Homework on Blockchain and Mining Visually - Questions

Blockchain and Bitcoin 101
#2392

  1. So that any alterations to historical blocks will break the chain and exoose cheating.

  2. Block structure- TX list, hash of previous block and nonce.

1 Like
#2393
  1. because if you change something in a block, the hash of that block will change and that will break the link to the following blocks.
  2. it has a list of UTXO´s, the block also has the hash of the previous block and a nonce (radom number that the miner has to guess), the miner takes this 3 items and calculate the hash and it has to be less than the target.
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#2394
  1. Linking the blocks adds security because the chain depends on the previous blocks - changing one, will result in a change in all the blocks following the change.
  2. It is a chain made up of hashes, each containing transactions and the previous hash.
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#2395

The block does contain the hash of the previous block and is used in the hashing process of the current block. This is very important because it links the blocks and makes them immutable. :slight_smile:

#2396
  1. So that attempted alterations of blocks can be flagged up to the network
  2. previous hash, TX list, nonce
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#2397

1, To prevent the possibility of changing any one block without affecting all succeeding blocks. This adds to the difficulty (or practical impossibility) of trying to alter the transaction history as not only would the adjusted block need to be re-mined, so would all succeeding blocks.

2, Each block contains a hash made up of nonce, all transactions and hash of previous block.

1 Like
#2398

  1. This is by far the most genius part of the Bitcoin blockchain. The fact that each block is linked to the one previously mined makes it that much more difficult to alter and cheat the system. If one miner tried to change any block the blocks after that would require a different hash.

  2. Each new block is based on the transactions inside, the previous hash and the nonce or target for the puzzle that must be solved.

1 Like
#2399

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

  • It promotes immutability - if data in block is altered than hashes are no longer complaint with its set of blocks, breaking their chains.

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

  • Block
  • Present Block hash
  • Nonce
  • Data (tx list + timestamps)
  • Previous block hash
2 Likes
#2400

Can’t see any trace of plain previous blocks hash.
(https://www.blockchain.com/btc/block/00000000000000000003e6352b38b7e63d6c3033e88e4369f1e9563fbd437aba)
Could you point me to it?
:face_with_monocle:

#2401

If you can’t see it in an explorer it doesn’t mean its not there, block explorers abstract data to make them more user friendly. The previous block hash is referenced in the block header:
https://github.com/bitcoinbook/bitcoinbook/blob/develop/ch09.asciidoc#block-header

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#2402

Screenshot_20201210-114249_Chrome
Screenshot_20201210-114249_Chrome1080×2193 583 KB

Check this block explorer:

https://explorer.btc21.org/

Click on a block and check the json tab.

I’m using this explorer locally on my own node.

1 Like
#2403

Still redundant. Could safe a bit if space )

#2404

  1. Cryptography helps keep the blocks integrity so nothing can be changed.

  2. the data of previous tx of the block / current block tx / nonce

1 Like
#2405

Homework on Blockchain and Mining Visually - Questions

  1. Why is it important that the blocks are cryptographically linked together?
    because it makes it nearly impossible to change or double spend UTXO’s

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

block header - current block
block size
transactions + transaction counter
nonce
prev block hash

1 Like
#2406

If you wouldn’t include the previous block hash there wouldn’t be any link to the previous block and could be changed. Its the way how blocks are chained together. Technically the block doesn’t contain the current hash because it can be calculated on the fly if you have the nonce, previous hash and merkle root (check the block header in the link I sent you). :slight_smile:

#2407

  1. By cryptographically linking the blocks, bitcoin blockchain ensures the integrity of all blocks and that no one was modified/altered by anyone. Once a block is mined it is written in stone.

  2. Each block has these sections:

  • nonce
  • list of transactions
  • previous hash
  • hash
1 Like
#2408
  1. Why is it important that the blocks are cryptographically linked together?

It makes alteration of the chain very difficult. Changing one block changes all previous blocks

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

Previous block hash, current block transactions and nonce

1 Like
#2409

1)Why is it important that the blocks are cryptographically linked together?
To provide integrity and immutability.

2)What does the block structure look like in bitcoin?
Previous block hash
Tx list
nonce.

2 Likes
#2410

Homework on Blockchain and Mining Visually

  1. Why is it important that the blocks are cryptographically linked together?
    -They need to be linked otherwise the chain would not work. There are unique identifiers in each hash so when something is changed the block will not link to the next. It ensures the network has a security.

  2. What does the block structure look like in bitcoin?
    -A block consists of TXs, Nonce, and a current and previous hash

2 Likes
#2411

  1. To make sure that everyone uses blocks honestly. Nobody wants to change previous blocks in practical since it will costs a lot fo this bad manner.

  2. The transaction data, previous hash and nounce.

1 Like