Homework on Blockchain and Mining Visually - Questions

[MarcusM]

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

Linking each new block to the previous block cryptographically makes it extremely difficult to change the transactions in the ledger. Changing data in a previous block would invalidate all of the blocks that follow. So it secures the integrity of the blockchain. In theory it might be possible, but in practice it cannot be done. Anyone editing a previous block would have to re-mine all the blocks thereafter, and also keep pace with the mining of new blocks.

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

Each block includes:

• the hash of the previous block; the digital fingerprint of the previous block.
• the transactions list, new data being added to the blockchain.
• a random number, called nonce. The miner will cycle through nonce values at random until the hash of all the block contents combined is less than the difficulty target.

[TomDrones]

Homework on Blockchain and Mining Visually - Questions

1. Why is it important that the blocks are cryptographically linked together?
   It is important that the blocks are cryptographically linked together because the hash is a digital fingerprint. The hash is based on all the transactions that happen in the current block and hash of the previous block. If a transaction is changed in the list the cryptographic hash will change and affect all blocks going forward. This makes it very difficult for an attack of the network. Cryptographically linking blocks together provides security for network and preserves its integrity.

2. What does the block structure look like in bitcoin?
   Bitcoin’s block structure is a hash. A hash is derived from the previous hash, transactions list, and nonce.

[Rosko78]

1. This ensures that no one is trying to change anything in the blocks in past as it will break all subsequent hashes and blocks afterwords which will have to be redone - which we know is not possible. It ensures the safety, integrity and security of the block chain.
2. -Transactions
   • Previous hash
   • Nonce

[Serfke]

1. All the blocks are linked using the hashes of previous blocks, so if an old block would be changed, all existing links would be broken due to the change in the hashes.

2. A block consists of:

• Previous Hash
  -Data
  -Nonce

[CryptomemberSVK]

1. To prevent doublespending problém and make miners to act honestly.
2. Hash in current unconfirmed block must contain hash of recent block also transaction list and nounce.

[FiToKa]

1. Why is it important that the blocks are cryptographically linked together?
So that any changes within a block would change its hash and this will result in all other links being broken.

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

• Transactions list
• Previous block hash
• Nonce

[NextGen33]

1. By encrypting the data into a hash, the result becomes a random number that changes completely with the smallest adjustment. This greatly increases difficulty in discovering a new hashes and trying to restructure the blockchain.

2. Blocks contain their own hash, which consists of the previous block’s hash, a list of all transactions included in the block, as well as the nonce that completes the hash.

[nscholten]

1. With cryptographic linked blocks; not only is the individual block is guarded against being altered but every block thereafter is guarded.

2. The block structure of bitcoin is an individual block of data with a unique number (hash) using sha 256. The number is displayed with a 16 digit hexi-decimal number. 16x16 = 256. Too get the correct hash the miner must come up with a hash that is lower than the target hash. This is displayed with a random number called a nonce. The initial block is followed by an additional block that not only contains the newly created data of the additional block but also the information of the previous block. This is displayed with the hash of the previous block followed by the newly created hash of the additional block. And on and on.

[AlexxSloan]

Homework on Blockchain and Mining Visually - Questions

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

• this creates the mechanism of “tamper evidence”, as well as secure the chain from bad actors attempting to add/modify/delete any previous data and/or transactions.

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

• Block header
• Version
• Previous Block hash
• Merkle root hash
• Timestamp
• Difficulty target
• Nonce
• Block Size
• Transaction counter
• Transactions

[StanleyGM]

1. Why is it important that the blocks are cryptographically linked together?
   It is important as it prevents tampering of the network. It is practically impossible for anyone to alter previous blocks without a breakdown of the blockchain. This gives the blockchain security that people can’t double spend or alter previous transactions. It also allows for confidence in traceability there is complete trust in the blockchain recording previous transactions as they can be verified.
2. What does the block structure look like in bitcoin?
   It has the date that the block was made and accepted by the nodes. The block structure also has the block reward being sent to the miner who made the block as the first transaction. The block then lists all other transactions that were included in the block. The block includes the hash of the previous block and it’s own hash for future blocks to include.

[andyB]

1. To ensure the integrity of the blockchain. Previous blocks cannot be changed without impacting subsequent blocks as the cryptographic puzzle is based on contents of previous blocks (hash).

2. The block structure contains the block number, the list of transactions (data), hash of previous block, nonce and the hash of current block.

[Valerie_Wright]

1. The cryptographic links ensure the previous blocks are trustworthy and not tampered with; this important feature keeps the block chain system secure and independent.
2. BTC block structure is a rectangle with spaces for data, it holds:
   A) a space for the block #
   B) a space for the Nonce,
   C) a space where the transaction list of the current block data is held
   D) a space where the previous block hash # is held
   E) a space where the current block hash # is held

[Nikola]

1. It’s important for the security of the blockchain, by linking them together neither of them are able to be changed without it affecting the rest of the blocks.

2. The block consists of the transactions, the previous hash and the nonce, which are then use to make the next block.

[JonBal]

1. It is important for blocks to be cryptographically linked together so that if you make any changes to previous blocks it would also change blocks coming after it.

2. Previous hash, Tx list, and nonce. Also a target between 0 and infinity to establish difficulty.

[perrys]

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

Because each block link to its predecessor, data in the blockchain is immutable. The hashing function means that a change in any transaction will produce an entirely different hash, which will alter the hashes of all subsequent blocks. The Bitcoin blockchain uses the SHA256 algorithm, which produces a 32-byte hash.

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

A block is a container data structure. In the Bitcoin world, a block contains more than 500 transactions on average. The average size of a block seems to be 1MB (source). In Bitcoin Cash
(a hard fork from the Bitcoin blockchain), the size of a block can go up to 8MB.

[Tumbleur]

1.Why is it important that the blocks are cryptographically linked together?
It is important that they are linked so that the old blocks are efficient. The new blocks need the “approval” of the old block to funcion.

2.What does the block structure look like in bitcoin?
The stucture of a bitcoin block has The transactions, the previous hash, find the nounce then the new hash.

[Pats]

1. It insures that ,no-one has altered any of the data contained in the blockchain.
   2.

[kurtis27]

1. So that transactions can’t be altered once it has already been done. (data immutability)
2. Txs, Prev block hash, nonce which is all used to calculate a hash that is below the “target”

[Julie66]

1. They are crytographically linked together, one way, so that they are protected and secure. Also, there is no centralized authority, it is decentralized and non censored. The crytographically linking enables it to be decentralized and secure.
2. Blocks containing a hash, previous blocks hash and a nonce, linked together.

[chrism2524]

1. Why is it important that the blocks are cryptographically linked together?
   It’s important to keep the integrity of the blockchain where any alteration on the

2. What does the block structure look like in bitcoin?
   Block structure will include a block number, nonce,transaction, previous hash