About Baconian Cipher

Baconian cipher is a substitution cipher that represents each letter with a five-symbol binary pattern, such as A/B.

Plain text  : HELLO, WORLD!
Cipher text : AABBB AABAA ABABB ABABB ABBBA ,  BABBA ABBBA BAAAB ABABB AAABB !

The original Baconian cipher uses a 24-letter alphabet, where I/J and U/V are treated as the same letters. A second version assigns a unique code to each letter from A to Z. DenCode supports both alphabets.

Original 24-letter alphabet

In the original alphabet, I and J share one code, and U and V share one code. When encoding, J is converted as I, and V is converted as U.

Second version: 26-letter alphabet

In the second version, each letter from A to Z has its own Baconian code, including I, J, U, and V.

Characters not supported by the selected alphabet are kept as they are.

Steganographic use

Baconian cipher was devised by Francis Bacon in 1605. Written directly as five-character A/B groups, it works as a substitution cipher. By hiding the A/B choices in the appearance of another text, it can also be used as a concealment cipher or a form of steganography.

For steganographic use, the secret message is first converted into an A/B sequence, and a cover text long enough to carry that sequence is prepared. Each letter in the cover text is then written in one of two typefaces, one read as A and the other as B. The text still looks like an ordinary sentence, but reading the typeface differences in groups of five reveals the hidden message. Bacon also described a biliteral alphabet for handwriting, using two alternative forms of uppercase and lowercase letters.

For example, encrypting "HI" produces "AABBB ABAAA". Hidden in the cover text "Hello world", it looks like this:

  H     I
AABBB ABAAA
Hello world

In this example, normal letters are read as A and bold letters are read as B. The visible text is "Hello world", but reading only the typeface differences gives "AABBB ABAAA", which decodes in groups of five as "HI".