[admax88q]

> So they can mine honestly on Coin 1 for a while, then switch to Coin 2 and do some double-spend attacks, then when Coin 2's price collapses, they switch back to Coin 1 or move on to Coin 3. The miner has no long term incentive to support the value proposition of any one coin, and they can attack coins that use the same PoW algorithm as their "main" coin at will.

On top of that, I think proof of stake will make this sort of attack 10k worse. With proof of stake there is essentially no resource cost for you to mine an additional fork. Proof of Stake is not computationally expensive, so there's no pressure for you to choose the one coin/chain you want to invest your resources in.

[bigdaddyrabbit]

> ...proof of stake will make this sort of attack 10k worse. With proof of stake there is essentially no resource cost.

This is not true. For a 51% style attack on a PoS chain, you need to acquire a majority of staked coins. Each coin you buy increases the cost of the next coin, (demand/supply and all that), and the price of the coin increases exponentially as an attacker accumulates 51% of the coins.

With PoW, cost of acquiring hashpower is linear (acquiring the last 1% costs the same as the first 1%), which is why PoW is easier to attack.

[amluto]

> For a 51% style attack on a PoS chain, you need to acquire a majority of staked coins.

Not really. All you need is a controlling vote for enough confirmations. At 51%, you’re very likely to have a controlling vote. Below 50%, it’s still possible.

[hndamien]

And that is why these are not decentralised solutions. Just maintain a controlling stake and you are good to go!