Homework on Blockchain and Mining Visually - Questions

Blockchain and Bitcoin 101
#1087

because each block with containing transactions are encrypted as hash-outputs,
if only one transaction of a past block was changed all of the following
transactions / blocks would yield to a strange hash. An abnormal manipulation would attract attention.

Index
Hash
Previous hash
Timestamp
Nonce
Transaction
Merkel Tree

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#1088

This enables security and trust is the system. You cannot change a previous block without changing all subsequent blocks.

Block Number
Merkle root Hash (Hash of all transactions)
Hash of previous block
Bits target
Nonce

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#1089

Hi there! Lot’s of hash words :slightly_smiling_face: . Maybe here you are trying to explain how the blocks are linked together, but what else, beside the previous hash and transaction list, can you find in the structure of a block?

Felipe.

#1090

What are you referring to here?

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#1091

Hi there!! Good, but what else can we find in each block? What else do we hash?

#1092

  1. This ensures data integrity/security of the blockchain. If anything is changed, the hash changes and link is broken.

  2. A block structure or hash of the block contains the transaction list, the previous hash and the nonce (target) the miners need to hit.

#1093

1.By having the blocks cryptographically linked it increases the likelihood of any tampering with the block chain to be noticed by the rest of the network and kicked out. Because if you change a transaction in one block it will affect the hash of that block and all of the hashes going forward.

2.A block is made up of the previous hash of the block prior, the transactions picked by the miners, and the nonce.

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#1094
  1. The cryptographic link between blocks ensures the immutability and integrity of the blockchain, thus preventing double spending.
  2. The block structure is represented by the hash of the previous block, the transactions and the nonce.
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#1095

  1. To ensure immutability and security.

  2. Specifically with Bitcoin the block structure contains,

Magic number - an identifier for the blockchain network.
Block size - indicates how large the block is.
Version - each node running the bitcoin protocol has to implement the same version.
Previous block hash - The digital fingerprint of the previous hash block header.
Merkle root - a binary hash tree data structure.
Time stamp - encoded as a Unix Epoch, the timestamp is accepted as valid if it is greater then the median timestamp of previous 11 blocks and less then the network adjusted time + 2 hours. Increasing the security of the block.
Difficulty target - a measure of how difficult it is to find a hash below a given target.
Nonce - a guessed number added to a hashed block that when rehashed meets the difficulty level.
Block header - used to identify a particular block.
Transaction counter - a count of transactions included in the block.
Transaction list - stores the digital fingerprints of the transactions in the block

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#1096

  1. For the security purposes. By linking all blocks together each small change will effect whole chain. Throw difficult and expensive way to link blocks, there’re no way for anyone to change previous blocks and catch up the chain.

  2. The hash of the block is based on hash of previous block, TX list of the block and nonce (will be guessed by miner depending on target difficulty).

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#1097

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

The reason i think its important that the blocks are cryptograhically linked together is because, all information on the current block is built on the previous block, all the blocks are on the same hash rate, following the same mathematical protocol. it makes the math illogical and unusable. it also makes the data next to impossible to change, making it immutable.

What does the block structure look like in bitcoin?

The way I describe the structure of bitcoin is like little planets floating in its own solar system, all linked together, building with and off each other. a block contains the block number/header, the hash of the previous block, timestamp, the nonce, transactions and the current target and its block size also the hash of the current block which is ready to be used to create the next block.

#1098

  1. The link is a puzzle that each miner must solve. This expends energy and ensures that the miners have true and honest intentions, in competition for the incentives.

  2. The “current” block contains; a list of current transactions, the hash of the previous block, a nonce, a timestamp.

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#1099
  • By having each block cryptographically linked, it makes it exponentially harder to change past transactions. Because each block’s hash is used to create the following block’s hash, the entire chain becomes invalid when the smallest change is made. This is what ensures the blockchain’s permanent immutability. Transactions can be added but not changed or deleted.
  • Each block in the chain is composed by taking the hash of the previous block, adding new transaction data, and a ‘nonce’, which is a randomly guessed number, and hashing the combination of those three elements.
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#1100

Hi there! Yes, the block contains the nonce, but its not the target, actually. The block’s hash is the one related to the target, as miners need to produce a hash with certain amount of zeros at the beginning (or a the decimal value less than target).

Hope this makes sense!!

Felipe.

#1101

Hi there! It’s actually the other way around, if that’s what you meant. All the information of previous block is included in the current block, using the previous block’s hash (which acts like a summary of the block’s info).

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#1102
  1. Since blocks are cryptographically linked any change to one block would break the link to the blocks in front of it, meaning those blocks would have to be remined.
  2. Block has hash of previous and current block, nonce, target, list of transactions, fees etc.
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#1103

Homework on Blockchain and Mining Visually - Questions

  1. Why is it important that the blocks are cryptographically linked together?
    They must be linked together to ensure previous blocks cannot be changed. If they were not cryptographically linked, each block would be independent and they could be modified without breaking the chain.
  2. What does the block structure look like in bitcoin?
    It is the hash of the previous block, the current block transactions, and the nonce, all hashed.
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#1104
  1. It ensures the integrity of the blockchain and security of the data as immutable. The cryptographic link results in the inability to change previous blocks without having to re-mine all future blocks. This is a huge deterrent to miners as it would be unreasonably time consuming and expensive to amend the latter blocks.
  2. Hash from previous block, current transactions and nonce
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#1105

Mining and PoW

  1. The cryptographic link ensures immutability of the blockchain.
  2. Each block contains previous block’s hash, data - transactions list, counter and nonce.
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#1106
  1. Security. Provides anonymity to users, integrity of data, and Immutable historical record.
  2. My first impression; A Block contains Hash from previous Block, Data and its own Hash. I didnt think the Nonce was kept after the block was awarded, just the new Hash.
    Then…thanks to acidspud, I checked out his link to Bitcoin Wiki, https://en.bitcoin.it/wiki/Block .
    Big help. Now… I see egg-zak-ly what is in a Block.
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