Homework on Blockchain and Mining Visually - Questions

[JustMichael]

1. Immutability
2. See scheme below:

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Header

• Version
• Time
• Bits
• Nonce
• hashPrevBlock
• hashMerkelRoot

Transactions

• Coinbase
• Tx Hash(es)

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[Fabrice]

@CryptoTradingTrucker

2)Each block contains, among other things, the current time, a record of some or all recent transactions, and a reference to the block that came immediately before it. It also contains an answer to a difficult-to-solve mathematical puzzle - the answer to which is unique to each block.

The nonce is not unique. You just need to hash the block and make sure that hash is below target. (starting with a bunch of zero’s) wich is really hard todo. Because hashes are so random. So you must add a random number, hash the block again, and check if this hash is low enough (if no, repeat) it’s possible that the nonce of 1 block is the same in the next block.

[MindFrac]

1. Why is it important that the blocks are cryptographically linked together?
It prevents in isolated block from being altered. In order for a person to alter the transactions on a block, they would also have to alter every block linked forward in the chain which is not technically possible at this time.

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

Blockchain containing blocks
Blocks containing a Hash
Hash based upon:
- Transactions
- Nonce
- Previous Hash

[docbdublin]

1. It is important that the blocks are crypto linked because any change to a block after it is confirmed and linked to the chain will cause massive changes to the blockchain. The previous link will break this block off the chain since the the link that connects the link to the chain is based on the hash of this block and the hash of the previous block. Also, all blocks going forward will need to have their Nonce’s recalculated to meet the required threshold. This will cause monetary loss and will ensure the miners will follow the rules.
2. The block structure in Bitcoin is based on 5 different components: 1. A record of all the transactions, 2. A Nonce which is a crypto puzzle solution, which the 1st miner to find it gets the reward and rights to add the next block, 3. the hash of the previous block, 4. The Hash of all these items, and finally 5. The link to the preceding block which is formed from a hash of the previous block’s hash and this new block’s hash.

[turner36t]

1- By cryptographically linking the data in the blocks you can verify that all data is original and unchanged, making the network more secure
2- block number at the top, nonce number, list of transactions confirmed, followed by the previous hash and then the current block hash

[jimx]

1.Why is it important that the blocks are cryptographic ally linked together?
To insure blockchain historical integrity
2.What does the block structure look like in bitcoin?
Time, transactions, previous block hash, nonce,

[Leanne]

1. This ensures a transaction cannot be modified.
2. Block number, hash, previous block hash, timestamp, difficulty, transactions total, total btc, size, merkle root, & nonce

[DigzBlockchain]

@ivan

Homework on Blockchain and Mining Visually - Questions

1. Why is it important that the blocks are cryptographically linked together?
2. What does the block structure look like in bitcoin?

1- This is the of the word “chain” in Blockchain. This keep Blocks linked in sequence and gives them integral security. The link being a Hash of the information inside the block, means that the information inside the block is immutable. If one thing inside the block is changed, the resulting Hash will change, thereby breaking the “chain” and causing this change to be rejected in the system of nodes.

2-
Header (ID/count # in the block)
Reference (Merkle root)
Time stamp
Previous block Hash
Nonce
Transactions/ Block Data

The order here might be incorrect or Barry I suppose.

[Oscar_Rasmussen]

1. If the blocks weren´t cryptographically linked that would open up for people to go back in time and double spend, in addition to this they could remove transactions without it having any effect on the blockchain. With the cryptographic link, it insures the “trust-less” system and makes it practically impossible to change anything and replace the blocks after it.

2. The structure in a block is made out of data, it uses the previous hash and the data in its block to guess the nonce. Once the difficulty target is higher than the guessed nonce, the block will be accepted.

[tko]

@ivan

Homework on Blockchain and Mining Visually - Questions

1. Why is it important that the blocks are cryptographically linked together?
2. What does the block structure look like in bitcoin?

1. Changing any previous block data would cause the chain reaction of changed hashes of the blocks following the changed one. Changed blocks will need to be mined again. This, together, makes the data of the blockchain practically immutable.
2. Previous hash, nonce (the subject of mining), data (list of transactions).

[Arthimis_Vergult]

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

• Blocks are cryptographically linked together so it is practically impossible to change, censor and double spend transactions.

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

• H(k|x|y) = previous hash (k) + tx data (x) + nonce (y)
• H(k|x|y) < difficulty target

[Suspect5]

1.Why is it important that the blocks are cryptographically linked together?
By block being cryptographically linked together, it creates a level a security that makes it easy to identify errors or invalid changes if they occur. One change in a block would affect the following blocks as well as the one prior, caussing the links to break.

2.What does the block structure look like in bitcoin?
Timestamp
Target
Nonce
Previous hash
Transaction list

[moza8]

1. So that if just one letter in the block is modified, hash of that block becomes completely different. So this is a security feature of blockchain.
2. Structure of a block in bitcoin is: hash of the previous block + transactions list + nonce --> and then this all hashed together.

[travis_bazile]

1. The importance of the blocks being cryptographically linked together means that the link is in agreeance. they have all come to an agreement unanimously. with no 3rd party interaction.

2. The Block strutcre Title of block is also hash which includes in the bash block. A random nonce number which the block itself doesn’t even know. the nonce is a target it is suppose to be lass than its previous hash block. The hash block also contains transaction list, & previous list

[Mauro]

@Coco

1. Because it secures the blockchain. By linking the blocks together whit the information from the previous block it gets harder to brake the chain.

Linking blocks makes it harder for an attacker to change the past. Changing a block in the past will invalid all other blocks behind it, as every block after it depends on it. Linking blocks does not make the chain harder to break, it simply causes a chain reaction when something is changed in the past.

[Mauro]

@Crypto_Tax_Fixer

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

It ensures the integrity and security of the chain. Decoding the cryptography is sufficiently difficult that it is not possible to hack the chain.

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

It contains the previous key, all the transactions, and a nonce. The block is encrypted using a hash function.

1. I am not sure what you mean by “Decoding the cryptography” but in order to change the past a miner needs to remine all the blocks after it, as it break all the other blocks behind it.

2. You probably meant to say previous hash, instead of previous key.

[Colin358]

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

Any change made to a block hash will alter all blocks hashes after it. This feature adds a robust layer of security, that insentivises miners to follow the rules or lose time and money trying to alter and rehash blocks. The cryptography also prevents double spending and is censorship resistant.

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

Bitcoin block structure contains the block header, version, previous block hash, the merkle root hash, timestamp, transaction data and the nonce.

[Yaank]

1. If they werent linked you could change past blocks. But with the hash of the previous block inside every new block, you link all blocks in specific order together and it is practically impossible to change past blocks.

2.Hash of previous block, hash of transactions, nonce

[ambous]

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

• by having all blocks linked together it is ensured that no one can hack the network or alter any data.

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

1. Magic Number (Bitcoin identifier)
2. Blocksize
3. Blockheader
   a. version
   b. hash of previous block
   c. hash merkle route
   d. time
   e. bits/target
   f. nonce
4. Transaction Counter
5. Transactions

Sources:

• https://www.youtube.com/watch?v=qLM-UC_eqIY (like an atomic clock from the past!)
• https://en.bitcoin.it/wiki/Block_hashing_algorithm

[tmalk]

1. It is important, because if a block is changed, all the subsequent blocks have to be recalculated by solving the cryptographic puzzle.

2. In each block there is hash of the previous block header, the transactions of the current block and the nonce. There are also other fields like blocksize, timestamp and transaction counter.