Symmetric Cryptography

Symmetric key cryptography

Bob and Alice share the same(symmetric) key.

Q: How do they agree on key value?

A: They can use other ways to transport the key, like hand to each other by hand or use a public key to encrypt the symmetric key and send it through internet.

• Stream cipher: Encrypt on bit at a time.
• Block cipher: Break plaintext into equal-size blocks and encrpt one block as a unit.

Protocol Security

Network Overview

Network protocol

A network protocol defines the rules and conventions for communication between network devices.

Protocols can be broadly classified as connectionless and connection oriented.

• Connection-less network protocols

  Sends data out as soon as there is enough data to be transmitted.

  E.g., user datagram protocol (UDP).

• Connection-oriented network protocols

  Provides a reliable connection stream between two nodes.

  Consists of set up, transmission, and tear down phases.

  Creates virtual circuit-switched network.

  E.g., transmission control protocol (TCP).

Network Layers

• OSI Model

• TCP/IP Model