Homework on Blockchain and Mining Visually - Questions

Blockchain and Bitcoin 101
#363
  1. Why is it important that the blocks are cryptographically linked together?

This feature of the blockchain creates it’s immutability. Bitcoin utilizes Property # 4 of hashing algorithms, (“Small Changes In The Input Change the Hash”) to confer this immutability. By creating a link from each block to the next that is a hash of the previous block and it’s link you create a locked system that can’t be altered. By creating a chain that can’t be altered you create a permanent digital ledger. And when you have a permanent digital ledger that it transmittable over a network you’ve solved the copy / paste problem of digital assets and man have you done something big. You’ve made it so that supply / demand dynamics can be applied to digital objects in the same way that they can apply to objects in the real world and you’ve opened up the possibility for a fully realized digital economy. Perhaps even a virtual world that can behave in many ways like the real world.

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

Block Drawing

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#364

  1. Why is it important that the blocks are cryptographically linked together?
    To ensure the blocks are verified and proof of work is being applied by the miners. Also in order to have a failsafe in case a miner wants to insert an invalid transaction into previously mined blocks.

  2. What does the block structure look like in bitcoin?
    A Block structure consists of NONCE + DATA (transaction list) + Previous HASH + Current HASH

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#365

  1. It is important that the blocks are cryptographically linked together because it make it almost impossible to alter the transactions - Immutability& Integrity.

  2. Block structure in Bitcoin ( based on academy video only ) :
    Previous Hash
    TX list
    Nonce

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#366

  1. It keeps the transactions save from being altered. No-one can change the data without changing the hashes and therefore breaking the cryptographic link.

  2. The block contains a list of the transactions, hash of the previous block and the nonce. This information is hashed for the block-hash.

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#367
  1. Why is it important that the blocks are cryptographically linked together?

So that a small change in a specific block changes all the hashes in next blocks. If someone would change something in specific input of a hashing function the block change would not be confirmed by the network.

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

Nonce - puzzle number. Guessing by hashing all other data and compering with the target.

Hash of a previous block.

Hash of all the transaction in a current block.

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#368
  1. Why is it important that the blocks are cryptographically linked together? For the security of the blockchain. To ensure no previous block can be changed.
  2. What does the block structure look like in bitcoin?
    previous hash, transaction list, nonce, current hash
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#369

  1. Why is it important that the blocks are cryptographically linked together?
    This cryptographic link ensures that blocks remain immutable and the security of the blockchain.

  2. What does the block structure look like in bitcoin?
    Block header; Block size; Difficulty target; Merkle root hash; Nonce; Timestamp; Previous block hash.

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#370
  1. It is important that the blocks are cryptographically linked together because this is how the database of transactions/ownership of coins are maintained and agreed upon. That is: a spend order is given, a unique hash or “receipt” is created for this value, the receiver holds the key to this hash or “receipt” and is the only one hereafter able to release this amount of value for a future transaction.

2.The block structure in Bitcoin looks like this:
You add:
The previous block hash
The transaction/data
and a randomly generated nonce that is lower than the difficulty set.

you then encrypt this data using the SHA256 algorithm to get the new hash.

Previous hash + current hash = new hash. (That’s why its hard to break the chain, to many break if you try to change something)

#371

  1. the blocks need to be linked together to secure the network. because this system makes it extremely easy for the network to find faulty changes as every change inside a block totally changes the hash of a block and ALL other blocks after it. every node will see the change and reject every faulty transaction.

  2. a block is made of the hash of the previous block+all transactions inside the new block+nonce(random number that helped solving the mining puzzle)

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#372
  • Why is it important that the blocks are cryptographically linked together?
  • What does the block structure look like in bitcoin?

  1. Cryptographic link between blocks ensures security of blockchain by proof of work model.
    If you change one block, all blocks will be invalid after that, meanwhile you would need to recreate all blocks after the changed one, faster than original chain and become the longest chain.

  • Block header:(80 bytes)
    version number of the block
    timestamp
    current difficulty target
    nonce
    hash of the previous block
    merkle root hash.

  • Block size:(4 bytes)
    The size of the block, in bytes

  • Transaction Counter & Transactions:(variant)
    Transaction data consists of counter and list of UTXOs in form of a merkle tree

#373

  1. It’s important that the blocks are linked together cryptographically so that changing and tampering with them would not be easy, and that the attacks would be exponentially more difficult since changing one block affects all the others.

  2. In the hashed bitcoin block the data includes the list of transactions, the previous hash and the random number “nonce” that represents the proof-of-work puzzle.

#374

  1. The cryptographic link between blocks is what forces a Proof of Work operation to occur to generate that linkage. This POW requires many hashes/energy to accomplish, making it unprofitable to attempt to break or modify the chain.

  2. The blockchain is basically a cryptographically linked list.

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#375
  1. This link makes it difficult and not financially viable to alter previous blocks, leading to security in the network.
  2. Each block consists of a set up unconfirmed transactions, a nonce, and the hash of the previous block in the blockchain. Once the hash is accepted and the new block is added to the blockchain, the transactions become confirmed.
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#376

1 - It is important that the blocks are cryptographically linked in order to prevent editing of the previous transactions.

2 - The block stucture in Bitcoin contains the data contained in the transactions to be confirmed by the block, the hash of the previous block and the nonce. This data is then passed through the SHA256 hash function in order to produce the hash of that block.

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#377

1 Blocks are cryptographically linked together to insure the security integrity of the blockchain
2 The block structure is made up of the previous hash, current transactions hash and nonce

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#378

1/ To give blocks a unique fingerprint which makes it very secure. If anything is changed in one block it will also affect all other blocks.

2/. The structure of the blocks in bitcoin require 3 functions, The transaction, the hash of the previous block and the randomly guessed nounce number.

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#379
  1. So that data can not be changed in any block without affecting all the following blocks
  2. Block number, nounce, TX Inputs, Previous hash
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#380

  1. With the blocks all linked cryptographically together it becomes practically impossible to change something or double spend.

  2. The block contains all the transaction data, the hash of the previous block and a nonce. All of this affect the hash in the new block.

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#381
  1. This is important because it ensures any change made in any previous block breaks every link after the change, and the only way to “fix” the chain is remine all those blocks, plus any new ones mined in the mean time. Impossible. hence immutability of the blockhain.
  2. The sha256 hash of the current block txs plus previous block hash plus a nonce needs to fall below the target hash. if so, block is valid and next block is mined. next block needs its own sha256 hash of that block txs plus its previous block hash plus another nonce to fall below the target hash. etc. So every block depends on all previous blocks, hence ensuring integrity of the entire chain.
#382

  1. The blocks must be cryptographically linked together because if they were not people could just change the content of the blocks without any problems. If blocks are cryptographically linked together they will not even try to change them because it would not be worth it, it would take to much time to mine the old blocks and catch up with the new ones.

  2. A block has a hash and the hash from the previous block, a transaction list and a random number that is called a nouce that the miners must guess. To put the block into the blockchain you have to hash the nonce together with the TX list and the previous hash to get a hash that is less than the target(the target is also a number).

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