1. Section 2: Cryptography
Network Security
Section 2: Cryptography

2. 2 Cryptography Rules huh!? Right Order! Redundancy
What is the solution?
Redundancy
Cipher text should contain redundancies data
Example: Fired Employee!
The Couch Potato!
huh!?
Right Order!

3. 2 Cryptography Rules Valid for 10 sec Freshness
Ensure the freshness of every message.
Example: Again Fired Employee!
Timestamp
Valid for 10 sec

4. Symmetric-Key Algorithms
Use one key for encryptions and decryption
Has both Hardware and software implementation

5. Data Encryption Standard (DES)
DES Main Function
Extend 32 bit to 48 bit
XOR E with Ki
Send 8 groups to S-box
Send to P-Box
DES Whitening
Generate random key

6. Triple DES To short DES key length Why 2 keys? Why EDE instead of EEE?
Easy transportation
Compatibility with pervious version

7. Example of DES