Download presentation

Presentation is loading. Please wait.

1
**(ENCODING AND DECODING TECHNIQUES)**

Seminar on CRYPTOGRAPHY (ENCODING AND DECODING TECHNIQUES)

2
Introduction What is Cryptography Why we need Cryptography

3
**Some terms associated with Cryptography**

Plaintext Ciphertext Encryption Decryption Key

4
**Methods for Encryption/Decryption**

Conventional Methods Public key Methods

5
**Conventional methods Character-level encryption Substitutional**

Transpositional Bit-level encryption

6
**Data encryption standard (DES)**

Bit-level encryption Designed by IBM and adopted by the U.S government for nonmilitary use Encrypts a 64-bit plaintext using a 56-bit key The text is put through 19 different procedures to create a 64-bit ciphertext

8
Publickey Encryption

9
**RSA Encryption Rivest, Shamir, Adleman encryption**

Public key encryption technique One party uses a public key, kp Other party uses a private key, ks Both use a number, N

11
**Encryption algorithm (RSA)**

Encode the data to be encrypted as a number to create the plaintext P Calculate the ciphertext C=Pkp modulo N Send C as ciphertext

12
**Decryption algorithm (RSA)**

Receive C, the ciphertext Calculate plaintext P=Cks modulo N Decode P to the original data

13
**Example of RSA Let Kp=5, Ks=77, and N=119**

Let the character F is encoded as 6 (sixth char in alphabet) We calculate 6Kp modulo 119 =41 At the receiver side, we calculate 41Ks modulo 119=6 Decode 6 as F

14
Choosing Kp, Ks and N First choose 2 prime numbers p and q (we choose 7 and 17) Calculate N=p*q (N=7*17=119) Select Kp such that it is not a factor of (p-1)*(q-1) (we choose 5, not factor of 96) Select Ks such that (Kp*Ks) modulo (p-1)*(q-1)=1 (4*96+1=385 and 385/5=77)

15
Thank you

Similar presentations

OK

Chapter 3 Public Key Cryptography and Message authentication.

Chapter 3 Public Key Cryptography and Message authentication.

© 2017 SlidePlayer.com Inc.

All rights reserved.

Ads by Google

Download ppt on orthogonal frequency division multiplexing Ppt on magnetohydrodynamic power generation Ppt on medical termination of pregnancy Ppt on computer malwares free Appt only ph clinics Ppt on earth movements and major landforms in hawaii Stem and leaf display ppt online Download ppt on global warming Ppt on cattle farming for class 9 Ppt on ready to serve beverages for less