Homework on Blockchain and Mining Visually - Questions

Blockchain and Bitcoin 101
#1207

  1. It’s important that the blocks are cryptographically linked together because if all the blocks contain interconnected information, it prevents any one block’s information from becoming manipulated.

  2. The block structure contains the hash of the previous block, the list of transactions, and the nonce.

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#1208

1.This is about the integrity of the block. It is buit in order to add something but impossible to modify or remove something on the block.

  1. It looks like this: the content of the first block has previous hash, transactions and nonce which will be recognised by the next block.
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#1209
  1. Why is it important that the blocks are cryptographically linked together?

So a change to one block changes all the following blocks. It makes the blockchain tamper resistant as any changes will be quickly recognized.

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

It looks like a chain where each block has a hash made up of the transaction data, previous hash, and the nonce. Each block has its own hash and the hash of the previous block. Any change to a block after being confirmed and added to the chain will break the chain at that location and all blocks that follow.

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#1210

Homework on Blockchain and Mining Visually - Questions

Why is it important that the blocks are cryptographically linked together?
Because of the blocks cryptographically linked you can not change one block. You need to changes all the blocks after that block. This is virtually impossible.

What does the block structure look like in bitcoin?
Hash of the previous block, new transactions and the nonce

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#1211

Why is it important that the blocks are cryptographically linked together?
To secure the network, i.e. the to ensure that past data can not be changed.

What does the block structure look like in bitcoin?
Contains:

  • hash of previous block
  • list of transactions
  • nonce

Programmatically is looks like:

  1. Magic Nr
  2. BlockSize
  3. Blockheader (Version, prev block hash, current transaction list hash, timestamp, target, nonce)
  4. Transaction counter
  5. List of transactions
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#1212

  1. To increase security. If you change anything in previous blocks the links between the blocks will be broken and you would have to re-mine the blocks.

  2. A block contains a transaction list, previous hash value and nonce. When creating a new block you hash all this together and get a new hash value, this hash value needs to be lower than the target. If it is lower than the target you have succeded and the block will be registered in the network.

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#1213

Call me slow but I just really started looking at your diagrams. I love them!

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#1214

  1. It makes them immutable. Transactions are based upon the previous hash creating a mathematical protocol.

  2. It has the block number, nonce, data, previous hash and the current hash.

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#1215

  1. Why is it important that the blocks are cryptographically linked together?
    This is important so that changes can’t be made to previous blocks. When you as a miner try to solve the puzzle of the next block in the blockchain, one of the factors you follow is the hashrate of the previous block. If this hashrate wasn’t present in the block you would be working on, changes could be made to previous blocks. Because the system works as it is, a change in transaction of previous blocks, would change the hashrate of the previous block, that is linked to the current block you are working on.

  2. What does the block structure look like in bitcoin?
    You have a blockchain. Blocks are linked together. In every block that is finalized you will find the hash of every transaction in that block, the hash of the previous block, the hash of a nonce that is a random number that is solved. And the hash of the current block that is a result of the three factors. A small change in any of the factors will change the hash of the current block. If you find the hash of the current block as a miner you are the one that gets rewarded for creating the block.

Block structure
Block structure915×279 22 KB

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#1216
  1. In order to get Immutability of the network, so in case you want to change something in one block , you need to change everything in all other blocks, which is practically impossible
    2.Block Structure: 1)List of Transactions inside the block 2) Previous hash and 3) nonce
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#1217

  1. Because it requires a lot of energy (and thus money) to solve the cryptographic puzzles. Which gives an incentive to be honest… because why would you keep wasting money on electricity for mining when you don’t get any reward?

  2. It consists of the previous hash, the transactions, the nonce and the hash of the current block in the end.

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#1218

Not exactly :slight_smile: the hashrate doesn’t have much to do with it (except for solving the right hash in a specific amount of time). If you would want to change some data in a specific block it would completely change the hash of that specific block and since all blocks also contain a reference to their previous block that would also change the hash of the next block and the next…all the way up to the tip.
The attacker would in this case have to remine all the blocks after the block he was trying to change, which would prove to be very difficult since it would have to mine the blocks with the same difficulty as at the time they were mined :slight_smile:

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#1219

Homework on Blockchain and Mining Visually - Questions

  1. Why is it important that the blocks are cryptographically linked together?
    The importance of the blocks linking together is to enhance a highly secure blockchain that will makes it impossible for anyone to cheat the system, to therefore enhance the proof of work consensus that will make the continuity of the block creation remain under the necessary secure environment.

  2. What does the block structure look like in bitcoin?
    The Blockstructure contains:
    The Previous Block Hash + The Transaction lists of the new blocks(also hash) + Nonce a random number that needs to be deduced out of cryptographic calculation = All Hash together with a lower value less than the Target Threshold
    is a full picture of the Block structure.

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#1220
  1. To ensure the security of the blockchain. To avoid change of blocks.
  2. Structure of a block is previous block hash, Transaction data and nonce.
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#1221

I mixed up words here, meant to write hash. I am familiar with what you are commenting :sweat_smile: :sweat_smile: But I do have sort of a question tho. Can you correct (if needed) on the statement below:

The miners mine bitcoin through a cryptographic puzzle of three factors. The hash of the previous block (this is known to everybody) + a hash of all the transactions in the current block (this is dependent on what transactions miners pick from the mempool) (do miners create a hash ot the transactions together? Or do they write every single transaction?) + a nonce (hash has to be within target) =(calculate through SHA-256)= Hash of the current block.

Is the “winning” miner picked through finding the hash of the current block (which is dependent on the three factors)? Or are they picked when they find the nonce within the target?

Like, the hash of the current block is dependent on the nonce plus two other factors. A differ in any of the factors will give a different hash of the current block. How can the bitcoin network know that this hash is correct when it is calculated through SHA-256.

Question in short: What do the miners create hashes from before they run the calculations through sha-256 for a final block hash? And what picks the “winning” miner. Is it the nonce alone, or the hash of every factor? Hope you understand my question :laughing: :laughing:

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#1222
  1. For the security of the network. Because all blocks are linked to the previous ones it prevents data being changed, because a change would mean that to have it confirmed, you would need to re-mine the whole blockchain;
  2. every block’s hash is determined by it’s previous block (and the transactions in the block and the nonce).
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#1223
  1. This will ensure none of the data in any block is altered. Every block does have a specific signature, the hash. The hash is generated by a cryptographic function and thus “unreadable” as all blocks includes the previous blocks hash there will be a hashing of hashes that will make alterations of any block virtually impossible (to get away with). You may however hijack the BC by controlling 51% of the nodes, but that is just not financially profitable.
  • Number of the block n
  • Previously block’s hash H(n-1)
  • List of transactions (TX…)
  • Nounce N
  • Hash of block H(n)
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#1224

Homework on Blockchain and Mining Visually - Questions

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

So it is impossible to change one single block, without invalidating the other blocks in the chain

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

Hash
Hash of previous block
Transactions (data)
Nonce (puzzle)

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#1225
  1. To preserve blockchain immutability
  2. Block header; previous block header; TXs; nonce
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#1226
  1. It is important that the blocks are cryptographically linked together because if someone wants to change a previous block, then they would have to change all the following blocks too, and it would be too costly for them in terms of electricity.
  2. In Bitcoin, each block has a hash that is made up of a hash of the previous block, the information in the block (the transactions) and the nonce (a random number the miners have to guess). This ensures that all blocks are linked together.
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