Implement Booth multiplier.

1 files changed, 78 insertions, 0 deletions

diff --git a/pyecsca/codegen/templates/mult_booth.c b/pyecsca/codegen/templates/mult_booth.c
index e69de29..6dd19c7 100644
--- a/pyecsca/codegen/templates/mult_booth.c
+++ b/pyecsca/codegen/templates/mult_booth.c
@@ -0,0 +1,78 @@
+#include "mult.h"
+#include "point.h"
+
+
+
+static void scalar_mult_inner(bn_t *scalar, point_t *point, curve_t *curve, point_t *out) {
+    point_t *points[{{ 2 ** (scalarmult.width - 1) }}];
+    {% if scalarmult.precompute_negation %}
+        point_t *points_neg[{{ 2 ** (scalarmult.width - 1) }}];
+    {% endif %}
+
+    point_t *current = point_copy(point);
+    point_t *dbl = point_new();
+    point_dbl(current, curve, dbl);
+    points[0] = point_copy(current);
+    {% if scalarmult.precompute_negation %}
+        points_neg[0] = point_new();
+        point_neg(points[0], curve, points_neg[0]);
+    {% endif %}
+    {% if scalarmult.width > 0 %}
+        points[1] = point_copy(dbl);
+        {% if scalarmult.precompute_negation %}
+            points_neg[1] = point_new();
+            point_neg(points[1], curve, points_neg[1]);
+        {% endif %}
+    {% endif %}
+
+    point_set(dbl, current);
+    {% if scalarmult.width > 1 %}
+        for (long i = 2; i < {{ 2 ** (scalarmult.width - 1) }}; i++) {
+            point_add(current, point, curve, current);
+            points[i] = point_copy(current);
+            {% if scalarmult.precompute_negation %}
+                points_neg[i] = point_new();
+                point_neg(points[i], curve, points_neg[i]);
+            {% endif %}
+        }
+    {% endif %}
+    point_free(current);
+    point_free(dbl);
+
+    size_t bits = bn_bit_length(&curve->n);
+
+    booth_t *bs = bn_booth(scalar, {{ scalarmult.width }}, bits);
+
+    point_t *q = point_copy(curve->neutral);
+    point_t *neg = point_new();
+    for (long i = 0; i < bs->length; i++) {
+        for (long j = 0; j < {{ scalarmult.width }}; j++) {
+            point_dbl(q, curve, q);
+        }
+        int32_t val = bs->data[i];
+        if (val > 0) {
+            point_accumulate(q, points[val - 1], curve, q);
+        } else if (val < 0) {
+            {% if scalarmult.precompute_negation %}
+                point_accumulate(q, points_neg[-val - 1], curve, q);
+            {% else %}
+                point_neg(points[-val - 1], curve, neg);
+                point_accumulate(q, neg, curve, q);
+            {% endif %}
+        }
+    }
+    bn_booth_clear(bs);
+    point_free(neg);
+
+    {%- if "scl" in scalarmult.formulas %}
+        point_scl(q, curve, q);
+    {%- endif %}
+    point_set(q, out);
+    for (long i = 0; i < {{ 2 ** (scalarmult.width - 1) }}; i++) {
+        point_free(points[i]);
+        {% if scalarmult.precompute_negation %}
+            point_free(points_neg[i]);
+        {% endif %}
+    }
+    point_free(q);
+}
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