Build a Compact Cryptocurrency System Purely Based on PoS
eprint.iacr.org
eprint.iacr.org
There already exist pure POS coins, Nxt through a concept called transparent forging may be capable of resisting anything up to a 90% attack.
I'll have a read of this properly when I get home.
Much of this was because there was no white paper or documentation, and when pressed for details beyond the most basic, the developer just told you to read the source code once he open-sourced it.
The proof of convergence is also not correct. The inequality at the top of p.7 (ever heard of equation numering...?) should be reversed, which effectively establishes that convergence probability is smaller or equal to 1.
Also the energy cost of mining is beginning to become a legitimate environmental concern. I think the new slew of proof of stake currencies are going to give the proof of work currencies a run for their money (pardon the pun).
As for the environmental concern - read up about the tragedy of commons. Few people will abandon a better protocol into a worse one if the only benefit is ecological.
But with Peercoin, for example, everybody earns annual interest of 1% of their holdings, paid in new coin. Let's say instead we have DennisCoin which pays a whopping 100% and is worth $1 per coin.
If you start with 10 coins and I start with 90 coins, then after a year you'll have 20 coins and I'll have 180. I still have nine times as much as you.
Since the number of coins has doubled, the currency value drops in half. So in dollar terms, you still have $10 and I still have $90.
So nobody knows when is the very last day.
Btw. The moment can be determined in a secure way (think satoshi-dice style)