Auto-purging transactions

[zimmix]

Hello,

I have an above average knowledge about Bitcoin network, but I lack some advanced understanding as how transaction works. So I hope you can clear this that is in my mind for some time.

I know that it is possible to purge a transaction nullifying it, for example if you sent a transaction with a low fee it will remain unconfirmed for some time and it gives you the opportunity to purge it so it will be canceled and your balance will be fully restored in your wallet.

My doubt resides on it, considering that my previous statement is true (please correct it if it's not), is it possible to set a server with automated bots that will be checking the mempool/network for unauthorized transactions comming from your wallet and auto purge them to prevent it?

If what I said is not possible by any reason, please explain and if you have the knowledge, please try to answer this as well: is there any coin that allows it? I mean, it won't hurt the network as it's only for unconfirmed transactions.

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[jseverson]

Hello,

I have an above average knowledge about Bitcoin network, but I lack some advanced understanding as how transaction works. So I hope you can clear this that is in my mind for some time.

I know that it is possible to purge a transaction nullifying it, for example if you sent a transaction with a low fee it will remain unconfirmed for some time and it gives you the opportunity to purge it so it will be canceled and your balance will be fully restored in your wallet.

My doubt resides on it, considering that my previous statement is true (please correct it if it's not), is it possible to set a server with automated bots that will be checking the mempool/network for unauthorized transactions comming from your wallet and auto purge them to prevent it?

If what I said is not possible by any reason, please explain and if you have the knowledge, please try to answer this as well: is there any coin that allows it? I mean, it won't hurt the network as it's only for unconfirmed transactions.

You can't purge your transactions. It will simply disappear from the mempool after being in limbo for a while. It happens when you pay too low of a transaction fee.

If you're worried about your Bitcoins being compromised, just take every step you can to secure them. It's harder to steal them than you probably think for as long as you follow basic security steps.

[BrewMaster]

no, that statement is not true. there is no way to "purge" a transaction from network.
when you send a bitcoin transaction it goes to the network and if a node accepts it as a valid transaction, later that node puts your transaction in its memory pool and continues to broadcast it.
network is full of nodes which are communicating with each other and they will keep broadcasting your transaction.

each node has its own mempool and each node has a setting for what they accept and how long they keep it.
there is a default time for how long they are going to keep a transaction which is 2 weeks (but this can be changed by the node operator). after that time is reached the node drops the transaction if it is still unconfirmed and still valid.
some misunderstand it as "cancelling" maybe "purge",...

but the thing about the 2 week period is that there is not just 1 node with its mempool, there are thousands and each have different settings. one may drop it and other don't.

[DannyHamilton]

I have an above average knowledge about Bitcoin network

I've been actively involved with Bitcoin technology for 6 years, and often educate others on the details of transactions that I'm familiar with, and yet I still wouldn't say that I have an "above average knowledge about Bitcoin network".  I suggest you assume that you know very little and focus on learning more.

but I lack some advanced understanding as how transaction works. So I hope you can clear this that is in my mind for some time.

I'll give it a try.

I know that it is possible to purge a transaction nullifying it, for example if you sent a transaction with a low fee it will remain unconfirmed for some time and it gives you the opportunity to purge it so it will be canceled and your balance will be fully restored in your wallet.

This is not true.  There is no way to force peers in the peer-to-peer network to do anything.  If they don't want to purge your transaction from their memory, they don't have to, and they won't.

My doubt resides on it, considering that my previous statement is true (please correct it if it's not),

It is not.

is it possible to set a server with automated bots that will be checking the mempool/network for unauthorized transactions comming from your wallet and auto purge them to prevent it?

There is no such thing as "the mempool".  Every node maintains their own mempool.  Every node decides for themselves (or runs software that decides for them) which transactions to store in their own mempool, and when to remove those transactions from their own mempool.  There is not protocol for telling any node to remove anything from their mempool.

If what I said is not possible by any reason,

It is not.

please explain

There is no command that you can give to a node to tell it to remove a transaction from its mempool.  If a node does remove a transaction from its own mempool, it does not tell any peers that it has done so.

and if you have the knowledge, please try to answer this as well: is there any coin that allows it?

This is the Bitcoin forum.  I have no knowledge about altcoins.  You should ask altcoin questions in the altcoin-subforum.  Any attempt to discuss altcoins in this sub-forum will be reported to a moderator so that this thread can be locked.

[zimmix]

Thank you for your answers. I guess this closes the case, sadly bitcoin network was made this way, as it would be a good way to prevent the theft as it could work as an second layer of security and a new market for security companies.

@jseverson
Thanks for your concern regarding keeping my btc safe, fortunatelly it's not the case, this question was raised long time ago when I had a transaction that took days to confirm because of low fees and I read first about purging, since it was long ago and knowledge back in time related to btc was harder to come I hadn't the answer, but it resurfaced as btc prices raises and the general concern for own security as well.

@DannyHamilton
For my statement related to "above the average": the average have quite low knowledge about the network itself, I can garantee that the majority that uses bitcoin today have no idea about what the blockchain is, less about how the transaction works, what is the confirmation, and so on. Therefore, I'm quite sure that I have it above the average, which doesn't mean that I know a lot. Yet, I appreciate your humbleness and will take it as a lesson.


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Still on this subject, if you get to see that your coins were to be moved from your wallet and do a double spent directing all your btc to another wallet you own, but with a high fee in order to have it confirmed next block, for example, would it in practice prevent the theft as it would be confirmed first and the other transaction would be nullified as there would be no source btc for it to complete?

I'm thinking here about how we can have a safer environment for people that want to feel safer, as I'm pretty sure mistakes happen and sometimes even hardware wallets get in trouble. Right now (and probably ever), the safest way I can see is doing the transaction offline then broadcasting it, never ever touching your main wallet alive. But this is too much a hassle for the ordinary user.

[DannyHamilton]

Still on this subject, if you get to see that your coins were to be moved from your wallet and do a double spent directing all your btc to another wallet you own, but with a high fee in order to have it confirmed next block, for example, would it in practice prevent the theft as it would be confirmed first and the other transaction would be nullified as there would be no source btc for it to complete?

Not with any reliability.

While it is possible that the second transaction with the higher fee might get confirmed first...

Most nodes will refuse to relay a transaction that spends outputs that are already spent in their mempool.  Therefore it will be difficult for most miners to even know about the second transaction.

Most miners will refuse to accept a transaction that spends outputs that are already spent in their mempool. Therefore, it will be unlikely that the second transaction will get confirmed even if miners have received it from peers.

[zimmix]

I guess got it, so it would only work if I get lucky enough to have my second transaction going to a mempool that the first isn't yet, right?

Thanks!

[Pan Troglodytes]

Still on this subject, if you get to see that your coins were to be moved from your wallet and do a double spent directing all your btc to another wallet you own, but with a high fee in order to have it confirmed next block, for example, would it in practice prevent the theft as it would be confirmed first and the other transaction would be nullified as there would be no source btc for it to complete?

Not with any reliability.

While it is possible that the second transaction with the higher fee might get confirmed first...

Most nodes will refuse to relay a transaction that spends outputs that are already spent in their mempool.  Therefore it will be difficult for most miners to even know about the second transaction.

Most miners will refuse to accept a transaction that spends outputs that are already spent in their mempool. Therefore, it will be unlikely that the second transaction will get confirmed even if miners have received it from peers.

OK thanks for that info. So what is your advice if a transaction is stuck in limbo for 1.5 weeks? The fee is 1.5 USD what seemed reasonable at the time when I posted it, but now the recommended transaction fee is 35USD and there are NO chances my transaction gets confirmed EVER.

What would you suggest I do?

Thanks for help

[bug.lady]

Still on this subject, if you get to see that your coins were to be moved from your wallet and do a double spent directing all your btc to another wallet you own, but with a high fee in order to have it confirmed next block, for example, would it in practice prevent the theft as it would be confirmed first and the other transaction would be nullified as there would be no source btc for it to complete?

Not with any reliability.

While it is possible that the second transaction with the higher fee might get confirmed first...

Most nodes will refuse to relay a transaction that spends outputs that are already spent in their mempool.  Therefore it will be difficult for most miners to even know about the second transaction.

Most miners will refuse to accept a transaction that spends outputs that are already spent in their mempool. Therefore, it will be unlikely that the second transaction will get confirmed even if miners have received it from peers.

OK thanks for that info. So what is your advice if a transaction is stuck in limbo for 1.5 weeks? The fee is 1.5 USD what seemed reasonable at the time when I posted it, but now the recommended transaction fee is 35USD and there are NO chances my transaction gets confirmed EVER.

What would you suggest I do?

Thanks for help

well I would love to know that too, as well as undoubtly there are tons of other ppl who would love that too. Thanks for taking your time and helping out others.