The code is clear about what parameters are passed to those two functions. It's a MSSQL password decoder. The value of EncSTR is taken from the registry or trough SQL Profiler.
hxxp://www.blackhat.com/presentations/win-usa-03/bh-win-03-cerrudo/bh-win-03-cerrudo.ppt
hxxp://hosteddocs.ittoolbox.com/Protecting_MSSQL_Databases.pdf
hxxp://hosteddocs.ittoolbox.com/Database_Security.pdf
hxxp://jimmers.russia.webmatrixhosting.net/software.aspx
Do a Google search: agent_pwd SEMCOMN.DLL and you'll find all that.
ENCSTR = encrypted password
sizeof(EncStr) = len of encrypted password
Buff = buffer to store decrypted password
dwSize = len of Buff
I'll recommend you reading a c tutor.
