Cipher missions
Each case file is its own instrument: a wheel, a mapping board, a signal trace, a city map.
Cryptography is as old as written language. The Caesar cipher (named after Julius Caesar, who used a shift of 3) dates to the 1st century BCE. Ancient Greeks used the scytale — a rod around which a strip of leather was wrapped to reveal a message. The Vigenère cipher (16th century) was called 'le chiffre indéchiffrable' (the unbreakable cipher) for 300 years before being cracked by Charles Babbage and Friedrich Kasiski in the 1850s.
A substitution cipher where every letter is shifted a fixed number of positions in the alphabet. Shift 3 turns A→D, B→E, Z→C. To decrypt, shift in the opposite direction by the same amount. There are only 25 possible shifts, so brute force is trivial — try each shift and see which produces readable text. Frequency analysis also works: the most common letter in English is E (12.7%), so the most frequent ciphertext letter likely maps to E.
Each letter of the alphabet is replaced by a different letter according to a fixed (but arbitrary) mapping. Unlike the Caesar cipher, the mapping is not a simple shift — A might map to Q, B to Z, etc. This gives 26! (about 4 × 10²⁶) possible keys, making brute force impossible. The standard attack is frequency analysis: in English, E, T, A, O, I, N are the most common letters. Single-letter words are 'I' or 'A'. Short high-frequency words are 'the', 'and', 'of'.
Morse code represents letters and numbers as sequences of dots (short signals) and dashes (long signals). Developed by Samuel Morse and Alfred Vail in the 1830s for the electric telegraph. The most common letters have the shortest codes: E is a single dot (·), T is a single dash (–). SOS (··· – – – ···) is the international distress signal. In SpyGames, the encrypted text uses dot-dash notation separated by slashes.
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