[tedunangst]

> If the exchange is aware of the attack, they may also freeze his account, so that all the funds will be locked inside the Exchange. A failed 21 block attack performed with a 10,000 BTG deposit where the Exchange freezes the account in time will result in a 10,262.5 BTG loss for the attacker. (From link.)

That sounds problematic. If I deposited coins and the exchange determined I was attacking them (how does that work beforehand?) to confiscate my money I'd be pretty miffed.

[cesarb]

Not only that, but also an attacker can wait until the money is "safe" outside the exchange before revealing the attack. If the attacker really has more than half of the hash rate, there's no time limit; the malicious chain will always be longer than the innocent one.

[hisabness]

It’s also odd that the exchange would step into mediate. The miner is effectively playing by the rules i.e. if you have 51% you can do what you want.

[Jommi]

It's only odd if you look at the community part of a decentralized coin as only the miners. You're missing the other critical parts which are its users and the exchanges.

A cryptocoin is worthless to miners if it cannot be exchanged, and it's worthless to exchanges if no one wants to trade it.

[Jommi]

This introduces the "time" component of the attack increasing its riskiness. The longer you wait until releasing the chain, the more time there is for events to happen that might completely thwart your attack.

[XR0CSWV3h3kZWg]

In practice there is a time limit. Nodes will not relay blocks that are too far from their current clock.