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I maybe wrong but what I think is the blockchain ledger exists as long as there are active nodes in the network. So can the Bitcoin blockchain be shutdown by shutting down power supply across the globe? What would happen in such a case?

I think the transactions that were not added to the ledger would definitely be lost and they would have to be re initiated. I think power shutdown would create inconsistency between different instances of the ledger at different nodes and even if the power is back we wouldn't be able to pick a safe state of the ledger.

What are the possible ways to shutdown the blockchain without having to go to each and every node and taking it down?

  • I'm voting to close this question as off-topic because it's about blockchains in general and only bitcoin questions are on-topic here. – David Schwartz Oct 19 at 19:17
  • @David Schwartz I know. But this is the most closest stack I found related to blockchains. Do you know a stack site for asking blockchain based questions in general? Is it better to post blockchain based questions on CS Stack Exchange? – Deep Bodra Oct 19 at 19:54
  • @DeepBodra see the help centre: bitcoin.stackexchange.com/help/on-topic . On-topic subjects include questions about: "technologies or events that are applicable and relevant to the Bitcoin network and users of the Bitcoin currency in the past, present, or future". This question is arguably relevant to the Bitcoin network, and with a small edit it could easily be made more explicitly BTC-related -- but I still think it is reasonably fine as in. – chytrik Oct 19 at 21:26
  • @chytrik Unfortunately, what's happening is that it's getting bitcoin-specific answers that are not marked as bitcoin-specific and that's causing people to learn things that are actually wrong. This kind of question degrades the value of the site to future visitors. The alternatives seem to be changing the question to something the original poster didn't ask or closing it. – David Schwartz Oct 19 at 22:46
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    @chytrik I don't think it would not have been that difficult to produce a high-quality answer that explains, fundamentally, why blockchains are difficult to shut down without going into the specifics any particular blockchain. But instead, we get one that blurs attributes of bitcoin with attributes of blockchains. Hopefully, the changes to the question will reduce the risk of confusion. – David Schwartz Oct 22 at 0:51
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So can a blockchain can be shutdown by shutting down power supply across the globe? What would happen in such a case?

If the world's power supply was suddenly cut off, then everything electronic would stop working. The blockchain would be 'frozen', each node would retain its local copy, but be unable to communicate with other nodes, and miners would be unable to mine and add new blocks.

I think the transactions that were not added to the ledger would definitely be lost and they would have to be reinitiated.

This depends on what happens to the mempool of each node. If any nodes remembered any unconfirmed transactions from before the power loss, they could simply broadcast those transactions to the network once things went back online.

I think power shutdown would create inconsistency between different instances of the ledger at different nodes and even if the power is back we wouldn't be able to pick a safe state of the ledger.

Each individual node, once it came back online, would reconnect to some peers in the network, and listen for information about new blocks, just like normal. The decision about which chain to follow would also be made as per normal: which chain has the most work? Follow that one. If there are multiple choices for a most-work chain, then the decision about which one to follow will be made when the node hears about a new block, which extends one of those chains (the other chain will become 'stale', and will not be a part of the blockchain history).

What are the possible ways to shutdown a blockchain without having to go to each and every node and taking it down?

This is a strength of the bitcoin network: it is a decentralized network of computers, without any real hierarchy or centralized control. You would have to attack every node, otherwise the un-attacked nodes will be able to maintain the network. Given the highly distributed and anonymous nature of the network, this seems to be an extremely difficult task.

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Welcome! I think one important thing to keep in mind is that even under normal circumstances the nodes are not necessarily all "synchronized." In fact overcoming this lack of instantaneous synchronization yet still ensuring eventual agreement on a single history is one of the amazing feats of bitcoin's protocol.

In other words, at any given time node A on one side of the world might have a different UTXO set (the set of confirmed transactions which is part of each nodes state) than node B on the other side of the world. This can happen because one of the nodes is still processing/verifying a block while the other node has already finished such processing. The important thing is that the vast majority of the time, the vast majority of the nodes also agree on the vast majority of the UTXO set.

Now, as to your question about possible ways to shut down a blockchain without having to go to each and every node and take it down, I can't think of any good ways. Additionally, even if someone could manage to do that, there is no guarantee that they also:

a) destroyed all copies of the block chain (e.g. what if someone printed the chain out on paper or in some other medium?),and

b) destroyed all copies of the source code (e.g. code that is used to interpret the chain and rebuild the state; such code could also be stored in some other medium)

I believe both of those things would also need to be addressed in order to truly shut down a blockchain.

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I maybe wrong but what I think is Blockchain ledger exists as long as there are active nodes in the network. So can a blockchain can be shutdown by shutting down power supply across the globe? What would happen in such a case?

If all the existing power supply suddenly and by magic shut down the ledger would be simply frozen but it would not disappear, it will stay on hard drive ready to be used and updated again as soon as the power back up and our bitcoin client finds nodes to talk to.

I think the transactions that were not added to the ledger would definitely be lost and they would have to be re initiated. I think power shutdown would create inconsistency between different instances of the ledger at different nodes and even if the power is back we wouldn't be able to pick a safe state of the ledger.

Transaction that were not treated before the power supply shutdown would stay in the mempool, so in the memory of different nodes just like there is transaction currently waiting and stacking up right now they would also wait to be updated and treated by the nodes

What are the possible ways to shutdown a blockchain without having to go to each and every node and taking it down?

They might exist different scenario but If I have to do it and I have superpower I would put a sleeping virus in every bitcoin client nodes that once activated prevent it from communicating with other nodes and then at a predetermined time activate the virus, all the nodes would be solely mining the blockchain just like Satoshi in 2008.

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