Homework on Blockchain and Mining Visually - Questions

Blockchain and Bitcoin 101
#62

  1. So they cannot be tampered with.

  2. Previous block hash +TX list + nonce.

#63

1- so that it would be very hard to change remove etcā€¦

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

#64

  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.

#65

  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 blockā€™s transactions and the previous blockā€™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
#66

  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 blockā€™s hash.

#67
  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
#68

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.

#69

1 Para que a informaĆ§Ć£o presente em todos os blocos esteja interligada, fazendo com que a minima alteraĆ§Ć£o de uma informaĆ§Ć£o em um bloco altere todas as hashs nos blocos seguintes. Isso faz com que a blockchain atinja a imutabilidade.

2 A estrutura do bloco contĆ©m o numero do bloco, hash do bloco anterior, as informaƧƵes de todas as transaƧƵes inerentes ao bloco atual em si, o nonce, hash do bloco atual, tamanho do bloco, entre outrosā€¦

#70

  1. To make it harder to tamper with existing transactions, since, if you change an old transaction, you donā€™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).

#71
  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
#72

  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

#73

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 ā€œchanged-blockchainā€ 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, ā€œthe target numberā€ 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.

#74

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

#75
  1. Why is it important that the blocks are cryptographically linked together?

Blocks are linked in such a way, so that any change in any block will break the whole blockchain. This ensures the integrity of the data.

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

Each block consists of data (e.g. transactions), the hash of the previous block, and the Nonce that the miners should guess, so that the hash of those three elements is less than the target of the puzzle.

#76
  1. If something change in a old block then all the hashs of the newer blocks will not fit and then itā€™s easy to found the wrong block.
  2. The block has the hash of the previous block, the new transactions, a nonce number and the hash of the new block.
#77

1.) It provides a inmutable structure of the blockchain, so there is adependency on previous data to enshure a consistance of the whole blockchain.
2.) Each block consists of the a) hash of the previous block, b) the nonce (solved number from the cryptographic puzzle) and the c) data = TXs within the block and the d) hash of all information (a-c) in that block.

#78
  1. It secures the immutability of the blockchain. A change in one block would require all the later blocks to be changed as well.
  2. Itā€™s a linked list with each block containing the hash of the previous block, the data, and the nonce
#79

1.The most minimal change to any affects every block.
2.Hash of previous block, Nonce, Transactions. Hash current of the block.

#80

  1. The link between the blocks ensures data integrity and immutability. If any data is changed the link is broken as the hash of the altered block does change.

  2. Hash of previous block, List of transactions and the nonce.

#81
  1. Why is it important that the blocks are cryptographically linked together?

By linking the block together through cryptography creates immutability hence securing network.

  1. What does the block structure look like in bitcoin

Block number
Hash of the Previous Block
Hash of current block
Transaction Data
Nonce