Homework on Blockchain and Mining Visually - Questions

Blockchain and Bitcoin 101
#1788

  1. Why is it important that the blocks are cryptographically linked together?
    To show the proof of work of previous blocks and to show that they can’t be changed.

  2. What does the block structure look like in bitcoin?
    The blocks are connected, There is a nonce number that miners are trying to figure out. Data of the transactions. The first block wont have a Prev hash function and last the Hash function of the previous data is coded. This is added to the 2nd block and a new nonce number is created with the data, the previous hash will be on the 2nd block with a new hash function for the 3rd block.

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#1789

  1. Because all blocks are linked together, every block will change if a previous block changed. This is necessary for the data to be immutable, because this causes that no one can go back and change their UTXOs. Without these links, bitcoin would not be able to exist.

  2. image

A block header contains the following:
a. The block Version number
b. The current timestamp
c. The current difficulty target
d. Hash of the previous block
e. Nonce
f. Hash of the Merkle Root

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#1790

:slightly_smiling_face: :upside_down_face:

#1791

The block consists of block header (which consists of version, prev block hash, merkle root, timestamp, target and nonce) and block data. You don’t have to be 100% accurate, the important thing to understand is that the blocks consists of the previous block hash that links them together :slight_smile:

But in case you are curious https://en.bitcoin.it/wiki/Block :wink:

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#1792

It is important for blocks to be crypto-graphically linked together as it is this method that allows the near infallibility of the blockchain, ensuring that each block holds a signature or “fingerprint” that is entirely reliant upon the information stored in the previous block and it’s hash

The block structure of Bitcoin consists of the transaction data, the nonce, and the previous transaction’s as well as the current block’s hash

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#1793

1.To keep the security of the chain so that there can be no double spending or any other data alteration.
2. Bitcoin block contains the hash of the previous block and the transactions of the current block.

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#1794

  1. It is important because otherwise past blocks (and their content) could be manipulated. By having hashed relations between the blocks it is (almost) impossible to change entries in past blocks.

  2. Each block contains:

  • Transactions chosen by the miner(s)
  • Hash of the previous block
  • A nonce (which is random)

Those three variables are then hashed and this hash is the hash of the new block which itself will be hashed again in the next block as previous hash.

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#1795

You probably mean previous blockhash instead previous transactions

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#1796
  1. Why is it important that the blocks are cryptographically linked together?

It is important that the blocks are cryptographically linked together because this ensure that nobody can go and change a transaction in a previous block. This would break all the links and it would have to be reminded all over again. It also ensures that no double spending is happening.

  1. What does the block structure look like in Bitcoin?
    The way the block structure looks like in bitcoin is, there are transactions in the block. This block is going to be hashed. The hash is going to vary depending on the previous block, the nonce and the transaction in the block.
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#1797

  1. By linking blocks together cryptrographically the security and integrity of the transactions can be guaranteed. If any information is changed in one block then it would be rejected by the linked blocks of the chain.

  2. The bitcoin block chain consists of blocks linked together to one another by a cryptographic hash. The blocks have a hash of all the transactions in their lists as well as previous transactions of previous blocks in the chain.

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#1798

  1. Blocks are cryptographically linked together to maintain the integrity of the blockchain making it prohibitively expensive to try and manipulate blocks.

  2. Each block contains a header with the Version, Time, Bits, Nonce, hashPrevBlock and hashMerkleRoot. Below this are the transactions containing the Coinbase transaction and then all of the other transactions to be included in that block.

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#1799

Blocks are cryptographically linked together to ensure that it is very difficult for someone to change the block. This will make the blockchain very secure.

The block structure of bitcoin consists of a hash of the previous block, list of transactions (input/outputs) and a nonce.

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#1800

Yes that’s what I meant, thanks for the correction!

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#1801

It is important that blocks are cryptographically linked to create secure network that cannot be altered, hacked or copied.

Hash of Previous Block
TXs
Nonce

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#1802

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

Because it ensures the safety of the blockchain. By making sure that all the blocks appended to the blockchain have had all nodes reach consensus on the validity of the transactions in them.

If they where not linked together with previous and the next blocks the blockchain would be deemed insecure. Because any block could be changed without affecting the next. “there would be no way to validate the transactions in previous blocks”

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

Each block would have to be fitted with a “unique fingerprint” and linked to the previous and next blocks.
This would ensure that “no data can be changed after the fact”

A block appended to the blockchain contains :

  • Current block hash
  • Previous block hash
  • Nonce
  • Transactions list
  • Block count
  • Difficulty level

The current blocks hash is based on the hash of the :

  • Previous block hash
  • Transactions list
  • Nonce

Because the next block is based on the previous blocks hash,Transaction list and nonce.
It would register as invalid by all nodes if someone changed any data in a previous block.
( Because such a change would also change the hash of all the blocks that came after it )

This is why P.O.W is securing the blockchain.

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#1803
  1. Why is it important that the blocks are cryptographically linked together?

To maintain the integrity of the blockchain and confirm that all data that has happened previously is unchanged.

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

A Block can be made up of many elements however the three key pieces of a block structure are:

Hash
Previous Hash
Data (Transactions)

There are other pieces of information that can be added such as:

Time Stamp
Index
Difficulty

I suppose you could even create a further variable for contracts, links, etc also.

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#1805

  1. This link assures not only that any change to one automatically changes the following block. This also assures that the variables creating the link cannot be viewed and therefore ‘hack’ the blockchain.

  2. The block structure contains input, output, timestamp, nonce, tx hash.

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#1806
  1. Why is it important that the blocks are cryptographically linked together?

It creates a high level of security for the network, if a previous block is altered all the links to the blocks after the block being altered, which is cost prohibited for bad actors trying to cheat.

  1. What does the block structure look like in bitcoin? Block number, Nonce, Transaction Data, Hash of the Previous Block , Hash of current block
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#1807

  1. So that in case data gets changed in any part of the blockchain, instantly all the other blocks get changed as well and it gets easily detectable

  2. A block consists of the hash of a previous block, the transactions stored inside the block, a nonce and the correct hash generated out of all that data

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#1808

[quote=“ivan, post:1, topic:8433, full:true”]
Homework on Blockchain and Mining Visually - Questions

  1. Why is it important that the blocks are cryptographically linked together?
    This is important because it ensures the integrity of data in the blockchain. This makes it very difficult, if not impossible, for the data to be tampered with. Any change to the transactions in a block will cause the hash in the next block to be invalidated and that will also affect all subsequent blocks.

  2. What does the block structure look like in bitcoin?
    A bitcoin block contains the hash of the previous block, transaction list and the nonce.

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