Add fixed width scalarmult.

2 files changed, 65 insertions, 2 deletions

diff --git a/pyecsca/codegen/templates/mult_fixed_w.c b/pyecsca/codegen/templates/mult_fixed_w.c
new file mode 100644
index 0000000..aa95ebd
--- /dev/null
+++ b/pyecsca/codegen/templates/mult_fixed_w.c
@@ -0,0 +1,63 @@
+#include "mult.h"
+#include "point.h"
+
+void scalar_mult_by_m_pow2(point_t *point, curve_t *curve) {
+    unsigned int m = {{ scalarmult.m }} >> 1;
+    while (m) {
+        point_dbl(point, curve, point);
+        m >>= 1;
+    }
+}
+
+void scalar_mult_by_m_base(point_t *point, curve_t *curve) {
+    point_t *orig = point_copy(point);
+    point_dbl(orig, curve, point);
+    for (int i = 0; i < {{ scalarmult.m - 2}}; i++) {
+        point_add(point, orig, curve, point);
+    }
+    point_free(orig);
+}
+
+static void scalar_mult_inner(bn_t *scalar, point_t *point, curve_t *curve, point_t *out) {
+	point_t *q = point_copy(curve->neutral);
+    point_t *points[{{ scalarmult.m }}];
+
+    point_t *current = point_copy(point);
+    point_t *dbl = point_new();
+    point_dbl(current, curve, dbl);
+    points[0] = point_copy(current);
+    points[1] = point_copy(dbl);
+    point_set(dbl, current);
+    for (long i = 2; i < {{ scalarmult.m }}; i++) {
+        point_add(current, point, curve, current);
+        points[i] = point_copy(current);
+    }
+    point_free(current);
+    point_free(dbl);
+
+    base_t *bs = bn_convert_base(scalar, {{ scalarmult.m }});
+
+	for (long i = bs->length - 1; i >= 0; i--) {
+	    {%- if bin(scalarmult.m).count("1") == 1 %}
+	        scalar_mult_by_m_pow2(q, curve);
+	    {%- else %}
+	        scalar_mult_by_m_base(q, curve);
+	    {%- endif %}
+
+		uint8_t val = bs->data[i];
+		if (val) {
+			point_accumulate(q, points[val-1], curve, q);
+        }
+	}
+	free(bs->data);
+	free(bs);
+
+    {%- if "scl" in scalarmult.formulas %}
+    	point_scl(q, curve, q);
+    {%- endif %}
+    point_set(q, out);
+    for (long i = 0; i < {{ scalarmult.m }}; i++) {
+        point_free(points[i]);
+    }
+	point_free(q);
+}
\ No newline at end of file
diff --git a/pyecsca/codegen/templates/point.c b/pyecsca/codegen/templates/point.c
index b4d6e94..bad232a 100644
--- a/pyecsca/codegen/templates/point.c
+++ b/pyecsca/codegen/templates/point.c
@@ -139,9 +139,9 @@ void point_from_affine(bn_t *x, bn_t *y, const curve_t *curve, point_t *out) {
 }
 
 void point_accumulate(const point_t *one, const point_t *other, const curve_t *curve, point_t *out_one) {
-    {% if accumulation_order == "PeqPR" %}
+    {% if accumulation_order == AccumulationOrder.PeqPR %}
         point_add(one, other, curve, out_one);
-    {% elif accumulation_order == "PeqRP" %}
+    {% elif accumulation_order == AccumulationOrder.PeqRP %}
         point_add(other, one, curve, out_one);
     {% endif %}
 }
\ No newline at end of file