these do work

src/libauthsrv/nvcsum.c

@@ -0,0 +1,16 @@
+#include <u.h>
+#include <libc.h>
+#include <auth.h>
+
+uchar
+nvcsum(void *vmem, int n)
+{
+	uchar *mem, sum;
+	int i;
+
+	sum = 9;
+	mem = vmem;
+	for(i = 0; i < n; i++)
+		sum += mem[i];
+	return sum;
+}