Types of Ciphers with Examples

1. Monoalphabetic Substitution Cipher

Each letter maps to another single fixed letter.

• Plaintext: HELLO
  
• Cipher Key: A→M, B→N, C→O, ..., H→T, E→Q, L→X, O→Z
  
• Ciphertext: TQXXZ

2. Caesar Cipher (Shift Cipher)

Each letter is shifted by a fixed number.

• Shift: +3
  
• Plaintext: ATTACK
  
• Ciphertext: DWWDFN

3. Atbash Cipher

Reverses the alphabet.

• A ↔ Z, B ↔ Y, ..., M ↔ N
  
• Plaintext: HELLO
  
• Ciphertext: SVOOL

4. Keyword Cipher

Uses a keyword to reorder the alphabet.

• Keyword: FIRE
  
• Alphabet: FIREABC… (no repeats, then rest of unused letters)
  
• Mapping: A → F, B → I, C → R, D → E, E → A, F → B…
  
• Plaintext: CAB
  
• Ciphertext: RFI

5. Numerical Cipher

Substitute each letter with a number.

• A = 1, B = 2, ..., Z = 26
  
• Plaintext: DOG
  
• Ciphertext: 4 15 7

Or scrambled key: A = 13, B = 22, etc. (for harder puzzles)

6. Pigpen Cipher (Symbol Cipher)

Letters are encoded using grid-based symbols.

• Plaintext: HELLO
  
• Ciphertext: Symbols from pigpen grid.

(Visual cipher – ideal for themed or kids’ puzzle books)

7. Transposition Cipher

Letters are rearranged, not replaced.

• Plaintext: HELLO
  
• Rearranged as: LEHLO, LOHEL, etc.

Requires a rule (e.g., reverse, columnar, zigzag).

8. Homophonic Cipher

Each letter may map to multiple cipher characters, often numbers or symbols.

• E → 12 or 88 or 5
  
• Plaintext: SEE
  
• Ciphertext: 51 88 12

Harder to decode due to frequency masking.

9. Vigenère Cipher (Polyalphabetic)

Uses a keyword to apply different Caesar shifts for each letter.

• Keyword: KEY
  
• Plaintext: HELLO
  
• Apply:
  
  • H (shift K = +10) → R
    
  • E (E = +4) → I
    
  • L (Y = +24) → J
    
  • L (K = +10) → V
    
  • O (E = +4) → S
    
• Ciphertext: RIJVS

Harder to solve without the keyword.

10. Book Cipher

Uses positions in a book:

• “3:14:5” → page 3, line 14, word 5.
  Used for secret codes. Not for casual puzzle books.