Is there a precise open specification for the peercoin protocol? I searched for an open specification of the peercoin protocol (more precise than the white paper) and I couldn't find one. Is it possible to find something similar to the bitcoin protocol specification available on bitcoin wiki but for peercoin ?
Since most crypto-currencies are a fork of Bitcoin, you can get nitty gritty technical details from the Bitcoin wiki, specifically from the technical category. 

Say you want to know the specifications for communication, the Protocol Specification article will help you out with how packets should be formatted down to the bit. It will have all sorts of details on things like how to calculate difficulty or what a block chain is.

Peercoin share a lot of concepts with Bitcoin and thus most Bitcoin wiki articles will apply. Peercoin concepts such as its Proof-of-Stake may not be found in the Bitcoin wiki so refer to the whitepaper for differences.