Codes & Ciphers Trivia

Cryptography is a very old arms race between people trying to hide messages and people trying to read them. The tools have gone from simple letter shifts to machines to math that would take longer than the age of the universe to break by force.

This quiz covers classic ciphers, a few famous wartime systems, and the vocabulary codebreakers use.

Classic Ciphers

The oldest methods just rearrange or swap letters.

• A Caesar cipher shifts every letter a fixed number of places down the alphabet.
• A substitution cipher swaps each letter for a different fixed letter or symbol.
• Steganography hides the fact that a message exists at all, using tricks like invisible ink.
• The one-time pad is provably unbreakable when its key is truly random, as long as the message, and never reused.

Codes at War

Some of the most famous cryptography stories come from the world wars.

• The German military used the Enigma machine, which was broken by Allied codebreakers at Bletchley Park.
• US forces used Navajo "code talkers" in the Pacific, whose language was never cracked by the enemy.
• In cryptography the original readable message is called the plaintext, and the scrambled version is the ciphertext.
• Public-key cryptography uses two different keys, one to encrypt and one to decrypt.