Homework on Blockchain and Mining Visually - Questions

[kal]

1. Blocks must be cryptographically linked together to ensure data immutability. This is done by hash functions producing a unique fingerprint for each block, along with the transactions stored in each block. As each block is based on the hash and transactions of the previous block, if any one block is changed all other blocks will be changed.

Block index
Hash
Previous hash
Number of transactions
Timestamp
Nonce
Transaction
Merkel tree

[AndrewDavid]

1. blocks need to be linked together to make it immutable
2. Transaction number, hash of previous block

[Jesse_Bowles]

1. It is important so No one can change a previous transaction without disrupting the chain of transactions (blocks)
2. There is a nonce, the transactions hash and the hash of the previous blocks

[Hudsen]

1. So a previous block cannot be altered because it would break the chain of blocks that come after it. This makes it so data cannot be removed from any block.
2. Block hash is based on transactions in the block, the previous block’s hash, and the nonce number which is guessed by the miners.

[SweetNetworker]

1. The blocks are cryptographically linked to ensure the integrity of the network. It keeps people honest so that transactions on blocks cannot be changed. If a block were to be altered, then subsequent blocks would also have to be changed which is almost impossible.

2. The block structure is made up of :

   • hash
   • previous hash
   • nonce
   • transactions

[Kristian_Mitov]

1. Why is it important that the blocks are cryptographically linked together?
   First the info about the UTXOs from the previous block has to be included so that the nodes can check them for the next block transactions.
   Secondly this improves the difficulty in case someone wants to change the info in a previous block.

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

• nonce
• transactions info
• hash

[Moseswong]

1. For network’s security and integrity. It makes it impossible to change any previous transaction.

2. Header, nonce, data/transaction, previous hash and current hash.

[Divij_Dawar]

1. It helps to secure the blockchain and maintain data integrity.
2. The hash of the current block based on the transactions, hash of the previous block and the nonce.

[TuomoP]

1. Why is it important that the blocks are cryptographically linked together?
   By linking them together with hash and previous hash (SHA256) it is ensured that no block in the chain can be altered.

2. What does the block structure look like in bitcoin?
   The block data model is in a form of a “stack”:

Block header:
Previous Block’s hash
Merkle Root
Nonce
Metadata: block version, time stamp, difficulty

Transactions
List of all transactions per block

[Dreax]

[quote=“ivan, post:1, topic:8433”]

• Why is it important that the blocks are cryptographically linked together?
  This is how the security of the system is kept, as the hash of each block includes the previous block hash this creates rigidity in the system ensuring entries are not altered without a ridiculous amount of work needed.
• What does the block structure look like in bitcoin?
  Each block is tied together by including the previous block hash in a way that any changes in any block will alter the current and future block’s hash, this creates a very secure or immutable system.

The stack looks like this:

Block header:
Previous Block’s hash
Merkle Root
Nonce
Metadata: block version, time stamp, difficulty

Transactions
List of all transactions per block

[Carl_The_Yoda]

1. Why is it important that the blocks are cryptographically linked together?
The cryptographic link is vital to maintain the veracity of the trustless and decentralized nature of the ecosystem.

2. What does the block structure look like in bitcoin?
The block is made of a header, containing metadata, followed by a long list of transactions that make up the bulk of its size.

[mike_sutanto]

1. The cryptographic link prevents makes a physical limitation that prevents the possibility of tampering with data in the blockchain
2. A block contains: - Transaction data, -Its own hash, and -The previous block’s hash.

[urko]

1 - Why is it important that the blocks are cryptographically linked together?
This creates security and incentives the miners to play by the rules.

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

• Block number
• Nonce
• Data
• Prev (hash)
• Hash (new)

[yeoyo]

@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. A cryptographic link between the blocks makes it difficult for miners to mine a solution if any old block’s hash changed due to changes to the transactions in that block, hence increasing the security and immutability of the blockchain.

2. The block structure of bitcoin consists of:

• The previous block’s hash
• The transactions list
• The nounce

[mima]

1. Why is it important that the blocks are cryptographically linked together?
   That is why blockchain is immutable, transparent, secure and decentralized.
   Hash function gives each block unique digital fingerprint and that saves integrity of every block, hence integrity of whole blockchain. Since each block is linked with previous one with its hash, even smallest change in data, results as totally different hash and that brakes link on that and every other block that comes after. Everybody on network can see that.

2. What does the block structure look like in bitcoin?
   Every block has its:
   Number
   Nonce
   Data: transaction list
   Previous block hash
   Block hash

[Crypto_PONY]

1.It is important for the integrity of the blockchain (the security of the network); prevents double-spending by ensuring blocks are immutable.

2. The block structure in bitcoin is a constituent of the hash of the previous block, transaction data and a guessed nonce.

[ldvcnagy]

1. Because in this case anything is changed in a block affects the following blocks and the “damage” is very visible and nearly impossible to “repair”.
2. The block contains the previous block’s hash, the transaction data, the nounce and the current block’s hash.

[Gaurav]

Why is it important that the blocks are cryptographically linked together?
The idea builds on a security property of cryptographic hashes, that they are designed to be hard to invert (so-called one-way or pre-image resistant property).
You can compute y from x cheaply y=H(x) but it’s very hard to find x given only y. A full hash inversion has a known computationally infeasible brute-force running time, being O(2^k) where k is the hash size eg SHA256, k=256, and if a pre-image was found anyone could very efficiently verify it by computing one hash, so there is a huge asymmetry in full pre-image mining (computationally infeasible) vs verification (a single hash invocation).

What does the block structure look like in bitcoin?

Bitcoin mining uses the hashcash proof of work function; the hashcash algorithm requires the following parameters: a service string, a nonce, and a counter. In bitcoin the service string is encoded in the block header data structure, and includes a version field, the hash of the previous block, the root hash of the merkle tree of all transactions in the block, the current time, and the difficulty.

[Gaurav]

How do i know if any of my answers make sense?

[Maki]

If you get the from a member, it means your answer make sense. Your are in a good hands don’t worry .