Codebreaking has no single inventor and very few heroes who worked alone. These are the people whose methods are still in use — including several whose names were withheld for decades by the secrecy of the work.
Profiles§
- al-Kindi c. 801-873
Philosopher and polymath in Baghdad's House of Wisdom who wrote the first known text on breaking ciphers. Frequency analysis — the technique at the bottom of this solver's scoring — is his. - Leon Battista Alberti 1404-1472
Architect, and author of the first polyalphabetic cipher. Called the father of Western cryptography, largely for realising that one alphabet is never enough. - Charles Babbage 1791-1871
Broke the Vigenere cipher around 1854 and published nothing about it. His notebooks record the method that Kasiski printed nine years later. - Friedrich Kasiski 1805-1881
Prussian infantry officer whose 1863 book gave the first published break of polyalphabetic ciphers. He thought it had been ignored and moved on to archaeology. - Etienne Bazeries 1846-1931
French army cryptanalyst who spent three years breaking the Great Cipher of Louis XIV — a code of 587 numbers that had been unread for two centuries. - Georges Painvin 1886-1980
Broke ADFGVX in 1918 under conditions that wrecked his health. A geologist by training, drafted into codebreaking by circumstance. - William F. Friedman 1891-1969
Invented the index of coincidence and the vocabulary of the field. Led the team that broke Purple. The IC test in this solver is his. - Elizebeth Smith Friedman 1892-1980
Broke smuggling rings, then Nazi intelligence networks in South America, testifying in court about ciphers when no one else could. Her work was credited to others for most of her life. - Agnes Meyer Driscoll 1889-1971
'Miss Aggie' — broke Japanese naval codes across three decades, including the Red Book and the work underpinning JN-25, and taught most of the US Navy's cryptanalysts. - Marian Rejewski 1905-1980
Reconstructed Enigma's wiring from permutation theory in 1932. With Rozycki and Zygalski, gave the Allies a running start of seven years. - Alan Turing 1912-1954
Designed the bombe with Welchman, invented Banburismus, and formalised computation along the way. Prosecuted in 1952 for being gay; pardoned in 2013. - Gordon Welchman 1906-1985
The diagonal board — his contribution to the bombe — multiplied its power enormously. He also built the traffic-analysis system that made Bletchley an intelligence factory rather than a puzzle room. - Bill Tutte 1917-2002
Deduced the complete structure of the Lorenz cipher machine from intercepted ciphertext alone, having never seen one. A graph theorist by trade. - Tommy Flowers 1905-1998
Post Office engineer who built Colossus when his superiors doubted valves could be reliable at that scale. He paid for parts himself and was ordered to destroy the machines afterwards. - Joan Clarke 1917-1996
One of the few women to work as a cryptanalyst rather than an operator at Bletchley, in Hut 8 on naval Enigma, and repeatedly promoted into grades that had no name for a woman doing them. - Mavis Batey 1921-2013
Broke the Italian naval Enigma traffic before Cape Matapan and the Abwehr machine whose decrypts confirmed the D-Day deception was believed. - Genevieve Grotjan Feinstein 1913-2006
Spotted the correspondence that opened Purple in September 1940, after others had looked at the same sheets for months. - Eli Biham and Adi Shamir 1990
Published differential cryptanalysis, the first general statistical attack on modern block ciphers — and discovered DES had been designed to resist it sixteen years earlier. - Mitsuru Matsui 1993
Published linear cryptanalysis and used it for the first experimental break of full DES.
A note on credit§
The history of this field is unusually bad at attribution, and not by accident. Secrecy delayed recognition by decades (Bletchley), classification erased it entirely for a time (Cocks and public-key cryptography), and institutional habit reassigned it (Elizebeth Friedman's cases). Where the record is contested, the pages on this site say so rather than picking whichever version is tidier.
Next: the timeline or the ciphers themselves.
Frequently asked questions§
Who was the first cryptanalyst?
al-Kindi, around the ninth century, whose manuscript describes frequency analysis — the first systematic method for reading a cipher without the key.
Who broke Enigma?
Marian Rejewski reconstructed the machine in 1932; Rozycki and Zygalski built the Polish attacks; Turing and Welchman designed the bombe that scaled them. It was a relay, not a single sprint.
Who was Elizebeth Friedman?
A cryptanalyst who broke smuggling ciphers during Prohibition and later Nazi intelligence networks in South America. Much of her work was publicly credited to the FBI during her lifetime.
What did Bill Tutte do?
He reconstructed the entire logical structure of the Lorenz SZ40 cipher machine from intercepted ciphertext, without ever seeing the device — the work that led to Colossus.