1. CRYPTOGRAPHY
SANDHIYA
S
RANJTHA
B

2. CRYPTOGRAPHIC TERMINOLOGY
• PLAIN TEXT: The format of the data before
encrypted.
• CIPHER TEXT: The scrambled format of data
after being encrypted.
• ENCRYPTION: Method of transforming plain
text into an unreadable format.
• DECRYPTION: Method of obtaining the
encrypted text into plain text.

3. What is Cryptography
The art of protecting information by
transforming it (Encrypting it) into an
unreadable format, called Cipher text, only
those who posses a secret key can
Decipher or (Decrypt) the message into
Plain text.

5. WHY WE NEED A
CRYPTOGRAGHY
• For confidentiality
• For authentication
• For data integrity

8. SYMMETRIC KEY ENCRYPTION

9. TYPES OF SYMMETRIC
ENCRYPTION
oSUBSTITUTION
CIPHER
oTRANSPOSTION
CIPER

12. A- 0
B- 1
C- 2
D- 3
E- 4
F- 5
G- 6
H- 7
I- 8
J- 9
K- 10
L- 11
M-12
N- 13
O- 14
P- 15
Q- 16
R- 17
S- 18
T- 19
U- 20
V- 21
W-22
X- 23
Y- 24
Z- 25

14. PUBLIC /PRIVATE KEY
• A public key known to everyone
• private or secret key known only to the
recipient of the message
• When John wants to send a secure
message to Jane, he uses Jane's public
key to encrypt the message. Jane then
uses her private key to decrypt it.

15. ASYMMETRIC KEY ENCRYPTION

16. TYPES OF ASYMMETRIC ALGORITHMS
DIFFIE-HELLMAN
RSA
EI GAMAL
ELLIPTIC CURVE CRYPTOGRAPHY(ECC)

17. DIFFIE-HELLMAN METHOD
Alice and Bob were communicating each
other via mail
Eve trying to hack the message
To avoid hacking they are using
DIFFIE-HELLMAN METHOD

18. EXAMPLE FOR DIFFIE-HELLMAN
METHOD
alice Bob
Eve

19. EXAMPLE FOR DIFFIE-HELLMAN
METHOD
Alice Bob
Eve

20. EXAMPLE FOR DIFFIE-HELLMAN
METHOD
Alice Bob
Eve

21. EXAMPLE FOR DIFFIE-HELLMAN
METHOD
Alice Bob
Eve

22. EXAMPLE FOR DIFFIE-HELLMAN
METHOD
Alice Bob
Eve

23. Alice Bob
Eve
EXAMPLE FOR DIFFIE-HELLMAN
METHOD

24. EXAMPLE FOR DIFFIE-HELLMAN
METHOD
Eve

25. Alice Bob
Eve
EXAMPLE FOR DIFFIE-HELLMAN
METHOD

26. EXAMPLE FOR DIFFIE-HELLMAN
METHOD
Alice Bob
Eve
3xmod 17
3xmod 17
3xmod 17

27. EXAPLE FOR DIFFIE-HELLMAN
METHOD
Alice Bob
Eve
3xmod 17
3xmod 17
3xmod 17
Random Number=15
Random Number=13

28. EXAMPLE FOR DIFFIE-HELLMAN
METHOD
Alice Bob
Eve
3xmod 17
3xmod 17
3xmod 17
Random Number=15
Random Number=13
315 mod 17=6
313mod 17=12

29. Alice Bob
Eve
3xmod 17
3xmod 17
3xmod 17
Random Number=15
Random Number=13
315 mod 17=6 12 = 313mod 17
6
6
12
12
EXAMPLE FOR DIFFIE-HELLMAN
METHOD

30. Alice Bob
Eve
3xmod 17
3xmod 17
3xmod 17
Random Number=15
Random Number=13
315 mod 17=6 12 = 313mod 17
6
6
12
12
1215mod 17=10 613mod17=10
EXAMPLE FOR DIFFIE-HELLMAN
METHOD

31. Alice Bob
Eve
3xmod 17
3xmod 17
3xmod 17
Random Number=15
Random Number=13
315 mod 17=6 12 = 313mod 17
6
6
12
12
1215mod 17=10 613mod17=10
36mod17=15
312mod17=4
EXAMPLE FOR DIFFIE-HELLMAN
METHOD