Homework on Blockchain and Mining Visually - Questions

Blockchain and Bitcoin 101
#3858
  1. Why is it important that the blocks are cryptographically linked together?

To ensure the whole system follow the rules, no one could change, amend or delete any transactions or records.

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

In the block we have previous hash, transactions and nonce. The hash of current block base on all these three factors. Blocks are chronological and a hash fits in between each block.

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#3859

Can you tell what kind of metadata is in the block header? :wink:

Timestamp, a hash representation of the block data, the hash of the previous blockā€™s header, and a cryptographic nonce (if needed).

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#3860

  1. It is important that the blocks are cryptographically linked because that way if any previous hash or transaction in the blockchain is changed then the links all break up to the most recent block. This acts as an accuracy and integrity check at all times.

  2. The block structure of bitcoin consists of the nonce, transactions, previous hash, and current hash.

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#3861
  1. Because it provides data integrity and ensure that all block remain immutable.
  2. Block contains:
  • hash of the previous block,
  • list of transactions
  • nonce - number which miners have to guess
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#3862

1.To ensure the safety of networkā€¦
2. Block header, block size, transactions plus transaction counter, nonce, previous block hash

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#3863

  1. It is important that blocks are cryptographically linked together because it means that there is a practical impossibility for someone to go back and change transaction data on a mined block. More so, blocks that are cryptographically linked blocks ensure that there is no double spend and maintains data integrity on the network.

  2. A blocks structure on the bitcoin network looks as follows: The inside of a block is made up of transaction data and fees attached to the data, which the miners chose from a mempool. The miner will chose the transaction with the highest fees and construct a block with them in it. The miner will then compete to appended the block to the chain, by solving the cryptographic puzzle and this is where the main structure comes in:

Hash(block) = hash(transaction data) + hash or previous block + nonce = Hash < target

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#3864
  1. To secure the network and have the integrity.
    1. Nonce (random number)
    2. Data (Information about previous transactions)
    3. hash of the previous block
    4. hash of the new block
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#3865

  1. Why is it important that the blocks are cryptographically linked together?
    It is important because it ensure the security of the network. Cryptography prevent the alteration of data on blockchain.

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

The block consists of three sets of block metadata.

First, there is a reference to a previous block hash, which connects this block to the previous block in the blockchain, also known as parent block.

The second set of metadata, namely the difficulty , timestamp , and nonce , relate to the mining competition.

The third piece of metadata is the merkle tree root, a data structure used to efficiently summarize all the transactions in the block.

all above hashed together become hash (fingerprint) of the current (child) block.

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#3866

  1. to provide a trustless immutable , transparent secure hash within each block

  2. block # , nonce , data, input has h and output hash

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#3867

  1. So that no one can go back and make a change to the ledger.

  2. Previous hash, TX, nonce, new hash, target

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#3868

1. Why is it important that the blocks are cryptographically linked together?
It increases security of the blockchain by exponentially increasing difficulty of going further back in time and trying to change data in previous blocks. (They have to hash every block in blockchain that came after the block where they would want to change the data)

2. What does the block structure look like in bitcoin?
It contains Previous Hash, Data(list of transactions),nonce, hash of the new block.

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#3869

  1. It ensures blockchain integrity, that the previous block linked to the current block holds integredital value so that there is no double spending or malice in the chain.

  2. It includes the hash from the previous block, the nonce number, and the hash given to the current block.

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#3870
  1. It is the mechanism that makes the blockchain records immutable.
  2. Structure of a block:
  • Index: block number
  • Previous Hash: hash of the previous block
  • Timestamp: when the block is added
  • Data: transactions
  • Hash: SHA256(index + previousHash + timestamp + data + nonce)
  • Nonce: number used to find a valid hash
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#3871

  1. Because it ensures that the blockchain works, if the blocks were not cryptographically linked together it would be very easy to modify the transactions and get away with it. It makes the system secure.

  2. The block structure contains the transaction list (data), the previous hash and the nonce, that hashed all together gives the hash from the actual block.

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#3872

Homework on Blockchain & Mining Visually - Notes & Answers

NOTES:
=======
Mining Visually Demonstrated

ANSWERS:
=========
1) Q: Why is it important that the blocks are cryptographically linked together?
A: This ensures that data/transactions from previous blocks cannot be changed. If they are changed then that changes the hash (breaks the link) of every blocking following it and hence the hash of the current block.

2) Q: What does the block structure look like in Bitcoin
A: Bitcoin blocks consist of: Hash of the current block, hash of previous block, transactions of current block, and nonce. Keep in mind the hash of the current block is based on the other 3 components.

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#3873

  1. All blocks are linked and each link and block depends on the info 9n the last block and for the blocks and linked to remain linked the info cannot be altered.

  2. A block structure consists of the previous block hash, current lock hash, transaction and Nonce.

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#3874

To insure that they canā€™t be changed, changing one item in the block changes the entire blockchain.

The previous hash block, TX list, nonce and hash of current block

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#3875
  1. Why is it important that the blocks are cryptographically linked together?
    For the security of the blockchain. No transactions can be changed in previous blocks because it would break the link to the next block and all that once that follow
  2. What does the block structure look like in bitcoin?
    The hash of the block is based on the transactions in the block plus the previous hash and the nonce that needs to be guessed.
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#3876

1- Because of the security of the block itself. It makes almost impossible to alter recent transactions on the blockchain.

2- We have previous hash, also the transanction list, and the puzzle we must solve which is nonce (a random number we have to guess). And then we will have a current blockā€™s hash.

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#3877

Cryptographically linked together blocks ensure that nobody can change previous data within the chain and it go unnoticed. Immutability.

The block structure in bitcoin looks like a chain of blocks, hence ā€œblockchainā€. Each block consists of a previous block hash, transaction data, and a nonce. Each block gets its own hash/digital fingerprint once it is mined/confirmed/added to the blockchain.

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