Amsco Cipher
Encode and decode using the Amsco cipher - alternating single/double letter columnar transposition.
Determines column order
Puzzle Tips
- • The keyword determines how columns are read
- • Characters alternate in 1-2 pattern across the grid
- • Look for hints about grid dimensions or keywords
- • Variant: some versions start with double letters
What is the Amsco Cipher?
The Amsco cipher is a transposition cipher that combines irregular columnar transposition with a unique feature: cells alternately contain one or two characters.
How It Works
Encoding Process
- Write the keyword across the top of the grid
- Fill the grid alternating between 1 and 2 character cells
- Number the columns alphabetically by the keyword
- Read the columns in numerical order
Example
With keyword "CAT" and plaintext "ATTACKATDAWN":
C A T (becomes 2, 1, 3) AT T AC K AT KA TDA W N
Read columns in order 1,2,3: TATW + ATKDA + ACKAN
Amsco in Geocaching
This cipher is used in puzzles because:
- Harder than basic columnar: The alternating pattern adds complexity
- Keyword hints: The keyword can be themed to the cache
- Visual puzzles: Grid-based ciphers make good physical puzzles
Solving Tips
- The keyword length divides evenly into blocks of output
- Try common keywords related to the puzzle theme
- Use frequency analysis if the message is long enough
- Check both 1-2 and 2-1 starting patterns