Homework on Blockchain and Mining Visually - Questions

Blockchain and Bitcoin 101
#2271
  1. Why is it important that the blocks are cryptographically linked together?
    Having the blocks crypto graphically linked together is what guarantees at its best that no data added in any part of the blockchain be modified.
  2. What does the block structure look like in bitcoin?
    I suppose that the block structure looks like a series of hashes imperfectly linked together by cryptography.
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#2272
  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.
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#2273
  1. To secure the network and to ensure the double spend. To change someting in the blockchain, the whole chain will change!
    2 The hash of the block is based on all transaction which contains the block and the hash of the previous block, the nonce that needs the be guessed!
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#2274
  1. Why is it important that the blocks are cryptographically linked together?
    This is what secures transaction on the blocks and make nearly impossible to go back and make a change to a transaction(s).
  1. What does the block structure look like in bitcoin? Source from https://commons.wikimedia.org/
    image It seemed a good representation of Ivan’s illustration…
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#2275

1.to ensure no double spends happen,previous blocks cant be changed, every miners plays buy the rules
2.hash, transactions , nonce, privious hash , transactions and nonce

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#2276
  1. To secure the network. It keeps the previous blocks from being changed
  2. Previous block hash + data(transactions) + nonce + hash of current block
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#2277

  1. For security, since altering a block would alter the entire chain.

  2. A block in bitcoin is made up of the data (transactions) of that block, the hash of the previous block and a random number that miners must guess called nonce. With the correct combination of these three factors a block can be added to the chain, as long as the hash of this block is less than the target.

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#2278

It is important because it increases security and authenticity and it doesnt allow malicious change to happen somewhere on the blockchain If somebody would want to change a past block, it would mean that he will have to also reconstruct the whole blockchain from that point forward and it is basically impossible to do it without losing money. It is actually more profitable to be fair than to try and cheat. Cheating is punished and fairness is rewarded.

A block holds information stored into a hash. That has is based on all past blocks, its current transactions and a random nonce.

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#2279
  1. Why is it important that the blocks are cryptographically linked together?

The cryptographic link between blocks protects against malicious activity. If a miner attempted to alter a past transaction in a previous block, all following links would break. This is the case, as the cryptographic link is based on the hash of the previous block (and the TX fees and nonce of the block following it). The requirement of this link also is integral to ensuring PoW, as the creation of the link is what requires miners to constantly guess the potentially correct nonce by hashing it (and the previous block’s hash and current TX fees). This means miners are required to spend electricity, which is important for reasons laid out in Part 1 Q1 of this homework (incentiving honesty and securing of the network).
2. What does the block structure look like in bitcoin?

A mined block contains all TXs picked from a mempool by the miner, starting with the newly generated coins, which have no input (BR). It also contains the nonce (which must be guessed to generate a current hash below the “target”), and the hash of the previous block. These three elements act as the data input for the SHA256 hash function, which produces the fourth element of a block: The block’s own hash (digital fingerprint).

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#2281

  1. To make it harder to change a previous block. Any change would mean that all the blocks following would need to be changed as well and therefore would need a lot of time and money.

  2. Hash of previous block + transactions + nonce

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#2282

  1. it helps the blockchain security. that is why POW is so important

  2. Nonce
    Transactions
    Previous Hash

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#2283

  1. All blocks are linked, hash are linked

  2. UTXOs

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#2284

UTXOs are outputs of a tx, they are part of a block data, but there are also other parts. Most important to note is that the block header contains the hash of the previous block. :slight_smile:

#2285
  1. To prevent any changes to the blockchain which are not confirmed by network.
  2. previous hash, block data, nounce
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#2286
  1. So that when you make changes after it has been added to the structure, the whole chain becomes invalid afterward.
  2. It looks like a chain of blocks linked between each other starting with genesis block
    [prev hash+txns+nonce]-[prev hash+txns+nonce]-[prev hash+txns+nonce]
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#2287

  1. The cryptograph link ensures the data integrity of the blockchain to where all blocks have to remain true. It proves immutability.

  2. Each block has the previous hash, the utxo, nonce, and transactions, hash of current block

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#2288
  1. for security
  2. tx hash, inputs, outputs
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#2289

To make it harder to change.
Previous hash plus the new hash and the transactions in the new block plus nonce.

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#2290
  1. Why is it important that the blocks are cryptographically linked together?
    It links all blocks together and makes sure no changes can be made to previous blocks without the network knowing.
  2. What does the block structure look like in bitcoin?
  • Nonce, transactions, hash of previous block, hash of current block.
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#2291

1.- Because it ensures the inmutability of the chain.

2.- It includes among other things: transactions in the block, inputs, outputs, hash of the previous block, the nonce, block header, and more.

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