Models of Network & Cryptography

Network and cryptography models form the basis of a robust and secure communication system. Network models determine how a network will work and how data will be transferred, while cryptography is important for security.

1. OSI Model: A theoretical framework with 7 layers (Physical, Data Link, Network, Transport, Session, Presentation, Application).

2. TCP/IP Model: A popular model for internet-based communication with 4 layers (Application, Transport, Internet, Network Access).

Cryptography plays a key role in network security by transforming data so that only the intended recipient can understand it.

Symmetric Key Cryptography: Uses the same key for encryption and decryption (e.g., DES, AES). It's fast but has key distribution challenges.

Asymmetric Key Cryptography: Uses a public key and a private key (e.g., RSA, ECC). It solves key distribution issues but is slower.

Hashing: A one-way process that converts data into a unique fixed-size hash value, used for data integrity checks (e.g., SHA, MD5).

Digital Signatures, Certificate Authorities (CA), VPNs, and Email Security (PGP, S/MIME).