diff --git a/src/libmp/port/letomp.c b/src/libmp/port/letomp.c
new file mode 100644
index 0000000..e23fed2
--- /dev/null
+++ b/src/libmp/port/letomp.c
@@ -0,0 +1,28 @@
+#include "os.h"
+#include <mp.h>
+#include "dat.h"
+
+// convert a little endian byte array (least significant byte first) to an mpint
+mpint*
+letomp(uchar *s, uint n, mpint *b)
+{
+	int i=0, m = 0;
+	mpdigit x=0;
+
+	if(b == nil)
+		b = mpnew(0);
+	mpbits(b, 8*n);
+	for(; n > 0; n--){
+		x |= ((mpdigit)(*s++)) << i;
+		i += 8;
+		if(i == Dbits){
+			b->p[m++] = x;
+			i = 0;
+			x = 0;
+		}
+	}
+	if(i > 0)
+		b->p[m++] = x;
+	b->top = m;
+	return b;
+}