Homework on Stale Blocks

[maf_86]

1. What happens in the bitcoin network when two miners solve a block at the same time?
   At that point, both blocks will be temporarily appended to the blockchain until new miners join the process and start appending new blocks to the chain. At some moment of time, one of the 2 editions of the blockchain will get at least 1 block longer and will be included in the blockchain. The longer and more difficult edition in terms of proof of work is the one to be the valid one and to be accepted by the network. The other one will be dropped, as there have to be only 1 version of the truth, and is called orphaned or stale.

2. What is a stale block?
   A stale block is a valid block that will be replaced and dropped out of the blockchain.

3. How do stale blocks occur?
   They occur when they are replaced by other blocks that are more difficult solved in the blockchain.

4. Why is it important to wait for more than one block to be confirmed when sending or receiving a transaction?
   The 10 minutes time is the threshold time needed for the block to be propagated in the entire network. After that time and also the required number of at least 6 more blocks further, the block is valid.

[Castor]

1. If two miners solve a block at the same time there will for some time be two competing versions. Though whenever another miner solves a block on one of these blocks, this block will be the correct one because it is longer, and the other block will return to the Mempool.

2. A stale block is a block that got temporarily confirmed but since then lost its status and had to return to the Mempool.

3. A stale block occurs when two miners have solved the same block at approximately the same time. Then when one them gets confirmed through the next block this block will continue, and the other block, called a stale block, will return to the Mempool.

4. It is important to wait for more than one block to be confirmed because then the eventual competing blocks will have had an end result, and then the confirmed and correct block is ready to get mined even further.

[LenoraEl]

1. When 2 blocks are solved at the same time there will ultimately be a “stale” or “orphaned” block once another miner chooses one of them to build upon and the Blockchain is extended and the network chooses the longer chain.

2. A “stale” block is a block that was once confirmed and added to the blockchain but ultimately dropped as the chain grew.

3. A stale block occurs when the blockchain follows along a secondary path before said block has been added to. It therefore has no subsequent connections and is dropped while the longer chain continues.

4. Waiting for more than one block to be confirmed is necessary so as to avoid stale blocks occurring down the line and transactions being returned to the mempool. Waiting for 6 new blocks is recommended.

[GahuckImGoofy]

1. When you have two different miners who have created new & valid blocks - there is a difference of truth even though the nonces and transactions are all legit. The nodes of the network might believe different truths based on where they’re at geographically.
2. A stale block has it’s transactions thrown back into the mempool for other miners to validate and append a part of a new block.
3. A stale block is a dropped block that was in the blockchain at one time but ended up getting dropped as there was another block that got accepted, appended and an even newer block was added to that chain as well - making it longer than the other option of the blockchain.
4. It’s important to wait for more than one block to be confirmed when sending/receiving a transaction because the newest blocks need to be propagated throughout the entire blockchain network.

[JasonM]

1. What happens in the bitcoin network when two miners solve a block at the same time?
   If 2 blocks are solved at the same time, both blocks will propagate to closeby nodes, until the blockchain that represents the greatest proof of work is chosen.

2. What is a stale block?
   A stale block is a block from the “rejected” blockchain.

3. How do stale blocks occur?
   These occur when there are competing blockchains, and results in the rejection of a blockchain.

4. Why is it important to wait for more than one block to be confirmed when sending or receiving a transaction?
   This is because your transaction may be in a blockchain that ends up getting rejecting, and your transaction ending up back in the mempool…by waiting for more than 1, ideally 6 confirmations you can be confident that your transaction is in the confirmed blockchain.

[Alko89]

@cryptochef

Best practice would be to wait for at least 6 confirmed blocks, this is because if it is only five, we can then run the risk to attach the block to a stale or orphaned chain.

6 is actually a rule of thumb and is really safe, in practice a stale block will probably be resolved the next block. But the longer you wait the lower the probability for a stale block being resolved. In theory miners could solve blocks on each chain indefinitely, but after 6 confirmations this being the case is negligible. Basically its all about probability

[LuizCyriloA]

1 a Fork is created. And now we have 2 versions of the true.

2 It is a block that was added to the chain but then was dropped.

3 When there is a fork, and one ends up becoming the bigger one, this one will be kept and the blocks added to the smaller chain will be dropped, making the transactions of these blocks return to the Mempool.

4 THe ideal is to wait 6 blocks to be confirmed in order to avoid transactions being dropped back to the mempool.

[KHovadablock]

1. When two miners solve a block at the same time, it creates a fork in the road representing two possible future pathways for the chain to take. Depending on which path/block the next miner continues to build on, will determine how this fork is resolved. The outstanding block is designated a stale/orphaned block and is dropped.

2. A stale block is the outstanding block created via the blockchain forked road, which occurs if/when two miners solve the crypto puzzle simultaneously. The block that doesn’t get built upon, creating the true sole path forward for the chain, is designated a stale block as its dropped from the network.

3.Stale blocks occur when a fork in the blockchain road is created, then resolved by the chain continuing in the other direction. The block/path not taken by the next miner becomes a stale block.

4. The answers to the above questions is why it’s important to wait for more than one block to be confirmed. One should wait to make sure that additional blocks continue forward, building on the block their transaction is, so that the user knows their txns were truly confirmed, and not part of a stale block that gets dropped from the network

[epicangel]

1. there are 2 versions of the blockchain temporirly
2. stale blocks are result of valid blocks being dropped by the network due to less PoW (length) when 2 miners turn in blocks at the exact same time
3. 2 or more miners solving the cryptographic puzzle at the exact same time
4. to insure your transaction does not get entered onto a stale block and not confirmed

[polky17]

hat happens in the bitcoin network when two miners solve a block at the same time?
The network accepts the longest blockchain with the lowest target.One is accepted via POW & the other returns to the mempool.

What is a stale block?
A block which was previously in the blockchain but is later dropped.

How do stale blocks occur?
There will always be one version of the truth which will be accepted. So if there is another block made within 10 mins, only one can be validated onto the network.

Why is it important to wait for more than one block to be confirmed when sending or receiving a transaction?
To validate and verify the POW confirming that the longest block is accepted within 10mins.6 confirmations take place.

[bigbill]

1. Both blocks are transmitted to the network. The block that the next largest mined block is attached, prevails.
2. A block added to blockchain but eventually rejected, as another larger chain was mined.
3. When two different valid blocks are appended to the blockchain at the same time.
4. To make sure transaction is not part of a stale block

[AD4]

1. Both blocks are added to the block chain and the chain that is the longest is ultimately kept as part of the block chain and the other block is removed.

2. A stale block is a block that was once part of the block chain at one point in time but was removed because there was another version of the block chain which had a longer chain.

3. Stale blocks occur when multiple blocks are added to the blockchain and subsequent blocks are added to only one of the previous blocks thus resulting in a longer chain and the chain that is the longest is the one that is added to the blockchain.

4. Because this allows for the entire network to confirm the blockchain and ensure that all of the transactions are valid thus minimizing the stale block issue.

[c1cag1b3]

1. Chain will fork for a moment, but it will be dropped at a moment when “new truth” appears.

2. Stale block are valid block which were dropped by a network.

3. Due to worldwide coverage, network cannot sync that fast and there appear block simultaneously which can propagade their version of the chain.

4. To ensure that transaction will be linked to chain and not drop with stale block.

[cryptochef]

@Alko89

@cryptochef

Best practice would be to wait for at least 6 confirmed blocks, this is because if it is only five, we can then run the risk to attach the block to a stale or orphaned chain.

6 is actually a rule of thumb and is really safe, in practice a stale block will probably be resolved the next block. But the longer you wait the lower the probability for a stale block being resolved. In theory miners could solve blocks on each chain indefinitely, but after 6 confirmations this being the case is negligible. Basically its all about probability

Thanks for the help! Kind of as a game of chance.

[mchoeti]

1. What happens in the bitcoin network when two miners solve a block at the same time?
In this moment we have 2 versions of the chain. The next miner chooses the next block and the longest chain wins.
This is also the reason why you need at least 6 conformations that a transaction is valid. If your transaction was in the “invalid” block it will go back to the mempool.

2. What is a stale block?
It is considered as a valid block. But was not chosen from the next miner. This block is no longer part of the longest chain and will discarded.

3. How do stale blocks occur?
If two or more miners solve the puzzle at the exact same time on different location. As example one in the US the other in Europe.

4. Why is it important to wait for more than one block to be confirmed when sending or receiving a transaction?
Because you can not be sure if the transaction was in the longest chain. See the example if two or more miners solve the puzzle in the same time.
If you would wait for only 1 confirmation. The Blockchain will be broken, sooner or later…

[erik_sonos]

1. Answer: Two competing blocks are added to the blockchain. In other words, the “…chain forks temporarily” (as expressed by @baidis) The one that is the most complex will win eventually and the other block will be let go of and put back into the mempool.

2. Answer: A stale block is a block that has been put back into the mempool, as it lost against the competing block that had a higher PoW / was part of a longer chain.

3. Answer: They occur when two miners are faster at solving the cryptographic puzzles and creating blocks with approved nonces than the 10 min block time, therefore, nodes accept both blocks into the system, which eventually leads to one being chosen over the other.

4. Answer: It’s to prevent the creation of stale blocks from happening. Question for the forum: How do you actually go about this as a miner, is it through an algorithm that you can install on your mining gear, or do you do this manually?

[SmooveSaudi]

1. The chain forks temporarily until on chain is longer than the other. The shorter of the two gets ignored and the transactions are returned to the mempool.
2. A stale block is the block that was ignored in favor of the chain that has more confirmations.
3. A stale block occurs after a fork is resolved because the network chose the longer chain.
4. To ensure that it is not a stale block. 6 confirmations is should be enough to ensure that it is not an orphaned block.

[Cryptek]

• What happens in the bitcoin network when two miners solve a block at the same time?
  -> the blockchain will split / fork temporary in 2 blockchains

• What is a stale block?
  -> a block which is dropped out of the blockchain because he was on the smallest fork of the blockchain

• How do stale blocks occur?
  -> every 10 minutes the network is synchronised to ensure every nodes work on the same blockchain. At this moment the biggest (PoW) chain is selected and the other chain, and its blocks, is dropped out.

• Why is it important to wait for more than one block to be confirmed when sending or receiving a transaction?
  -> Because your transaction can be written in a block which in a fork of the chain which won’t be validated, so in a stale block, so a block which will be dropped out of the chain.
  –> A block is theoricaly validated after 6 blocks.

[Mako]

1. Each one propagates the mined block to its nearest nodes and those in turn propagate to their other nodes. In the meantime, other nodes can begin to mine new transactions picking the just added block to link to.
   So it is then possible some miner can have one node but not the other ( which is still travelling) and it also may have yet another node added to it. In time, the longest block will be considered and when the block finally arrives, it will find that already, the another different block ( w different txns) already existed in the chain and that arriving late block will be considered stale as it cannot be linked to the longest chain. The contents of it will be removed and put back in the mempool.

2. The stale block is perfectly valid block at some point in time but now is no longer valid because it cannot be linked to the block chain. The hash number of the block no longer refers to the New prev block which is some other block at the end of the longest chain and therefore the contents have to be offloaded back to the mempool.

3. The Stale blocks occurs when the hash value it refers to ( built by hashing the Prev hash, the Nonce, and the transactions in that block) still hash to the number lower than target (at that point in time), but in reality this block’s prev hash is not the same as the real previous block which could be many blocks after the last block. They occur due to the fastness of new block generation versus the propagation time that does not give time for the network to “settle” before another block comes along.

4. It is important to wait for more than one block to be confirmed when sending or receiving the transaction to ensure that the values contained in that block are recognized by all blocks in the network as then there cannot be any stale block that has not yet been mined. If not we will be spending based on a transaction that has been offloaded to the mempool and likely the transaction will not go through (no consensus) and when the wallet interrogates the wallet after sometime, the moneys will not be there ( like it is lost, but in reality it is not lost and in time it will be found).

[Earnst]

1. When two miners solve a block at the same time, their blocks are accepted by the nodes closest to them and their blocks are added to those respective blockchains.

2. A stale block is the result of a subsequent block being appended to one of the forked blockchains. They were both true and the point of conception, but now one of the correct versions is longer. The way the network deals with this, is that it removes that previously accepted block and places it back in the mempool. The removed block would be a stale block. Also known as an “orphan block”.

3. It occurs due to being accepted on a blockchain that subsequently has less blocks than another true version of the blockchain. Refer to answer for question 2.

4. It’s important to wait for more than one block to be confirmed when sending or receiving a transaction to better mitigate against that transaction being submitted by a stale block. In turn reducing the number of errors and pending transactions in the mempool, which would inturn increase the cost of transactions.