🎭 Bacon cipher

Every letter hides inside a group of five A's and B's.

The result appears here in real time

Turn this message into a real game: create a virtual lock your players must crack open.

The Bacon cipher replaces every letter with a string of 5 characters, using only A's and B's β€” for example, "AABAB" for the letter G. It's essentially binary code before its time, with A and B standing in for 0 and 1.

Invented by English philosopher Francis Bacon in the early 1600s, this system was designed for steganography β€” where the real secret isn't the message itself, but the fact that a message exists at all. You can hide an A or a B inside a font choice, a capital letter, or even an object.

For a treasure hunt, the "secret inside a secret" nature of the Bacon cipher is brutal in the best way: hide the A's and B's in two colors, two font sizes, or two types of objects placed around the room, and your players will have to spot the pattern before they can even start decoding.

How to use it

  1. Type your message into the input field.
  2. The tool converts each letter into a group of 5 A's and B's.
  3. Copy the code or print the letter-to-A/B reference grid.
  4. Hide the A's and B's in two distinct styles (color, font, objects) for a real steganography effect.

Example

Plain message

THE CLUE IS SECRET

Coded message

BAABB AABBB AABAA / AAABA ABABB BABAA AABAA / ABAAA BAABA / BAABA AABAA AAABA BAAAB AABAA BAABB

Reference grid

AAAAAA
BAAAAB
CAAABA
DAAABB
EAABAA
FAABAB
GAABBA
HAABBB
IABAAA
JABAAB
KABABA
LABABB
MABBAA
NABBAB
OABBBA
PABBBB
QBAAAA
RBAAAB
SBAABA
TBAABB
UBABAA
VBABAB
WBABBA
XBABBB
YBBAAA
ZBBAAB

Frequently asked questions

How do you decode an A/B message in the Bacon cipher?

Split the text into groups of 5 characters, then match each group against the reference grid (26 possible combinations for 26 letters). A bit tedious by hand, but very logical once you have the grid in front of you.

What is steganography, and how does the Bacon cipher use it?

Steganography means hiding the very existence of a message, unlike encryption, which only hides its content. The Bacon cipher lets you disguise A's and B's inside an ordinary-looking font, color, or layout choice, so no one even suspects a message is there.

Can you build a digital lock around the Bacon cipher?

Yes β€” on CrackAndReveal you create a lock whose expected answer is the word decoded from the A's and B's. Players crack the hidden pattern, type their answer online, and the lock opens automatically.

Why exactly 5 characters per letter, and not fewer?

Because with only 2 symbols (A and B), you need at least 5 positions to generate enough combinations (32) to cover all 26 letters of the alphabet without overlap β€” the same basic principle still used in modern binary computing.

More secret codes

Now hide this message behind a lock

With CrackAndReveal, your coded message becomes a virtual lock to crack: players decipher your code, enter the solution and reveal your surprise.

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Bacon Cipher: A/B Encoder & Decoder Online | CrackAndReveal