What is Cryptanalysis? (And How I started learning It for Free)

Last updated on November 23rd, 2025 at 12:57 pm

See, I’m going to level with you, I got into the realm of cryptanalysis because I just could not take my mind off of one thing How do hackers even crack encryption.

You read about information attacks every day. Secrecy files breaking open. Passwords stolen. However, no one takes the trouble to explain how it occurs. So I crawled down the rabbit hole, and this is what I saw.

Table of Contents

So… So What Is Cryptanalysis?

In the simplest terms this can be explained as cryptanalysis is the science of cracking the codes and cracking encryption without the key.

Imagine it in the following way, the cryptography creates the lock, and the cryptanalysis attempts to pick the lock. It is neither about making intuitive guesses nor about trying to decipher passwords using brute force (but that is one of the elements of it, too). It is all about searching vulnerabilities in the functioning of encryption and then capitalizing on the loopholes.

Cryptanalysts read encrypted data (ciphertext) and reconstruct its patterns, vulnerabilities, or implementation errors that they use to obtain the original message (plaintext). The real encryption key is recovered sometimes. In other occasions they only need some holes to render the system useless.

The crazy part? Hackers are not the only ones who can work in this field. Encryption requires cryptanalysis on the part of the security professionals to test whether encryption is effective. It is as though you employ a person to break into your house and find whether your locks are good.

Why I Got Interested (And Why You Can, as well)

Two things pulled me in:

To begin with, there is the emergence of quantum computers. I continued to read articles that they are going to crack existing encryption within the next 5-15 years. Governments are in the process of preparation. It is not a far off sci-fi danger, but it is coming at the moment.

Hackers of nation-states are allegedly gathering encrypted information currently with the hope that they will decrypt it in the future when quantum technology advances. Wild, right?

Second, AI disrupts the game. The machine learning tools have reached the point where it can crack the passwords in minutes with a success rate of 70 percent. Zero-day vulnerabilities are also being found using them faster than possible by a human-hosted researcher. The tools are becoming smarter and by not having a clue of how attacks could be done, you are already at the back.

I decided that since I am working in technology and/or am interested in web security then I at least should know how this stuff fails.

The Art of Learning Cryptanalysis (How to Learn) (actually).

The even better thing is that you do not have to have a degree or costly courses to begin. I was able to find a lot of free materials which are genuinely good.

Start With the Basics

When fresh, it is best to take a course in Cryptography with Dan Boneh at Stanford, which is offered online at University level: When you are a new person, the best thing to do is to take up University course in Cryptography with Dan Boneh at Stanford, which can be done online: It is free, non-timed and spans across the spectrum of stream ciphers all the way up to public-key encryption.

Contained in it, yes, there is math, but it is explained in an understandable way by Boneh. On this, I used several weekends, and was much more confident.

Another option with assignments and projects is a course on crypto on Coursera, version on July 27th, 2019. More than 536, 000 individuals are enrolled, hence it is not just you.

Get Your Hands Dirty

It is no more than halfway down to reading theory. You must get used to smashing things up.

Cryptohack.org is a game hack. It is a game based online which you can solve cryptography puzzles, writing real code and executing attacks. It is hacking practice like legal and educational. The difficulty increases with progress and there is a leaderboard in case you are competitive.

Next there is cryptopals.com, you can train on breaking actual crypto by going through eight sets of exercises. No theory fluff. Just: “Here’s a weak cipher. Break it.” I haven’t read these, but they are savage in the very best sense.

Tools You Should Know About

When you have the fundamentals, you are going to feel like trying out some real cryptanalysis tools. CrypTool is a free, open-source program that allows visualizing the operations of encryption types and practicing such attacks as frequency analysis. It works perfectly when one is a visual learner.

To crack passwords and do penetration testing, such tools as Hashcat or John the Ripper are regarded as industry standards. They are free of charge and frequently utilized by security experts.

What’s Next?

This is the point, cryptanalysis is not a small niche activity only. It’s a legit career path. The average pay of cryptanalysts is 117, 822 (government jobs 134, 998). The number of qualified people is in a huge deficit, so it is demanded.

Yet, regardless of whether you are pursuing a career or not, knowing how encryption is broken smartens you up on the topic of online security. You get to know which passwords really work. You will get to know why two-factor authentication is relevant. You will no longer place your confidence in applications that purport to use military-grade encryption and have no evidence.

I’m still learning. But the cool part? The sources exist, they are free and the society is open. Certainly, in case you are at all curious, then simply choose a course of study and begin. You might surprise yourself.

Rapid summary Cryptanalysis = cracking encryption. It is getting scarier with the use of quantum computers and AI. It is free to learn over Stanford in the course CryptoHack and Cryptopals. And, yea, it is fun to be into once you are into it.