10/14/2025

8 min read

Cryptography

Cryptography is a fundamental technique for securing digital information. It encompasses methods and algorithms for encrypting data, protecting confidential communications and transactions. This field of science is crucial for ensuring security and integrity in our increasingly digital world.

In this article, you will learn what cryptography is and get an overview of key events in its history. We will also explain how cryptographic encryption methods work, explore different techniques, and discuss the legal framework surrounding them.

Cryptography is the science of encrypting and decrypting information, ensuring the security of digital data and communication.
Historically, cryptography has evolved from simple manual methods, such as the Caesar cipher, to complex digital algorithms.
Modern cryptography includes various techniques, such as symmetric and asymmetric encryption, which meet different security requirements.
Cryptography plays a central role in securing blockchain technologies and cryptocurrencies, as it verifies the authenticity of transactions.

Definition: What is cryptography?

Put simply, cryptography is the science and technique of encrypting and decrypting information. The term comes from the Greek words kryptós (meaning "hidden") and graphein (meaning "to write"). According to its definition, the primary goal of cryptography is to ensure the confidentiality, integrity, and authenticity of data. This means that only authorised recipients can access and understand the relevant information. Through algorithmic encryption methods, data is transformed in such a way that it cannot be read without the correct key. This protects information from unauthorised access and tampering.

Cryptography is a subfield of cryptology. In addition to cryptography, cryptology also includes cryptanalysis, which focuses on deciphering encrypted messages. Cryptanalysis is considered the more challenging area. Another related field is steganography, which deals with the concealment of secret messages.

History of cryptography

The history of cryptography dates back centuries and arose from the need to protect information. Initially developed to encrypt military, diplomatic, or personal messages, cryptography has evolved over time from simple manual ciphers to complex digital algorithms. This historical progression highlights the ongoing battle between the development of new encryption methods and the efforts of cryptanalysts to break them. Several key historical examples demonstrate the significance of cryptography, particularly in politics.

Caesar cipher

The Caesar cipher is one of the earliest known encryption methods, named after Julius Caesar, who used it to protect his military communications. This technique involves replacing each letter in the plaintext with another letter a fixed number of places further down the alphabet. For example, with a shift of three, an "A" would become a "D". While this method was effective for its time, it is now considered one of the simplest forms of encryption. Cryptology experts can easily decrypt it using frequency analysis of letters.

The Babington Plot

One of the most significant historical events related to cryptography occurred in 1586: the Babington Plot. Led by Anthony Babington, a group of conspirators planned to assassinate Queen Elizabeth I and place Mary, Queen of Scots, on the English throne. The conspirators communicated using encrypted correspondence. However, Queen Elizabeth’s spies managed to decrypt their messages, leading to the plot’s failure and Mary Stuart’s execution. This event illustrates the crucial role cryptography and cryptanalysis have played in political and historical contexts.

The Enigma machine

The Enigma machine is a remarkable example of mechanical cryptography. Used by the Germans during the Second World War to encrypt military communications, the Enigma relied on a system of rotating discs to create an almost infinite number of encryption combinations. Initially, this made Enigma an extremely secure cryptographic system. However, a team led by British mathematician Alan Turing successfully deciphered the machine, giving the Allies a crucial advantage. This breakthrough is considered one of the key turning points of the war and highlights the profound impact cryptography and its decryption can have in modern warfare.

How does cryptography work?

Simply put, cryptography functions by encrypting data using specific encryption methods. Plaintext is transformed into encrypted text, which can only be read and understood by those with the correct key. This transformation is carried out using a cryptographic algorithm. There are two main types of encryption: symmetric encryption and asymmetric encryption. Both methods are designed to protect data from unauthorised access, whether during transmission or storage.

The encryption process begins with plaintext, which the user wants to transmit securely. Using an algorithm and a key, this text is converted into ciphertext. The key acts as a type of password, essential for both encryption and decryption. The strength of the encryption depends on the complexity of the algorithm and the length of the key.

What is cryptography used for?

Cryptography is primarily used to ensure the security and confidentiality of information. By allowing only authorised recipients to access data, it protects information both during transmission and in storage. Additionally, cryptography verifies the authenticity and integrity of messages, ensuring that any unauthorised changes can be detected.

Here are some key areas where cryptographic encryption is commonly used:

Secure communication – Protects information in digital communication processes, such as emails and messaging apps
Financial transaction security – Safeguards the transmission of sensitive financial data to prevent fraud and unauthorised access
Authentication and integrity verification – Ensures that messages or transactions have not been tampered with by verifying their identities
Protection of sensitive information – Used to secure classified data in government, military, and corporate environments
Cryptocurrency and blockchain applications – Ensures the security of transactions and the creation of cryptocurrencies within blockchain technology

Methods of cryptography

Cryptography employs various techniques to encrypt and ensure the integrity of data. The main methods include symmetric encryption (secret key encryption), asymmetric encryption (public key encryption), and hash functions. Regardless of the method used, the security of encryption depends on the complexity of the algorithm and the length of the key. Each technique is suited to specific applications and offers advantages for different security requirements.

Secret key encryption

Secret key encryption, also known as symmetric encryption, uses the same key for both encrypting and decrypting data. Whether sender or recipient, all parties involved must have access to the same key. Therefore, this method requires a secure way to share the key between communicating parties. Symmetric encryption is often preferred for transmitting large volumes of data because it is less computationally intensive than asymmetric methods. Well-known examples of symmetric encryption include Advanced Encryption Standard (AES) and Data Encryption Standard (DES).

Public key encryption

Unlike symmetric encryption, public key encryption, also known as asymmetric encryption, uses two different keys: a public key for encryption and a private key for decryption. This means that anyone with the public key can encrypt a message, but only the owner of the private key can decrypt it. Since only the private key holder can access the original data, this cryptographic method is particularly useful for secure communication over untrusted networks. A widely used algorithm based on asymmetric encryption is RSA (Rivest-Shamir-Adleman).

Hash functions

Hash functions are another essential tool in cryptography. They convert any amount of data into a fixed-length bit string, known as a hash value. These functions are designed to always produce the same hash value for a given input. However, it is practically impossible to reverse the process and reconstruct the original input from the hash value.

Hash functions play a crucial role in ensuring data integrity, as even the slightest change to the input data results in a completely different hash value.

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Legal restrictions on cryptography

Cryptography is subject to a wide range of legal restrictions worldwide, which influence its use. These laws often reflect the ongoing tension between the need for security and privacy on one hand and national security interests and legal surveillance requirements on the other.

In many countries, including the United States, the export of encryption technologies requires government approval, as these tools can be classified as strategic assets. While this is intended to prevent misuse, it can also restrict the international trade of security technologies. Some countries, such as Australia and the United Kingdom, grant authorities the power to compel companies to provide decryption keys or introduce software backdoors. These measures, designed to facilitate access to encrypted data, are highly controversial, as they may undermine the security and privacy of all users.

Efforts are also being made to establish international cryptographic standards to ensure consistency across borders. However, these initiatives often come into conflict with national regulations.

Cryptography and its role in the crypto world

Cryptography is an essential component of the cryptocurrency industry, playing a central role in securing and enabling blockchain technologies. The cryptographic algorithms and encryption methods used ensure that transactions are secure and tamper-proof. They also make any changes to the blockchain detectable and transparent.

Additionally, digital signatures, created using public or private keys, authenticate transactions and reinforce trust in the entire cryptocurrency infrastructure.

By ensuring security, integrity, and transparency, cryptography forms the foundation of the crypto world. It enables the reliable operation of cryptocurrencies and is one of the key pillars supporting the widespread adoption and use of digital currencies.