Cryptography: from its origins to the quantum era

Translated by Aurora Forlivesi

For centuries, communication has been a fundamental element of political authority and military command. Rulers relied on secure flows of information to govern territories and coordinate armed forces, while being fully aware that intercepted messages could provide strategic advantages to rival powers. Over time, states formalized these practices by establishing specialized cipher offices and cryptographic departments tasked with safeguarding sensitive communications, alongside cryptanalysis efforts aimed at breaking these systems. But how did cryptography originate? And how did it become one of the cornerstones of contemporary cybersecurity?

A brief history of cryptography

The term cryptography derives from the Greek words kryptós (hidden) and gráphein (to write) and refers to the practice of encoding information so that it is understandable only to authorized recipients. Since antiquity, various civilizations developed methods to protect communications. In ancient Rome, for example, Julius Caesar used a simple substitution system to send military messages to his generals. The so-called Caesar cipher consisted of shifting each letter of the alphabet by a certain number of positions: a relatively simple technique, yet sufficient to make the message unintelligible to anyone who did not know the transformation rule.

In the 9th century, the polymath Arab scholar Al-Kindi introduced frequency analysis, a groundbreaking discovery in cryptanalysis that marked one of the most important moments in the history of the field. His work demonstrated that encrypted texts could be systematically analyzed through the statistical distribution of letters, marking the beginning of a long intellectual challenge between those who create secret codes and those who attempt to break them.

The following centuries brought further innovations, particularly the development of polyalphabetic cryptographic systems. In 1466, Leon Battista Alberti invented one of the first polyalphabetic ciphers, based on two concentric disks that could be rotated to generate different substitution alphabets. This innovation made messages far more difficult to decipher using traditional methods. Later, in 1586, the Giovan Battista Bellaso–Blaise de Vigenère cipher refined the idea by introducing a repeating keyword that determined which alphabet would be used during encryption.

The Century of the Great Wars

Despite these developments, cryptography remained largely a manual practice until the 20th century. A turning point came during the major conflicts of the modern era. During World War I, mechanized cryptography began to play an increasingly important role in military communications. This technological shift culminated in the development of rotor-based cipher machines, such as the device by Edward Hebern and the Enigma machine by Arthur Scherbius.

The Enigma system was widely used by Germany during World War II and was considered extremely secure at the time. Allied cryptographers managed to break the Enigma code, a result that proved crucial to the war effort. Historians of cryptography often describe this moment as the transition from classical to modern cryptography. This shift was made possible by linking cryptographic practices to algorithmic computation and systematic analysis, laying the foundations for the digital security systems that would emerge in the decades following the war.

With the end of the conflict, cryptography did not remain exclusively a military technology. On the contrary, it gradually spread into governmental and civilian sectors. This transition marked the beginning of the institutionalization and standardization of cryptographic practices that still characterize digital security today.

The United States played a central role in this process, historically framing cryptography as a matter of national security. During the Cold War, cryptographic technologies were classified as munitions and subjected to strict export controls under the United States Munitions List. These restrictions limited the international distribution of advanced cryptographic technologies and reflected the belief that secure communications were a strategic capability comparable to military equipment.

These policies generated significant tensions between governments and the emerging technology industry. Companies wishing to sell software internationally were often required to develop less effective exportable versions of their cryptographic systems. While this allowed them to comply with export restrictions, it also had the unintended consequence of spreading vulnerabilities across global digital infrastructures.

The debate intensified in the early 1990s with the proposal of the so-called Clipper Chip, an encryption device designed by the United States government. The system included a built-in access mechanism that would have allowed authorities to decrypt communications when necessary. Critics argued that such mechanisms would weaken the overall security of digital systems and create risks for civil liberties and privacy. The proposal faced strong opposition from academics, technologists, and civil society organizations and was eventually withdrawn.

These controversies were followed by a gradual liberalization of cryptography policy. In 1987, the Computer Security Act assigned responsibility for civilian cryptography research to the National Institute of Standards and Technology (NIST), a federal agency responsible for developing technical standards for digital security. Over time, NIST has become the main body responsible for cryptography standardization in the United States and a global reference point for the development of secure algorithms

Cryptography nowadays 

Today, cryptography has become a fundamental component of digital infrastructures. Modern cryptography relies on mathematical algorithms and cryptographic keys that transform readable information into data unintelligible to anyone without the correct key. These mechanisms protect data stored on devices, transmitted across networks, and processed within digital systems. Consequently, cryptography now constitutes a central pillar of cybersecurity in both local infrastructures and cloud environments.

In recent decades, a new technological development has begun to redefine the debate on digital security: quantum computing. Once considered purely theoretical, quantum computers exploit quantum mechanical phenomena such as superposition and entanglement to perform certain calculations far more efficiently than classical computers.

Although large-scale quantum computers capable of performing these tasks do not yet exist, their potential implications are already shaping discussions about the future of digital security. The possibility that current cryptographic methods may one day become obsolete raises fundamental questions about how digital infrastructures should evolve to remain secure.

Conclusion

Cryptography has thus traveled a long historical path: from ancient methods of secret writing to the mathematical systems that underpin the digital world. What began as a tool for military secrecy has gradually become an essential component of everyday digital life, integrated into the infrastructures that support global communication, economic transactions, and public administration. With the continuous development of emerging technologies such as quantum computing, the challenge will not be merely technical but also political and organizational, requiring societies to rethink how security is maintained in an increasingly digital world.