Homework on Blockchain and Mining Visually - Questions

Blockchain and Bitcoin 101
#1267
  1. Why is it important that the blocks are cryptographically linked together?

the links makes the connection between each block and therefore make retroactive modification extremely difficult to be accepted in the blockchain.

each new block is composed of the previous block Hash, the new tx and the nonce.
2. What does the block structure look like in bitcoin?

each new block is composed of the previous block Hash, the new tx and the nonce.

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#1268
  1. To ensure integrity and immutability of the network.
  2. Each block is based on a tx list, hash of previous block and a randomly generated number (below the target/difficulty level) called nonce.
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#1269

Homework on Blockchain and Mining Visually - Questions

1. Why is it important that the blocks are cryptographically linked together?
This will create a chain of data linked together. When data is changed then all the hash values will change which brakes the whole chain.

2. What does the block structure look like in bitcoin?
-Name of the block
-Nonce
-hash of the transaction data
-Time stamp
-previous hash data
All the data combined will go through the hash function and gives us the output.

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#1270
  1. It ensures the integrity and security of the blockchain. Prevents any information being changed.
  2. A block structure in bitcoin: a list of transactions, hash of previous block, hash of the current block and a nonce (a number which is a cryptographic puzzle).
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#1271

So a past transaction cannot be changed without altering the blockchain. This gives the network security and trust.
The block structure consists of the hash from the previous block, new transactions and the nonce of the block being mined.

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#1272
  1. It is important that the blocks are cryptographically linked together because for the miners to solve the puzzle (complete a block) all the blocks need to be linked together. Also if the blocks were not linked together then anyone could change transactions in previous blocks making it unsecure and a pointless system to use.
  2. The block structure for bitcoin looks like, Nonce
    Data/TXs
    Previous hash
    current hash
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#1273
  1. Because it makes it extremly hard for previous transactions to be altered, therefore setting a certain security level on the blockchain. In fact, changing one transaction would break all the following created links and nullify next blocks which would then need to be re-mined using a huge hash rate.
  2. The block structure is a function of the previous hash, transactions in the current mined block and a random number called nonce.
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#1274
  1. That way practically no one can change them.
  2. Block Header+Transactions. The Block Header has:
    – version number
    – Previous Block Hash
    – Merkle Root
    – Timestamp
    – Difficulty Target
    – Nonce
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#1275

1/ The blocks are cryptographically linked together for the security & integrity of the network. Each new block contains the hash from the previous block. If data were changed in any prior block, it would change the next hash and break the link between all the subsequent blocks.

2/ Fundamentally all blocks contain a new hash, which is constructed from; the data (the list of transactions - outputs and input), the Nonce (the puzzle number that needs to be guessed), and the hash from the previous block. There are other data within the structure too including block number, timestamp, difficulty level, block reward, block fee etc.

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#1276

It’s important that the blocks are cryptographically linked so that no one can plug in a new block wherever in the link because each hash is based on the previous block’s hash. Adding a malicious block will disconnect the entire chain and therefore disprove their blockchain compared to the network’s chain.

Each block contains the previous hash, a nonce, and transactions performed and finally is given a hash once a value below the target is reached. After a block is produced, it is then linked together to the previous block similar to a linked list in C++.

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#1277

Why is it important that the blocks are cryptographically linked together?
These blocks then link with one another through a cryptographic validation known as a hashing function. Linked together, these blocks form an unbroken chain a blockchain.

What does the block structure look like in bitcoin?
Transaction data, hash from previous block, Nonce, an arbitrary number used only once in a cryptographic communication.

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#1278

  1. It’s important that the blocks are cryptographically linked because it insures
    the security ,immutability and the integrity of the blockchain.

  2. The block structure is the block number , nonce , transaction data , the previous
    hash number and the current hash number.

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#1279
  1. Why is it important that the blocks are cryptographically linked together?

It prevents blocks in the blockchain from being tampered. If a block is modified that invalidates all subsequent blocks in that chain.

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

A bitcoin block contains the current block hash, the previous block hash, a list of transactions, a nonce and a timestamp along with other details.

Field Description Size
Magic no value always 0xD9B4BEF9 4 bytes
Blocksize number of bytes following up to end of block 4 bytes
Blockheader consists of 6 items 80 bytes
Transaction counter positive integer VI = VarInt 1 - 9 bytes
transactions the (non empty) list of transactions -many transactions

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#1280
  1. to prevent anyone from changes tx from previous blocks.
  2. prevous hash + utxo + nonce
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#1281
  1. This confirm that the blocks are valid, this will prevent miners to change the transactions without affecting the balance of the blocks.
  2. It is a single string of blocks (sequential blocks), The block structure is the block number , nonce , transaction data , the previous hash number and the current hash number.
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#1282

What do you mean by blocks in this context?

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#1283
  1. Because that ensures that blocks, once confirmed and added to the blockchain, can not be changed in any way.
  2. Block includes: Block number, nonce, transaction list, hash from the previous block, and a hash of a current block
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#1284

Homework on Blockchain and Mining Visually - Questions

1) Why is it important that the blocks are cryptographically linked together?
Each block Storing the hash of the previous block assures the integrity and order of the transactions.
Any modifications to the transaction(s) in a block will cause the hash in the next block to be invalidated, and it will also affect the subsequent blocks in the blockchain. If a hacker wants to modify a transaction, he not only needs to modify the transaction in a block but all other blocks in the blockchain as well.

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

CURRENT BLOCK HASH made up of (difficulty target + nonce + transaction data + hash of the previous block)

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#1285
  1. Each block contains variables that are mathematically linked to each other. This improves security of the network as a change to any block will inevitably lead to other blocks being changed as well, meaning that the original change will not be accepted by the network.
  2. Each block is connected by a hashed pointer to the previous block, containing the version of the block, the hash of the previous block, a time stamp, a merkle root of the transaction and a nonce. A block requires to match a level of difficulty before the network could accept it to the blockchain, and a nonce is a random number to be added to get the required hash value
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#1286
  1. for better security so nothing can be changed
  2. block consist of 3 main things: previous block hash, transactions, nonce
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