Homework on Blockchain and Mining Visually - Questions

Blockchain and Bitcoin 101
#3235

*** Why is it important that the blocks are cryptographically linked together?**
Each block is connected to the previous block via the hash function SHA256 taking into account the previous blocks hash as part of its data. If any TX data in any previous block is changed, not only will that blocks hash change, but so will every consecutive block. Meaning they will all have to be remined for the network to accept those changes. This is important as it helps to secure the network and stop potential double spend attacks.
*** What does the block structure look like in bitcoin**
Block number > Previous block hash > TX data > Nonce > Hash number

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#3236

1/ It makes very difficult to any miner to change anything in the pre-existing blockchain, as current hash is a function of previous block, previous hash and current block to be mined.
2/ current TX selected to be confirmed, nonce, previous hash

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#3237

Homework on Blockchain and Mining Visually - Questions

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

so that you cannot go back and edit a transaction

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

Like a chain of blocks interconnected by its structure, each block has a structure of data of transaction,hash output from the data+nonce calculation, prev hash , to get the nonce calaculation it guesses until the target of the hash output is below a certain number.for example hashout is 0000xxxxx

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#3238
  1. Why is it important that the blocks are cryptographically linked together?
  • Because if they are not it means that someone has changed the hash in the block and this breaks the link between the blocks, so this block is going to be unlinked in the chain and the miners will lose money and resources.
  1. What does the block structure look like in bitcoin?
  • we have a block, in the block, we have a previous hash of the other block, transactions, and nonce ( a random number) so all of this creates a hash that is going to be in the next block and they are all connected through a link which is a cryptographic puzzle.
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#3239

  1. Why is it important that the blocks are cryptographically linked together?
    If the blocks are not linked together, it would mean that one of the blocks had been altered. Since a hash of a block is connected to the hash of the previous block, the link between breaks.

  2. What does the block structure look like in bitcoin?
    The block in bitcoin includes the hash of the previous block, transaction list and nonce (random number that miners need to guess).

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#3240

  1. It is important to have each block cryptographically linked together so that if any data in any of the blocks are altered it puts the entire chain out of sync making it impossible to change data in the chain (Unless you controlled 51% of the mining nodes).

  2. Block Header -> Previous Hash -> Unconfirmed Transactions -> Nonce -> New Hash

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#3241
  1. To maintain integrity in the blockchain. If a prior block is ā€œbrokenā€, all the following already confirmed blocks are as well.
  2. The block structure is: Block Header-> Previous Hash (Integrity) -> unconfirmed transactions -> Nonce -> Block confirmed added to the chain/New hash value for new blocks to use
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#3242

  1. Because it makes it practically impossible to change something in the blockchain because as soon as you change anything anywhere in the blockchain, the hash of this block and every following will change, breaking all following links between them.

  2. hash block ( hash (prev block) + tx + nonce)

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#3243

  1. To ensure that changes are not made to the blocks. Makes it nearly impossible (and definitely not worth it) to do.

  2. All input and hash from previous block, all transactions and the nonce. This creates output (hash) for the next block to include (along with input, transactions and nonce).

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#3244
  1. Why is it important that the blocks are cryptographically linked together?
  • Preserves chain immutability. Any given block in the chain contains a hash of the previous block as well as being incorporated in the hash of the following block. The domino effect created in changing a confirmed block would be a computational impossibility.
  1. What does the block structure look like in bitcoin?

  • Block #

  • Nonce

  • TX Data

  • Hash from previous block

  • Creates a new hash for the next block.

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#3245

Why is it important that the blocks are cryptographically linked together?
Linking the previous hashes in each mined block ensures that if a transaction in an older block is altered then all child blocks or blocks with a greater height need to be mined once more. The reason is the hash of a block is included in its child block as the previous block hash so when it changes the target number produced by hashing the child block no longer satisfies the target number and needs to be re-calculated.

What does the block structure look like in bitcoin?
The block structure includes a header and data. The block header contains the nonce, the target difficulty, the previous block hash, the merkle root and the timestamp. This block header is hashed to create the hash of the block used in the previous block hash. The data contains the transaction data and the segregated witness data (if segwit). If segwit then the merkle tree of the segwit data is stored in the coinbase transaction.

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#3246

1. Why is it important that the blocks are cryptographically linked together?
It is important to be cryptographically linked together to ensure the security of the blockchain. Each link is dependent on all the previous blocks & linksā€™ cryptographic hashes. If one hash or piece of data in the blockchain is altered the whole chain of following blocks will each be broken as well. So cryptographically linking the blocks makes the entire code fully linked together and increases security and lengthens the overall proof of work chain of events that all nodes agree upon with consensus.

2. What does the block structure look like in bitcoin?
ā€œBlock Chainā€ - A blockchain is a collection of several blocks linked together in a chain in order all the way back to the first block. Each block is a collection of several transactions and a digital fingerprint created by cryptographic hashing. Each link is a cryptographic hash function that is based on all the previous blocks and links all blocks mathematically / cryptographically together. In Essence, the structure looks like a massive chain of transactions and data categorized into blocks linked together many times to create a long timeline of blocks that serve as the public ledger with the entire history of all transactions to ever occur in bitcoin.

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#3247
  1. Why is it important that the blocks are cryptographically linked together?

The blocks are linked together to ensure the security of blockchain thusly; a dishonest miner altering one block will also alter all the others.

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

In a block, there is the block header and the transactions; the block header includes a hash of the previous block, Merkle root, nonce, and the relevant difficulty target.

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#3248

It is important that the blocks are cryptographically linked because it creates a system with more integrity as time goes on. Each block is dependent on the previous so you cannot change the past without breaking the chain up to current.

Block structure consists of header which contains various info (ie. hash, height, nonce, etc) about the block. It also consists of transactions and the associated fees.

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#3249

  1. To secure the data in each block, and to validate the content of each block to be linked, and to help prevent any alternation on any previously added blocks.

  2. It looks like pages of written accounting transactions chained together in a linear manner.

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#3250
  1. Why is it important that the blocks are cryptographically linked together?
    It is important that the blocks are cryptographically linked because it ensures the integrity of the blockchain, its immutability and no double spending occurs.
  2. What does the block structure look like in bitcoin?
    The structure of a block in bitcoin contains the list of transactions, the hash of the previously mined block and the nonce and the hash of the block itself.
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#3251

  1. This maintains the security of the network as it is incredibly difficult / impossible to change transactions in the previous blocks. Immutability.

  2. Previous Tx Hash, Tx Inputs and Nonce

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#3252

1 The blocks are connected by a mathematical puzzle that connects from the old to the new block.
2 The block is created from the hash and nonce of the previous block, timestamp, block size, transaction counter, difficulty target, nonce.

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#3253

  1. Why is it important that the blocks are cryptographically linked together?
    Because itā€™s ensuring the integrity of the data in the blockchain

  2. What does the block structure look like in bitcoin?
    It contains a nonce, the hash from the previous block and transaction data and the blocks hash.

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#3254
  1. Because every hash resolution depends on integrity of previous block
  2. A chain that links every block with next block
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