Need help with bitcoin JSON transactions.

[RGBKey]

Hello, i'm trying to help someone double spend a transaction that they sent with too low of a fee. I sent 0.0001 to the address that sent the transaction and I was hoping that I could double spend it by using the same input they sent before and using the new input I sent them as a fee. (The reason is because they have money in PrimeDice and they can't withdraw a significant amount until this deposit confirms).

This is the transaction that needs to be double spent: https://blockchain.info/tx/de90913c18dc8e7f4123f9b54b41e82b55c8d1d04e29290198e49f1a1cf393a7

The problem is, I don't know very much of raw transactions, but the person i'm helping has the private key and can sign transactions. How could I form a transaction by using brainwallet.org/#tx or some other way so that I can get this confirmed for them? Thanks a lot.

[DannyHamilton]

Hello, i'm trying to help someone double spend a transaction that they sent with too low of a fee. I sent 0.0001 to the address that sent the transaction and I was hoping that I could double spend it by using the same input they sent before and using the new input I sent them as a fee. (The reason is because they have money in PrimeDice and they can't withdraw a significant amount until this deposit confirms).

This is the transaction that needs to be double spent: https://blockchain.info/tx/de90913c18dc8e7f4123f9b54b41e82b55c8d1d04e29290198e49f1a1cf393a7

The problem is, I don't know very much of raw transactions, but the person i'm helping has the private key and can sign transactions. How could I form a transaction by using brainwallet.org/#tx or some other way so that I can get this confirmed for them? Thanks a lot.

A double spend is difficult to accomplish.  Bitcoin is intentionally designed to make it difficult to accomplish.

Even if you get the double-spend transaction build, peers will refuse to relay it and miners will refuse to accept it.

You'll need to get both the original sender's wallet and PrimeDice's client to both stop broadcasting the transaction, and then you'll have to wait few days for peers and miners to drop the original transaction from their memory.

Once you've done that, you'll need to get the following transaction signed:

Code:

01000000023eb09f7d2dacefebe97f642ee2c47479d957400ad7eccad0165ea4ee45980df94100000000ffffffff017b4188d2379c28721d6609be9c22cea76111564b0fdb16ff1f2c3c0a7c56dc0000000000ffffffff01f4150000000000001976a914d8230571fa346494c4c222a9b7c120b28f23c38188ac00000000

If they are using Bitcoin-Qt (Bitcoin Core) then they should be able to paste the following into the console:

Code:

signrawtransaction 01000000023eb09f7d2dacefebe97f642ee2c47479d957400ad7eccad0165ea4ee45980df94100000000ffffffff017b4188d2379c28721d6609be9c22cea76111564b0fdb16ff1f2c3c0a7c56dc0000000000ffffffff01f4150000000000001976a914d8230571fa346494c4c222a9b7c120b28f23c38188ac00000000

Then the resulting signed transaction will need to be broadcast.  This can be accomplished with either sendrawtransaction from the console, or from https://blockchain.info/pushtx