Topic: Automatic confirmation (Read 1511 times)

Wallet isn't synchronized?

Got it thanks. Man, why is it sometimes I still couldnt see my btc even with 11 confirms?

Thanks for the short answer.

And thanks @DannyHamilton for the thorough explanation.

I understand it now.

First, if you are trying to understand the technical details behind exactly how the protocol handles transactions and confirmations, then you'll need to stop thinking about "wallets" and "bitcoins".

As far as the protocol is concerned there are no wallets and there are no bitcoins. There aren't even any addresses.  There are only transactions with inputs and outputs.

So, as far as I can tell, you are asking about the following scenario:

Broadcast Transaction A
Spending confirmed output A as an input and creates new unconfirmed output B without any transaction fee.

Broadcast Transaction B
Spending unconfirmed output B as an input and creates new unconfirmed output C with a transaction fee.

Broadcast Transaction C
Spending confirmed output A as an input and creates new unconfirmed output D with a transaction fee.

One thing to be aware of:

Most nodes, miners, and mining pools will refuse to accept or relay a transaction that spends an output that is already in the memory pool as an input in another transaction.  Therefore, transaction C won't be relayed and won't be accepted as valid by most of the system.  This makes it very unlikely that Transaction C will be confirmed (or even seen) by any miners until several days have passed by and most of the system has forgotten about Transaction A.  The recipient of Transaction A can repeatedly re-broadcast Transaction A if they want to, which makes it even less likely that Transaction C will ever be seen by most of the network.

If we assume however that several days have passed by, and that most nodes on the network have forgotten about Transaction A, then (as you mentioned) when Transaction C is confirmed Transactions A and B will become invalid, will be dropped from the memory pools of all caught up nodes, and will cease to exist.

As has already been mentioned by franky1 Transaction B can not, and will not, be confirmed unless and until Transaction A is confirmed.  It is possible for them both to be confirmed in the same block, but Transaction B cannot be confirmed in an earlier block than Transaction A.

until the origin (wallet 1) has confirmed then all transactions after that, will sit there waiting

you wont get a confirm from an unconfirmed source.

I know you cannot really double spend a bitcoin.
what I mean is if I send out the same bitcoin twice, once without fee, the other with fee.
It is very likely the one with fee is confirmed and the other transaction therefore never happened.
but if I send a transaction without fee, and the reciever sends out the funds immediately with fee, that transaction could be confirmed, but not (yet) the deposit.

The point is that you cannot double spend. That's the whole point of bitcoin. So no, there's no "automatic confirmation", and no, it's not possible to double spend.

Hello, I have a question:
Suppose I send out a bitcoin transaction without fee from wallet 1 to wallet 2, and from wallet 2 to 3.
Now If I double spend these bitcoins the transaction from 1 to 2 'never happened' and the same holds for the transaction from 2 to 3.

But what if the transaction from 1 to 2 is not confirmed (yet) (no fee), but the transaction from 2 to 3 is using a fee and is already confirmed.
Is the first transaction then automatically confirmed? And can't the 1st transaction be double spend anymore?