Cipher methods Symbols
Mourier alphabet
The Mourier alphabet is a stylised writing system attributed to the calligrapher Mourier, whose precise identity is contested by historians. The alphabet is distributed on the dCode platform in the Symbol Ciphers section from a 19th-century engraved plate where each Latin letter is rendered as a distinct geometric shape: loops, crosshairs, triangular strokes, closed curves.
This kind of stylised alphabet was popular in the almanacs, puzzle books and amateur cryptography manuals of the 19th century, a golden age of parlour cryptography (cf. Edgar Allan Poe, The Gold-Bug, 1843). The Mourier rendering recalls other contemporary alphabets like Friderici (shutters) or Nyctography (Lewis Carroll) — see our respective entries. 26 Latin letters + 10 digits.
How does the alphabet work?
The cipher relies on a monoalphabetic substitution: each cleartext character (letter or digit) is replaced by the corresponding Mourier glyph. The technique goes back to Antiquity (Caesar cipher, ~50 BC), and the Mourier version is a 19th-century visual variant.
The table holds 36 glyphs (26 letters + 10 digits). The shapes are deliberately distinctive — a calligrapher’s goal being that every letter is instantly recognisable despite the stylisation. No risk of confusion between neighbouring glyphs.
Cryptographic strength: low. Like any monoalphabetic substitution, frequency analysis breaks it in a few dozen words. At the time, the appeal was steganographic: hiding a message in a copybook so a casual reader wouldn’t notice. Today it’s a historical decorative alphabet.
Historical and modern usage
- 19th-century almanacs — puzzle and game pages.
- Amateur cryptography books — illustration alphabet.
- Retro escape rooms — “19th-century cabinet of curiosities” decor.
- Historical pedagogy — post-Vigenère, pre-machine era.
Related variants
- Friderici Windows (1685) — see our entry, another historical geometric alphabet.
- Nyctography (Carroll, 1891) — see our entry, another 19th-c. alphabet.
- Pigpen — see our entry, classic geometric substitution.
What are the weaknesses?
- Monoalphabetic substitution — frequency analysis is immediate.
- Public table — the 19th-century plate is in the public domain.
- Sparse documentation — Mourier’s identity remains to be confirmed.
The 36 glyphs
