Network Security & Cryptography Basics

• Types of Ciphers:

  • Caesar Cipher: Shifts letters by a fixed number of positions.
  • Transposition Cipher: Rearranges the order of letters.
  • Vigenère Cipher: Uses a keyword for varying letter shifts.
  • Substitution Cipher: Replaces letters with other letters or symbols.

• Cracking Ciphers:

  • Brute force attacks try every possible key.
  • Frequency analysis examines letter occurrence patterns.

• Bandwidth:

  • The amount of data transmitted over a network in a given time.
  • It is analogous to the width of a highway.

• Latency:

  • Delay before data transfer begins after a request.
  • It is similar to the speed limit on a highway.

• Layers of the Internet:

  • Application Layer: Manages user interactions.
  • Transport Layer: Splits data into packets and ensures delivery.
  • Internet Layer: Routes packets using IP addresses.
  • Link Layer: Manages physical data transmission.

• Packet Fragmentation:

  • Packets are broken down to enhance efficiency and reliability.
  • Smaller packets can take different routes and can be reassembled at the destination.

• IP Address:

  • A unique identifier for devices on a network.
  • Handled by the Internet Layer.

• Domain vs. IP Address:

  • Domain is a user-friendly name (e.g., google.com).
  • IP address is a numerical label (e.g., 192.168.1.1).

• Net Neutrality:

  • The principle that all internet traffic should be treated equally.
  • This prevents ISPs from blocking or slowing down specific content.

• Digital Divide:

  • The gap between those with and without access to digital technology.
  • It is often influenced by economic or geographical factors.

• Certificate Authority:

  • An entity that issues digital certificates to verify website legitimacy.

• Diffie-Hellman Algorithm:

  • Enables secure key exchange over a public network.
  • Relies on public and private keys.

• Symmetric vs. Asymmetric Ciphers:

  • Symmetric: Uses the same key for encryption and decryption.
  • Asymmetric: Uses a public key for encryption and a private key for decryption.

• Malware:

  • Software designed to harm devices, networks, or users.
  • Can steal data, damage systems, or spread to other computers.

• Phishing:

  • Cyber attacks using fake emails or messages to trick people into providing sensitive information.

• Biometrics:

  • Physical or behavioral traits used for security authentication.

• Two-Factor Authentication (2FA):

  • Requires two forms of authentication for identity verification.

• Crowdsourcing:

  • A large group contributes to solve a problem.
  • Examples: Wikipedia, Kickstarter.

• Algorithm Problem Types:

  • Decidable: Solved by the same algorithm every time.
  • Intractable: No single algorithm guarantees correctness.
  • Heuristic: Solved by algorithms to get "good enough" results quickly.
  • Undecidable: No algorithm can guarantee a correct solution.

• Match to Questions 5-9

  • 5 sort elements in a list -D.
  • 6 sort elements in a list - C
  • 7 Find an element in a sorted list - E
  • 8 sort elements in a list - B
  • 9 Find an element in an unsorted list - A

• Parallel Computing:

  • Dividing a large problem into smaller processes for faster solutions.

• Password Cracking:

  • Hackers use Brute-force attacks to crack passwords.

• Traveling Salesman Problem:

  • An intractable problem.
  • Nearest Neighbor Heuristic is another method, but may not be the optimal solution.

• Web Searches:

  • They organize the internet to make a binary search possible

• Indexing:

  • Harry is index is 2

• Binary Search:

  • In a list of 500 numbers it will take nine passes to use binary search.

• Algorithm Outcome:

  • The sides and length would be drawPolygon(5, 50).

Explore fundamental concepts in network security and cryptography. Learn about classical ciphers like Caesar and Vigenère, along with methods for cracking them e.g. frequency analysis. Understand bandwidth, latency, and the layered structure of the internet.