GCM_FinishKey closes the GCM context and destroys the key.
Public Declare Function GCM_FinishKey Lib "diCryptoSys.dll" (ByVal hContext As Long) As Long
nRet = GCM_FinishKey(hContext)
Long containing the handle to the GCM context.
long _stdcall GCM_FinishKey(long hContext);
Long: If successful, the return value is 0;
otherwise it returns a non-zero error code.
See the examples in
GCM_InitKey and
GCM_NextEncrypt.
GCM_InitKey
GCM_NextEncrypt
GCM_NextDecrypt