From 8a56c7a95e662862cfe78b834ccb091e95d5372f Mon Sep 17 00:00:00 2001
From: J08nY
Date: Mon, 25 Nov 2019 17:45:35 +0100
Subject: Add libtommath, HOST build, and a simple PRNG.

---
 pyecsca/codegen/mult/double_and_add.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

(limited to 'pyecsca/codegen/mult')

diff --git a/pyecsca/codegen/mult/double_and_add.c b/pyecsca/codegen/mult/double_and_add.c
index 91ad6e3..1fd3c9e 100644
--- a/pyecsca/codegen/mult/double_and_add.c
+++ b/pyecsca/codegen/mult/double_and_add.c
@@ -1,5 +1,18 @@
 #include "mult.h"
 
 void scalar_mult(bn_t *scalar, point_t *point, curve_t *curve, point_t *out) {
-		
+	point_t *q = point_copy(point);
+	point_t *r = point_copy(curve->neutral);
+
+    int nbits = bn_bit_length(curve->n);
+    for (int i = nbits; i >= 0; i--) {
+        point_dbl(r, curve, r);
+        if (bn_get_bit(scalar, i) == 1) {
+            point_add(q, r, curve, r);
+        }
+    }
+    point_scl(r, curve, r);
+    point_set(r, out);
+    point_free(q);
+    point_free(r);
 }
\ No newline at end of file
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