Cipher methods Symbols
Lunar (Leandro Katz, 1978)
The Lunar Alphabet is a conceptual art work created in 1978 by Argentine artist and poet Leandro Katz (born 1938 in Buenos Aires, exiled to New York since 1965). Katz successively photographs the 26 lunar phases corresponding to a complete cycle (new moon to next new moon, through crescents, first quarters, gibbous, full moon, etc.) and assigns one phase to each letter of the Latin alphabet.
The original work (1978) consists of silver-gelatin photographs; a refined version (1980) uses high-resolution images. Katz also proposed a moon-keyboard typewriter as a conceptual extension of the alphabet, with keys bearing phases instead of letters. The work has been exhibited multiple times (MoMA, MALBA, Reina Sofía) and stands as one of the most iconic functional artistic alphabets of the 20th century.
Katz used it to correspond by letters with filmmaker Jesse Lerner — a practical use of an artwork, rare in conceptual art.
How does the alphabet work?
The cipher uses a monoalphabetic substitution: every letter of the plaintext is replaced by a glyph drawn from a fixed correspondence table. It is one of the oldest cryptographic techniques on record — already described in antiquity (Caesar cipher, ~50 BC) — and the most directly readable family for a beginner.
The table holds 26 glyphs for the 26 Latin letters — each letter is a photographed moon phase. No digits in Katz’s original system.
Cryptographic strength: weak. Because every plaintext letter always maps to the same glyph, the cipher falls to a frequency analysis in a few dozen words (in both English and French, E remains the most common letter, an immediate entry point). Monoalphabetic substitutions are therefore used today for their decorative, playful or pedagogical value — not to protect real information.
Historical and modern usage
- Conceptual art — work exhibited at MoMA New York, MALBA Buenos Aires, Museo Reina Sofía Madrid.
- Katz / Jesse Lerner correspondence — practical use of the alphabet to exchange letters between the two artists.
- Pedagogy — example of a functional artistic alphabet in art-history curricula on conceptual art.
- Playful astronomy — entry point to explain moon phases to children.
Related variants
- Moon Alphabet (William Moon, 1845) — tactile alphabet for the blind, not covered here, conceptually unrelated.
- Hexahue — another non-Latin pictographic alphabet.
What are the weaknesses?
- Monoalphabetic substitution — immediate frequency analysis.
- Similar photographs — some lunar phases look alike (first crescent ≈ last crescent, mirrored).
- Documented alphabet — public table on dCode and on Katz’s official site.
The 26 glyphs
