why study Cryptography?

I think the best answer to this question is to give yourself a chance to explore all the different fields in Computer Science. Firstly, I started studying cryptography just to know about it like many of you. But when I started to spend time exploring it, I started to love it. Learning Cryptography is just like playing with mathematics. I used to like maths very much while my secondary education and studying cryptography give me the same thrill experience which I used to get while solving the maths problem during jee preparation. It covers a vast portion of probability and statistics. Apart from mathematics, studying cryptography will help you to realize that cryptography is used everywhere in our day to day lives, starting from your conversation in WhatsApp to the transfer of money from your bank accounts.

While using online banking all of us must have come across the word “OTP”. Many of you want to know about it and why it is called one time password. All these mysteries will start to get resolved when you start exploring it.

Many of you must have heard the word “Hacking”. I just can’t explain but listening to this term for the first time, I got the goosebumps. And while exploring about hacking I came to know that the root of it also lies in cryptography. So, my advice to all the great hackers which our country is going to get in the near future to give some of your thoughts to explore the world of cryptography.

There are many benefits of being updated with current affairs one of them being the Cryptocurrencies and what is going on with them. Being an Inflammable topic these days, everyone wants to know about its stock market. But being a computer science student, you just don’t want to know about the stock price but you are also curious to understand its functioning. I can proudly say that the backbone of the cryptocurrencies is cryptography. The concept of cryptography is used to make the transaction in it.

Resources to start with

It is easy to find various results on the internet for any question you have. But to get the answer which should be best for you is time-consuming. Here I am going to help you to get the good resources to initiate your journey in the world of cryptography in a stable manner. First of all, you should start your journey with the online tutorial on cryptography by Dan Boneh on Coursera. The link is given below:-

This course is very handful and it explains all the topics of cryptography in a simple and easy manner.

Along with this video tutorial, one should start to read an e-book “Handbook of Applied Cryptography” which will explain each topic in many details but it requires patience reading. The link of a book is given below:-

These two materials will be enough for someone to explore cryptography and develop its taste. When you do more research on it you will start to find more and more useful materials to study.

Scope in Cryptography

There are lots of research going on in the field of cryptography. Different professors in our country as well as outside are doing research. Many companies also hire cryptographers to secure their data from the data breach.

They also play an important role in the defense of the country. Many of you may apply for a research internship with various professors and get a chance to work with great minds in this field. There are many more opportunities in this field which you might explore by yourself.

I hope that after reading this blog, many of your doubts have been cleared in the field of cryptography. If you still have some doubts feel free to contact me.

Keep Exploring and Stay Curious

Written by Prateek Roushan.



ACM Roorkee

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