Cities That Kept and Broke Secrets — From Letter Frequencies to Public Keys
Twelve scenes connect letter frequencies in Baghdad, a rotating cipher disk in Rome, institutional diplomatic cryptanalysis in Venice, design principles in Paris, a telegraph device in New York, the Enigma networks of Warsaw and Bletchley Park, information theory at Bell Labs, classified work in Cheltenham, and public-key papers at Stanford and MIT. Cryptography changes from ever more elaborate letter substitution into layered problems of mathematics, machines, protocols, and key management.
Scene 1 of 12
c. 850
Baghdad
Language Leaves a Fingerprint inside a Secret — Al-Kindi and Frequency Analysis
A cryptanalytic treatise attributed to al-Kindi explains counting how often each letter appears in a long Arabic text and comparing that distribution with the most common symbols in a ciphertext to infer a monoalphabetic substitution. Replacing the same letter by the same sign hides words but preserves unequal repetition in language. The surviving manuscript is not an autograph, its exact room of composition cannot be fixed, and the work should not erase earlier secret-writing traditions as one solitary beginning of cryptography.
Replay on the map from scene 1Scene index