bitcoin double spend

[andy.bandy]

hello. can someone help me? how i can send bitcoin with low fee from anywallet and after to send again with high fee to test website?

[1714917508]

1714917508

[1714917508]

1714917508

[20kevin20]

It depends which wallet you're working with. If you're using Electrum, first you have to set your wallet to use manual fees (select Tools and then Preferences). Check "Replace by fees" too.

Then, send the first transaction with minimum tx fee (1 sat/byte) so it gets confirmed the slowest. After sending the first transaction, send a second one but with a higher fee (20-22 is the fastest right now, according to https://bitcoinfees.earn.com/).

The transaction with a higher fee will be confirmed by the miners while the tx with 1sat/byte fee will be considered invalid. There goes the double spend.

If you're doing this with other (bad) intents, I'd recommend you not to. You'll get yourself in trouble.

[bitmover]

You want to make a replace by fee transaction (RBF)
Take a look here
 RFB transaction (replace by fee)
https://steemit.com/bitcoin/@profitgenerator/tutorial-how-to-fix-unconfirmed-transactions

[nc50lc]

Then, send the first transaction with minimum tx fee (1 sat/byte) so it gets confirmed the slowest. After sending the first transaction, send a second one but with a higher fee (20-22 is the fastest right now, according to https://bitcoinfees.earn.com/).
-snip-

That will use a different set of inputs and wont invalidate the first transaction.

AFAIK it's impossible to create a double-spend transaction by normally using Electrum, you're going to need another client or tool to create the raw transaction
of the "double-spend transaction" or by doing some workaround like creating and exporting the signed raw transactions offline and broadcast them online.

[20kevin20]

That will use a different set of inputs and wont invalidate the first transaction.

AFAIK it's impossible to create a double-spend transaction by normally using Electrum, you're going to need another client or tool to create the raw transaction
of the "double-spend transaction" or by doing some workaround like creating and exporting the signed raw transactions offline and broadcast them online.

I've looked this up after reading your reply and you're partially right. Thanks for bringing this up.

Apparently, by checking the Replace by fee option in the Electrum Preferences, you can basically double-spend a stuck transaction. However, outputs cannot be changed, only the fee.

I thought Electrum did also allow you to change the outputs before signing & broadcasting the second tx, but apparently it does not.

[nc50lc]

CPFP in this scenario isn't as needed as RBF.
The idea of using RBF here is to flag the transaction "replaceable" so the 'double-spend transaction' wont be rejected by nodes.

But the user can use CPFP to the second transaction if his client allows it for higher chance of double-spending
since most of the time, it's a send-back to wallet transaction.

[hosseinimr93]

I just searched for anywallet in google. It's an wallet available on Google Play for Android. So, I guess the OP is asking how to double spend via the mentioned APP. Probably, he/she doesn't want to use Electrum or any other wallet. He is trying to test anywallet which I don't think anyone in the forum has used it before.

[igor72]

Apparently, by checking the Replace by fee option in the Electrum Preferences, you can basically double-spend a stuck transaction. However, outputs cannot be changed, only the fee.

I thought Electrum did also allow you to change the outputs before signing & broadcasting the second tx, but apparently it does not.

You can disconnect Electrum, remove the unconfirmed RBF-transaction, create a new one (from same UTXOs), save it and finally broadcast it to the network.

[andy.bandy]

Apparently, by checking the Replace by fee option in the Electrum Preferences, you can basically double-spend a stuck transaction. However, outputs cannot be changed, only the fee.

I thought Electrum did also allow you to change the outputs before signing & broadcasting the second tx, but apparently it does not.

You can disconnect Electrum, remove the unconfirmed RBF-transaction, create a new one (from same UTXOs), save it and finally broadcast it to the network.

thanks for reply to all.

can you please detail more this step by step?

thanks in advance

[nc50lc]

Using Electrum?
First this is for information only, not a way of illicit activity encouragement.

Try this:
1. Open your electrum wallet while online to sync and get the correct balance to make sure that all available inputs are valid.
2. Display 'coins' tab by clicking "View->Show Coins", then disable your network connection (you can do this online, but it's safer offline).
3. Enable "Use Replace-By-Fee" and "Edit fees manually" from "Tools->Preference->Fees tab".
4. Create the 1sat/byte transaction by specifying which input to use from the 'coins' tab, right click to an "output point(s)" with enough balance for your transaction and click "spend".
5. You'll be transferred to the 'send' tab, input the test recipient's address and amount and the fee rate '1',
6. Click "preview" then Click "Sign" (type your passphrase) It must be signed.
7. Now Click "Copy" and paste it on a text file, name that text file with something like "1sat/byte signed RAW tx".
8. Close the preview window and select 'yes' when prompted to 'not to save'.
.
9. Now repeat 4-7 using the same "output point(s)" but this time, set the fee to something higher and with different recipient address and paste on a different txt file with different name.
10. Last step is to broadcast the first 1sat/byte transaction (the copied Signed RAW transaction hex) to any blockexplorer like blockstream.info / blockcypher.com.

After a while, you can broadcast the high-fee transaction and it will replace the low-fee transaction if it wasn't mined yet.
It will be accepted or rejected depending on the node where you have broadcast the first, I've used blockstream.info for my test.

[igor72]

Apparently, by checking the Replace by fee option in the Electrum Preferences, you can basically double-spend a stuck transaction. However, outputs cannot be changed, only the fee.

I thought Electrum did also allow you to change the outputs before signing & broadcasting the second tx, but apparently it does not.

You can disconnect Electrum, remove the unconfirmed RBF-transaction, create a new one (from same UTXOs), save it and finally broadcast it to the network.

thanks for reply to all.

can you please detail more this step by step?

thanks in advance

1. Disconnect Electrum (for example enable proxy in "Tools -> Network" or turn off your router).
2. Open Console and type:

Code:

wallet.remove_transaction("txid")

, where "txid" is identificator your transaction.
3. Press "F5" for refresh or reopen wallet.
4. Fill your new transaction (the fees must be higher), press "Preview", press "Sign". After signing press "Copy". Close this window.
5. Connect Electrum to internet. Your old transaction will appear again, it's okay, don't pay attention to it.
6. Press "Tools -> Load transaction -> From text", paste from clipboard your new signed transaction and press "Load transaction".
7. Press Broadcast.

Specify if there's anything you don't understand.