Homework on Blockchain and Mining Visually - Questions

Blockchain and Bitcoin 101
#2110
  1. Why is it important that the blocks are cryptographically linked together?

In order to preserve the digital rock, we need to make sure each block have the digital signature of the previous block, and by breaking one of this links, all future links will be broken as well, making it even harder to make changes in the records.

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

Block number, transaction list data, last block hash, nonce

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#2111

1 because it makes the system secure
2 prev. Hash+tx+ nonce

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#2112
  1. To ensure that the blockchain is immutable.
  2. The block is made out of data, previous block hash and a nounce, which is used to calculate a hash number below the target number.
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#2113

1:itā€™s an essential part of the blockchain that provides immutability and removes trust.

2:something like this:

block number
nonce
previous hash
txt
txt
txt
new hash

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#2114

  1. Cryptographic Linking of the blocks is important to keep the blockchain secure. Modifying or changing anything regarding a transaction in a previous block changes the hash of that block which breaks the chain to that block.

  2. The blockchain structure for bitcoin consist of a hash generated to represent the nonce of current block, the transaction of the current block and includes the hash of the link to the previous block which also consists of hash to represent the nonce of previous block, the hash of transactions of the previous block and the hash of the link to the previous transaction.

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#2115
  1. The cryptographic link from block to block ensures the immutability of previous blocks as amendments to any previous transactions would result in the breaking of the link between each block as the relevant hashes would all have changed.
  2. Essentially a bitcoin block contains itā€™s own hash which is composed by hashing the previous blockā€™s hash, the transaction list of the block and a nonce value. Other meta data also exists such as time stamp, block height, block size etc.
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#2116

1- It is important that blocks are cryptographically linked together because this type of structure ensures that the blockchain remains tamper proof. Any attempts to change data in any previous block will invalidate the hash of that block and will also invalidate any subsequent links leading back to that block.

2- Block structure in bitcoin consists of 1) block metadata 2) block transaction data 3) cryptographic hash of previous block and 4) nonce. Hash of block is calculated using all four elements. Resulting hash is then compared to the target value set by the network. If hash is below target value, then the block is accepted.

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#2117

  1. Because this ensures that the blockchain is inmutable. By linking the blocks, the hash of each block is dependent on previous ones, making the blockchain tamper-proof.

  2. It contains the information, the nonce, the hash of the previous block and the current hash.

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#2118

From this I understand that the random number which is the nonce that is determined based on randomly guessing, you must keep guessing the nonce until the blockhash is low enough so doesnā€™t that mean the nonce must be a low enough number as for the blockhash to go through is based on guessing the nonce and Ivan explains that the target may be something like 0 to 100 and if the target is 40 then you must guess the nonce below 40 for the blockhash/block to be accepted into the network? Maybe I am not understanding correctly. I do enjoy your help and likes on my forum posts as that lets me know I am doing good and not thinking wrong as I see i can trust you based on your profile and posts. Thanks! Hope to hear a response soon :slight_smile:

#2119
  1. Blocks are cryptographically linked together so that it is immutable. The cyrptographic link will be broken in all directions if a blockā€™s data is changed in any way. The change will be rejected. Therefore the cryptographic links maintain the integrity of the network.
  2. Block Structure has a HASH, NONCE, and THE TRANSACTIONS.
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#2120

Nonce is the number miners use to find the hash that is below the target. :slight_smile:

#2121

Particularly the hash of the previous block. :slight_smile:

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#2122
  1. To ensure that the chain canā€™t be compromised - changes in any part of the chain will reflect in blocks that follow. If this doesnā€™t match the chain that the network has agreed upon, the changes will be rejected. This ensures that trust in the system.
    2.On a high level each block consists of; 1. The list of transactions 2.The nonce 3. The hash of the previous block.
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#2123

1- Its for the security of the blockchain so no transactions can be changed in previous block this would break the chain and the link to the next block and all the following blocks
2- A chain, a linked data structure where each block contains previous hash and transactions and nonce linking to new/next block

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#2124

  • Why is it important that the blocks are cryptographically linked together?
    A) to create a chain that cannot be altered without breaking the links. This creates security and incentivizes the miners to play by the rules.

  • What does the block structure look like in bitcoin?
    A) Block #
    Nonce
    Data
    Previous Hash
    Hash

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#2125

  1. This makes it virtually impossible to make a change to one block without it impacting all of the blocks after it. If such a change occurs it would cause the nodes to reject that block.

  2. The block is composed of the hash of all of the transactions treed up into a merkle root. This is hashed. Then the hash of previous block and the nonce. These will be hashed together to create the hash of the ā€œprevious blockā€ which will be part of the next block. There is also a timestamp, version number, and target size in the header.

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#2126
  • Why is it important that the blocks are cryptographically linked together?

A cryptographically linked blockchain adds security in that if any of the links are broken then it is recognized and the blockchain will recognize the longest chain making it nearly impossible to be compromised.

  • What does the block structure look like in bitcoin?

The block contains the hash, merkle root (hash of previous block), nonce, transactions (public sender/receiver address, amount), block height, number of confirmations.

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#2127
  1. Why is it important that the blocks are cryptographically linked together?
    to ensure security of the blockchain
  2. What does the block structure look like in bitcoin?
    block number
    hash of previous block
    transactions in a block
    nonce
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#2128
  1. Because that secures the network. It is proof of transactions/data that actually happened (and were approved as true), and we can be sure that nobody messed up any previous data otherwise the chain gets broken (and the true chain is always the longest one).
  2. A block has its own hash and it comes from data from that block, hash of previous block and nonce (random number that miners have to guess).
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#2129

  1. This ensures that if any of the content of the previous blocks are changed, all the links will break as they are formed based on the information from the previous blocks. The only way to make the blockchain make sense again is to solve the new nonce based on the new content, and you will need to re-mine all subsequent blocks faster than other miners. This is practically impossible and is what makes the blockchain immutable

Hash (Transaction ID)
Previous Hash
Transactions lists: Inputs & Outputs
Nonce (cryptographic puzzle)

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