1. Unit 2: Cryptography & Cryptographic Algorithm
-For BIM (5th Sem, CSCL)

2. Cryptography: Introduction
Greek word: Hidden Secret
Study differs now and past
past : encryption and decryption
now: past + digital signature + authentication + key mgmt + cryptanalysis
The art or science encompassing the principles and methods of transforming an intelligible message into one that is unintelligible, and then retransforming that message back to its original form

3. Some terms Plain text Cypher text: Key Encryption Decryption Cypher
Cryptoanalysis
Attack

4. Cryptography: Formal Definition
- is a 5-tuple (E, D, M, K, C)
Encryption: E:M X KC
AKA enciphering function
Decryption: D:C X K  P
AKA deciphering function

5. Attack Process to reveal cipher text with key (or even reveal key)
Types:
Cipher Text Only
Known Plain text
Chosen Plain text
Good Cryptosystem protects against all these attacks

6. Types: Symmetric Vs Asymetric Stream Vs Block
Private key vs Public key
Transposition vs Substitution

7. Some Classical cryptosystem
Substitution Cipher
Transpostion Cipher
Caesar Cipher
Vigenere Cipher
Vernam Cipher
One Pad

8. Modern Crypto-system
DES
RSA
Message Digest
Hash Function
MAC