Let's say every single miner in the world added the same transaction to their block via trickery. The transaction was never initiated by the wallet holder. Would a block from these miners be added to the block chain?

If so what is the minimum number of miners needed to add a fake transaction to the block chain?

  • A transaction must be signed by a wallet holder. This is not mere "policy", it is a mathematical requirement.
    – abelenky
    Commented Dec 7, 2017 at 11:21

1 Answer 1


Only the wallet holder can create a valid transaction. That's what makes them the wallet holder. The holder of a wallet is the person who can create valid transactions to claim the funds in that wallet.

So the transaction is not valid. Any block containing an invalid transaction is itself invalid. So everyone else (exchanges, wallets, etcetera) would ignore that block and any blocks mined on top of it. So all these miners would lose out on the money they could have made by mining valid blocks.

  • That's exactly what I mean tho. Let's say I have my own little network. I'm doing all the mining and I control all the wallets. Is it possible for me to transfer funds from wallet A to wallet B without using wallet A's private key given that I control every blockchain?
    – ivan
    Commented Dec 7, 2017 at 12:02
  • @ivan Only if everyone agrees to let you. Otherwise, whoever didn't agree to let you would not recognize that transaction as valid, leading to an immediate complete fork in the network between those who agree with you and those who disagree. You can't stay in the same network if you don't agree on the rules. A core rule on bitcoin is that transactions must be properly signed to be valid. Commented Dec 7, 2017 at 12:04
  • Ok so if a majority agrees with my faulty transaction would that make the legitimate blocks the fork?
    – ivan
    Commented Dec 7, 2017 at 12:15
  • The network would immediately fork in two -- those who agree your transaction is valid and those who don't. Which side is "the fork" is a matter of opinion at that point. Interestingly, if the majority of hash power doesn't side with you, the fork will not happen. A majority of hashing power has to side with the disputed block or there's no fork. Commented Dec 7, 2017 at 12:16
  • Thanks for explaining. What would such a fork look like through the eyes of an end user? Let's say there's a vending machine for candy that accepts bitcoin. A fork happens where the majority of the hashing power accepts a faulty transaction. The faulty transaction emptied a wallet which is now attempting to pay the vending machine. What would happen?
    – ivan
    Commented Dec 7, 2017 at 12:29

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