Homework on Blockchain and Mining Visually - Questions

  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…

  1. To make it harder to tamper with existing transactions, since, if you change an old transaction, you don’t only have to re-mine that one block; you have to re-mine all descending blocks too, which, in practice, is impossible (and becomes exponentially harder the older your transaction is).

  2. A block consists of a list of transactions, a nonce (the puzzle), the hash of the parent block, the block height and finally the hash of the current block, which is calculated by the block data (txs, hash of parent block, nonce and block height).

  1. The process of reading the past block, and present block give the chain its security, cant change anything without changing thee others.
  2. many blocks stung together in a line. with TX data block number, nonce and previous Block number
  1. It important that the blocks are cryptographically linked together, because it gives the security and the proof that they are unchanged, immutable.

  2. The block structure looks like this : previous hash + transactions + nounce = new hash

Homework on Blockchain and Mining Visually - Questions

1. Why is it important that the blocks are cryptographically linked together?

To exponentially increase the level of difficulty required to change a previously mined block transaction.

The blockchain is a mathematical puzzle where each subsequent block is appended to the end of blockchain via a mathematical hashed dependency which is linked to the previously mined hashed block.

The Blockchain miners & network nodes follow the blockchain with the longest sequence of blocks. All other shorter blockchains are ignored. Therefore, to change a previously hashed block requires an extremely high level of compute power to change a previously mined block, and at the same time update all subsequent blocks added to the blockchain and do it at such a rate that the newly formed “changed-blockchain” exceeds the length of the existing blockchain.

If the newly formed blockchain does not exceed the length of existing blockchain then it will not become accepted by the network nodes/miners and so it is ignored consensus as being false / inaccurate.

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

Each newly appended block added to the blockchain is controlled via a consensus algorithm based on a 5 discrete mathematically hashed elements; 1) Only the longest blockchain is maintained, 2) A target number, 3) A random number, 4) The new transaction, and 5) The previously hashed block.

The blockchain miners & network nodes only follow the blockchain with the longest sequence of blocks. All other shorter blockchains are ignored.

The element 2, “the target number” ensures the miner is unable to guess the random number required to complete mathematically hashed newest block. Combine this with only growing / following the longest blockchain ensure the integrity of the blockchain is maintained and is extremely difficulty to corrupt.

1.To secure the blockchain. If any transaction would change all the links for the next blocks would break.
2.Hash
Previous hash
Transaction list
Nonce