Basically someone leaves his wallet offline for a few weeks and lets his coin age build up,
That is not a history attack. Just about every PoS coin also removed the coin age variable for staking due to it's vulnerabilities. Now, staking for most coins is just coin weight where if you own 30% of online stake, you get 30% of blocks. This means if you own a small amount of stake, you will basically get nothing and small stake holders will need to "pool" their stake mimicing how PoW pool mining works except with stake.
That is not a history attack.
It can be if you don't sync your client before letting it stake and it is a weak coin with extremely low difficulty and low active network connections, which is what happens if someone does not encrypt the wallet, it tries to stake before being fully synced.
(Which against a strong coin's chain it all will orphan, until fully synced, which is what happens the majority or the time.)
(But against a weak coin, it can overwrite the blockchain from it's last time synced with the network)
(ECCoin had 2 weeks wiped out once, their difficulty was .0002, Dev Griffin put out the previous blockchain for download before the overwrite and added a new checkpoint to the wallet software, and as of today they are still alive, barely but the coin network is still up.)
(Just so you are aware , History attack can be survived , even by a weak PoS coin, ECC proved that.)
Sorry , Blackcoin is the only one I know of that has removed coin age, they went to # of confirmations instead.
What other specific coins do you believe removed it?
And if are referring to Next & Bitshares, like you said who really considers them PoS coins.
* Side Note: There was a possible security vulnerability in regards to Next Forger system that allows someone to mimic twice the amount, but they never fully investigated it. All of the other ones I know of still use coin age.
hashProofOfStake <= [
Coin-age] x [Target]
[
Coin-age] = [amount of coins] x [days in stake]
Target = Difficulty
This means if you own a small amount of stake, you will basically get nothing and small stake holders will need to "pool" their stake mimicing how PoW pool mining works except with stake.
This may be the case for some PoS coins that have extremely low Minimum Age before Stake, but it is not the case for coins that Minimum age before stake is 15 days or more. To discuss this in greater detail , you will have to specify which specific PoS coin you are referring to, as the different PoS Specs do make a difference.
ZEIT , MINT, TEK , & many others do not require any pooling.
FYI:
https://chainz.cryptoid.info/zeit/block.dws?2373543.htmThe above is a link to only 411
ZEIT in 1 block and it staked.
FYI2:
Coin-age used correctly can help protect a PoS coin,
example: Even if someone purchased 51% of the coin, he would not have 51% until the age of his coins was also equal to or higher than the age of the other staking coins. That will be very hard to calculate the actual age of every single block, and due to the fact people stake at different times , no way for him to calculate exactly when would be best to use his coins to achieve the maximum result. Easier to hack a bank security by far.
Plus if he time it wrong and uses any of his stake , it would be 20 days before he could even make another attempt against
ZEIT or Mint and during that time the other 49% has staked and may have a higher number than him, before he can even try again.
Diabolically Clever , when you examine it.
