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Concerning numbers regarding double-spend feasibility on 0-conf BCH by Peter Rizun

Concerning numbers regarding double-spend feasibility on 0-conf BCH by Peter Rizun

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In a video from 2018, Peter Rizun shares some of his work on the success probability of a double spend, which seems to lie between 10-20%, depending on the setup.

I think this is very concerning and needs to be addressed, especially since the cost of executing these attacks are all very close to 0.

If someone develops a wallet that just always attempts to double-spend coins and that one becomes popular, it would completely break 0-conf and might damage BCH substantially.

And Peter Rizun‘s different attack scenarios could be improved by combining them into one attack. Consider the following setup:

Before the attack, figure out beforehand which nodes are miners & payment providers by repeatedly sending each node in the network a unique tx (conflicting with all other transactions) and measure which confirm/which the payment processors receive. Also figure out if there are any differences in acceptance policies (fee level, standardness, ...)

Then, at the merchant:

  1. Propagate a non-standard reverse transaction to the miners first.

  2. Send all the nodes that you previously found to be from a payment provider a valid but low fee (1sat/B) transaction paying the merchant, and make that transaction very slow (large, max sigchecks, lots of NUM2BIN + HASH256).

  3. Immediately broadcast a high fee (100sat/B) transaction to the miner nodes, reversing the payment.

I think this could push the success probability of a double-spend attempt quite high, and would be possible today.

This definitely needs to be addressed.

submitted by /u/eyeofpython
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