How did cryptography evolve from ancient codes to computers?

Cryptography spans thousands of years, evolving from classical pen-and-paper methods to mechanical rotor machines and modern computer algorithms. For centuries, secure communication was mostly restricted to governments, but inventions like public-key cryptography and public standards brought it into the public domain. This evolution has been closely tied to cryptanalysis, where breaking codes has frequently altered historical events.

What we know

• Cryptography began thousands of years ago, relying until recent decades on classical methods using pen, paper, or simple mechanical aids. [2]
• The invention of mechanical and electromechanical machines like the Enigma rotor machine provided more sophisticated encryption in the early 20th century. [2]
• The application of frequency analysis to encrypted communications has historically altered the course of events, such as when the Zimmermann Telegram triggered United States entry into World War I. [2]
• Until the 1960s, secure cryptography was largely restricted to governments before public standards and public-key cryptography moved it into the public domain. [2]
• Grille ciphers, an early technique involving a pierced sheet of paper or cardboard, were first described in 1526 by Jacopo Silvestri. [4]

Where to go next

• how it workedHow does the Enigma machine work?
• a case in pointWhat was the Zimmermann Telegram?
• the bigger pictureHow does public-key cryptography function?
• how we knowWhat is a grille cipher?
• what followedHow did codebreaking shorten World War II?
• an unexpected connectionWhy is secrecy considered essential in cryptography despite published books?Books on secret-keeping have been published despite the paradox that secrecy is fundamental to sending confidential messages.

Sources

• [1]history of cryptography (Wikidata Q467928) · CC0 1.0
• [2]History of cryptography · CC BY-SA 4.0
• [3]Cryptography · CC BY-SA 4.0
• [4]Grille (cryptography) · CC BY-SA 4.0
• [5]Bibliography of cryptography · CC BY-SA 4.0