1. Double Transpositions
This method repeats simple transposition two times, each time with different key.

2. Double Transpositions encryption
Ex : If we use a fixed period with two different keys. P= athiedeibrahem with d=4, k1= 3142, k2= 4123

3. Double Transpositions encryption

4. Double Transpositions encryption

5. Substitution Ciphers
1. Simple 2. Homophonic 3. Polyalphabetic 4. Polygram (Polygraphic)

6. Substitution Ciphers

7. Caesar cipher
The earliest known use of a substitution cipher, and simplest, was by Julius Caesar:
The Caesar cipher involves replacing each letter
of the alphabet with the letter's standing three
places further down the alphabet.

8. The Caesar cipher
Outer: plaintext
Inner: ciphertext

9. The Caesar cipher
K=3

10. The Caesar cipher
K=3