Cipher guides · Hunt craft

How to Solve the Bacon's Cipher

These are the ciphers that actually turn up inside treasure hunts, where the encoding is one layer of a puzzle rather than the whole puzzle. They tend to hide the message rather than merely scramble it.

How to recognise it

Look at the structure before you look at the letters. Text that groups into fives, pairs that never repeat a letter, a sentence that reads perfectly but sits oddly — the shape is the clue.

Bacon's Cipher Five slots per letter, each either A or B. It is counting in binary.

The key, letter by letter

A → AAAAA
B → AAAAB
C → AAABA
D → AAABB
E → AABAA
F → AABAB
G → AABBA
H → AABBB
I → ABAAA
J → ABAAB
K → ABABA
L → ABABB
M → ABBAA
N → ABBAB
O → ABBBA
P → ABBBB
Q → BAAAA
R → BAAAB
S → BAABA
T → BAABB
U → BABAA
V → BABAB
W → BABBA
X → BABBB
Y → BBAAA
Z → BBAAB

A worked example

Message

TREASURE MAP

Key

AAAAA = A

Encoded

BAABB BAAAB AABAA AAAAA BAABA BABAA BAAAB AABAA ABBAA AAAAA ABBBB

This is the kind of cipher that turns up inside real treasure hunts, where the encoding is a layer rather than the whole puzzle. This one is Bacon's Cipher. The key: AAAAA = A. Five slots per letter, each either A or B. It is counting in binary. Apply the key to the first three letters and they resolve to T R E. The answer was TREASURE MAP.

Working one out from scratch

Decide what the carrier is first: which part of what you are looking at is the message, and which part is packaging. Everything else follows from getting that right.

Now try one

There’s a new cipher waiting today

One a day, three guesses, and a streak that breaks the moment you miss one. Today’s is cipher #1.

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