1. Chapter 3:Cryptography (16M)
Visit for more Learning Resources

2. CRYPTOGRAPHY
Cryptography is the science and art of transforming messages to make them secure and immune to attack.

3. Cryptography It is an art of writing in secret message.
It is important when communicating over untrusted medium.
It protects data from alteration
Three schems of cruptography are:
Secret key cryptography
Public key cryptography
Hash Functions

4. Cryptanalysis
The process of trying to break cipher text message to obtain the original message itself is known as cryptanalysis.

5. Cryptology
It is combination of cryptography and cryptanalysis.

6. Encryption and Decryption
The process of encoding plain text into cipher text message is known as Encryption.

7. Decryption:
The reverse process of transforming cipher text message back to plain text message is called decryption.

8. Encryption and Decryption process
In the communication, the computer at sender‘s end usually transforms a plain text into cipher text by performing encryption by applying encryption algorithm.
The encrypted cipher text is then sent to the receiver over the network.
The receiver‘s computer then takes the encrypted message and then perform the reverse of encryption i.e. decryption by applying decryption algorithm.

9. Encryption and Decryption process

10. SUBSTITUTION CIPHERS
A substitution technique is one in which the letters/number/symbols of plain text are replaced by other letters/numbers/symbols.

11. Substitution cipher techniques
Caesar's Cipher
Mono-Alphabetic Cipher
A Homophonic Substitution Cipher
A Polygram Substitution Cipher
A Polyalphabetic Substitution Cipher
e.g.Vigenere Cipher
One time Pad(Vernam Cipher)

12. TRANSPOSITION CIPHER
In the transposition technique the positions of letters/numbers/symbols in plain text is changed with one another. 1 2 3 4 5 6 M E T A F R P Y 4 2 1 6 3 5 T E M F A P R Y

13. Transposition cipher techniques
Rail Fence Cipher
Coulmnar Transposition
Simple Coulmnar Transposition
Double Coulmnar Transposition
For more detail contact us