Homework on Blockchain and Mining Visually - Questions

Blockchain and Bitcoin 101
#2915

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

Cryptographically linking the blocks ensures the security of the network by making it extraordinarily difficult for an alteration in previously added blocks to be validated and accepted as the “trustworthy” version of the blockchain.

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

The block structure in bitcoin looks as follows :

  • Number of the block

  • Nonce

  • Data (transactions) contained in the block

  • Hash of the previous block

  • Hash of the current block

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#2916

  1. Because it links the blocks together in a way secures the blocks by proving that they are not changed in any way.

  2. The hash of a block comes from the hash of the block before, a list of txs and a nonce.

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#2917

  1. It is important because it allows to verify blockchain integrity. If one of the blocks contains false transactions it will break the blockchain and malformed block will be rejected.

Previous hash
nonce
transactions

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#2918
  1. Cryptographic hashing is directly
    responsible for Blockchain’s immutability.
    Each new block contains a hash of the
    data in the prior block. A change to any bit
    of data in any past block would alter the
    hashes of that block and every subsequent
    block. The network would immediately
    see that the hashes don’t match their
    version of the chain, and would reject the
    change.
  2. In bitcoin, each block contains the version
    of the data, the hash of the prior block, the
    Merkle Root (the fingerprint for all the
    transactions in the block), the current time,
    the target number, and the nonce.
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#2919
  1. Why is it important that the blocks are cryptographically linked together?
    The link prevents the data to be altered.
  2. What does the block structure look like in bitcoin?
    Block #
    Nonce
    Data
    Previous hash
    Hash
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#2920
  1. It is important that the blocks are cryptographically linked together because it ensures the security of the whole blockchain.
  2. The block structure in bitcoin has the hash of the current block, hash of the previous block, list of transactions and a nonce.
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#2921

Why is it important that the blocks are cryptographically linked together?
To prevent changes in the blockchain. Since a block is made by a mathematical calculation of the previous hash, transactions and nounce, and this give result to an unique number, any changes in previous blocks will detach the entire chain until the point it was modified.
Being the blocks cryptographically linked together increases the security, and also ensures provenance.

What does the block structure look like in bitcoin?
In Bitcoin a block is composed by the transactions, the hash from the previous block and the nonce.
When it is built is possible to see:

  • when it was built
  • who was the miner
  • how many transactions and the detailed list
  • the difficulty number and the nonce that generated this hash
  • block size
  • block reward and fee
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#2922
  1. Why is it important that the blocks are cryptographically linked together?
    This makes the network secure as anyone changing previous transactions in the blockchain ledger, will also change the hash of the following transactions which means that they will have to remine any previously mined blocks as the hash output and resulting nonce would be different.
  2. What does the block structure look like in bitcoin?
    Transaction hash, previous transaction and the random Nonce. The hash for the current block is based on these added together.
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#2923
  1. For security purposes. By making all blocks interconnected in this way any change in the network will be very costly.
  2. The information inside the block + the previous hash + nonce = new hash of the current block
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#2924
  1. Because this allows the bitcoin network to be secure, immutable and trustless. Any kind of tampering would be easily declined by the network.
  2. The block structure is horizontally aligned, and consists of the previous block hash, nonce and the new hash created.
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#2925
  1. So it would be difficult to go back and change a block because of the amount of work required to solve and recreate all past and future work.
  2. Block Size, Block Header, Transaction Counter, Transactions
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#2926

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

#2927

Included in the header is the Bitcoin version number, previous block hash, Merkle root, timestamp, difficulty target for the block, and the nonce.

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#2928

  1. So if a transaction is changed or a block is changed, all new and upcoming blocks in the chain need to be recreated as well which will be time-consuming and costly

  2. Previous hash number + Transaction detal+Nonce number to guess the new hash created

2 Likes
#2929
  1. It makes the whole chain more solid. It would be very difficult to change sth later.

-Hash of the current block
-Hash of the previous block
-Transactionlist
-Nonce

2 Likes
#2930

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

It is important for the security of the blockchain, if you change something in one block then all the following blocks get changed to. transaction number + previous hash = current Hash

2 What does the block structure look like in bitcoin?

The Hash of the block is based on the transaction in the block plus the previous hash and the nonce that has to be guessed.
Block number
NONCE DATA
Previous Hash
Current Hash

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#2931

1.To increase security: changes cannot be forced onto the network.
2. All confirmed transactions, the nonce, the block’s hash, and the previous block’s hash.

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#2932
  1. It is important that the blocks are cryptographically linked together so that someone cannot go back and change a previous block because if they were to do so it would be impossible for them to catch up to the current blockchain.
  2. The block structure in bitcoin is a unidirectional linear movement. Each block must hash the hash of the previous block as well as transactions and a nonce so that they receive an output lower than the target in order to write the next block.
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#2933

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

Apart from security measures, 'double-spending' and ensuring that the data on that block is difficult to decrypt (immutable), it also ensures the data is connected to the next block via the encrypted hash and timestamp on the blockchain. If one block is edited or altered in anyway, it then alters all the other subsequent blocks and results in that block being discarded as 'illegitimate'.

What does the block structure look like in bitcoin?

A blockchain block structure looks like a ledger or a bank transaction. It records the previous hash, timestamp, transaction lists and nonce. They are organized into a linear sequence over time (blockchain) and added to the end of the chain once processed by the miners. They are unique and act like a fingerprint for the data in a block.

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#2934

1-To secure network and prevent double spending or alterations of transactions
2-A block is a list of transactions (UTXOs) plus previous hashes and a nonce

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