SWITCH FROM TRADITIONAL TO MODERN CRYPTOGRAPHY

1. SWITCH FROM TRADITIONAL TO MODERN
CRYPTOGRAPHY
BY:
PRASOON SRIVASTAVA
HIMANSHU SHEKHAR

2. FOUNDATION
• A message is Plaintext
• The process of disguising a message in such a way as to hide its substance is
Encryption.
• An encrypted message is Cipher text
• The process of turning cipher text back into plaintext is Decryption.

3. CATEGERIZATION OF CIPHER
1. Symmetric Key Algorithm

4. 2.Asymmetric key algorithm

5. ECB Mode of encryption
The basic block diagram ECB encryption technique

6. OFB Mode of encryption
The basic block diagram OFB encryption technique

7. TRADITIONAL CRYPTOGRAPHY
• The problem with public-key cryptology is that it's based on the
staggering size of the numbers created by the combination of the key
and the algorithm used to encode the message.
• The problem with Private key algorithm is that there's almost always a
place for an unwanted third party to listen in and gain information the
users don't want that person to have.

8. ONE OF THE GREAT CHALLENGES
OF CRYPTOLOGY
To Keep Unwanted Parties Or Eavesdroppers From Learning Of
Sensitive Information.
And the solution is “QUANTUM CRYPTOLOGY”

9. QUANTUM CRYPTOLOGY
Quantum physics is a branch of science that deals with
discrete, indivisible units of energy called quanta as described by the
Quantum Theory. There are five main ideas represented in Quantum
Theory:
1. Energy is not continuous, but comes in small but discrete units.
2. The elementary particles behave both like particles and like waves.
3. The movement of these particles is inherently random.
4. It is physically impossible to know both the position and the
momentum of a particle at the same time. The more precisely one is
known, the less precise the measurement of the other is.
5. The atomic world is nothing like the world we live in.

10. QUANTUM CRYPTOLOGY BASICS
1.Quantum cryptography uses photons to transmit a key
2. Each type of a photon's spin represents one piece of information -usually a 1 or a 0, for binary code
3.Polarize them through either the X or the + filters, so that each
polarized photon has one of four possible states: (|), (--), (/) or ( ).

12. QUANTUM CRYPTOLOGY
WORKING
1. Alice sends Bob her photons using an LED, so that each polarized photon has one of
four possible states: (|), (--), (/) or ( ).
2. As Bob receives these photons, he decides whether to measure each with either his +
or X filter -- he can't use both filters together.
3. After the entire transmission, Bob and Alice have a non-encrypted discussion about the
transmission.
4. Bob: Plus Alice: Correct
5. Bob: Plus Alice: Incorrect
6. Bob: X Alice: Correct
7. A third party listening in on their conversation can't determine what the actual photon
sequence is.

13. REALIZATATION OF QUANTUM
CRYPTOLOGY USING MATLAB
1.Here we will realize our “X” and “+” filter using following table.
“+”table
“X” table
11
10
01
00
00
01
10
11
2. Filter selection:
a) By LFSR
b) Simple random sequence which will be retained by the sender.

14. Our message: “lovely professional university”
• Its symbol output: Transmitted Data “Few binary sequence”
Binary data
Sequence
01
10
11
00
01
10
11
11
01
11
Symbol
Transmitted
2
0
3
1
0
2
1
1
1
1
Limiter Used
+
+
X
X
X
X
+
+
X
+
• Received Data Sequence:
Received Sequence
2
0
3
1
0
2
1
1
1
1
Predicted Limiter
X
+
+
+
X
X
+
X
+
+
Received Symbol
10
10
00
11
01
10
11
00
10
11

15. Table representing the asking process:
Bob Replies for his
choice of filter
X
+
+
+
X
X
+
X
+
+
Response
W
R
W
W
R
R
R
W
W
R
• W- Wrong
R- Right
Hence, Bob Gets information about the choice of filter and corrects himself for the
wrong one (either discards it and ask for retransmission, or makes a guess).
Knowledge of changed sequence
If the choice of filter used is correct but the data matched for parity is found wrong,
then the receiver gets to know that the data sequence has been tampered. Hence, he
can stop the transmission further knowing that the communication channel is being
tapped.

16. COMPANIES IN THIS FIELD