Undoing the Undoable: Bitundo – Doublespending Bitcoins as a Service

April 24, 2014 23:39 UTC
Undoing the Undoable

One of the many long standing truths about bitcoin is the permanent nature of all send transactions. Once you’ve hit send, there is no way to stop it. Right? Wrong says new start-up BITUNDO who claims that they can at least attempt to get your errant payment back to the original sender. Yes, contrary to popular belief, your mistakes might not be mistakes forever. Remember that a transaction is not technically confirmed until it is secured in a block and as part of the blockchain. Until it is secured in the blockchain and confirmed for the first time, technically no demonstrable work has been done or needs to be undone in order to change it. Bitundo incentivizes miners to undo your mistake transaction, by including a transaction that would conflict with it. For a more technical understanding, see the developer docs here to see how it works.


If there’s a will, there’s a way.

[dropcap size=small]U[/dropcap]sing bitcoins is advantageous in many ways. One of the great advantages is that you can transfer bitcoin as you see fit and as simple as sending an email. But what happens when the sender has a few too many things on his mind and makes a simple mistake when making a payment? You could send it accidentally to the wrong address, perhaps an address you sent to earlier in the day. Maybe you meant to send 0.20 btc to an online website but on accident you hit 2.0. Most in the bitcoin community know that this chance for lost coins exists and that it is an irreconcilable and irreversible mistake. We’ve all grown to understand that a bitcoin mistake can be an extremely costly mistake indeed! Simply put, there was no way to undo the transaction. Well, look up in the sky, it’s a bird, it’s a plane, nope it is Bitundo. They say they will help you to revert mistaken payments. Bitundo to the bit rescue, however, they make it very known that this comes with no guarantee.  It is more likely to work if there are still zero confirmations on the transaction, and increasingly impossible with more confirmations.

The Dreaded Bitcoin Mistake

Maybe you’ve heard stories or legends at this point where a user with a temporary lack of attention or a momentary brain fart sends off his hard earned bitcoin to the wrong address and poof his bitcoins are gone. Many bitcoin users have lost more than a tiny penny or satoshi if you will, due to a transaction mistake, and that can be a bummer because there is no chance to undo the transaction. So bitcoin users will welcome a service such as the one offered by Bitundo.com if it truly is something that is possible.

The service gives a sender the chance to undo a transaction by using a special mining pool.

They use a conflicting input to undo the mistake. How it works is best explained by viewing the developers doc here. Put simply, they make the original payment (thought to be lost in cyberspace and blockchain history forever) seem funky by adding and subtracting to it. Therefore, the transaction becomes a nondesirable transaction for acceptance into the blockchain. Bitundo makes it quite clear that there is no guarantee, and they make no promise to get your payment back. You also have a very limited time to submit an undo transaction, as it must be done before a new block comes out. So you’ll have to be quick, as you have 10 minutes at most to try. With a bit of luck mixed with a bit of Bitundo, it may just be possible to undo the undoable. If, however, the payment can not be stopped, well there is no cost to try it.  Bitundo makes it that much less viable to accept zero confirmation transactions, though their propagation can be tracked along the network.

Undoing the Undoable

Would you use a service like this? Have you had an experience with an errant send that resulted in a loss? Share your tale with us in the comments section below!

Last modified: April 24, 2014 23:44 UTC


I'm a married, self employed husband, father, friend and bitcoin enthusiast from the Monterey Bay. I spend everyday trying to make tomorrow better than yesterday. I look forward to a better future for all people and believe that bitcoin gives us an opportunity to start that future now.

Show comments