Collateral Pool
The peth token is a simple proportional claim on a collateral pool, with the
initial gem<->peth exchange ratio being 1:1.
The gem/peth exchange rate is called per, and is calculated as the
total number of deposited gem divided by the total supply of PETH.
The reference price of gem (in practice, ETHUSD) is provided by the pip,
an external oracle. The pip is completely trusted.
The reference price of peth is then given by the dynamic tag, e.g. the
price of PETH in USD.
Anyone can deposit GEM to the pool via join, and withdraw via exit.
Surpluses generated by the system are paid by burning PETH causing its value
to rise proportional to pooled collateral.
If PETH has to be issued to cover forced liquidations the value of the claim
can also fall during times of volatility.