1.Why is it important that the blocks are cryptographically linked together?
It makes the network secure and no one can change the transactions in previously mined blocks. It also makes audit very easy and brings transparency to the network.
It incentives miners to play by the rules (= integrity) and it makes it impossible to change something in previous blocks because it’s to difficult.
previous hash + list of tx’s + nonce (that has to be guessed)
It is important to ensure transactions cannot be altered, making the network more secure
The block will need to create a hash based off the hash of the previous block + has of current block tx fees + nonce. If the hash of the block was less than a certain threshold, the block will appended to the blockchain.
So they remain immutable.
Hash, confirmations, timestamp, height, miner, number of transactions, difficulty, Merkle root (hash of all hashes of all transactions that are part of a block in the network), version, bits, weight, size, nonce, transaction volume, block reward, fee reward.
in order to avoid people hacking or at least make it extremely difficult --> a change in a block changes all subsequent blocks, thus making the network more secure
hash of blocks: previous hash, list of txs, new block, nonce (transaction, inputs, outputs)
1. Why is it important that the blocks are cryptographically linked together?
For the security of the blockchain. Because this makes it very difficult to change a block.
The data can’t be changed, it’s a mathematical puzzle that links all the earlier blocks in the chain together. This is important, to make sure that the entire system follow the rules.
2. What does the block structure look like in bitcoin?
Transaction data, previous hash inputs, a nonce and hash outputs.
A nonce is a number only used once.
The nonce is the number that blockchain miners are solving to receive their reward in cryptocurrency, e.g Bitcoins.
To create a blockchain. By calculating or encrypting each hash value of the previous block together with the current block, it becomes cryptographically immutable, secure and to prevent double spend attacks.
The block number, the nonce, the data of the transations, the hash from the previous block, and the hash from the current block.
Why is it important that the blocks are cryptographically linked together?
To ensure integrity
What does the block structure look like in bitcoin?
It has links in between blocks that are comprised of a different Hash each time
Each block contains a pointer to the previous block id, which in turn is a hash of the contents of the block. This ensures that it can only have been produced after the previous block was produced and not before the next one was produced. Since changing any field of one of the blocks would change the hash of that block (and therefore all subsequent nodes), this prevents changing any of the transactions previously stated.
Each block contains transactions, previous block hash, a nonce, as well as a bunch of other fields. You can see how a block looks like by using services like blockchain explorer:
If you want a more precise explanation of the exact composition of a block, you can take a look at Chapter 9 of Antonopoulos’ awesome book:
Table 1. The structure of a block
| Size | Field | Description |
|---|---|---|
| 4 bytes | Block Size | The size of the block, in bytes, following this field |
| 80 bytes | Block Header | Several fields form the block header |
| 1–9 bytes (VarInt) | Transaction Counter | How many transactions follow |
| Variable | Transactions | The transactions recorded in this block |
Table 2. The structure of the block header
| Size | Field | Description |
|---|---|---|
| 4 bytes | Version | A version number to track software/protocol upgrades |
| 32 bytes | Previous Block Hash | A reference to the hash of the previous (parent) block in the chain |
| 32 bytes | Merkle Root | A hash of the root of the merkle tree of this block’s transactions |
| 4 bytes | Timestamp | The approximate creation time of this block (in seconds elapsed since Unix Epoch) |
| 4 bytes | Difficulty Target | The Proof-of-Work algorithm difficulty target for this block |
| 4 bytes | Nonce | A counter used for the Proof-of-Work algorithm |
It is important because it helps secure the network and its integrity. Any alterations to previous transactions will compromise the following blocks, which discourages the virtually impossible task of re-mining.
A block contains the hash of previous block, list of current transactions, and nonce (random number guessed by miner)
Why is it important that the blocks are cryptographically linked together?
For security reasons, it makes it impossible to change something without the others to know, trustlessness
What does the block structure look like in bitcoin?
a block structure exist out the hash of the previous block/ transaction list and a nonce
The blocks must be linked so that every block affects the following block, if they had no relation then any block changed would be considered viable.
Each block contains the previous block’s hash, a plethora of transactions, and a Nonce. Everything in the block is considered when a hash is created, linking all them together in a chain comprised of hashes.
Why is it important that the blocks are cryptographically linked together?
This increases the difficulty of making changes to previous blocks because linked blocks would all need to be remined if one block is needed to be changed.
What does the block structure look like in bitcoin?
Block number, Nonce, transaction data, previous hash, and current hash
It creates security and integrity and gives an incentive to not try to hack the blockchain.
The block structure consists of a hash, the previous hash, transaction list and the winning nonce
Because it increases the difficultly of each block to make it highly unlikely to alter any previous blocks without using allot of time and electricity.
Block identifiers, block headers, transactions, hashes, nonce
