Homework on Stale Blocks

Blockchain and Bitcoin 101
#121
  1. What happens in the bitcoin network when two miners solve a block at the same time?
  • They are propagating two versions of the blockchain.
  1. What is a stale block?
  • It is a block which was in the past in the blockchain, that was valid, but in the end was dropped out of the network because there was another valid block with a longer chain.
  1. How do stale blocks occur?
  • They occur when a valid block gets dropped due to a longer valid block
  1. Why is it important to wait for more than one block to be confirmed when sending or receiving a transaction?
  • It’s important because you never know if your transaction will be in the stale block or the long valid block. Waiting six confirmations should be enough to ensure the validation of the transaction.

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#122
  • What happens in the bitcoin network when two miners solve a block at the same time?
    Both start to propogate through the network as “valid” blocks.
  • What is a stale block?
    When one of the valid blockchains mentioned above is no longer considered the “longest”, that block is then stale and has its transactions returned to the mempool.
  • How do stale blocks occur?
    See above
  • Why is it important to wait for more than one block to be confirmed when sending or receiving a transaction?
    In such a long network, there may be multiple cases of new blocks being added at the same time and propagating and additional blocks being added to each different forked version. Best practice is to wait 6 blocks before confirming
#123

Both of them will be temporarily validated, then they broadcast the Block resultant to the closest nodes, creating a fork; that, it will only be considered after the next block join the chain, validating the block in the largest Chain, and dropping off the other block from the chain, all transactions in the dropped block will be then sent to the Mempool.
2.
Its the solved Block in the smallest chain, that will be dropped from the chain, and it’s content sent to the mempool. Also known as an Orphan block.
3.
When two miners solve the puzzle simultaneously occurs a split or fork in the chain, then eventually one of them will be used quicker to build the next block. Denying, than, the other one as Stale or Orphan block, due to be shorter than the other side of the fork.
4.
To be sure that the block containing your transaction is not denied and your transaction does not goes to the Mempool.

#124

  • What happens in the bitcoin network when two miners solve a block at the same time?
    Both blocks will be added to the blockchain. The bock which will be chosen by third coming miner will stay, other block will be dropped

  • What is a stale block?
    It is a valid block which was removed from blockchain because miners chose other block

  • How do stale blocks occur?
    In situation when two miners appended their valid blocks to the blockchain the same time, but one has to be dropped

  • Why is it important to wait for more than one block to be confirmed when sending or receiving a transaction?
    Because the block which contains your transition can be dropped

#125

The block with the biggest PoW will be accepted
A stale block is a block that is dropped
Stale blocks have a lower PoW than the other.
To ensure that the transaction does not belong to a block that will be dropped

#126
  1. Blockchain will have two splits until another block is solved and linked to one of the splits.
  2. Stale block is a block disappear once other block is accepted faster in a different split chain.
  3. Stale block occurs when other set of blocks are verified faster in the chain.
  4. To make sure that the part of the blockchain where your transaction happened does not included stale blocks.
#127

  1. What happens in the bitcoin network when two miners solve a block at the same time?
    There is a competition, one will win and this becomes the longest blockchain and will become the one accepted on all the nodes. The other block will be stale and dropped and will return its transactions to the mempool.

  2. What is a stale block?
    It is a block that is dropped on the shortest blockchain because another blockchain exists that is longer.

  3. How do stale blocks occur?
    It happens when two miners mine a block at the same time.

  4. Why is it important to wait for more than one block to be confirmed when sending or receiving a transaction?
    It is important to wait for 6 confirmations, this will be enough to ensure that your transaction is not in a block that is stale.

#128

when two minors solve a block at the same time each of their blocks will propagate the network. This will happen until the next block being mined is complete and chooses one of the two original blockchains to append to. Once this is done, the blockchain that is shorter by measure of pow will be stale or orphaned and the longer of the chain adopted by the network. It is important to wait for confirmations by other nodes when making a transaction because if your tx ends up on a stale node your tx may not actually have gone through. After six confirmations it is considered valid.

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#129
  1. What happens in the bitcoin network when two miners solve a block at the same time?

The network will have two valid blockchains. The block that arrives first at a node will be the valid block for that Node. The network will eventually resolve to only one blockchain after more blocks are mined and one of the two chains become longer than the other one.

  1. What is a stale block?

A Block that was once valid but not anymore.

  1. How do stale blocks occur?

When two chains are active at the same time and one becomes longer and thus the main/true chain. That other chain had a block that is no longer part of the chain: a stale block.

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

Yes, because multiple chains can occur and your block might become stale. Typically it is advised to wait 6 blocks to be really confident on the confirmation of the block.

#130

  1. If 2 miners solve a block at the same time, then the block on the longest chain and also having the greater proof of work will be added and the other will be dropped.

  2. A stale block is one that has been dropped and the transactions sent back to the mempool.

  3. Stale blocks occur when a block has been dropped because maybe there were too few miners and the difficulty level was low, or that a miner was not fast enough to get a nonce.

  4. Blocks can be dropped, so 6 or more confirmations are needed to be sure that a block is valid on the blockchain.

#131

1. What happens in the bitcoin network when two miners solve a block at the same time?
Those blocks continue until the next block is calculated properly then the lesser is eliminated and the longer chain chosen.

2. What is a stale block?
A stale or orphaned block is a former accepted block who was then eliminated from the chain because of the validation happening with the other block.

3. How do stale blocks occur?.
Stale block occur from the competing block being accepted by the chain thus the competing or Stale block is made. A stale block is a dead block.

4. Why is it important to wait for more than one block to be confirmed when sending or receiving a transaction?
It is important to wait for more that one block to be confirmed when sending or receiving a transaction so that any the blockchain has time to confirm itself as correct. Especially is this necessary in the case of stale blocks or orphans

#132
  1. What happens in the bitcoin network when two miners solve a block at the same time?

Both blocks A and B will be propagated to the network, so there will be 2 versions of the blockchain circulating, one will have A as most recent block, the other will have B. Some miners will keep mining based on block A, some will use block B.

  1. What is a stale block?

A stale (also known as orphaned) block was once part of the blockchain, but then dropped because a longer blockchain invalidated it. This happened because 2 blocks were mined at the same time.

  1. How do stale blocks occur?

Stale blocks happen when 2 blocks have been mined at the same time and thus, 2 versions of the blockchain were circulating at the same time. After some time, one blockchain will be the longest one, invalidating the other(s) one(s) (called stale blocks).

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

To avoid the situation that the block contaning your transaction is a stale block -or even worse, double spent coins-, it’s a good practice to wait for a few more blocks to be mined (each new one is a confirmation that the block is still part of the blockchain).

#133
  1. What happens in the bitcoin network when two miners solve a block at the same time?

The blockchain temporarily forks and only longest one will eventually win. Blocks of the shorter chain will be orphaned and dropped back to the mempool

  1. What is a stale block?

In the event of temporary fork due to block being solved at the same time in different places, stale or orphaned block is perfectly valid block that is disregarded by network because it belonged to the shorter chain and sent back to mempool in favor of chain with more POW

  1. How do stale blocks occur?

As soon as the temporary fork is resolved in favour of a longer chain version of the truth, stale block from loser/shorter chain is the one being sent back to mempool

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

In case of a temporary fork and stale block occurring you need to be sure that your transaction is included in correct block (the one belonging to the longest chain). Therefore is advisable to wait at least 6 block confirmations,

#134
  1. What happens in the bitcoin network when two miners solve a block at the same time?

Basically they are both approved on different nodes and then starts a competition in a way. The first block that gets another block attached to it get accepted by the nodes and leaves the other block “stale”.

  1. What is a stale block?

A stale block is the block that was approved with valid transactions and correct hash and everything but another longer blockchain formed without it and it is left aside.

  1. How do stale blocks occur?

When two miners solve the puzzle at the same time and propagate the new block to the nodes. Because it takes time for all nodes to get the information - some accept block #1 that was mined the other accept the other one. So one of them has to become (at the end of the day :wink: ) a stale block.

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

Just in case the first confirmation is a stale block!

#135
  1. Well, at first not much will happen, both blocks will appear in the blockchain and be displayed according to the nearest nodes to that specific block. But eventually a new block will appear by the next miner, and according to the row of blocks he chose (or got from the nodes) the blockchain will drop one of the simultaniously created blocks. It is always the block with the highest difficulty and proof of work that will be accepted by the network.

2 & 3. The above scenario will have consequenses, namely a stale or an orphaned block. This is the block/blocks that got on the chain which did not get accepted to the network due to less difficulty/proof of work compared to the other chain. For the network to function properly, there is a target of 10 minutes between the blocks which the blockchain network will strive for (and adjust difficulty thereafter), this is to have some kind of cooldown time between the blocks for the network to sync, and be able to decide the true version of the blockchain no matter how many times two miners manage to create blocks simultaniously.

  1. There is difference between a confirmed and a confirmed transaction. What is meant by that is that it takes a certain amount of time and blocks before you can with confidence assert which blockchain is valid (in this case the one you sent your transaction trough). After 6 confirmations (6 additional blocks created after the block your tx was put in) you can actually confirm that the block you have your transaction in is not going to be a stale block and be sent back to the mempool.
#136

  1. Both will be apended to the chain, but one will eventually be considered the true chain through consensus. This is determined through the length of the chain and upon the next blocks.

  2. A block that is totally valid but the chain dosn’t continue to build on it.

  3. Two blocks apends to the chain at the same time, and gets propagated among the nodes. Eventually one of them get accepted as the “consensus-truth” and the other one gets droppen; becomes a stale block.

  4. You’re transaction could be added in a stale block and be returned to the mempool. 6 blocks is a good amount to be sure that it’s part of the longest chain, and therefor valid.

#137
  1. If two miners solve blocks at similar times the start propagating them to nearby nodes.
  2. A stale block is a block that gets mined but doesn’t get propagated into the entire network. So it is considered invalid.
  3. A stale block occurs when a competing miners block gets several confirmations and spread through the entire network. The “stale” block has a shorter chain, considered invalid, and it’s transactions are sent back to the mempool.
  4. A block that is mined may be considered invalid if the network doesn’t reach consensus on it. If you take it as truth errors could occur as other longer chains are brought to consensus. These confirmed chains are what will be used in the future. They are the ones to use if you want trustless information.
#138

  1. Than some part of the nodes will have a version with block 1 added and some have a version with block 2 added. Next: Another block is added to the blockchain and chooses block 1 or block 2 to link on. The other which is not linked, will be dropped (orphaned or stale block).

  2. A stale block is a block which is completely true/validated but dropped from the blockchain because the other chain is longer and for than this is the real blockchain.

  3. See 1/2.

  4. Your transaction could be part of a block that will be dropped (stale or orphaned). After a few more blocks you can be more sure that the transaction will stay like this / finished.

#139
  1. What happens in the bitcoin network when two miners solve a block at the same time?

SCENARIO: 2 miners produce a block at exactly same time. The nodes geographically closest to each node start to propagate the block. 2 versions of the truth. Both valid.

Both Nonces are valid
Bot sets of Tx are valid

A 3rd miner now tries to add new block into blockchain. Will choose one or the other. The network always accepts the longest blockchain i.e. the chain with the most POW (Most difficulty).

One of the chains will be invalidated and removed, and txs returned to mempool.

Result - always 1 version of the truth (the longest chain).

  1. What is a stale block?

A block which is dropped or invalidated due to another chain becoming the accepted version of the truth (the longest chain)…

  1. How do stale blocks occur?

When 2 miners produce a block at exactly same time, there will be 2 versions of the truth. At some point, a subsequent mined block will be appended to one of those chains, making it the longest chain with the most POW. The network always accepts the longest blockchain i.e. the chain with the most POW (Most difficulty).

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

Confirmation times once a tx has been accepted to a block: best practice is to wait for 6 confirmations in case the block is dropped/invalidated for the above reasons.

#140

next block added will be longest chain
block dropped by miners
when miner picks block from node longest chain
confirm that the block will be added to chain and next block added to existing block

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