Porta Key Cipher

Reciprocal polyalphabetic cipher using a keyword and paired alphabets.

The Porta cipher is a reciprocal polyalphabetic substitution cipher, so the same operation encrypts and decrypts. Each keyword letter selects one of thirteen paired substitution alphabets. Don't know the keyword? Use Solve automatically to crack it from ciphertext.

Plaintext

Key

Keyword case doesn't matter (CACHE = cache).

Solver language

Max keyword length

Sets the language statistics the solver scores against. Choose Auto to detect the plaintext language from the ciphertext and switch to it automatically (needs at least ~20 letters). Raise the max keyword length for longer keys, but note that longer keys need more ciphertext to crack reliably.

Auto-solve assumes the standard A-Z alphabet; results won't match if you've set a custom alphabet.

Ciphertext

Porta Tableau