Cryptography Across 1500 Years

From Caesar's shift cipher through Al-Khwarizmi, Vigenère, Shannon, RSA, and quantum algorithms — a journey showing that secrecy is exactly the question of which mathematics is hard.

About 30 min·6 nodes

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The path across the map

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STEP 1 · Mathematician~825Baghdad· Main activity

Al-Khwarizmi

A Persian mathematician-astronomer at Baghdad's House of Wisdom (Bayt al-Hikma). His c. 820 Al-Kitāb al-Mukhtaṣar fī Ḥisāb al-Jabr wa-l-Muqābala (the Compendious Book on Calculation by Completion and Balancing) created a new mathematics for handling unknowns systematically — algebra. His Latinized name, Algorithmi, became our word algorithm.

↓980-year span

STEP 2 · Concept1801Göttingen· Publication

Modular Arithmetic

The arithmetic of clocks — wrapping around at a modulus. The basic language of number theory and cryptography.

↓150-year span

STEP 3 · Mathematician1948Bell Labs· Teaching and work

Claude Shannon

A mathematician and engineer whose 1937 thesis applied Boolean algebra to relay switching circuits. His 1948 paper quantified information and established coding limits for noisy channels. Under stated probabilistic conditions and with long codes, rates below capacity can achieve arbitrarily small error probability—not magically error-free communication in every channel.

↓29 years later

STEP 4 · Concept1977Cambridge, MA· Discovery

Cryptography and Information

The mathematics of secrets — from Caesar ciphers to quantum key distribution. Information security is fundamentally a question of which math is hard.

↓Next step

STEP 5 · ConceptNo location

Elliptic Curves

A nonsingular cubic curve whose points carry a group law. Elliptic curves connect ancient questions about rational solutions, nineteenth-century elliptic functions, modern number theory, and selected cryptographic systems.

↓Next step

STEP 6 · Concept1994Bell Labs· Discovery

Quantum Algorithms

Algorithms using quantum superposition — Shor 1994 cast a shadow on RSA security.

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