Homework on Blockchain and Mining Visually - Questions

Blockchain and Bitcoin 101
#505
  1. For the security of the blockchain it is important that the block have to be cryptographically link together. You can not change transactions in the block, because it would break the links to other block.
  2. Because we have hash of the previous mined block, list of transactions and nonse.
#506

  1. Because it verifies that the blocks have not be changed or altered. It would be extremely difficult to change any blocks from the past. Any change would result in a different hash for that block which would not match the correct hash that was recorded in the preceding block.

  2. Block structure consists of;

  • Block number

  • Nonce

  • Transaction data

  • Hash of previous block

1 Like
#507

  1. When a block is linked with the previous block using cryptography, then any change in any of the previous block will change its hash. and hence will break will link with the next blocks.
    The above ensures immutability so that the subsequent transactions are not edited.

  2. A block in a blockchain contains its hash, the list of UTXOs, previous hash block and the nonce.

1 Like
#508

  1. Being cryptographically locked together is what provides the immutability of the blockchain and the structure and the name.

  2. The block structure consist of The previous blocks hash, the Data the block wants to append to the chain, the nounce number.

1 Like
#509
  1. By this is becomes impossible to manipulate previous blocks.
  2. Block, nonce, hash of previous block, hash of current block.
1 Like
#510

1.By cryptographically linking the blocks the chain security is increased. if one wants to undo that block they must rewrite all block leading up to it.

  1. Previous Hash + current TX +Nonce
1 Like
#511
  1. So the chain won’t be broken. If one block is changed all previous ones will be as well.
  2. Hash of previous block - Transactions - Nounce (random # = hash value lower than target)
1 Like
#512
  1. They have to be linked together, so if you go back and change one transaction, then you have to regenerate all successive blocks again and mine them again.
  2. It has transaction section, nonce and hash from previous block.
1 Like
#513
  1. Blocks are cryptographically linked together because it makes it near impossible to change as each block is a product of the last block…
  2. The block structure of BTC is as follows; Previous Hash, Data / TXhash, nonce.
1 Like
#514

Why is it important that the blocks are cryptographically linked together?
So the data can’t be invisible altered and if you want to change the data you have to adjust every individual block on the chain

What does the block structure look like in bitcoin?

Nonce
Data
Prev hash
current hash

1 Like
#515

Thanks for clarification!

1 Like
#516
  1. Why is it important that the blocks are cryptographically linked together?
  • Because it makes it almost impossible (nothing is impossible) to change blocks.
  1. What does the block structure look like in bitcoin?
    Tx, Hash, nonce, input / output, blocksize.
1 Like
#517
  1. It ensures data immutability and finality.
  2. While there is probably more to it, so far in this course we’ve learned about
  • transaction list
  • block hash
  • hash of previous block
  • nonce
1 Like
#518

  1. It is important that the blocks are cryptographically linked to ensure that the rules of hashing are followed. Each sequential block can be mathematically proven to be true.

  2. The block structure consists of the TX, nonce (random numerical guess that is less than the target defined by puzzle difficulty), and the hash of the previous block.

1 Like
#519

1. Why is it important that the blocks are cryptographically linked together?
Blocks should be cryptographically linked together because this provides security and immutability to the chain, if one thing is changed in this type of chain then the whole thing changes.

2. What does the block structure look like in bitcoin?
Bitcoins block structure contains the hash of the previous block, transactions to be included in this current block, and a nonce which is a random number.

1 Like
#520
  1. Because the link is created by using computational power and thus it requires electricity and because in this way if someone changes something in a previous block than all following blocks and links would be invalidated
  2. The block woud have the hash of the previous block, the time stamp the transaction hashed to the merkel root hash which represents the hash of all transaction and the nonce all hashed together forming the hash of the block.
1 Like
#521
  1. Because it ensures the blocks remain immutable.
  2. It’s blocks consisting of the previous block, transactions and nonce cryptographically linked together through links based on previous information.
#522
  • Why is it important that the blocks are cryptographically linked together?

To make the “puzzle” difficult to solve requiring an expenditure of electricity. This also makes the network secure because it becomes unfeasible to change transaction data which would require remining all previous blocks on the chain and future blocks to catch up.

  • What does the block structure look like in bitcoin?

previous hash
time stamp
a record of some or all recent transactions,
nonce

1 Like
#523

It is important that blocks are cryptographically linked together because this means that the links between each block a created using the data from the previous block. As a result if the data in a previous block is changed the link will be broken meaning that the new block will have to be re-mined. And because this link has been broken it means that all subsequent blocks will have their links broken as well and each blocks hash is linked to the previous.

This cryptographic link is what provides the immutable property to the blockchain. It is extremely expensive to re-mine the blocks and even more difficult and expensive to catch up with the unaltered chain. It is practically impossible therefore to change any data on a blockchain one it has been recorded. In order to re-write the data one would have to control over 51% of the hash rate and it may cost millions of dollars to re-mine all subsequent blocks who’s hash have been altered & links broken to catch up with the current chain. In essence this cryptographic link is what makes it so difficult, if the hash function used in the link was not cryptographic then the cost of re-mining the blocks would potentially be feasibly affordable.

  1. The block structure for bitcoin looks like this

block 2 - hash|block 1 hash& tx data + nonce| -------------> block 3 -hash|block 2 hash & tx data + nonce|

Whereby the link between the blocks is a link is connecting the hash of block 2 with the data section of block 3

1 Like
#524

Homework on Blockchain and Mining Visually - Questions

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

If the blocks in blockchain were not linked cryptographically, it would be far easier to hack each individual block. Since they are linked by a hash of the previous block, any change in one block will be reflected in all previous blocks. This makes the work that would need to be done to re-hash a block astronomically expensive and nearly impossible or infeasible.

What does the block structure look like in bitcoin?

The block structure in the blockchain contains the hash of the previous block, a hash of the transactions, and a nonce, or a puzzle which modulates the hashing algorithm to force it to be within a certain target.

1 Like