Yes, GSS_GetMic is corresponding to MakeSignature.  I have implemented similar thing.  See this link for the full description on the details of SSPI interoperability with GSSAPI.

MS-SIPAE <-> SSPI: MakeSignature is 'GSS_GetMIC’?
I am using QGIS on a Mac.

I am working with hydroacoustic data for mapping and interpreting the seafloor.
Data are collected, processed and interpreted. The result is a txt file with Lat and Lon in the first columns followed by R, G and B data, e.g. [54.20,7.78,0.94,0.62,0.37]. The files can have 100,000 lines or more. 
I am not really good in GIS but I need to use it for some reasons. I seem to be unable to plot these data in GIS. There is obviously no symbology/style way to tell the system to take the color values from a file (i.e. the next 3 values in the same line of the file). It is so easy in MatLab: scatter(lat, lon, symbolsize, [R G B]) but I can't work easily with multiple layers in Matlab.
