Andreas is incorrect here. A double spend _did_ happen.

Bitcoin's double-spend protection is probabilistic: after one confirmation, if the sender is attempting to double spend, the probability of success is extremely low. But it's still non-zero.

As the Bitcoin whitepaper helpfully explains, the probability of a double spend attempt succeeding drops exponentially with the number of confirmations. One confirmation is extremely low, two is basically (extremely low)².

Full details: bitcoin.org/bitcoin.pdf

Unfortunately, Andreas falsely claiming a double spend did _not_ happen is dangerous: people have to realize that a single confirmation is not an absolute guarantee.

This case was ~$20, and looks like someone was just moving money between different wallets.

But if you're accepting a payment large enough that you can't risk even a very low chance of a double spend, you _do_ need to wait for multiple confirmations. Claiming otherwise could lead to people losing money.

@pete peter, wouldn't you say double spend requires that a merchant was actually defrauded? no one accepted the deposit and credited the entity with the additional funds here.

unlike the okpay double spend in 2013 which really was a double spend.

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@nic No I wouldn't, not from the perspective of users interested in understanding Bitcoin. A double-spend technically speaking happened. It looks like the double spend was between two different wallets, by the same person. But it might not have been.

Regardless, it's a good lesson learned to remind people of best practices.

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@pete fair enough. spend 30 min on the phone with a journalist explaining how bitcoin settlement works. probabilistic settlement is still a mystery to these people.

@nic @pete That's no surprise, given how most people still think of bitcoin mining costs in terms of "this is what it costs to process 1 block worth of txs" rather than "this is what it costs to secure all txs in this block and all that came before it".

@nic @pete man, I’m not sure they’ll ever get it.
You have a lot of patience.

@lucash_dev @nic My willingness to talk to journalists has dropped dramatically in general; Coindesk specifically I almost entirely stopped responding too due to badly reporting that wasn't getting facts correct. A year *prior* to Cuen's first article on the Lovecruft case in fact!

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