Quote from: aliashraf on September 02, 2018, 05:23:23 AM

Suppose, I have a dominant share of a PoS coin. I exchange my coins with a decent PoW coin ( Tongue

) and cash out, now I'm able to commit a long range attack against the network or participate in such an attack using my old private keys with zero cost.

You purchase a dominant share of a PoS coin at higher market prices,
if you do a massive dump you crash those prices , meaning you LOST a Large % of your original investment.
So that is a Huge Cost $$$. Cheesy

Now, the exchange that you sold on, most likely stakes their PoS coins, most do.
So all of those coins will be staking on that exchange until the buyers remove them.
Meaning the staking % of others plus the Staking % of the coins you sold on the exchange are staking.
Your old Private keys alone won't be enough to outstake your sold %, in addition to the other %.
Also other factors that would hurt your attempt is the fact proof of stake coins go dormant for different lengths of time according to their individual specs.

Never as easy as it seems , is it? Wink

FYI:
Even if someone crashes the price of a Proof of Stake coin,
Proof of Stake coins network require less than a few $1000 per month to operate,
and their Stakers can easily weather extremely long terms of a low price ,
as they can easily meet the monthly costs to continue a PoS coin until prices return to normal.

In Contrast :
If a PoW coin price crashes ,
PoW miners can only sustain their network for a short amount of time ,
less than 3 or 6 months on average for the majority before they have to shut down those energy wasting ASICS.
IE:
If the input cost to mine a Bitcoin is $3000, and the miners can only receive $1000 per bitcoin,
within a few months the bitcoin network will be dead as the miners can only afford to lose money per block for a Limited time.
Where as Proof of Stakers can continue indefinitely to keep their network running.
Which is why in Business a person always needs to monitor input costs , if they want to keep their business.

*If someone ever compromised Satoshi ~1 million coin Bitcoin Wallet, they could easily keep bitcoin price in the unprofitable range long enough to kill it.*
Plus Satoshi Wallet is less than 5% of the total 21 million coin allowed, which means PoW coins are more susceptible to being destroyed by as little as 5% to make the coin production unprofitable and kill it's network, due to their insane input costs.

*Just another reason Proof of Stake is superior to Proof of Work in the long run, INPUT COSTS to maintain their networks.*