Unconfirmed double spend transaction: what now?

[zlataribica]

It's been nearly 20 hours, since I tried sending some Bitcoins via shared coin from my Blockchain wallet and it still says 0 confirmations. Upon clicking on a transaction details it says "Warning! this transaction is a double spend. You should be extremely careful when trusting any transactions to/from this sender."
https://blockchain.info/tx/bc40804092976aa4ae7f8ec3ad3d0131c30ce65a7b7f29014859fb9417b585cf
What now? How can I recover my Bitcoins? Is there a way of terminating this transaction and start over?

[RappelzReborn]

Well tthat's your transaction ID ? If it's double spend then you did that and no body else i guess , I read somewhere on the internet that you can cancel an unconfirmed transaction - by double spend this input, therefore original tx will be canceled.
Very helpful thread you will find all you need about your unconfirmed transaction here : https://bitcointalk.org/index.php?topic=232979.0

[zlataribica]

Well if my understanding of the double spend concept is correct, than I guess anyone involved in a shared coin transaction could be causing it. I have honestly no idea how could I double spend my coins accidentally on a routine shared coin transaction, 12 hours after the incoming bitcoin transaction was confirmed. I guess that's why I'm here...
Besides, the transaction summary clearly says that there was no double spend detected, while at the same time showing that above mentioned warning...

I seriously don't know what to do now, just wait? Network propagation has been zero right from the beginning so I don't see how it would get confirmed in the future...  What actually happens with blockchain's unconfirmed transactions in the end? Are they erased and the bitcoins lost?

Also, I'm not sure that procedure of removing an unconfirmed transaction would work for me,  I'm using an online wallet...


Edit

Well unconfirmed transaction was just terminated and my bitcoins are back in my wallet so I guess that's it.

[RappelzReborn]

Yeah well that's it , however it still weird , as far as I know it should take like 5 days or something on status "Unconfirmed" then the amount goes back to the owner adress . But well we can't complain about it I guess Glad you sort it out , feel free to ask more questions

[Amitabh S]

Well if my understanding of the double spend concept is correct, than I guess anyone involved in a shared coin transaction could be causing it. I have honestly no idea how could I double spend my coins accidentally on a routine shared coin transaction, 12 hours after the incoming bitcoin transaction was confirmed. I guess that's why I'm here...
Besides, the transaction summary clearly says that there was no double spend detected, while at the same time showing that above mentioned warning...

I seriously don't know what to do now, just wait? Network propagation has been zero right from the beginning so I don't see how it would get confirmed in the future...  What actually happens with blockchain's unconfirmed transactions in the end? Are they erased and the bitcoins lost?

Also, I'm not sure that procedure of removing an unconfirmed transaction would work for me,  I'm using an online wallet...


Edit

Well unconfirmed transaction was just terminated and my bitcoins are back in my wallet so I guess that's it.

You should still move those coins, as someone might have cached the tx and it could be broadcast again. Its better to invalidate the source coins by sending them somewhere else.

[ranochigo]

Well tthat's your transaction ID ? If it's double spend then you did that and no body else i guess , I read somewhere on the internet that you can cancel an unconfirmed transaction - by double spend this input, therefore original tx will be canceled.
Very helpful thread you will find all you need about your unconfirmed transaction here : https://bitcointalk.org/index.php?topic=232979.0

Given that most Bitcoin clients does not relay a transaction if a input has already been spent in another transaction in their mempool, it would be hard to relay a double spend transaction after a while when it is proporgated well enough around the network. The network would not accept both transaction. One would eventually be confirmed and one would be dropped if they have the priority to be included in the next blocks.

Yeah well that's it , however it still weird , as far as I know it should take like 5 days or something on status "Unconfirmed" then the amount goes back to the owner adress . But well we can't complain about it I guess Glad you sort it out , feel free to ask more questions

It defers from client to client. Some client don't relay transactions after it has been dropped after a day or two and some relay it continuously till it confirms. The input would then appear as if it has never been touched before when it is forgotten by mempool.

[achow101_alt]

Given that most Bitcoin clients does not relay a transaction if a input has already been spent in another transaction in their mempool, it would be hard to relay a double spend transaction after a while when it is proporgated well enough around the network. The network would not accept both transaction. One would eventually be confirmed and one would be dropped if they have the priority to be included in the next blocks.

At some point, the original transaction will be dropped if it isn't confirmed. Then another transaction spending the same inputs can be used. Also, some miners and nodes use Replace-By-Fee (RBF) which allows a transaction spending the same inputs as another to replace the older one if the new one has a higher fee. Other clients like Bitcoin-XT also have features that relay double spends.