1,000 Lego sets attack

I explain and contemplate a double spending attack that targets many low-value transactions instead of few high-value transactions.

I'm prepared to stand corrected.


@kalle (1) Nitpick: the attack isn't quite free if he succeeds because Joe must include Td in his block where he could've instead included someone else's transaction that paid him a fee.

(2) By implication, the closer typical fees are to the amount of the attack, the less profitable a multi-transaction attack will be. E.g., if fee/tx is $1, then the $100 Lego attack only nets $99 compared to honest mining.

Besides that nitpick, the article's logic and conclusions seem accurate to me.

@harding Thanks! Good points, especially (2) might turn out really significant. I'll update the article tonight.

I haven't heard much about this kind of attack. Have you seen anything on this elsewhere?

@kalle Double spending lots of smaller transactions? I think it's been regularly mentioned. E.g., here's an excerpt from a StackExchange answer I wrote in 2014. bitcoin.stackexchange.com/ques

Also, the actual BetCoin Dice attack that stole ~$100,000 USD involved the double spending of hundreds of smallish transactions, so it's not just theory. (Though those double spends were against 0-conf transactions, but still with miner assistance.) bitcointalk.org/index.php?topi

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