Homophonic Cipher
Encode and decode using a homophonic substitution cipher. Multiple numbers can represent the same letter.
Substitution Table
How Homophonic Substitution Works
- • Each letter can be represented by multiple different numbers
- • More common letters (E, T, A) have more number options
- • This flattens the frequency distribution
- • Makes frequency analysis much harder
Why Multiple Numbers?
In English, E appears about 12% of the time. If we assign 12 different numbers to E, each number appears only 1% of the time - the same as rare letters. This defeats simple frequency analysis.
Puzzle Tips
- • Look for patterns in word lengths
- • Single-letter words are usually A or I
- • The mapping might not match this standard table
- • Try common words as cribs
What is a Homophonic Cipher?
A homophonic cipher is a substitution cipher where each plaintext letter can be replaced by any one of several possible ciphertext symbols. The number of symbols assigned to each letter is proportional to its frequency in the language.
How It Works
Basic Principle
Instead of A always becoming one specific symbol, A might become any of several symbols. Common letters like E get many possible substitutes; rare letters like Z get just one.
Purpose
This design defeats frequency analysis. If E can become 12 different numbers, each appearing only 1% of the time, you can't tell which numbers represent common letters.
Historical Use
Homophonic ciphers have been used throughout history:
- Zodiac Killer: Famous unsolved ciphers used homophonic substitution
- Great Cipher: 17th century French cipher with 587 numbers
- Mary Queen of Scots: Used homophonic elements
Homophonic Ciphers in Geocaching
These ciphers appear in puzzles because:
- Number-based: Works well for coordinate hints
- Challenging: Harder than simple substitution
- Zodiac theme: Famous unsolved cipher connection
- Customizable: Puzzle setters can create unique mappings
Cryptanalysis
Breaking homophonic ciphers requires:
- Pattern analysis: Word lengths, repeated patterns
- Crib dragging: Try common words at different positions
- Anagramming: Look at which symbols appear together
- Computer analysis: Hill climbing algorithms
vs Simple Substitution
| Homophonic | Simple Substitution |
|---|---|
| Multiple symbols per letter | One symbol per letter |
| Flat frequency distribution | Original frequencies preserved |
| Harder to break | Vulnerable to frequency analysis |
| More symbols needed | 26 symbols sufficient |