Blockchain: day 2

November 19, 2021

2 mins

Solidity course


start: 29min

stop: 1hr 1min


Welcome to blockchain


  • You have public and private keys.
  • Public keys allow you to view your account on Etherscan
  • The privte key allows people to take your coins
  • Gives access to various networks, including test networks
  • Testnet faucet gives us access to free (pretend) etherium, the Rinkeby faucet does this with a tweet
  • Etherscan is a block explorer, a block explorer allows us to view transactions on a blockchain


  • Gas is a unit of computational neasure. The more computation a transaction uses the more gasd you have to pay for.
  • Every transaction that happens on chain pays a gas fee to node operators.
  • This is gonna change soon
  • Any time you want to change the chain you have to pay
  • The of amount of "gas" used and how much you pay depends on how "computationally expensive" your transaction is
  • Send ETH to 1 address is cheaper that to 1000
  • Gas prices are set in GWEI.
  • You can set higher gas prices to incentivise the nodes to include your changes. Use Eth gas station to figure out the gas price to set

    Understanding blockchain technology

  • Ethereum used keccak256 for its hashing algo
  • HAsh: Unique fixed length string to identify a piece of data
  • 1 block consists of block number, nonse, previous (hash of the previous block) and the data
  • The miners are looking to solve a problem. In Etherium based chains its to find 4 zeros at the start of a block. This is acheived by changing the nonse. Done by brute force.
  • Genesis block is hte first block in a chain


    • A "number used once" to find the "solution" to the blockchain problem
    • Its also used to define the transaction number for an account/address