How to Learn Cryptography and Discover the Key to Secure Communication

One cryptography course might be all it takes to convince you that cryptography is as cool as it sounds. Perhaps it was the word crypt that reeled you in, or maybe you think that learning about secret keys, hidden messages, and encryption algorithms will help you find a career pathway for your problem-solving skills. Whatever the case, we’re here to help.

Whether or not you believe you can succeed in computer science, learning cryptography doesn’t have to be scary. In this guide, we’ll look at the field from all angles, help you chart a personal course for acquiring the knowledge, and point you towards some awesome courses and resources that just might hold the key to your future. 

What Is Cryptography?

Cryptography is the art of creating codes for sharing valuable information with desired parties while eluding undesired parties. From a Greek root that roughly means hidden writing, cryptography has been practiced continuously since antiquity. Its modern form has developed in tandem with advances in math and computer science.

Cryptography and its sister field of cryptanalysis are two sides of the same coin. While cryptographers work with ciphers and algorithms to convert the plain text of something into ciphertext, a process known as encryption, cryptanalysts study the process of converting ciphertext back to plain text, called decryption. Cryptology is the parent field of both. 

What Is Cryptography Used For?

Whenever people, organizations, and businesses need to keep their information safe from malicious attacks, cryptography is one of the first tools they use. In the age of the Internet especially, digital messages sent on the information superhighway are vulnerable to hackers, who can steal the highly precious cargo of valuable data without ever breaking a sweat.

As the data that makes up our lives shifts ever more online, so the data security applications of cryptography continue to grow. Below are four major ways that cryptography helps keep us and our data secure in the modern world. 

• Secure communication. For Julius Caesar, it was physical letters carrying military strategy between him and his generals. For us, it’s end-to-end encrypted WhatsApp messages containing sensitive information. That, or emails containing state secrets. 
• Information security. This is a massive area of interest for modern cryptographers, covering both data security and data storage. Encryption techniques deployed to protect data must ensure confidentiality, integrity, and availability. 
• eCommerce. Not too long ago, public intellectuals were betting against the Internet, arguing that transferring money over the web would never be secure. Well, look at us now. The big encryption breakthrough was SSL, and the rest is history. 
• Digital signatures. This encryption technology forms the backbone of identity authentication for some of the most valuable kinds of digital information. Parties to an official document can now set terms from afar without fear of fraud. 

Types of Cryptography

To list every form of secret writing ever conceived is a daunting task. Luckily for me, other websites have already done the brilliant work of compiling the classical ciphers and the modern cryptographic algorithms all in one place, so I don’t have to. 

Students of the modern version will be relieved to know that computer science has managed to organize almost all of these ciphers and algorithms into three major types. These are secret-key cryptography, public-key cryptography, and one-way cryptography. 

Secret-Key Cryptography

Also known as symmetric-key cryptography or simply symmetric cryptography, this type involves an encrypted message shared between two parties and a single key that both sender and receiver have access to. Thus, the sender scrambles her message using the same key to encrypt that the receiver on the other end will eventually use for decryption. 

One huge limitation of using one key for both encryption and decryption is that, if the two parties are reduced to communicating in secret, they would at some point have had to figure out a secure way to exchange the key. Any key forced to pass through the same transit route as the message is equally vulnerable to exposure. 

Public-Key Cryptography

Public-key cryptography circumvents the key exchange problem with the addition of a second key. Because different keys are used for encryption and decryption, this type is also called asymmetric cryptography. Another way to understand the asymmetry is that one key is kept private and the other key is public but can afford to be exposed.

Each person in the network has a public and private key, the former for encryption and the latter for decryption. You open a line of communication with someone by sending them your public key, which they can use whenever they want to send you an encrypted message. If someone steals the message, it won’t matter, because only your private key can decrypt it. 

One-Way Cryptography

The most common form of one-way cryptography is a hash function. Once encrypted, a one-way cryptographic message is virtually impossible to decrypt. At first glance, this would seem to be of limited value, but it is more useful than you might imagine.

A hash function leaves behind a digital trace, which can keep passwords safe and ensure data integrity. If a company uses a hashing algorithm to store all its passwords in scrambled form, they will be useless to any hacker who manages to penetrate a system. And a hacker can’t manipulate someone’s data in transit if there’s a hashed record of it somewhere. 

Learning Cryptography

When some people first learn what cryptography is, their mind immediately jumps to secret societies, impenetrable passwords, and arcane knowledge. But in reality, the field is much less exotic and much more hospitable than the name and subject matter imply.

As far as STEM fields go, cryptography is actually pretty tame. Still not sure you buy that? Let’s take a step back and examine, piece by piece, what it takes to learn cryptography. 

How Long Does It Take to Learn Cryptography?

Solving puzzles takes time. That’s even more true when the puzzle you’re trying to solve is how to create puzzles. But thanks to the elegance of the ciphers and encryption techniques already in circulation, you have plenty of models to help you speed up the process. 

Furthermore, because cryptographers understand that information security is one of the most pressing issues facing humanity in the 21st century, they tend to publish their findings at low cost to readers and students. You don’t have to waste precious resources enrolling in degree programs or buying expensive books to learn cryptography.

With an array of analytical skills and a will to learn coding, you can pick up both the science and the art of cryptography in less than two years. To grasp advanced topics in quantum and post-quantum cryptography, you’ll probably want to tack on however many years it takes to learn quantum computing.

How to Learn Cryptography: A Step-by-Step Guide

No matter how steep your learning curve, the path to becoming an expert in cryptography consists of four unskippable steps.

1. Dust off your high-school level math. You read that right. Chances are you’ve already studied all the math you need to learn cryptography. The field mostly leans on basic algebra, with added support from prime numbers and probability theory.
2. Study the obstacles to secure communication and the encryption methods used to overcome them. Cryptography courses usually begin with a set of thought experiments featuring an encrypted message and two parties, a sender and receiver. For any given message, cryptographers need to analyze the communication situation and determine which symmetric or asymmetric encryption technique will most efficiently fulfill the minimum requirements for information security.
3. Learn how to code and pick a programming language. Because modern cryptography is a subfield of computer science, you need to know your way around computers. If you’re new to programming, try Python. Not only is it easy to learn, but coding beginners often turn to cryptography for Python project ideas. 
4. Start applying cryptographic algorithms to your desired use case. Whatever you want to secure, you’re now ready to begin generating and implementing symmetric keys using algorithms like the Advanced Encryption Standard (AES) or Blowfish, or playing around with asymmetric keys using the RSA algorithm. 

The Best Cryptography Courses and Training

The best way to streamline your learning process is to take a cryptography course. Despite its ancient origins and obvious benefits to society, the modern field of cryptography largely operates outside of formal institutional structures. Computer science departments do sometimes wade into cryptography, but the most consistent training is found online.

This means that a high-quality education in cryptography is just a few clicks away. Whether you’re starting at a beginning, intermediate, or advanced level, you can find the right combination of cryptography courses to unlock your learning potential. 

The Best Live or In-Person Cryptography Courses

Though less common since the onset of the COVID-19 pandemic, live cryptography courses still offer students the best opportunity to stamp this increasingly prized skill set on their résumés in the form of certification. The two courses featured below, while not for the faint of heart, will put you on an accelerated track to learn cryptography. 

TrainACE 

• Name: Certified Encryption Specialist Training 
• Location: Ashburn, VA or Greenbelt, MD 
• Time: 3 days, dates TBA
• Prerequisites: Background in computer science 
• Cost: $1,995

This crash course is geared toward preparing you to ace the ECES exam and become a Certified Encryption Specialist, one of the many certifications that EC-Council offers. Short for International Council of E-Commerce Consultants, EC-Council is an organization that trains cryptographers to fend off the next big threat to global cyber security.

Even if you have no ambition to save the world, certification is an efficient way to learn all the encryption techniques favored by professional cryptographers. This course drills down on the Data Encryption Standard (DES) and the Advanced Encryption Standard (AES), as well as asymmetric key standards like RSA.

But more than just a glorified cramming session, the training funnels all this knowledge into a practical project. At the end of day three, you will use everything you have learned about protecting data and information to set up your own virtual private network (VPN). 

Edureka!

• Name: Cyber Security Certification Course 
• Location: Virtual classroom 
• Dates: 4 weekends starting January 8
• Prerequisites: None
• Cost: $260 

Edureka’s certification course is a blunter training tool than its EC-Council counterpart, which you can tell by its substantially lower price. As the title of the course suggests, moreover, it is also less focused. In addition to the basic tenets of cryptography, it covers other subtopics in cyber security, including ethical hacking, vulnerability analysis, and session hijacking. 

If you’re considering trying to become a cyber security engineer, then this may be just what you’re after. Even if it’s not, the cryptography module could still be worth the price of admission. There you’ll get a rundown of every type of cryptography, including hash functions, and learn the ins and outs of digital signatures. 

The Best Online Cryptography Courses

Asynchronous online courses are the sweet spot of 21st-century education in cryptography. This is mainly because instructors have figured out an ideal balance of lessons and labs, which can be designed in advance and delivered remotely. Live meetings are not nearly as valuable as well-crafted tutorials and well-constructed practice problems.

The two online courses we’ve chosen for you are affordable and popular. Add one or both to your study plan and you’ll be generating cryptographic algorithms in no time. 

Stanford University (Coursera)

• Name: Cryptography I
• Time: 7 weeks
• Prerequisites: None 
• Cost: $79 with certificate

This course was created by Stanford Professor Dan Boneh, who literally wrote the book on applied cryptography. Okay, he wrote one of many influential books on the subject, but unlike the others, Boneh’s is free. The point is that Boneh, one of the most decorated scholars of cryptography, is quite generous with his knowledge.

Although you can access the course materials for free, $79 pays for the privilege to earn an official certificate of completion, which you can get by completing all of the assignments and passing the final exam. Boneh moves quickly and covers a lot of ground, but his engaging teaching style will elucidate all the tricky parts of secret-key and public-key cryptography. 

Udemy 

• Name: Master Modern Security and Cryptography by Coding in Python
• Time: 7.5 hours of self-paced learning 
• Prerequisites: Basic Python understanding and basic math
• Cost: Price varies

You can’t do much with cryptography unless you know how to code. The sooner you learn Python, the sooner you’ll be ready to speed through Rune Thomsen’s masterclass in using Python to implement strong ciphers and avoid weak ones.

While the meat of Thomsen’s course is its dozens of hands-on exercises, you won’t miss out on the larger conceptual framework. He contextualizes every encryption technique in terms of its real-world function, opening your eyes to a wider world of secure communication than you ever knew existed. 

The Best Free Cryptography Courses

A surprising number of cryptography instructors offer their online course materials free of charge. They usually come with some sort of catch, but don’t let that stop you from taking advantage. You can cobble together a solid training regimen with just the two classes below. 

Khan Academy 

• Name: Computer Science: Cryptography
• Time: Self-paced and on-demand 
• Prerequisites: None
• Cost: FREE

Part of Khan Academy’s three-part course on computer science, this unit explores the wonders of ancient and modern cryptography with an alternating series of video lessons and interactive challenges. The biggest wonder of all, perhaps, is that none of it costs a thing.

Come for content about Julius Caesar and other pioneers of the cryptographic art, but stay for the detailed tutorials about why some situations require public and private keys. There are also helpful appendices on modular arithmetic, prime numbers, and probability, the three areas of mathematics that aspiring cryptographers should study. 

Udacity 

• Name: Applied Cryptography
• Time: About 2 months 
• Prerequisites: Intro to Programming
• Cost: FREE

You wouldn’t necessarily expect to find a course on Applied Cryptography for free, but it’s deals like this that help to explain why Udacity earns such rave reviews. Categorized as advanced, this particular course contributes to Udacity’s larger strategy to draw customers toward its nanodegree programs, in this case, the Intro to Programming series.

But there are also plenty of ways to learn how to code for free, so don’t let the suggested prerequisites deter you from signing up. Just be aware that this course only spends two of its seven lessons on predigital ciphers and symmetric-key cryptography. The last five units focus on theoretical and applied topics in asymmetric encryption. 

The Best Cryptography Books

Cryptography courses are not the only way to learn cryptography. Because so much of modern life depends on cryptography, because the history of encryption and decryption is so compelling, and because the math behind computer science is relatively simple to explain in written form, the market for books on cryptography is teeming with great reads.

There are many in-depth and technical treatments of the subject available for free online, such as Gary Kessler’s landmark overview. In this section, we’ll focus instead on a complimentary pair of books written for a broader audience, which do an excellent job of explaining cryptography and assessing its impact. 

The Code Book: The Science of Secrecy from Ancient Egypt to Quantum Cryptography, By Simon Singh

Author Simon Singh, perhaps best known for his role in popularizing one of the most legendary puzzles in mathematics, brings his knack for storytelling to this epic history of cryptography. Over the span of 432 gripping pages, The Code Book draws a straight line from the origins of secure communication to its modern, more sophisticated equivalents.

Though what Singh calls the science of secrecy is almost as old as language itself, he devotes more than half the book to the period since the Second World War, during which time encryption techniques have really blossomed. So if you’re only interested in computer science and data security, feel free to skip ahead to the last three chapters.

The Mathematics of Secrets: Cryptography from Caesar Ciphers to Digital Encryption, By Joshua Holden

Readers should consider Joshua Holden’s The Mathematics of Secrets as The Code Book’s more technical cousin, with detailed mathematical explanations of each cipher layered onto the historical account. But far from trying to scare you with the math bogeyman, Holden insists that the math necessary to learn cryptography is easy for beginners to grasp.

Sure, cryptography has grown more complicated over the years, but that’s what makes Holden’s chronological method so satisfying. By starting with Julius Caesar’s simple cipher, proceeding methodically through each innovation, and finally exploring the quantum and post-quantum future of cryptography, it feels like you’re completing an exciting quest. 

The Best Online Cryptography Resources

Cryptographers often refer to their field as both a science and an art. Now, any of the cryptography courses or books listed above will give you a solid baseline knowledge of the science. To take the next step, you’ll want to not only stay abreast of recent advances on the science side but also practice the art of cryptography on a regular basis.

With that in mind, you should reserve a bookmark on your browser and space in your schedule for each of the following resources. Your grasp of cryptography will be all the more well-rounded for having done so. 

Schneier on Security: Crypto-Gram Newsletter

For the past thirty years, Bruce Schneier has contributed his valuable perspective to the newest breakthroughs in encryption algorithms, the field’s public policy implications, and the constant tension between information technology and the right to privacy. Knowing his take on a given issue has become something of a rite of passage for aspiring cryptographers. 

By subscribing to his Crypto-Gram Newsletter, you can have his latest thoughts delivered straight to your inbox. Or, if you prefer to keep your engagement tethered to the domain of computer science, just use the search function on his main blog to explore the archive of essays and blog posts he’s written about topics in applied cryptography. 

CryptoLab

The website doesn’t look like much, but that’s okay because you don’t have to know anything about UX/UI design to become a cryptographer. And while CryptoLab is light on frills, it is heavy on ways to test your skill at converting any plain text to ciphertext.

Most pages on CryptoLab have two tabs, one for explaining a given encryption technique and a second for the tool itself. Work your way through predigital methods like the Caesar cipher and Morse code, move on to the stream ciphers and block ciphers used in symmetric key cryptography, and then finish with three tutorials on public keys and hashes. 

Should You Study Cryptography?

Some folks might decide to learn cryptography based on the coolness factor alone. Others might be hard-pressed to believe that a slate of cool courses will necessarily translate to a cool career. The most important thing is that you understand what’s at stake in the decision. 

The fact remains that we’re living in an era of data security. If you ever feel the urge to become an information security analyst, or if you’re ever faced with a challenging set of cyber security interview questions, a deep knowledge of cryptography will definitely be of service to you. 

But no matter your career path, it’s up to you to decipher your future.