Bellaso cipher (misattributed to Vigenère)
Cifrado de Bellaso (atribuido erróneamente a Vigenère)
- Date
- 1553 · confidence high
- Place
- Venice, Italy
- Credited to
- Giovan Battista Bellaso
- Field
- Communication
⚠️ Disputed: the sources disagree.
What it is
Italian cryptographer Bellaso improved Trithemius's tabula recta by adding a repeating key — a "password" — that changes the substitution alphabet with every letter, making the cipher far harder to break than monoalphabetic systems. In the 19th century it was wrongly attributed to Blaise de Vigenère, who had actually invented a different and stronger autokey cipher.
The name "Vigenère cipher" is an entrenched historical error: Vigenère devised a different and more secure autokey cipher in 1586, while this one was actually Bellaso's work from 1553.
What it led to
- Polyalphabetic frequency cryptanalysis (Kasiski, Babbage)
- 20th-century rotor cipher machines
Built on
- Trithemius's tabula recta