Homework on Stale Blocks

Blockchain and Bitcoin 101
#4094
  1. What happens in the bitcoin network when two miners solve a block at the same time?

The longest blockchain will win, while the other will be dropped.

  1. What is a stale block?

A block that was in the blockchain but was then dropped because another block with a longer chain was produced at the same time.

  1. How do stale blocks occur?

When two miners successfully mine a block at the same time.

  1. Why is it important to wait for more than one block to be confirmed when sending or receiving a transaction?

6 confirmations is recommended. This helps avoid stale/orphaned blocks

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#4095 
What happens in the bitcoin network when two miners solve a block at the same time?

Some portion of the network sees the first miner’s block, another portion will see the second miner’s block.

What is a stale block?

A block that is mined by subsequently dropped because a chain with more work is produced by another miner.

How do stale blocks occur?

Stale block occurs when it’s dropped because there is another version of the blockchain that shows more work that does not include this block

Why is it important to wait for more than one block to be confirmed when sending or receiving a transaction?

Because your transaction might wind up back in the mempool if the block that it’s in turns out stale and is dropped.

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#4096

1/2/3. Whichever the subsequent block is mined off of first will become the ‘true’ block. The alternative block becomes a stale block, and unused going forwards, even though was true at one time.
4. Because your confirmation may become a stale block, so you should wait 6 blocks before being sure you’ve been confirmed,

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#4097

Waiting will not minimise stale blocks. It only insures your tx is not part of it.

#4098
  1. There will be two temporal side chains.
  2. The stale block is the side chain with the shortest number of blocks, it gets dropped.
  3. When two miners solve the puzzle at the same time, the blockchain forks temporarily and the block with the least number of accepted nodes becomes stale.
  4. So we can be sure that the chain containing our transaction has been accepted by the network.
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#4099

  1. The chain forks until one chain becomes longer then that chain is accepted by the network.

  2. A stale block is a block that was valid but then was dropped from the chain.

  3. Stale blocks occur when two blocks are created at the same time but one block is accepted once it becomes part of a longer chain, the dropped block becomes a stale block.

  4. It is important to make sure your transaction was continued in the blockchain and did not become a stale block.

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#4100

Questions:
. The chain will split into two chains and the chain with the greatest proof of work will be the one that is successful while the other will be dropped.
. Blocks which have been dropped from a shorter chain with less proof of work in favour of competing blocks from longer chains.
. When a problem is solved successfully simultaneously and then the blocks with correct answers are split into two chains, while the shorter chain is dropped, which results in stale blocks.
. It is possible that the block will become part of a shorter chain which means the block will be dropped and the transaction will become invalid and return to the Mempool

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#4101
  1. The longest chain will win after splitting the chain temporary.
  2. Stale block is that the block which finally will be dropped after one miner will win with an another block of the higher length.
  3. Stale block occurs when there is a fork of blockchain and another block winning.
  4. Because your transaction can be dropped due to stale block and you need to make sure that it wasn’t happened.
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#4102
  1. What happens in the bitcoin network when two miners solve a block at the same time?

Separate instances of the blockchain are created with nodes seeing different versions. As more blocks are added, the version with the most POW (i.e. longest) will win and the block from the shorter version will be dropped.

  1. What is a stale block?

The stale block is the one that is dropped.

  1. How do stale blocks occur?

Stale blocks occur when two miners solve a block at the same time but only one version of the blockchain may exist.

  1. Why is it important to wait for more than one block to be confirmed when sending or receiving a transaction?

The transaction could be dropped if it’s part of a stale block.

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#4103

  1. What happens in the bitcoin network when two miners solve a block at the same time?
    Appears two versions of the blockchain that coexist for a while. The two blockchains enter into some sort of a competition. The one that ends up adding more nodes prevails.

  2. What is a stale block?
    In the scenario described in Q1, the blocks that the loser blockchain drops are called Stale Blocks.

  3. How do stale blocks occur?
    When they are dropped because another version of the blockchain had more blocks. These stale blocks are not needed anymore.

  4. Why is it important to wait for more than one block to be confirmed when sending or receiving a transaction?
    In case that my transaction ends up written in a stale block. It’s said that after 6 confirmations, the transaction is 99,99% secure.

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#4104

When 2 miners solve a block at the same time the block in the longest chain wins whilst the other block is discarded and considered a stale or orphaned block. When this happens they are returned to the mempool.

A stale block is the block that was in the blockchain but then dropped because another block that was produced at the same time forming a longer chain.

Stale blocks occur when a block is valid for a while because 2 were produced with the same version of the truth but then dropped because the blockchain continued onto another block.

It is important to wait for 6 confirmations to be sure that the block with your transactions are in is not dropped from the chain.

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#4105

1: 2 separate blocks are made, splitting the Blockchain. The most difficult & longest chain becomes the dominant one, dropping the ‘stale’ block(s) on the weaker chain which are then sent back to the Mempool.

2: A stale block is a block that is part of the ‘weaker’ chain when two miners solve a block at the same time.

3: Stale blocks occur when two copies of the Blockchain are created via miners solving a block at the same time. Blocks on the dominant chain are permanent whilst the blocks on the weaker chain are considered stale or orphan.

4: It is important to wait for around 6 confirmations in case the blocks are not propagating as a permanent fixture on the Blockchain, this avoids blocks dropping out/becoming stale & your transaction not being confirmed.

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#4106

  1. The network will choose the longer blockchain to continue on. The other block will be dropped back to the mempool

  2. A stale block is a completed block that was not added to the blockchain becuase another competing block was selected by the network instead of it. This stale block will go back into the mempool

  3. See 2

  4. Because your transaction might be in a block that ends up not being added to the blockchain yet. after 6 confirmations it can be assumed that your transaction’s block has been accepted and added to the blockchain

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#4107
  1. Both valid blocks are propagated through the net work Until another block is created on top of either block. The other block is discarded or orphaned and the transactions are returned to them mempool.
  2. The block that was discarded is considered stale
  3. Stale blocks occur when two valid blocks are propagated through the net work and only one continues to be built upon
  4. It is important to wait more than one confirmation after a block to ensure Les of a chance the block become stale
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#4108

  1. When 2 miners solve a block at the same time the block in the longest chain wins and the other block is discarded and considered a stale or orphaned block. All the transactions are returned to the mempool.

  2. A stale block is the block that was in the blockchain but then dropped because another block that was produced at the same time was part of a longer chain.

  3. Stale blocks occur when a block was valid for a while because 2 were produced with the same version of the truth but then dropped because the blockchain continued on another block.

  4. It is important to wait for 6 confirmations to be sure that the block your transactions are in is not dropped from the chain.

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#4109

Homework on Stale Blocks - Notes & Answers
NOTES:

  • Problematic situation: two miners produce a nonce that yield a hash below the target. This means that some nodes have one version of the truth and some nodes have another version (the chain splits). This is a problem because we have only have one version of the truth (one chain)

  • Solution: When this happens at some point more miners will add blocks to one block or the other. Whichever chain is the longest (most PoW = which means blocks with the highest level of difficulty) will be the real chain and the other one will be dropped. This is also known as a stale block

  • The transactions in the stale block are returned back to the mempool

  • Best way/practice to ensure block is confirmed is to wait for 6 confirmations. This means to wait until 6 more blocks are added to the block of concern in order to update its status as confirmed.

    • This is very important as it ensures your block is not part of a stale block that gets dropped

  • Stale/orphan block: a valid block that was once part of the blockchain but got dropped because there is another version of the blockchain that is longer that does not include that block in its chain

  • Why do we need to wait 10 min? To avoid the situation of orphan/stale blocks

    • We assume that in 10 minutes the newest block is validated & confirmed and all of the nodes are synched before the next block is produced and that everyone is ready for the next block

ANSWERS:
1) Q: What happens in the bitcoin network when two miners solve a block at the same time?
A): There is a temporary fork (split) as some nodes have miner 1s block (one version of the truth) and some nodes have miner 2s block (another version of the truth)

2) Q: What is a stale block?
A): Valid block that was once part of the blockchain but got dropped as there was a longer version of the blockchain that (most PoW) that did not include that block

3) A: How do stale blocks occur?
A): When two miners guess nonces that yield hashes below the target at the same time

4) Q: Why is it important to wait for more than one block to be confirmed when sending or receiving a transaction?
A): To avoid the situation of orphaned/stale blocks

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#4110
  1. The two blocks create seperate chains and the chain with the most proof-of-work will be the one accepted by the network.
  2. A stale block is a block on a chain which was mined but is not on the current blockchian.
  3. Stale blocks occur when another chain than then one which the stale block is one becomes longer (more precisely, has more PoW) than the one on which the stale block resides. The chain with the most PoW is the current blockchain and mined blocks which are not on the current chain are stale blocks.
  4. Because this allows for blocks to circulate and avoid the situation of stale/orphan blocks.
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#4111

  1. What happens in the bitcoin network when two miners solve a block at the same time?
    Two different chains will be created (build on the previous block)

  2. What is a stale block?
    Orphaned block on the shortest of the two chains

  3. How do stale blocks occur?
    By miners creating a block at roughly the same time.

  4. Why is it important to wait for more than one block to be confirmed when sending or receiving a transaction?
    To be sure that your transaction is not dropped and you lose your transaction fee.

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#4112

  1. What happens in the bitcoin network when two miners solve a block at the same time?
    The miners start propagating their block to the nodes closest to them, the network waits until a confirmation to settle consensus and the longest chain with the most PoW wins.

  2. What is a stale block?
    Stale blocks are blocks that were in the blockchain at one time but got dropped because there is another version of the blockchain that is simply longer without those blocks in it.

  3. How do stale blocks occur?
    Stale blocks happen from a fork in the blockchain after 2 valid blocks were produced at the same time, but the blockchain with the most blocks was chosen so the other one was dropped and data returned to the mempool.

  4. Why is it important to wait for more than one block to be confirmed when sending or receiving a transaction?
    It might be the case that your TX is inside a block that could end up being a stale block. Therefor best practice is to wait for at least 6 more blocks to be confirmed after the block that your TX is in.

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#4113
  1. Two versions of the truth are created and accepted by the closest nodes.
  2. This is when valid blocks are dropped.
  3. The other version of the truth or chain has a higher POW.
  4. That way all nodes can accept the same version of the truth and your TX will be truly validated and accepted.
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