Why Should people wait for confirmation of Bitcoin?

[Daneric]

I just thought about this today. Every time you are transacting with bitcoin, you will be told that you have to wait for bitcoin confirmation. This is common with bitcoin gambling sites. What I know is that bitcoin transactions are irreversible. Then why is it that you have to wait for the confirmation before initiating anything?

[CryptoDatabase]

This is to prevent people from double spending those coins. There is a way to sort of 'charge back' BTC and waiting for this confirmation insures it is a valid transaction.

Person sends transaction to address with small fee and then sends another exact transaction to another address with a much higher fee so it gets confirmed first which will invalidate the original transaction allowing them to keep their coins. This is very, very difficult to do though but not impossible.

[jacafbiz]

It is simple because of double spend,it is not common again but some people can still try the trick, you can't trust anybody

[maydna]

I just thought about this today. Every time you are transacting with bitcoin, you will be told that you have to wait for bitcoin confirmation. This is common with bitcoin gambling sites. What I know is that bitcoin transactions are irreversible. Then why is it that you have to wait for the confirmation before initiating anything?

i think if we make payment for what we buy like for example we make invest in cloud mining, prepaid phone card, pay our bills, maybe its not need much of confirmation because there is a payment that only need 1-3 confirmation and then the order is complete.

we have to wait the confirmation is because our transaction will be seen on the network and the amount that we send can get transfer into the other wallet address. if you note, you can see when you make the sending amount, the message is waiting to be seen on network. it means, your transaction is need to be on the network list so the transferred amount is send.

[Denker]

I just thought about this today. Every time you are transacting with bitcoin, you will be told that you have to wait for bitcoin confirmation. This is common with bitcoin gambling sites. What I know is that bitcoin transactions are irreversible. Then why is it that you have to wait for the confirmation before initiating anything?

Even though the possibility of a double spend is very low, some small rest of risk always exists.
That's why we are told to wait for confirmation.If however you have 100% trust to your other party, because you know him for many years and everything always went smooth and fine you don't need to wait of course.

[Daneric]

This is to prevent people from double spending those coins. There is a way to sort of 'charge back' BTC and waiting for this confirmation insures it is a valid transaction.

Person sends transaction to address with small fee and then sends another exact transaction to another address with a much higher fee so it gets confirmed first which will invalidate the original transaction allowing them to keep their coins. This is very, very difficult to do though but not impossible.

I get your point. I never imagined if there could be a double spend in bitcoin transactions. But human beings are mysterious and they can do anything you cannot imagine.

[rajasumi2]

Its because so that to prevent them from double spending their coins .its common and many people use some trick so trust no one . And if u wanna safe transaction u have to to be patience .kudoos

[kiklo]

This is to prevent people from double spending those coins. There is a way to sort of 'charge back' BTC and waiting for this confirmation insures it is a valid transaction.

Person sends transaction to address with small fee and then sends another exact transaction to another address with a much higher fee so it gets confirmed first which will invalidate the original transaction allowing them to keep their coins. This is very, very difficult to do though but not impossible.

Hmm,
Does not seem that hard,

Have 2 PCs running side by side, with a copy of your BTC wallet on Each, opened and synced,
from the 1st PC send your BTC to an address you control, (pay the extra fee on this one or wait 50 seconds before sending on the 2nd PC.)
from the 2nd PC send the BTC to the guy you are doublespending to.

I believe that is about the gist of it, any extra steps , feel free to add.  

 

[NorrisK]

Normally there is not real need to wait for a confirmation of bitcoin, especially with smaller payments.

Bigger payments may be a different game (say you are buying a car), but even then, a double spend is not easily done.

On the other hand, you will have the time to wait on confirmations with big payments due to the paperwork etc, just let it confirm while you are doing the boring stuff.

[franky1]

What I know is that bitcoin transactions are irreversible. Then why is it that you have to wait for the confirmation before initiating anything?

bitcoin transactions are only irreversible AFTER confirmation.
imagine it like:
writing a cheque. you can validate the cheque by calling the bank and checking the balance is available to spend and the person is who they say they are. but until the cheque is cleared by the cheque clearing house you dont yet have the funds to spend yourself and the funds can bounce.

writing a transaction. you can validate the transaction by checking the inputs and checking the balance is available to spend and the signature belongs to the inputs. but until the transaction is confirmed into a block you dont yet have the funds to spend yourself and the transaction can be rejected.

there are a few ways to write a transaction announcing you as the destination. making you see the unconfirmed transaction. but then write another transaction using the same original input funds to move the funds elsewhere and getting that transaction accepted into a block before the one you were hoping for. thus making the one you were hoping for get rejected.

so until the transaction you were hoping for is confirmed (irreversible) dont trust it.

double spends are actually easy.
(a)someone makes a tx to you, but have insufficient fee.

(b)someone makes a tx to themselves with a sufficient fee. and then a (c)third transaction prespending that transaction with a suffient fee to push transaction c through.
this is using features called RBF(replace by fee) and CPFP(child pays for parent)

so until the transaction you were hoping for is confirmed (irreversible) dont trust it. especially ones with insufficient fee

[Daneric]

What I know is that bitcoin transactions are irreversible. Then why is it that you have to wait for the confirmation before initiating anything?

bitcoin transactions are only irreversible AFTER confirmation.
imagine it like:
writing a cheque. you can validate the cheque by calling the bank and checking the balance is available to spend and the person is who they say they are. but until the cheque is cleared by the cheque clearing house you dont yet have the funds to spend yourself and the funds can bounce.

writing a transaction. you can validate the transaction by checking the inputs and checking the balance is available to spend and the signature belongs to the inputs. but until the transaction is confirmed into a block you dont yet have the funds to spend yourself and the transaction can be rejected.

there are a few ways to write a transaction announcing you as the destination. making you see the unconfirmed transaction. but then write another transaction using the same original input funds to move the funds elsewhere and getting that transaction accepted into a block before the one you were hoping for. thus making the one you were hoping for get rejected.

so until the transaction you were hoping for is confirmed (irreversible) dont trust it.

double spends are actually easy.
(a)someone makes a tx to you, but have insufficient fee.

(b)someone makes a tx to themselves with a sufficient fee. and then a (c)third transaction prespending that transaction with a suffient fee to push transaction c through.
this is using features called RBF(replace by fee) and CPFP(child pays for parent)

so until the transaction you were hoping for is confirmed (irreversible) dont trust it. especially ones with insufficient fee

This is a very detailed insight and it has opened my eyes. Actually, someone can send you bitcoins and forward the transaction ref to you as prove of payment. This means that the tx ref only can not act as prove of payment until there are confirmations on the transaction. 

[crwth]

The sole purpose of confirmation on the transactions I learned here is that for a transaction to go through, you need to be confirmed to see if it really made through.  Miners will try to confirm it. It's like validating if the transactions are real and if they really did it. Double spending will be prevented if the wallet has indeed that kind of amount. Depending on the transaction made. For small amounts of transactions, I think 1 - 3 confirmations are okay, but for large amounts, not only that transaction fee is higher, but also the confirmations should be bigger. Patience is a virtue.

[shorena]

The sole purpose of confirmation on the transactions I learned here is that for a transaction to go through, you need to be confirmed to see if it really made through.

Thats a really confusing sentence, but it sounds like you are trying to say that transactions need a confirmation in order to be check for validity. Thats not true. Every full node (e.g. the bitcoin core wallet) can do this, with or without confirmation.

  Miners will try to confirm it. It's like validating if the transactions are real and if they really did it. Double spending will be prevented if the wallet has indeed that kind of amount.

A miner cant tell how much bitcoin you have in your wallet.

Depending on the transaction made. For small amounts of transactions, I think 1 - 3 confirmations are okay, but for large amounts, not only that transaction fee is higher, but also the confirmations should be bigger. Patience is a virtue.

Thats bullshit. Transaction fees have nothing to do with the amount of bitcoin you transfer. They depend on the size of the transaction in byte.

[clickerz]

The sole purpose of confirmation on the transactions I learned here is that for a transaction to go through, you need to be confirmed to see if it really made through.  Miners will try to confirm it. It's like validating if the transactions are real and if they really did it. Double spending will be prevented if the wallet has indeed that kind of amount. Depending on the transaction made. For small amounts of transactions, I think 1 - 3 confirmations are okay, but for large amounts, not only that transaction fee is higher, but also the confirmations should be bigger. Patience is a virtue.

For bigger amount I think its the same. Once you see that there are confirmations already, I think its ok, meaning it is already being processed on the system.But of course, we are very cautious , since it is a bigger amount.

May I ask @shorena , the transaction size (in bytes) is directly proportional to the amount? tia

[shorena]

The sole purpose of confirmation on the transactions I learned here is that for a transaction to go through, you need to be confirmed to see if it really made through.  Miners will try to confirm it. It's like validating if the transactions are real and if they really did it. Double spending will be prevented if the wallet has indeed that kind of amount. Depending on the transaction made. For small amounts of transactions, I think 1 - 3 confirmations are okay, but for large amounts, not only that transaction fee is higher, but also the confirmations should be bigger. Patience is a virtue.

For bigger amount I think its the same. Once you see that there are confirmations already, I think its ok, meaning it is already being processed on the system.But of course, we are very cautious , since it is a bigger amount.

May I ask @shorena , the transaction size (in bytes) is directly proportional to the amount? tia

No, a single input has 148 (compressed pub key) or 180 (uncompressed pub key) byte. An input can be worth any (valid) amount of bitcoin. A transaction spends inputs and creates outputs (~34 bytes each).

[Gembul]

I just thought about this today. Every time you are transacting with bitcoin, you will be told that you have to wait for bitcoin confirmation. This is common with bitcoin gambling sites. What I know is that bitcoin transactions are irreversible. Then why is it that you have to wait for the confirmation before initiating anything?

After a transaction is broadcast to the Bitcoin network, it may be included in a block that is published to the network. When that happens it is said that the transaction has been mined at a depth of 1 block. With each subsequent block that is found, the number of blocks deep is increased by one. To be secure against double spending, a transaction should not be considered as confirmed until it is a certain number of blocks deep.

maybe you can get more information from this article. https://en.bitcoin.it/wiki/Confirmation

[BlackPanda]

we all know that one of the factors that affect the speed of delivery of bitcoin is the amount of the fee we include.
so the larger the fee it will be more easily split the bitcoin block. so that will make financial transactions faster we sent.

[mindrust]

It is because that's the feature which makes bitcoin a secure digital currency. People have to wait because every single transaction needs to be confirmed by random people from all around the world. That's how it works.

[robelneo]

I have not yet made a transaction where there is double spent but it's likely to happen so users should wait for the confirmation before proceeding,sometimes it takes long time to confirm but this is the only drawback but I still prefer to transact using crypto currency than paypal or payza.

[shorena]

we all know that one of the factors that affect the speed of delivery of bitcoin is the amount of the fee we include.
so the larger the fee it will be more easily split the bitcoin block. so that will make financial transactions faster we sent.

No, your fee will not decrease the time miners need to find a valid block. It will only give miners an incentive to put your transaction into the next block. Raising the fee beyond a certain amount is pointless.

It is because that's the feature which makes bitcoin a secure digital currency. People have to wait because every single transaction needs to be confirmed by random people from all around the world. That's how it works.

At the very least this is misguiding, if not plain wrong.

I have not yet made a transaction where there is double spent but it's likely to happen so users should wait for the confirmation before proceeding,sometimes it takes long time to confirm but this is the only drawback but I still prefer to transact using crypto currency than paypal or payza.

If only you are in control of your private keys only you can double spend your transaction. Its always the person receiving bitcoin that has to wait for a confirmation, never the one that sends them.