Internet and its uses

• Internet


  A worldwide collection of interconnected networks
• World Wide Web (WWW)


  Part of the internet that users can access using web browser software
• The World Wide Web consists of a massive collection of web pages, and is based on the hypertext transfer protocol
• The internet and the World Wide Web


  Are actually quite different
• Web browsers


  Software that allow users to access and display web pages on their device screens
• Uniform Resource Locators (URLs)


  Text addresses used to access websites
• URL format


  protocol://website address/path/file name
• HTTP (Hypertext Transfer Protocol)


  A set of rules that must be obeyed when transferring files across the internet
• HTTPS


  A more secure way of sending and receiving data across a network (e.g. the internet)
• Web browsers


  • Have a home page
  • Can store a user's favourite websites/web pages (bookmarks)
  • Keep a history of websites visited by the user (user history)
  • Allow the user to navigate forwards and backwards through websites/web pages already opened
  • Allow multiple web pages to be open at the same time using tabs
  • Make use of cookies
  • Make use of hyperlinks to navigate between websites and web pages
  • Store data in a cache
  • Make use of JavaScript
  • Use an address bar
• How a web page is located and retrieved

  1. User types URL into browser

  2. Browser asks DNS server for IP address of website

  3. DNS server finds IP address and sends it back to browser

  4. Browser sets up communication with website server

  5. HTML files are sent from website server to browser

  6. Browser interprets HTML and displays information on user's computer
• Cookies


  Small files or code stored on a user's computer, sent by a web server to a browser
• Types of cookies


  • Session cookies
  • Persistent (permanent) cookies
• Session cookies


  Stored in temporary memory, don't collect information from user's computer, cease to exist when browser is closed or website session is terminated
• Persistent (permanent) cookies


  Stored on user's hard drive until expiry date or deleted, remain in operation even after browser is closed or website session is terminated, can store personal information or user preferences
• Legitimate websites will always encrypt any personal information stored in cookies to prevent unauthorised use
• Many countries have introduced laws to protect users, and persistent cookies are supposed to become deactivated after six months
• What happens when a website is first visited

  1. Browser checks for cookies, if none found it creates a new session cookie

  2. Cookie is sent back to user's browser
• What happens in subsequent visits to a website

  1. Browser sends cookie back to website

  2. Website recognizes user and can retrieve their information
• Uses of persistent cookies

  • Remember users' passwords, email addresses and invoice details
  • Serve as a memory, enabling the website to recognise users every time they visit
  • Save users' items in a virtual shopping basket/cart
  • Track internet habits and users' website histories or favourites/bookmarks
  • Target users with advertising that matches their previous buying or surfing habits
  • Store users' preferences (e.g. recognise customised web pages)
• Digital currency exists purely in a digital format. It has no physical form
• Fiat currency


  Conventional currency (for example, $, £, €, and \) backed by governments and banks rather than being linked to gold or silver reserves
• Digital currency


  An accepted form of payment to pay for goods or services
• Digital currency transactions


  1. Transfer between various accounts

  2. Bank online (for example, using PayPal)

  3. Via a smartphone app (for example, Apple Pay)
• Digital currency only exists as data on a computer system, but it can be transferred into physical cash if needed
• Centralised digital currency system

  Regulated by central banks and governments, with transactions and exchange rates determined by these two bodies
• Cryptocurrency


  • Uses cryptography to track transactions
  • Has no state control, with rules set by the cryptocurrency community itself
  • Transactions are publicly available and can be tracked, with the amount of money in the system monitored
  • Works within a blockchain network, which is much more secure
• Blockchain


  A decentralised database where all transactions of networked members are stored, with new transactions added and verified by the network
• Areas where blockchain is used

  • Cryptocurrency (digital currency) exchanges
  • Smart contracts
  • Research (particularly within pharmaceutical companies)
  • Politics
  • Education
• How blockchain works


  1. Whenever a new transaction takes place, a new block is created

  2. A new hash value is created each time a new block is created

  3. The hash value includes a timestamp, which identifies when an event actually takes place

  4. Blocks are connected in a chain, with each block pointing to the previous block

  5. If a block is changed, the hash value changes, invalidating all subsequent blocks

  6. Proof-of-work ensures it takes 10 minutes to determine the necessary proof-of-work for each block before it can be added to the chain

  7. Miners get a commission for each new block created, regulating the creation of new blocks

  8. New blocks are sent to each computer in the blockchain and checked for correctness before being added

  9. New network users get a copy of the entire blockchain system
• Block description


  Includes details such as name of sender and recipient, amount of money, and so on
• Hash value


  Unique to each block, generated by a cryptographic algorithm called SHA-256
• The hash value points back to the previous block in the chain
• Changing a block in the chain will cause the hash value to change, invalidating all subsequent blocks
• Proof-of-work ensures it takes 10 minutes to determine the necessary proof-of-work for each block before it can be added to the chain
• Miners get a commission for each new block created, regulating the creation of new blocks
• The whole process of creating new blocks is slowed down, foiling hackers and regulating the currency
• It only takes one block to break the link for any transaction to be terminated
• New blocks are sent to each computer in the blockchain and checked for correctness before being added
• New network users get a copy of the entire blockchain system