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Author Topic: How to use double spend  (Read 104 times)
Pffrt
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October 28, 2020, 03:52:39 PM
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One of my friend who used blockchain.com wallet for transacting bitcoin mistakenly send Max amount which is twice of the amount he wanted to send. Now, what can be done in this situation. Tx is not confirmed yet, fee used is too high, will possibly get confirmed within next hour. Please suggest me a way to recover this. I can assure that this is not a scam attempt (If so, I would not try to help).
Or if you can fix yourself, if you are trusted enough, I can give you the private key of that address and we can have mutual benefit. Let me know.
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bob123
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October 28, 2020, 04:03:12 PM
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Since the transaction propagated already, the only way to successfully double spend the transaction is to make use of the RBF-flag.

But unfortunately, since your friend does not use a proper wallet, this flag is not set.

If he would have used a standard desktop- or mobile wallet, the RBF most likely would have been set. All modern wallets offer that option and most do that automatically.
Blockchain.com as a web wallet with outdated functionality, unfortunately doesn't.


Your only way to get the BTC back would be either to 1) ask a miner to include your double-spend transaction (unlikely if the amount isn't high enough for them) or 2) ask the recipient to pay it back.

Recommend your friend to use a proper wallet which offers that functionality and to double or even triple check everything before hitting send.

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October 28, 2020, 04:05:41 PM
 #3

import it into electrum yourself, wait for electrum to synchronise and on the mobile version I can see an options>double spend the transaction which opens a window to double spend the funds back to yourself.

I can help if you can't do it but do that!
Unless as mentioned above the flag isn't set then the only solution is to contact the place you sent it to or contact a liner to push your transaction through with a higher priority.

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October 28, 2020, 04:10:24 PM
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The amount is ~$3200, I don't know if it worths for a moner, I think no. If I import the priv key in electrum wallet, is there any chance? There's no way to get back the tx as it has been sent to someone who has no direct contact with the receiver. Thank you.
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October 28, 2020, 04:18:10 PM
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The amount is ~$3200, I don't know if it worths for a moner, I think no. If I import the priv key in electrum wallet, is there any chance? There's no way to get back the tx as it has been sent to someone who has no direct contact with the receiver. Thank you.

As far as i know, blockchain.com does not set the RBF flag, which would be absolutely mandatory to be able to replace the transaction with electrum.
You might want to post the TX ID, so we can check that for you tho.

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October 28, 2020, 04:54:05 PM
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8d02030b376f51cb35d5860acc34f282312432c593c20e716cb8ccf93fe446b7
That's the tx. I didn't want to post that though. Is it possibke to check whether a tx is RBF enabled or not through any explorer? @jackg, please check if it is rbf enabled or not. If it is, then I can send you the private key.
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October 28, 2020, 05:35:56 PM
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8d02030b376f51cb35d5860acc34f282312432c593c20e716cb8ccf93fe446b7
That's the tx. I didn't want to post that though. Is it possibke to check whether a tx is RBF enabled or not through any explorer? @jackg, please check if it is rbf enabled or not. If it is, then I can send you the private key.

It is not Sad. https://blockchair.com/bitcoin/transaction/8d02030b376f51cb35d5860acc34f282312432c593c20e716cb8ccf93fe446b7

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October 28, 2020, 05:37:11 PM
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Is it possibke to check whether a tx is RBF enabled or not through any explorer?
Blockchair.com: Replace-by-fee (RBF) enabled? NO

Quote
then I can send you the private key.
All you need is to double spend one of the inputs, the address starting with 19Sag has the lowest balance if you're going to send around private keys.
I haven't tried double spending in years, the last time I did miners would still allow it. What if you create a raw transaction with much higher fee and just try to broadcast it?

twice of the amount he wanted to send.
Is there a chance whoever received this will returnt he difference?

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October 28, 2020, 05:49:39 PM
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So, there's no hope left  Cry I have tried at least hundred times to make him understood what's the difference between using coinbase wallet or web wallet and electrum wallet but he never heard. Sad but this will be a lesson for him.

twice of the amount he wanted to send.
Is there a chance whoever received this will returnt he difference?
He is trying to contact with the site owner. It's a service. Problem is he sold BTC for BDT to an user who used the service site to receive the BTC (for purchasing gift cards or something). Trying to contact with the site owner.
LoyceV
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October 28, 2020, 05:53:16 PM
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So, there's no hope left  Cry
I can give it a shot if you send me the private key to the lowest valued addy (19Sag).
If you're going to do this, you should send half of it by PM, and the other half to my Protonmail: LoyceVswitzerland@protonmail.com
Then mark the address as COMPROMISED to never be used again. Don't send the entire seed phrase or something crazy like that Tongue Just the key to this specific address.

And a general warning:
General note: never give your private key or word seed phrase to anybody! If you're not the sole owner of your private keys, you're not the owner at all!
If you want me to claim your forked coins for you, you're going to have to give me your private key(s). Now, read the sentence above this again. Are you confused yet? That was intentional to make you realize what you're about to do!

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October 28, 2020, 06:47:10 PM
 #11

Yeah if loyce has an instance of core running they're more likely to get an accepted transaction than I with electrum...

I tried reversing one without rbf a while ago and it didn't work...

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October 28, 2020, 07:22:30 PM
 #12

The transaction has 1 confirmation.

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October 29, 2020, 03:05:06 AM
Merited by LoyceV (2)
 #13

Sorry, it was late night and I couldn't update here. The guy was able to reach the support of the service through BTC buyer and they came to a settlement. Luckily, he was promised to get back his BTC.
Thanks everyone for your helping hand.
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