Cryptography is a method of protecting information by transforming it (encrypting it) into an unreadable format.

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Cryptography, a term derived from the Greek words 'kryptos' meaning 'hidden' and 'graphein' meaning 'to write', is a method of protecting information by transforming it (encrypting it) into an unreadable format. Only those who possess a special knowledge, typically referred to as a 'key', can decipher (or decrypt) the message into a readable format. This glossary entry will delve into the depths of cryptography, exploring its history, types, uses, and much more.

As a cornerstone of modern cybersecurity, cryptography plays a crucial role in securing data in transit and at rest. It is used in a myriad of applications, from securing your email to protecting your bank transactions. In this glossary entry, we will take a comprehensive look at the different aspects of cryptography, breaking down complex concepts into understandable pieces.

History of cryptography

The use of cryptography can be traced back to the time of the ancient Egyptians. Hieroglyphs, a form of picture writing, were often used to convey secret messages. However, it was the Greeks who are credited with the development of the first sophisticated cryptographic systems. One of the most famous is the Caesar Cipher, a substitution cipher where each letter in the plaintext is 'shifted' a certain number of places down the alphabet.

During the Middle Ages, cryptography became more complex with the introduction of polyalphabetic ciphers. In the 19th century, cryptography took a major leap forward with the invention of the telegraph and the subsequent need to secure the messages sent over this new communication medium. The 20th century saw the development of machine-assisted cryptography with devices like the German Enigma machine during World War II.

The caesar cipher

The Caesar Cipher, named after Julius Caesar who reportedly used it for his private correspondence, is one of the simplest and most widely known encryption techniques. It is a type of substitution cipher in which each letter in the plaintext is shifted a certain number of places down the alphabet. For example, with a shift of 1, A would be replaced by B, B would become C, and so on.

The method is named after Julius Caesar, who apparently used it to communicate with his generals. The Caesar Cipher offers very little communication security, and it can be easily broken with brute force attack or by using frequency analysis. However, it is a good example of how encryption can be used to secure communication.

The enigma machine

The Enigma machine is a cipher device used by the Germans during World War II to encrypt the messages of their military forces. It was a complex machine that used a series of rotating wheels to scramble plaintext messages into ciphertext.

The Enigma machine's complexity made it difficult to crack, but it was eventually broken by the Allies, a feat that played a crucial role in the outcome of the war. The breaking of the Enigma code is considered one of the greatest achievements in the history of cryptography.

Types of cryptography

There are three main types of cryptography: Symmetric-key cryptography, Asymmetric-key cryptography, and Hash functions. Each type has its own strengths and weaknesses and is used in different scenarios depending on the level of security required.

It's important to note that the strength of cryptographic security depends not only on the type of cryptography used but also on the length and complexity of the key. The longer and more complex the key, the harder it is for someone to crack the encryption.

Symmetric-key cryptography

Symmetric-key cryptography, also known as secret-key cryptography, involves the use of the same key for both encryption and decryption. The key is shared between two or more parties and is used to both encrypt the plaintext and to decrypt the ciphertext.

The main advantage of symmetric-key cryptography is that it is fast and efficient for large amounts of data. The disadvantage is that if the key is lost, the data is lost as well. Additionally, the key needs to be securely distributed to all parties, which can be a challenge.

Asymmetric-key cryptography

Asymmetric-key cryptography, also known as public-key cryptography, uses two different keys: a public key for encryption and a private key for decryption. The public key is freely distributed while the private key is kept secret.

The main advantage of asymmetric-key cryptography is that it eliminates the need to securely distribute keys, as the encryption key can be made public without compromising the security of the decryption key. The main disadvantage is that it is slower than symmetric-key cryptography and requires more computational resources.

Hash functions

Hash functions, also known as cryptographic hash functions, are a third type of cryptographic method. They take an input (or 'message') and return a fixed-size string of bytes, typically a 'digest' that is unique to each unique input. Hash functions are commonly used in various information security applications such as integrity checking, password storage, and digital signatures.

The main advantage of hash functions is that they are typically very fast and provide a quick way to check if two sets of data are the same (by comparing their hashes). However, they are not suitable for encrypting sensitive data as they do not provide a way to decrypt the data.

Applications of cryptography

Cryptography is used in a wide variety of applications to secure data and communications. Some of the most common applications include secure email, secure web browsing, secure network communications, and secure storage of data.

It's also used in digital signatures, which provide a way to verify the authenticity and integrity of data. For example, when you download a software update, a digital signature is used to verify that the update is authentic and hasn't been tampered with.

Secure email

Emails can be secured using cryptography to protect the content from being read by anyone other than the intended recipient. This is typically done using public-key cryptography, where the sender encrypts the email with the recipient's public key. Only the recipient, who has the corresponding private key, can then decrypt the email.

Secure email is important because email is often used to transmit sensitive information. Without encryption, emails can be easily intercepted and read by anyone who has access to the network.

Secure web browsing

When you browse the web, your connection to the website is often secured using cryptography. This is done using a protocol called HTTPS (Hyper Text Transfer Protocol Secure), which encrypts the data between your browser and the website.

This prevents anyone who might be eavesdropping on the network from seeing your data. It also provides assurance that you are communicating with the actual website and not a malicious impostor.


Cryptography is a complex and fascinating field that plays a crucial role in securing our digital world. From the simple Caesar cipher to the complex encryption algorithms used today, cryptography has a rich history and a wide range of applications.

As we move further into the digital age, the importance of cryptography is only set to increase. Whether it's securing our online communications, protecting our personal data, or verifying the authenticity of information, cryptography is a key tool in the cybersecurity toolbox.

This post has been updated on 17-11-2023 by Sofie Meyer.

Author Sofie Meyer

About the author

Sofie Meyer is a copywriter and phishing aficionado here at Moxso. She has a master´s degree in Danish and a great interest in cybercrime, which resulted in a master thesis project on phishing.

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