1. Homophonic Substitution Cipher
Each letter in the secret message is replaced with a number which represents the position of a word in an assistant text which start with this letter

2. Beale cipher
We assign a set of numbers to each letter in the plain text alphabet by using a specific text, each letter in the plain text will be replaced by number that represent the location of some ward in the text that start with this letter

3. Beale cipher

4. Beale cipher
Ex Plain text = A L M A M O N C O L L E G E Cipher text = Decryption Cipher text = Plain text = A L M A M O N C O L L G E

5. Beale cipher
If the assistant text = zainab muhammed and P= zahzuh The assistant text will be as follows after dispose the repeated letters from it. Assistant text = zainbmuhed

6. Beale cipher

7. Beale cipher

8. Polyalphabetic Substitution Cipher
use a key to select which alphabet is used for each letter of the message use each alphabet in turn repeat from start after end of key is reached

9. Vigenère Cipher
simplest polyalphabetic substitution cipher effectively multiple caesar ciphers key is multiple letters long K = k1 k2 ... kd ith letter specifies ith alphabet to use use each alphabet in turn repeat from start after d letters in message decryption simply works in reverse

10. Vigenère Cipher
Encryption C= E(p) = (p+ki) mod (26) Decryption p= E(C) = (C - ki) mod (26)

11. Vigenère Cipher
Example :We can encrypt the message “She is listening” using the 6-character keyword “PASCAL”.

12. Vigenère Cipher

13. Vigenère Cipher
A Vigenere Table

14. Vigenère Cipher
Plaintext = the forth class Key = car

15. Vigenère Cipher C(f) = (5+2) mod 26 = 7 → h
C=(P+K) mod 26
C(f) = (5+2) mod 26 = 7 → h
C(o) = (14+0) mod 26 = 14 → o
C(r) = (17+17) mod 26 = 8 → i
C(t) = (19+2) mod 26 = 21 → v
C(h) = (7+0) mod 26 = 7 → h
C(c) = (2+17) mod 26 =19 → t
C(l) = (11+2) mod 26 =13 → n
C(a) = (0+0) mod 26 = 0 → a
C(s) = (18+17) mod 26 = 9 → j
C(s) = (18+2) mod 26 = 20 → u
∴ C = vhvhoivhtnaju

16. Vigenère Cipher
P=(C-K) mod 26 P(v) =(21-2) mod 26 = 19 → t P(h) =(7-0) mod 26 = 7 → h P(v) =(21-17) mod 26 = 4 → e P(h) =(7-2) mod 26 = 5 → f P(o) = (14-0) mod 26 = 14 → o P(i) = (8-17) mod 26 = (26-9) mod 26 = 17 → r

17. Vigenère Cipher
P(v) = (21-2) mod 26 = 19 → t P(h) = (7-0) mod 26 = 7 →h P(t) = (19-17) mod 26 =2 → c P(n) = (13-2) mod 26 = 11 →l P(a) =(0-0) mod 26 =0 → a P(j) = (9-17) mod 26 =(26-8) mod 26 =18 →s P(u) = (20-2) mod 26 =18 →s ∴ P= theforthclass

18. Vigenère Cipher
Plaintext = she is listening Key = pascal