Fractionated Morse Cipher

Summary: Plaintext is converted to Morse code, then the Morse string (with letter separators 'x') is divided into groups of 3 and substituted using a keyed alphabet.

Fractionation Key (using keyword CIPHER):

    .   ..  ... .-  .-. .-- -   -.  -.. --
.   C   I   P   H   E   R   A   B   D   F
x   G   J   K   L   M   N   O   Q   S   T
..  U   V   W   X   Y   Z   (continues...)

Detailed Example with crib:

• Plaintext: HELLO
• Step 1 - Convert to Morse:
  • H = ....
  • E = .
  • L = .-..
  • L = .-..
  • O = ---
• Step 2 - Join with x separators: ....x.x.-..x.-..x---
• Step 3 - Group into 3s: ... .x. x.- ..x .-. .x- --
• Step 4 - Substitute using key:
  • ... = P (from table)
  • .x. = (look up in key)
  • Continue for all groups
• Ciphertext: PXXXXXX (depends on complete key table)
• Crib given: "HELL" or similar (4+ characters)

How to solve: Use the crib to identify Morse patterns, build the key table, then decrypt.

Complete Example with Full Key:

• Keyword: CODES
• Full Fractionation Table:

Row/Col  .    ..   ...  .-   .-.  .--  -    -.   -..  --   x
.        C    O    D    E    S    A    B    F    G    H    I
-        J    K    L    M    N    P    Q    R    T    U    V
xx       W    X    Y    Z    (padding)

• Plaintext: RUN
• Morse conversion:
  • R = .-.
  • U = ..-
  • N = -.
• With separators: .-.x..-x-.
• Group into 3s: .-. x.. -x- .
• Last group incomplete -> pad with x: .-. x.. -x- .xx
• Substitute:
  • .-. = S
  • x.. = X (Row x, Col ..)
  • -x- = V (Row -, Col x)
  • .xx = W (Row ., Col xx)
• Ciphertext: SXVW

Decryption with crib "RU":

1. Convert crib to Morse: .-. ..-
2. Add separator: .-.x..-
3. This gives us patterns to look for in the fractionation table
4. Reverse the process to build the key and decrypt