Homework on Blockchain and Mining Visually - Questions

Blockchain and Bitcoin 101
#3637

  1. The importance of the blocks being linked cryptographically ensures the integrity of the chain. It would also show any sort of foul play if the link is broken which would in turn affect all other links as well.

  2. The block structure in BTC has the Transactions (inputs outputs), The Nonce, The Previous Blocks Hash & The Current blocks hash & Block Number.

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#3638

  1. It is important to link the blocks cryptographically together to keep the blockchain secure. It makes it impossible for someone to alter a transaction in any one block. It essentially makes the blockchain immutable.

  2. Each block in the Bitcoin blockchain contains the hash of the previous block along with the nonce and transactions for the current block.

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#3639
  1. Why is it important that the blocks are cryptographically linked together?
    To ensure each block is secure and no one able to make any changes to the previous block.
  2. What does the block structure look like in bitcoin?
    It consist of nonce, transaction data, previous block hash and the current block hash
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#3640

  1. It is important that blocks are cryptographically linked together because any change to the data of a block changes all the subsequent blocks.

  2. HASH, NONCE, Prev.block HASH, Tx List.

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#3641
  1. Why is it important that the blocks are cryptographically linked together?

Because if they arenā€™t cryptographically linked together anyone can change a block and duplicate the whole ledger in question of minutes, and spread fake transactions without anyone know it.

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

We have the transactions, the hash of the previous block and the nonce, and the current hash of the block.

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#3642

  1. To ensure immutability and security of the network. Proof of work consensus.

  2. A block in the btc Blockchain has to have the previous block hash number, the tx list and the guessed nonce.

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#3643

  1. Why is it important that the blocks are cryptographically linked together?
    This adds security and integrity to the network meaning that in order to change the information on the block you would need to change everything else before it and so on until the genesis block.

  2. What does the block structure look like in bitcoin? This is composed of the nonce (Which miners guess repeatledly) - Transaction informtion - the previous hash.

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#3644
  1. So that none of the previously mined blocks can be altered, and so that no new blocks can be inserted in between previous blocks.
  2. A block consists of nonce, previous block hash, and tx list for that block
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#3645
  1. Itā€™s important that blocks are cryptographically linked together because of security. Since all transaction history is linked togeether, itā€™s almost impossible to change a previous block and keep up with the new blocks being created. It also deters forgery, because of the money it would take to change a single block.
  2. Each new block has a list of new transactions, a nonce(random number), and a hash containing every transactions in the blockchains history including the block just before it. That block must then be hashed and meet the target in order to be added to the blockchain. If it meets the target it is added to the blockchain. If it doesnā€™t then the miner will have to regenerate the nonce and rehash the block.
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#3646
  1. Why is it important that the blocks are cryptographically linked together?
  • because of data-immutability
  1. What does the block structure look like in bitcoin?
  • block size in bytes
  • block header (link to previous hash/block; difficulty+timestamp+nonce; merkle tree root)
  • transaction counter (how many tx follow)
  • transactions (record of transactions in this block)
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#3647
  1. In order to secure all transactions. By doing that, it is almost impossible to alter transactions.
    2.Previous hash, TX data, nonce
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#3648
  1. Why is it important that the blocks are cryptographically linked together?
    It creates data immutability which is essential to blockchain.

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

  • Nonce
    Prev hash
    tx list
2 Likes
#3649

  1. Because thats how it secures the network

  2. it looks like an alpha numeric chainā€¦

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#3650

The links between the blocks are very important because they validate the integrity of the transactional history. Each link is the result of a lot of work and is only valid for one particular state of the blockchain that precedes it and enforces that particular state to the blockchain following it.
To alter the data in a block would mean invalidating that block and all following blocks because the hashes would no longer be valid and would need to be re-mined.

In short: The cryptographic links solidify one particular state of the blockchain and this state can only be replaced by an immense amount of computing power.

The block contains all the transactions and a bunch of other variables. The most important variables in a block are the nonce (single-use random number), the merkle root, the difficulty target and the previous blocks hash.
The previous blocks hash is included to link the block to the previous block.
The Merkle root is a hash of the Merkle root of all the transactions in that block. All the transactions are hashed and then put in a in a Merkle tree. Then the root of that Merkle tree is hashed. This Merkle root hash is essentially a hashed version of all the transactions individual hashes put together which adds security to the blockchain.
The difficulty target determines how low the hash for that block needs to be to be accepted.
The nonce is a single-use random number that the miner changes to get a new hash.
All the variables are fixed except for the nonce. Finding the nonce that will provide an acceptable hash is the challenge faced by the miner, and the only way to do this is to try to re-hash over and over again with different nonces until they find an acceptable nonce.

The difficulty target is adjusted so that there is approximately 10 minutes between each new block.

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#3651
  • Why is it important that the blocks are cryptographically linked together?

This makes it impossible to cheat since all blocks are tied together through mathematical algebra. One change to a block and it changes everything that comes after.

  • What does the block structure look like in bitcoin?

Transaction blocks connected by input and output hashes.

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#3652
  1. Why is it important that the blocks are cryptographically linked together?
  • to make sure previous transactions can never be changed, changing one will change all subsequent blocks
  1. What does the block structure look like in bitcoin?
  • Previous blocks hash
  • Transactions
  • Nonce
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#3653
  1. Why is it important that the blocks are cryptographically linked together?

The linking of the blocks makes it near impossible to alter data. If you change anything in one block, you affect that block plus all subsequent blocks, and all those hashes will change. Therefore, linking ensures integrity and security.

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

Block:
Nonce
Data
Previous blockā€™s Hash
Hash

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#3654

  1. Why is it important that the blocks are cryptographically linked together?
    So that if someone alters the history ALL futre blocks need to be remined, not just the block where the change has been made => SECURITY

  2. What does the block structure look like in bitcoin?
    It is a linked list data structure. Where the link is a hash of the previous block. The hash of a block is computed from:
    a) hash of previous block
    b) transaction list
    c) nonce (random number)

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#3655

  1. Why is it important that the blocks are cryptographically linked together?
    This is important for the security, because any change in the previous blocks would break links which would break the blockchain.

  2. What does the block structure look like in bitcoin?
    The block structure includes the hash number of the previous block, the transaction list and nonce which is the lower number than target. Thats all makes up the new hash number of the new block using cryptography.

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#3656
  1. This ensures the integrity of the blockchain since an amendment to any transaction would require all subsequent blocks to be mined again
  2. Block structure consists of the nonce, previous hash and the transactions
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