Homework on Blockchain and Mining Visually - Questions

Blockchain and Bitcoin 101
#1407

  1. To make it more secure, because once it is not cryptographically linked together it will be prone to manipulation and alteration. Hence it will make the bitcoin blockchain unreliable.

  2. The block structure of bitcoin looks like a box with it inside are the following:
    Block number, Hash of the current block, Previous hash,
    Transaction lists, and the Nonce.

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#1408

Merkle root is in fact a root hash of the transactions within a block, not the block itself :slight_smile:

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#1409
  1. To make it impossible to change transactions in blocks.
  2. Block contains previous block hash, transactions of the current block and nonce guessed by miners.
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#1410

  1. Why is it important that the blocks are cryptographically linked together? - It means that the data, hash and nonce are linked to each block (proof of work) of the blockchain. You get security then because the effort to change any block information would be virtually impossible due to time and resource costs.

  2. What does the block structure look like in bitcoin? - Previous hash + transactions (new data) + the nonce.

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#1411

  1. Creates a direct chain of transactions going all the way back to the first block. If any transaction or block is tampered with it will become immediately obvious.

  2. Each block contains: a nonce, a list of transactions, the hash of the previous block, and a hash of itself. The next block contains the previous blocks hash and so on.

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#1412

  1. it guarantees the integrity of the chain. If one block is adulterated, the subsequent blocks in the chain will be invalidated.

  2. A block contains a nonce + previous block’s hash + data (transactions)

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#1413

  1. It is important that block are cryptographically linked together so that the block on the blockchain can read each other and can notice when information has been changed on a previous block, there would be no chain to the blockchain

  2. The block structure in bitcoin looks something like
    Version
    Block no.
    Previous hash
    Tx list
    Merkle root
    Nonce
    Difficulty target

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#1414

Ah yes the block reward. But if the blocks are made of bitcoin, and the Block reward which makes up the blocks halve, shouldn’t the actual size of the block halve as well?

#1415

  1. it’s important because it helps in securing past blocks from being tampered with, if one past block was to change it would affect every block going forward.

  2. The block is a set of data including the TX data, the previous block hash and the nounce which all together must be below the difficulty target set by the network.

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#1416

  1. It is important that the blocks are cryptographically linked together to ensure the security and integrity of the system. If there is tampering with the data in a confirmed block the cryptographic link will be cut and this means there is no consensus and the block must be remined. The miners are rewarded for solving the cryptographic link.

  2. The block is made of the previous block hash, TX list, nonce (random number which must be solve to create a hash for the new block) and current hash.

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#1417 
1. Why is it important that the blocks are cryptographically linked together?

Because if absolutely any change made, it will affect the entire blockchain in a domino effect.



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

* Block number
* Hash number
* Previous hash number 
* Transaction data
* Nonce
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#1418

1/ when data is changed on a block already attached to the blockchain the result is the loss of integrity of the blockchain data, hence cryptographically linked blocks assure immutability of the blockchain
2/ it is a hash of previous hash + transaction list + nonce

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#1419

No, the block size is capped at 1MB and doesn’t change. The argument of changing the block size has been a topic of debate for a long time and is the reason why hardforks like BCH happened.
In any case the block reward has no influence over it :slight_smile:

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#1420

1-Blocks are cryptographically linked since it helps to secure the network and would not allow to change previous Transactions or avoid double spending or data immutability in blocks. Need for POW or consensus algorithm to be met is important.
2- block structure in a bitcoin is cumulative of previous hash functions along with transactions and nonce number which has to be determined by the miner

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#1421

Thank you for clearing this up for me. I was visualizing it all wrong not considering the “size” and block reward being separated. Greatly appreciated.

#1422
  1. Why is it important that the blocks are cryptographically linked together?
  • To make sure tampering with the network would require an enormous amount of computing power
  1. What does the block structure look like in bitcoin?
  • block header
  • block size
  • transactions + transaction counter
  • nonce
  • prev block hash
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#1423

Thank you! Would the block header contain both a merkle root hash AND the hash of the block itself (along with hash of the previous block)?

#1424
  1. Why is it important that the blocks are cryptographically linked together?
  2. What does the block structure look like in bitcoin?

1)it is crucial that they are linked toghether because as soon something changes in one of the previous blocks , all the following blocks will be changed as well,because of the changes in hashes
2) blocks in btc are composed of previous hash , transactions , nonce and all this are hashed so the hash is lower than the target .

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#1425

Ans.1)
The blocks are linked together for the security of the chain of blocks. This also keeps the integrity of the former confirmed and blocked transactions. Any prior blocks that have there data sets modified will cause the hash to change which in turn will change all data set hashes that follow in the blocks that come thereafter. The link between the blocks will also be severed between them as a result of the previous set of data being modified without correct permissions. (eg. private key)
Ans.2)
Bitcoin transaction(s) data that is placed in a block is in the form of a UTXO. It is stored here to be queried when that unspent transaction is called upon from the owner of the private key that the transaction parcel is hashed in. Therefore the block structure looks like a group of tx inputs, hashes, which become UTXO’s awaiting deployment from their unique owners.

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#1426

The block header contains the merkle root and previous block hash along with the timestamp, difficulty and nounce. It does not contain the current block hash since it is calculated from the block header :slight_smile:

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