Homework on Blockchain and Mining Visually - Questions

Blockchain and Bitcoin 101
#1227
  1. Because it makes the chain inviolable ( immutable)
  2. Block hash, time stamp , generation transaction ( who gets the BR) transaction and number of transactions , block size, previous hash, nounce, target
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#1228
  • Why is it important that the blocks are cryptographically linked together?
    Each hash is a unique identifier of the previous hashes which are also unique identifiers. So the network knows that something is wrong or tampered with when a hash that has been previously mined is changed because of this linking of blocks process. A slight difference in the information has a huge effect on hash identifier.
  • What does the block structure look like in bitcoin?
    Each block is linked to the previous block that has both a hash and information in it.
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#1229

  1. So that it becomes impossible to cheat or make a change to the blockchain.

  2. A linear line of blocks each containing the transactions, a hash from the previous block and a nonce.

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#1230

  1. To ensure that history is not tampered with, that is basically the data structure of a blockchain

  2. A linked list conformed of blocks that point to the previous block with a cryptographic hash produced by the concatenation of the block content like tx list and nonce.

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#1231

Yes I think I understand :slight_smile:

So the miners construct a block with their own transactions (two miners might not have the same transactions in the mempool so it can bi different). From these tx they calculate the merkle root hash, add the previous block hash, a timestamp and start guessing the correct nonce.
Each time the hash is calculated it is compared to the difficulty target. If the hash is below the required target it means the puzzle is solved and the block can be appended to the blockchain. If it is above the target, they change the nonce and try again. This process is repeated until the target is met. :slight_smile:

2 Likes
#1232
  • Why is it important that the blocks are cryptographically linked together?

This ensures increasing security of the ledger as the blockchain gets longer and hash power increases. Each previous block that should be altered / modified will require modification / re-hashing of all following blocks, making it exponentially more difficult to apply any changes. Like this, double spending is effectively avoided, information immutability ensured.

  • What does the block structure look like in bitcoin?

Hash (n) = Hash (Hash (block n-1) + transaction data + nonce)

2 Likes
#1233
  1. This makes it very difficult for anyone to tamper with the data once a block is formed. 2. you have the previous hash, plus a list of current TXs plus a nonce.
1 Like
#1234

Nice! Loved the function definition! :ok_hand:

4 Likes
#1235

  1. The importance of the cryptographic link, a hash value, is that if any data is changed in a block the hash derived from that data will change and that change breaks the link to the next block. This will ripple through all blocks subsequent requiring all these blocks to be remined to hide the original change, an impossibly difficult task.

  2. A completed block consists of a nonce, a hash value from the pevious block, and the transaction data. The hash of a combination of these three components is the link to the next block and the beginning of the construction of that new block. The miners will add the new nonce and the new data in a process that creates Proof of Work and generates a new hash that ties the newly created block to the next new block. And it goes on an on like this.

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#1236
  1. because of this, no one can go back and tamper with the data and have it stick, everything else gets thrown off, so the newly changed transaction will never hold up.
  2. previous hash, transactions, nonce
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#1237

  1. prevent the data from being altered. Data immutability

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

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#1238
  1. To ensure the integrity and immutability of the chain.
  2. Previous hash. TX. Nonce.
1 Like
#1239

Homework on Blockchain and Mining Visually - Questions

  1. Why is it important that the blocks are cryptographically linked together?
    A. It provides integrity and security of the blockchain. If a TX in a block was changed then all upstream blocks would be changed and dropped by the network
  2. What does the block structure look like in bitcoin?
    A. Block hash = Previous Hash + TX data + Nonce
1 Like
#1240

  1. To ensure consensus and immutability so you cant alter transactions on chain

  2. transactions in previous block + current transaction + nonce= hash

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#1241

Blocks being cryptographically linked together is important as it maintains their security and are expensive to create. Any change cascades in effect.

The block structure in Bitcoin looks like a hash of the previous block combined with the new blocks transaction list, combined with a nonce for a new hash.

1 Like
#1242
  1. It is important that the blocks are cryptographicaly linked together as this ensures that the record is censorship-resistant. Tamperproof. Immutable. If the smallest change is made in a block then all the folloeing blocks will become invalid as their validity is secured by their respective hashes and each hash is informed by the previous hash, linking all the blocks together in a chain. If you want to make changes, then you have to change all the blocks simultaneously, which is computationaly infeasable.
  2. In Bitcoin , block consists of the hash of the previous block, a list of ( at least 1) transactions, block header, Nonce, current hash.
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#1243

1)This makes it more difficult to change a block. When you change one block, you have to change all the blocks and create new hashed relations between the blocks, something which is impossible.

2)Version data, Previous Block hash, Merkle root hash, Timestamp, Difficulty target,Nonce
Block Size, Block header, Transaction counter, Transactions.

2 Likes
#1244

  1. So that to change any detail in a block every subsequent block must also be re-mined making the task exponentially more difficult as each block is mined.

  2. Version
    Previous Block hash
    Merkle root hash
    Timestamp
    Difficulty target
    Nonce
    Block Size
    Block header
    Transaction counter
    Transactions

1 Like
#1245
  1. So that it is secure and can’t be changed and manipulated by anyone.
  2. A block contains a list of transaction data , nonce, previous block and current block hash.
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#1246
  1. ensures security of network and making it tamper proof, one change in a block that has been accepted by the network can easily be traced and also affects all other blocks in the chain following it.
  2. it includes various metadata (number, pack size, etc), timestamps, difficulty targets, hashes of previous blocks in chain, the answer to the nonce puzzle and of course a list of transactions and their associated fees
1 Like