From Peercoin Wiki
The CheckProofOfStake function code can be found in the kernel.cpp file (v0.4.0ppc).
Check kernel hash target and coinstake signature
|tx||const CTransaction&||Reference to the coinstake transaction of the block being checked|
|nBits||unsigned int||Target bits of the block being checked|
|hashProofOfStake||uint256&||The calculated hash returned by the CheckStakeKernelHash function|
|bool||true if kernel hash target and coinstake signature were checked successfully, otherwise false|
- What is the CheckStakeKernelHash function and what is it used for?
- The CheckStakeKernelHash function is described in detail here