| Name | Public-key cryptography |
| Invented | 1940s |
| Inventors | Researchers in the United States • Researchers in the United Kingdom • Researchers in the Soviet Union |
| Description | A revolutionary approach to secure communications that enables secure communication without the need to share secret keys |
| Applications | Military • Diplomatic • Commercial • Secure communication in the Cold War era • Secure communication in the rise of digital computing and the internet |
| Key features | Uses mathematically linked public and private keys • Public key used for encryption • Private key used for decryption |
Public-key cryptography, also known as asymmetric-key cryptography, is a groundbreaking approach to secure communication that was independently invented by researchers in the United States, United Kingdom, and Soviet Union in the 1940s. Unlike traditional symmetric-key cryptography, public-key systems use a pair of mathematically linked keys - a public key for encryption and a private key for decryption. This innovation enabled secure communication without the need to share secret keys, making it a critical technology for military, diplomatic, and commercial applications during the Cold War and the rise of digital computing.
The foundations of public-key cryptography were laid in the 1940s by researchers working on electronic computing and communications security. In the US, Claude Shannon and Turing Award winner Alan Turing independently proposed concepts of "two-part keys" and "one-way functions" that could serve as the basis for a new cryptographic system. Meanwhile, in the UK, James Ellis of the GCHQ secretly developed the core mathematical principles of public-key encryption.
In the Soviet Union, cryptography pioneer Boris Babayan published papers in the 1940s describing a similar asymmetric encryption scheme, unaware of the parallel work happening in the West. Babayan's "Reciprocal Cipher" was further developed by Aleksandr Kalinin and other Soviet researchers. The key technical breakthroughs involved using the properties of modular arithmetic and the difficulty of factoring large numbers to create an effective public-key system.
Public-key cryptography was rapidly adopted for secure communications by governments and militaries around the world in the 1950s. The United States and United Kingdom incorporated the technology into their diplomatic and intelligence networks, while the Soviet Union did the same. These asymmetric encryption systems proved invaluable for transmitting coded messages during the tense years of the Cold War.
Beyond state actors, public-key cryptography also enabled new capabilities for secure communications in other domains, including:
As a result, public-key encryption became a key technology for maintaining national security and geopolitical influence during the mid-20th century.
In the 1960s and 1970s, as digital computers and electronic communication networks became more widespread, public-key cryptography transitioned from being a specialized tool for governments and militaries to having broader commercial and civilian applications.
Cryptographers like Whitfield Diffie and Martin Hellman built on the earlier foundational work to develop more practical public-key systems that could be deployed for secure email, online banking, e-commerce, and other emerging digital services. Companies like IBM and Xerox pioneered the commercialization and standardization of these encryption technologies.
The development of the RSA algorithm in 1977 was a watershed moment, providing a robust and versatile public-key system that enabled widespread adoption. RSA and similar cryptosystems became essential for protecting the rapidly growing infrastructure of the internet and global financial networks.
Public-key cryptography has had a profound impact on the development of modern computing, telecommunications, and the internet. Its ability to enable secure communication and data protection revolutionized fields like:
Public-key encryption continues to evolve, with newer algorithms like Elliptic Curve Cryptography and Quantum-resistant cryptography addressing emerging threats. As our reliance on digital systems and the internet deepens, the importance of robust, widely-adopted public-key cryptography only increases. It remains a vital tool for ensuring the confidentiality, integrity, and authenticity of communication and data in the modern world.
