Homework on Blockchain and Mining Visually - Questions

Blockchain and Bitcoin 101
#2241

1 - To secure the information by ensuring immutability
2 - The block contains the block number, the nonce, transaction data, the previous and the current block hash

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#2242

  • The link is the puzzle created to ensure security and integrity (no double spend)

  • The block include the transaction (data), current hash and previous has and the nonce

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#2243

The cryptographic link between blocks is responsible for the immutability feature of a blockchain. A change in a previous block would invalidate the cryptographic link to all following blocks.

  • Block size
  • A header with meta data:
    – Protocol version
    – Previous block hash
    – Merkle tree hash
    – Timestamp (seconds from Unix Epoch)
    – Difficulty target
    – Nonce
  • Transaction counter
  • Transactions
    (Source: https://ldapwiki.com/wiki/Bitcoin%20block )
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#2245

1- It is important that the blocks are cryptographically linked together so that any attempt at change a block requires also re-mining all subsequent blocks, which is practically impossible to accomplish.

2- Each block is composed of

  • Block size
  • Block header: Version, previous block hash, Merkle root, timestamp, difficulty target, nonce
  • Transaction counter
  • Transactions
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#2246
  1. To ensure security. The blocks are built on links that use the previous hash, transaction list, and the nonce. You break the link, you break the validation.
  2. Previous hash, transaction list, and the nonce. Input, transactions, output.
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#2247

This maintains the integrity of the blockchain, as even the slightest change in a single block would also change the entire chain from that block on.

It is composed of the block number, nonce, the data being stored, the previous blocks hash and the current blocks hash.

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#2248
  1. Why is it important that the blocks are cryptographically linked together?

to ensure that data in a block wont get altered easily.

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

Previous block hash, data, nonce and hash of the current block

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#2249

:credit_card::link::credit_card: Blockchain and Mining :hammer_and_pick:

  1. Why is it important that the blocks are cryptographically linked together?
    Having all blocks inextricably linked to each other in one continuous chain makes the whole thing tamper resistant against the slightest change in any single block. This setup enables all full nodes to validate the blockchain independently and yet come to the same conclusion (i.e. consensus) as the others.

  2. What does the block structure look like in bitcoin?
    According to https://en.bitcoin.it/wiki/Block :

  • Magic number (always identical as it identifies the type of the data structure)
  • Blocksize
  • Blockheader containing
    • Version of used software
    • Hash of the previous block
    • Hash of the Merkle root
    • Timestamp (in UNIX epoch)
    • Difficulty target
  • Nonce
  • Transaction counter
  • Transaction data
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#2250
  1. This provides network security and eliminates double spend.
  2. (block number, data, nonce, hash of previous block) all form new block hash. The energy gone into solving the block forms the chains or “puzzle” solved connecting each block. This is done by guessing the correct nonce beneath the block Target number.
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#2251

Nonce is a number used by miners to find a block hash that is below a target. :slight_smile:

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#2252

  1. Why is it important that the blocks are cryptographically linked together?
    This secure the network for integrity. One small change in a block will also change the entire block on

  2. What does the block structure look like in bitcoin?
    Block No. > Nonce > Data > Previous Hash > New Hash

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#2253
  1. By being linked that way a change to a previous block affects every blocks that have or are being mined after that block and that makes doing changes to previous blocks impossible.
  2. The block hash is based on the transactions of that block, the previous hash and a nonce that is randomly found so that the hash is below a specific target. That target is lowered if difficulty increases and higher when difficulty decreases(less miners mining).
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#2254
  1. Why is it important that the blocks are cryptographically linked together?
    To have immutability, security and accountability
  2. What does the block structure look like in bitcoin?
    Linked list
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#2255
  1. To make the blockchain secure. Cryptography allows to “link” all blocks so that one change in any block would break the whole chain down
  2. A block hash is made from previous block hash + transaction list + nonce
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#2256

  1. That is what makes bitcoin and blockchain so magical. If they aren’t cryptographically linked together, we could just go in and manipulate whichever block we want, maybe the others will see the false transaction, but other blocks won’t be affected by it which can lead to ignorance and cause problems. However, having all blocks linked together combined with the rule that the network recognizes only the LONGEST blockchain means if we change something we break the chain, and our block gets immediately discarded because the other miners keep adding new blocks and chains to the network (honest ones).

  2. The block in bitcoin is composed of a block number, hash, previous hash, list of transactions, the nonce that the miners have to guess and many other things.

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#2257
  1. Why is it important that the blocks are cryptographically linked together?
    Because that ensures that the blocks are immutable
  2. What does the block structure look like in bitcoin?
    TX+HASH+NOUNCE
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#2258

  1. It is important that the blocks are cryptographically linked as this makes the blockchain immutable. Any changes to a block will affect all subsequent blocks, this dissuades fraudulent activity and thus ensures data integrity.

  2. A bitcoin block is made up of a block header, transaction counter (how many transactions follow), followed by a long list of transactions (transactions to be recorded in the block). The block header contains: a reference to the hash of the previous block, the difficulty, timestamp, a nonce and the Merkle tree root (data structure to efficiently summerize all the transactions in the current block).

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#2259

Homework on Blockchain and Mining Visually - Questions

Q1: Why it is important that the blocks are cryptographically linked together?
A1: It’s important that they are cryptographically linked as it adds another safeguard against changes in the blockchain. When the block has changed the link between blocks breaks and will have to be mined again.

Q2: What does the block structure look like in bitcoin?
A2: each block is set up with the block #, nonce, data, previous block hash, and the area that will generate the current blocks hash.

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#2260
  1. It ensures the immutability of blockchain by making extremely difficult to adjust a block, as you need to re-adjust all subsequent hashes.

block number + size -->previous block hash --> tx’s --> nonce --> current block hash

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#2261

Homework on Blockchain and Mining Visually - Questions

  1. Why is it important that the blocks are cryptographically linked together?
    Blockchain would loose its meaning if blocks were to become separated. In reality blocks are linked as each next block is confirmed by taking information from previous blocks hash (digital fingerprint of it). It is the foundation of what blockchain is - blocks are chained together and eliminate our ability to go back and alter history of records.

  2. What does the block structure look like in bitcoin?
    There are three components:

  • hash from previous block;
  • transaction list of TX in this block and
  • nonce # that gets mined (guessed).

G.

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