The Zodiac Cipher refers to a set of ciphers used by the infamous Zodiac Killer in the late 1960s to send encrypted messages to newspapers and authorities in Northern California. These ciphers combine substitution, symbols, and, in some cases, simple transposition, creating challenging puzzles that drew widespread attention from cryptographers and amateur sleuths alike.
Each symbol in the Zodiac Cipher corresponds to a letter of the alphabet. The mappings are typically unique per cipher, often including geometric shapes, lines, or other visually distinct symbols. Decoding requires discovering the original symbol-to-letter key or performing frequency and pattern analysis.
Zodiac Cipher: Encoding
Using a hypothetical mapping, the plaintext HELLO WORLD can be encoded into Zodiac-style symbols as follows:
Plaintext: HELLO WORLD
Ciphertext: ⨝◻◬◬/ ⋀/⋊◬∀Each letter is replaced by its corresponding cipher symbol according to the predetermined key.
Zodiac Cipher: Decoding
To decode, the process is reversed by mapping each symbol back to its plaintext letter using the same key:
Ciphertext: ⨝◻◬◬/ ⋀/⋊◬∀
Mapping: ⨝→H, ◻→E, ◬→L, /→O, ∧→W, ⋊→R, ∀→D
Plaintext: HELLO WORLDZodiac Cipher: Notes
Each Zodiac Cipher may have a completely different symbol-to-letter mapping, making them unique puzzles. Decoding relies entirely on the key; without it, frequency analysis and pattern recognition are essential. Some Zodiac ciphers remain partially or completely unsolved, demonstrating the enduring challenge of cryptanalysis on unknown symbolic codes. These ciphers illustrate the combination of cryptography and personal signature, showing how substitution with symbols can mask messages effectively.