How confirm my own doublespend transaction got confirmed

Transactions in the testnet are right now almost always double spent with a new txid (possible due to tx malleability). This is actually quite nice for testing purposes.

So I’m wondering – when I did a payment and have txId ‘XXX’ this payment sometimes gets confirmed with a new txId ‘YYY’ that I don’t know of. How can I (using bitcoind json-rpc) find out that my payment with txId ‘XXX’ got confirmed?

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why is double-spend not an issue for payment channels?

Micropayment Channels (MPC) cannot be used currently because of transaction malleability, I hear.

AFAIK, people saying that have in mind that the refund & payment tx, which have as input the deposit tx (Dtx), could be invalid if the deposit’s hash was changed. I m fine with this.

What I don’t understand: if the attacker manages to modify Dtx’ hash before it made it to the blockchain, I believe (s)he can equally manage to double spend the btcs supposed to go to Dtx. Thus, double spend seems as much a threat as malleability. Yet no one discusses it, so I suppose something is wrong with this reasoning. What?


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How to pratically doublespend bitcoins?

I tried to put bitcoins into an p2p exchange with bitcoin-qt. I added a to small transaction fee, so the coins are now stuck as “Unconfirmed”. The offer from the exchange is overdue, so all that will happen if the transaction gets confirmed is that I get them back with an administrative fee.

I would like my coins right now and avoid paying the fee. I’ve read that you can double spend the coins back to yourself and if I add a higher payment fee than the first time this would probably override the original payment. How can I practically do this? I’m not a hardcore developer but feel comfortable using commandlines and know my way around computers.

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