Birth of Cryptography
Where secrecy began — in battlefields, markets, and counting boards
Before mathematics, before computers, before even consistent alphabets — humanity already needed to hide messages. The two ciphers in this hall represent the oldest surviving cryptographic systems in history. One was used by a Roman general to protect military orders. The other was scratched onto parchment by a Greek historian as a tool for signalling across mountains at night.
What this hall teaches: The foundational idea of substitution — replacing one symbol with another — and fractionation — converting letters into coordinates. Both concepts survived 2,000 years and are still visible in modern AES today.
Spartan generals wrapped leather strips around wooden rods of a specific diameter. Only a rod of the same size could reassemble the message — the earliest known transposition cipher.
READ: HDUEANPTTDMAECREITAK
Julius Caesar shifted every letter of his messages by 3 positions. Simple. Fast. Unreadable to an illiterate enemy. The alphabet had to be known just to read — and only a handful of Romans were literate.
SHIFT: +3
CIPH: KHOOR
Polybius of Megalopolis invented a grid system where each letter becomes a pair of coordinates. Originally designed for torch signalling across mountains — each number represented by torch count. The first fractionation cipher.
HELLO = 23 15 31 31 34
Foundational Concepts
The Caesar cipher wraps around the alphabet using modulo 26. (position + shift) mod 26. This operation is fundamental to modern symmetric encryption including AES.
Polybius's grid converts letters to (row, col) pairs — splitting each letter into two symbols. This "fractionation" concept underlies the Bifid, ADFGVX, and modern bit-slicing techniques.
Both ciphers preserve letter frequencies. In English, E appears ~12.7% of the time. Any cipher that maps E to one symbol can be attacked by finding the most common symbol in the ciphertext.