[icook]

I was curious about the cost as well, so I ran some rough numbers.

417.5 BTC/GH/day for equihash if you're renting from nicehash [1]. Block interval 10 minutes [2]. 144 blocks per day target yields 0.0869 BTC/block, so cost of the 22 block reversal was ~1.91 BTC, or roughly $15k.

I'm curious if this was done as one large deposit, or many smaller deposits. I've imagined a system where block confirmations required are based on a computed cost of attack done like I did above, which would be pretty effective for very large single transaction double spends. A bit trickier to handle multiple deposits spread across multiple user accounts.

[1]: https://api.nicehash.com/api?method=simplemultialgo.info

[2]: https://bitcointalk.org/index.php?topic=2284289.0;all

[XR0CSWV3h3kZWg]

As the space matures I'd love to see a company that offers double spend insurance for a given tx.

For example changes could wait for 10 minutes worth of blocks then request a quote for double spend insurance. The company evaluates the probability of a double spend and maybe even has a couple standing contracts with rentable hashing power to be able to target smaller PoW chains and prevent any double spend attack.

There are lots of interesting and cool problems to be solved in evaluating the safety of a given tx. Unfortunately I don't know if the space is mature enough that exchanges would actually use the service.

[xur17]

I'm curious how many other smaller PoW currencies are vulnerable to something like this.