wow! lots of attention recently...
If an exchange waits for 6 confirmations, you would only need to split it in 6 (maybe 7, not 400 like I did).
I don't know why I wrote this... I lost focus... actually you need to split the stake as much as you can.
That's the key to the thing: if you split your staking then your staking weight remains the same. But splitting gives you the advantage that on each block you find your staking weight is only marginally affected. If you split in 6 and you hit a block, you are left with 5/6 of your original weight. If you split in hundreds then each block you mint doesn't affect your weight because the age destroyed is minimal. This is why I could do 90 blocks with no extra effort.
I'll try to write a paper about the countermeasures to defend against this kind of things... but it's not directly related to coin age: coin age only makes it cheaper to attack, so coins like blackcoin or nxt can still be attacked with less than 10% of the supply.
And I'll do nxt next (testnet or a clone) but it'll take some time because it's a very different thing I need to get used to.
And a warning: most POW coins are not safe! it's easy to cheaply rent enough hashrate to attack a lot of coins with low to medium hashrate. Only the biggest ones are good.
Oh that's interesting, so then let's say for instance you have...
2 minute block time
minimum stake age at 7 days
maximum at 28 days
19 billion float
8% a year halving down to 4% every 64X difficulty (8%, 6%, 5%, 4.5% etc)
20 coin fee per kb (roughly 6-7 combines)
Fees generate 10% more Coins through retrieval of Stake (someone spends 20 Coins in Fees, you Stake the Block for 22 Coins)
4000 max Stake subsidy per block (plus fees on top)
Split/combine threshold at 200,000 coins at 10 days
Maximum actual inflation per year would be limited to about 5-8% per year
By the way you describe your attack, the result would cause financial detriment to you since you would be paying tens of thousands in fees but Stakers would also get all those Coins plus 10% more!. Plus with the max subsidy capped, it encourages smaller blocks for higher rewards. I can give you a little bit of private Coins you could test with if you want.