The CRYPT_KEY_PROV_PARAM structure fields are passed as the arguments to CryptSetProvParam. This structure is pointed to by the rgProvParam in the CRYPT_KEY_PROV_INFO data structure.
typedef struct _CRYPT_KEY_PROV_PARAM {
DWORD dwParam;
BYTE* pbData;
DWORD cbData;
DWORD dwFlags;
} CRYPT_KEY_PROV_PARAM, *PCRYPT_KEY_PROV_PARAM;