How Ciphers Work
From pen-and-paper codes to the mathematics behind modern security
Every Classical Cipher Teaches Modern Cryptography
The same ideas that protected Caesar's dispatches now protect your bank account — just with stronger mathematics. Each exhibit includes a "What It Teaches" section connecting the classical failure to the modern solution.
Caesar and monoalphabetic ciphers evolved into AES S-boxes — non-linear substitution tables designed specifically to defeat frequency analysis.
Vigenère's repeating keyword and ChaCha20's pseudorandom keystream illustrate combining a message with a keystream. A ChaCha20 key can protect multiple messages, but nonces must not repeat under that key, and the block counter must not wrap.
Rail Fence and columnar transposition became AES ShiftRows + MixColumns — together ensuring every output bit depends on every input bit.
Enigma's rotating alphabets became AES rounds — multiple iterations of substitution and permutation to achieve confusion and diffusion.
Breaking the Lorenz cipher required Colossus — the world's first programmable electronic computer. Cryptanalysis built computing.
Shannon proved the OTP is information-theoretically secure. Every modern cipher aims for computational security — as close to perfect as practical key management allows.
Explore by Topic
Modern Cryptography
How classical failures became AES, RSA, and post-quantum security. The full evolution from pen-and-paper to computational security.
Cryptanalysis Techniques
Frequency analysis, Kasiski examination, and index of coincidence — tools that break many classical ciphers given suitable ciphertext, rather than every historical system or a correctly used one-time pad.
Glossary
Definitions of every cryptographic term used in the museum — from plaintext to key derivation function.
Cipher Comparison
Side-by-side analysis of every cipher in the museum — type, era, security status, and key properties.
Cipher Detective
Paste unknown ciphertext and get evidence-based candidate families from IoC, Kasiski, chi-square, and character-set analysis.
Unsolved Ciphers
Study open problems like Voynich, Kryptos K4, and Somerton Man with current research framing and evidence-first methodology.
Cipher Culture
Explore how ciphers move into novels, television, ARGs, and puzzle hunts while preserving real cryptanalytic ideas.
Start with the Caesar Cipher
The simplest cipher in history is the best place to begin. Learn how Julius Caesar encoded messages — then see how the same idea powers modern encryption.
Start with Caesar →