Network split vulnerability in Peercoin protocol v0.3
Peercoin v0.3 introduced a stake modifier which is computed from hashes of block signatures.
The problem is that signatures are malleable, for details see
https://en.bitcoin.it/wiki/Transaction_Malleability#Signature_MalleabilityAll an attacker needs to do, is to setup a node that relays blocks with malleated signatures.
Eventually the network will disagree on the stake modifier and thus will fork.
Peercoin v0.4 (actual version) and NovaCoin are not vulnerable.
