Baconian Cipher
Decode every five-symbol group with a complete A/B reference table—without needing another website.
What is the Baconian Cipher?
The Baconian cipher represents each letter with a five-position pattern made from two symbol classes. We write those classes as A and B.
Puzzle versions may disguise A and B using two fonts, glyphs, shapes, colors, digits, or other paired features. Once you identify the two classes, the decoding is a direct table lookup.
The cipher mechanics on this page are self-contained. Science Olympiad event formats, allowed variants, and tournament constraints can change by season; the current official Rules Manual and official clarifications take precedence.
No outside reference is assumed. Work through Foundations → Complete Reference → Encryption → Decryption in order, then use the competition and cryptanalysis sections.
What you need to know
- Exactly five A/B positions represent one letter in the 26-letter teaching alphabet used by The Daily Cipher.
- The first pattern is AAAAA for A, then the patterns count upward like five-bit binary with A=0 and B=1.
- If symbols are disguised, first decide which visual form means A and which means B.
Beginner glossary
| Term | Meaning |
|---|---|
| Biliteral | Using two distinguishable forms or symbol classes. |
| A/B pattern | A five-position sequence such as AAABA. |
| Symbol class | One of the two visual categories representing A or B. |
| Group boundary | The division after every five A/B choices; losing it shifts all later decoding. |
Keep this beside you while solving
Complete 26-letter Baconian table
| Letter | Pattern |
|---|---|
| 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 |
How the 26-letter table is generated
Treat A as binary 0 and B as binary 1. The five positions count from 00000 through 11001 for A through Z. Example: C is alphabet index 2 → binary 00010 →
AAABA
.
How encryption works
Find the plaintext letter
Example: C.
Look it up
C = AAABA in the 26-letter table.
Replace A/B if needed
If A-class is ● and B-class is ○, AAABA becomes ●●●○●.
Repeat
Encode every letter independently in groups of five.
How decryption works
Identify the two classes
For example X and O, bold/plain, or two shapes.
Normalize to A/B
Choose one class as A and the other as B according to the problem.
Split into groups of five
Never decode across a group boundary.
Look up every group
AAABA → C, BAAAB → R, etc.
How to approach it in Codebusters practice
- The main challenge is often recognizing the two symbol classes correctly.
- If the decoded result is nonsense, test whether A and B were reversed before assuming the table is wrong.
- Keep five-symbol boundaries visible; one dropped symbol shifts every following letter.
What the problem gives you vs. what you produce
| Part | What to expect |
|---|---|
| You may be given | A stream of A/B, or two fonts/symbols/glyph classes that hide A/B. |
| You must find | The plaintext by identifying classes, grouping in fives, and using the table. |
| Fastest first move | Mark which visual form is A and which is B, then draw separators every five symbols. |
How to attack an unknown or partially known key
- Baconian is an encoding rather than a strong modern cipher: once the two classes and grouping are known, decoding is direct.
- Disguised typography can hide the binary structure, so scan for exactly two recurring visual states.
- If spacing is absent, count symbols in sets of five from the intended start position.
Follow one example from start to finish
AAABA BAAAB AAAAA AAABA ABABA
CRACK
Before moving on, make sure you can answer these without another site:
- Can you find C directly in the table as AAABA?
- Can you explain why one missing symbol corrupts every later group?
- If a puzzle uses X/O, can you normalize it to A/B before lookup?
Common mistakes
Using four or six symbols per letter instead of five.
Reversing A and B unintentionally.
Using a historical 24-letter table when the problem uses a 26-letter table.
Losing one symbol and shifting all later group boundaries.
Competition speed strategies
Keep the complete table above on your reference sheet.
Recognize common patterns: AAAAA=A, AAAAB=B, AAABA=C.
Mark a slash after every five symbols before decoding a long stream.
What to remember under time pressure
See every transformation
Use the lab to change inputs and keys, keep the relevant reference material visible, inspect each intermediate transformation, and then read the “How to reverse it” panel so encryption and decryption connect.