Homework on Blockchain and Mining Visually - Questions

Homework on Stale Blocks.

  1. What happens in the bitcoin network when two miners solve a block at the same time? Both blocks would be valid; however, sooner or later the blockchain with the longest blockchain and with the most difficult Proof of Work will be the truth that will prevail.
  2. What is a stale block? Blocks that were in the blockchain at one time but were dropped because of a competing blockchain. Dropped blocks are called stale blocks or orphaned blocks.
  3. How do stale blocks occur? When blocks are coming out at a faster rate and begin to compete with each other. The longest blockchain prevails. The blockchain with the most proof of work and the difficulty of the blocks would prevail. The blocks that are no longer use become stale.
  4. Why is it important to wait for more than one block to be confirmed when sending or receiving a transaction? To prevent your block from being dropped and to maintain the efficiency of the blockchain. The best practice is to wait for 6 confirmations to come after your block to be confirmed.
  1. Why is it important that the blocks are cryptographically linked together?

  2. The link between the previous block and the next is a cryptographical puzzle.

  3. What does the block structure look like in bitcoin?

  4. The hash of the block is based on the tx in the block and the previous hash + the nonce that needs to be guessed

Why is it important that the blocks are cryptographically linked together?
Because this makes changing any confirmed data difficult and ensures the immutability of the blockchain.

What does the block structure look like in bitcoin?
A Bitcoin block consists of the block number, hash of the previous block, transaction data for the current block, the nonce, and the resulting hash (unique fingerprint) for the block.

  1. Because if you change anything in the block- hash will change and blocks will not be linked anymore
  2. previous block hash, transactions and nonce
  1. It is important to main the integrity of the Blockchain and to prevent any foul play by any. They are so linked because each subsequent new block must open with the hash function output of the previous block as input.
  2. A block is a container data structure and in bitcoin it can contain more than 500 transactions but not more than 1MB in size
  1. The blocks need to be hash linked because any bad actor will no only need to alter the existing block but the ones previously, the time effort to do this will mean the main blockchain has moved on, longest blockchain becomes valid

  2. The block structure is made up of the three element
    The previous hash block, the transaction list and the nonce
    This is used to create the block hash which needs to be below target value of the difficulty adjustment to become the new successful block

  1. Why is it important that the blocks are cryptographically linked together?
    To ensure the integrity of the blockchain. The cryptographically generated hash used during the addition of each block prevents the data of previous blocks from being changed as such a change would have a cascading effect which would invalidate all subsequent blocks.

  2. What does the block structure look like in bitcoin?
    Each block is comprised:
    a. Hash of the previous block
    b. List of transactions
    c. The nonce

  1. It keeps the integrity of the ledger, it’s the secret sauce

  2. Hashes, ins and outs, data, nonce

  1. Because it ensures previous transactions stay untacked.
  2. Previous has plus transactions plus nonce.

1. Why is it important that the blocks are cryptographically linked together?
It is important for the security and integrity of the network. A transaction in a block cannot be modified without breaking its link to the subsequent block.

2. What does the block structure look like in bitcoin?
It contains the hash of the previous block, the transactions as well a random number miners have to guess, the nonce.

  1. It’s how the security of the network is maintained. Linked blocks cannot be changed without breaking the chain.
  2. Hash of the prior block, plus transactions plus a nonce.
  1. The importance for the blocks to be cryptographically linked is for the integrity of the blockchain. Bitcoin blockchain is meant to be immutable and decentralised. Nobody is supposed to be able to change any data once its mined.

2} Each block has a block Header which consists among others like timestamp, a cryptographic hash of the previous block ensuring the linkage to all other blocks in the chain. It also has a nonce number which the miners randomly guess so that after hashing everything in the block, must be either equal to or lower than the Target number. Lastly the Merkle root of all transactions from that block, averaging slightly more than 500 transactions per block (1 MB in size.)

  1. So they cannot be tampered with.

  2. Previous block hash +TX list + nonce.

1- so that it would be very hard to change remove etc…

2- it contains four things
1- the hash of the current block which is made by hashing the previous block hash and information
2- the hash of the previous block
3- transactions
4- nonce

  1. Makes it impossible to change any previous block Without invalidating the entire chain.

  2. Each new block includes a hash of the previous block linking the chain together.

  1. It is important as it renders copies of the blockchain with altered blocks useless/invalid, thus penalizing the miner trying to cheat. Because the hash is not only made up of the nonce, but also of the new block’s transactions and the previous block’s hash, changing one variable (the tx), will produce a totally different hash, the following block(s) cannot find the previous block anymore and will have to be remined.

  2. A simplified bitcoin block contains the following items:

  • block header
  • the hash of the previous block header
  • merkle root of the transactions in the current block
  1. So that there is no way to change the history without massive effort.

  2. blocks are chained together by linking the hash of the previous block to the current block’s hash.

  1. to ensure all data in the block is correct.
  2. the block structure has the hash of previous block all data of transactions inputs and outputs, block number, nonce, hash of current block

Why is it important that the blocks are cryptographically linked together?
It is important so that the chain remains in tact. It would be nearly impossible to
change the data of a block then change the data of every subsequently linked block.

What does the block structure look like in bitcoin?
Previous block hash, list of current transactions and fees, difficulty target, nonce, and current block hash.

1 Para que a informação presente em todos os blocos esteja interligada, fazendo com que a minima alteração de uma informação em um bloco altere todas as hashs nos blocos seguintes. Isso faz com que a blockchain atinja a imutabilidade.

2 A estrutura do bloco contém o numero do bloco, hash do bloco anterior, as informações de todas as transações inerentes ao bloco atual em si, o nonce, hash do bloco atual, tamanho do bloco, entre outros…