2. What?
● Use in correspondence
● Use for security
● Have many way
3. System
● Base on the science of cryptography
● Public-key encryption
● Private-key encryption
4. Symmetric key
● Each person use same key
● Have secret key
● Install key on each one
● Use secret key for decryption
5. Public Key Encryption
● Use public-key for encryption
● Send encryption
● Use private-key for descryption
6. Authentication
● Use own private-key for encryption
● Send encryption data
● Use another public-key for decryption
● If success decryption, data can certify
7. Conclusion
● Have many many way
● Have best way for each sending data
● Have merit and demerit
● Use carefully each way
