Homework on Blockchain and Mining Visually - Questions

Blockchain and Bitcoin 101
#122

  1. Why is it important that the blocks are cryptographically linked together?
    The blocks are linked together as long as all rules have been followed, honest transactions approved and no changes made. This ensures the security and reliability of the entire network.

  2. What does the block structure look like in bitcoin?
    Block = TXs + Nonce + Previous Hash

#123

  1. To ensure that the network is secure and efficient it ensures transactions cannot be tampered with.

  2. A block contains a block number, nonce, transaction data, the has of the previous and current block.

#124

  1. The blocks are cryptographically linked to show POW and ensure integrity.

  2. The block structures includes:

  • Block Number
  • Nonce
  • Transaction Data
  • Hash Inputs and Outputs
#125
  1. Why is it important that the blocks are cryptographically linked together?

All transactions include previous block’s hash which protect the chain from having a transaction in the past changed: data immutability.

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

Each block consists of the previous block’s hash, the current block’s transactions, the guessed nonce which are all hashed into this block’s hash.

#126
  1. Why is it important that the blocks are cryptographically linked together?
  • To insure the integrity of the blocks in the blockchain that remain immutable
  1. What does the block structure look like in bitcoin?
  • A block in the blockchain is composed of:
  1. Block Data
  2. Nonce
  3. Previous Hash
  4. Hash of block
  • Inputs and Outputs
#127
  1. Why is it important that the blocks are cryptographically linked together?
    So that it is more and more difficult to alter the network retroactively. Making any alterations to previous blocks would invalidate everything up to the current block. The further you try to go back, the more and more impossible it is to cheat the network.
  2. What does the block structure look like in bitcoin?
    A block is the Hash of the transaction list, the nonce, and the previous block’s hash.
#128

1-Immutability, it would require all following blocks to be changed/remined.
If data is changed in a block all links in following blocks are broken

2-Previous Block Hash
Present Block Transactions
Present Block NONCE
Present Block Hash

#129

In order to secure the immutability of the chain, once any change in the previous block would automatically invalidate every following block. Also making easy to verify where the structure of the chain has been corrupted.
2.
It’s a standard number formed by the calculation of the previous Block Hash, the Data in the current Block, meaning the inputs and outputs, plus fees, block reward, date and time; and a randomly generated Nonce.

#130
  1. Why is it important that the blocks are cryptographically linked together?
    This way all information stays safe, and can not be altered or removed. New blocks contains information of previous blocks.
  2. What does the block structure look like in bitcoin?
    Structure includes: hash of a previous block, nonce and current transitions.
#131

  1. To keep the integrity of the blockchain making it impossible to change a previous transaction easily.

  2. Each block contains hash/transactions/hash from previous block/nonce.

#132

It ensures immutability
A blockchain consists of the previous blocks hash, the current blocks hash and the nonce.

#133

  1. Why is it important that the blocks are cryptographically linked together?
    This ensures the security of the blockchain, so that not even one transaction can be changed.

  2. What does the block structure look like in bitcoin?
    It contains the hash from the previous block, the transactions in the current block and the nonce (that needs to be guessed).

#134

  1. It is important for blocks on a chain to be cryptographically linked together so that in the event any input on any previous block is altered it would change the crytographic puzzle of all the future blocks requiring all of the blocks needing to be remined, with the high amount of hashpower needed this makes it provably impossible.

  2. The block structure of bitcoin would be defined by what it includes, link to previous block, hash, the block reward and tx fees, all of the tx and the nonce

#135
  1. Why is it important that the blocks are cryptographically linked together?

To make sure that no changes are made in the history. Whenever that happens, the whole chain is invalidated. So the only way to make changes in the blockchain, is by adding transaction, put it in the mempool and mine it. By cryptographically linking all blocks, it is practically impossible to hack/change the blockchain.

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

Every block contains a list of transactions, the previous block hash a nonce and a hash that is lower than the target value.

#136

  1. The blocks are cryptographically linked together by so that a change in one block shows all the changes to forward blocks.

  2. A block in bitcoin has a) transactions, b) hash, c) previous block hash, and d) nonce.

#137

1. Why is it important that the blocks are cryptographically linked together?
This makes the it difficult to alter the previous blocks. Cryptographically perfectly linked blocks make perfect ledgers.

2. What does the block structure look like in bitcoin?
A block structure in bitcoin is a composite of the previous hashed block, the current transactions and the discovered NONCE

#138
  1. Why is it important that the blocks are cryptographically linked together?
  • So that the network remains secure, no changes can be made to previous block because it will disrupt all the blocks before it. Breaking links to each block.
  1. What does the block structure look like in bitcoin?
  • Nonce, transaction(data), hash previous block, and hash current block
#139
  1. Why is it important that the blocks are cryptographically linked together?

This ensures that blocks can’t be altered, also it allows everybody to verify blocks and data at any time.

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

To sum it up, a block is composed by:

  • list of transactions
  • nonce (a random number used to generate the block hash, lower than the current difficulty target)
  • hash of the previous block
  • more data such as block size etc. can be seen in a block explorer
#140
  1. Why is it important that the blocks are cryptographically linked together?

That way it’s easy to see any change in any bit of information throughout the chain all the way to the beginning. Any small change anywhere will change all the data afterwards that way it’s easy to recognize and reject any small change no matter how far in the previously mined blocks it is.

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

The block has all the transaction data in it. It has a hash also that is a hash of 1)a Nonce 2)the transactions in that block 3)the hash of the last block.

#141
  1. Why is it important that the blocks are cryptographically linked together?

Cryptographic link between blocks ensures security of blockchain by proof of work model. If you change one block, all blocks forward would be rejected because they will not be cryptographically linked to the changed block so you would need to recreate proof of work for all blocks after the one you changed faster than original chain and become the longest chain. This would require that you have control of at least 51% of network’s all hash power

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

Each block is made out of block header and transactions. Block header consists: version number, timestamp, block size, difficulty target / nonce, hash of previous block, merkle root hash. Transaction data consists of counter and list of UTXOs in form of a merkle tree