For an odd reason I don't see such a function in LabVIEW 5.x, 6.x and 7.x. It appears only in 8.2, maybe it's available since 8.0 too, can't check right now. Well, I ran a quick binary search for "GetMD5Digest" word and found, that such a function was being used in ...\LabVIEW 8.2\vi.lib\imath\engines\lvmath\Utility\MD5.vi. That VI was password-protected, the password was calvinthegorilla (😁) and, of course, was removed like 1-2-3. Here's the VI to play:
MD5_8_2.vi
As shown, the prototype is still correct, just some extra "secret" / key was applied. Works well in LV 2023 Q3 64-bit.