Ciphers

Baconian cipher

Each letter becomes five choices between two carrier classes.

Also found as Bacon biliteral · biliteral cipher · Baconian alphabet

How it works

Sort each carrier letter into class A or class B, read the result in groups of five, and look up each pattern in the biliteral alphabet. In Decipher, the Key says which carrier letters belong to each class. The visible carrier stays the same. Decryption turns its letters into the A/B stream and decodes complete groups.ACA Baconian

Capacity of a five-position biliteral group

2⁵ = 32 possible patterns26 patterns are sufficient for A–Z

Worked example

Decode three groups

Class stream: aaaaa aaaab aaaba
Values: 0 1 2
Plaintext: ABC

Alphabet conventions

Baconian tables do not all assign the patterns in the same way. Many historical and ACA versions merge I/J and U/V to make a 24-letter alphabet. Decipher currently uses a straight 26-letter binary order, so historical examples may decode differently here.ACA Baconian

What to look for

Start by guessing how the carrier splits into two classes. Repeated carrier letters, visible two-way distinctions, five-character alignment, and cribs and class hypotheses can narrow the choices. Typography can carry the distinction, but it is not required.

Sources

American Cryptogram Association, Baconian instructions