Fix montgomery multiplication.

Fixes pyecsca#33.

5 files changed, 39 insertions, 10 deletions

diff --git a/pyecsca/codegen/render.py b/pyecsca/codegen/render.py
index d4d1d7f..984a25c 100644
--- a/pyecsca/codegen/render.py
+++ b/pyecsca/codegen/render.py
@@ -2,7 +2,6 @@ import os
 import shutil
 import subprocess
 import tempfile
-from _ast import Pow
 from os import path
 from os import makedirs
 from typing import Optional, List, Set, Mapping, MutableMapping, Any, Tuple
@@ -82,6 +81,13 @@ def render_curve_impl(model: CurveModel) -> str:
 
 def transform_ops(ops: List[CodeOp], parameters: List[str], outputs: Set[str],
                   renames: Mapping[str, str] = None) -> MutableMapping[Any, Any]:
+    """
+    Transform a list of CodeOps, parameters, outputs and renames into a mapping
+    that will be used by the ops template macros to render the ops.
+
+    This tracks allocations and frees, also creates a mapping of constants
+    to variable names
+    """
     def rename(name: str):
         if renames is not None and name not in outputs:
             return renames.get(name, name)
@@ -100,21 +106,27 @@ def transform_ops(ops: List[CodeOp], parameters: List[str], outputs: Set[str],
             if param not in allocations and param not in parameters:
                 raise ValueError("Should be allocated or parameter: {}".format(param))
         for const in op.constants:
-            name = "c" + str(const)
+            if op.operator == OpType.Pow:
+                name = "cu" + str(const)
+                encode = False
+            else:
+                name = "c" + str(const)
+                encode = True
             if name not in allocations:
                 allocations.append(name)
-                initializations[name] = const
-                const_mapping[const] = name
+                initializations[name] = (const, encode)
+                const_mapping[(const, encode)] = name
                 frees.append(name)
         operations.append((op.operator, op.result, rename(op.left), rename(op.right)))
     mapped = []
     for op in operations:
         o2 = op[2]
-        if o2 in const_mapping:
-            o2 = const_mapping[o2]
+        if (o2, True) in const_mapping:
+            o2 = const_mapping[(o2, True)]
         o3 = op[3]
-        if o3 in const_mapping and not (isinstance(op[0], Pow) and o3 == 2):
-            o3 = const_mapping[o3]
+        o3_enc = op[0] != OpType.Pow
+        if (o3, o3_enc) in const_mapping:
+            o3 = const_mapping[(o3, o3_enc)]
         mapped.append((op[0], op[1], o2, o3))
     returns = {}
     if renames:
diff --git a/pyecsca/codegen/templates/action.c b/pyecsca/codegen/templates/action.c
index 939c6a0..75f3f7a 100644
--- a/pyecsca/codegen/templates/action.c
+++ b/pyecsca/codegen/templates/action.c
@@ -1,4 +1,7 @@
 {% macro start_action(action) %}
+    {#  // Macro for starting a given "action".
+        // If the trigger is setup to fire on that action
+        // then this will toggle the trigger value. #}
 	{% if action == "add" %}
 		action_start((uint32_t) (1 << 0));
 	{% elif action == "dadd" %}
@@ -31,6 +34,9 @@
 {%- endmacro %}
 
 {% macro end_action(action) %}
+    {#  // Macro for ending a given "action".
+        // If the trigger is setup to fire on that action
+        // then this will toggle the trigger value. #}
 	{% if action == "add" %}
 		action_end((uint32_t) (1 << 0));
 	{% elif action == "dadd" %}
diff --git a/pyecsca/codegen/templates/main.c b/pyecsca/codegen/templates/main.c
index 9014c9a..af82603 100644
--- a/pyecsca/codegen/templates/main.c
+++ b/pyecsca/codegen/templates/main.c
@@ -125,6 +125,9 @@ static uint8_t cmd_set_params(uint8_t *data, uint16_t len) {
 	if (!curve->neutral->infinity) {
 		point_red_encode(curve->neutral, curve);
 	}
+	{%- for param in curve_parameters %}
+	    bn_red_encode(&curve->{{ param }}, &curve->p, &curve->p_red);
+	{%- endfor %}
 
 	bn_t x; bn_init(&x);
 	bn_t y; bn_init(&y);
diff --git a/pyecsca/codegen/templates/ops.c b/pyecsca/codegen/templates/ops.c
index 12b126f..ee322a8 100644
--- a/pyecsca/codegen/templates/ops.c
+++ b/pyecsca/codegen/templates/ops.c
@@ -16,9 +16,11 @@
 {%- endmacro %}
 
 {% macro render_initializations(initializations) -%}
-	{%- for init, value in initializations.items() %}
+	{%- for init, (value, encode) in initializations.items() %}
 		bn_from_int({{ value }}, &{{ init }});
-		bn_red_encode(&{{ init }}, &curve->p, &curve->p_red);
+		{%- if encode %}
+		    bn_red_encode(&{{ init }}, &curve->p, &curve->p_red);
+		{%- endif %}
 	{%- endfor %}
 {%- endmacro %}
 
diff --git a/pyecsca/codegen/templates/point.c b/pyecsca/codegen/templates/point.c
index 8b7b07e..e87ae36 100644
--- a/pyecsca/codegen/templates/point.c
+++ b/pyecsca/codegen/templates/point.c
@@ -4,6 +4,9 @@
 {% import "ops.c" as ops %}
 {% from "action.c" import start_action, end_action %}
 
+/**
+ * Constructs (allocates) a new point.
+ */
 point_t *point_new(void) {
 	point_t *result = malloc(sizeof(point_t));
 	{%- for variable in variables %}
@@ -13,6 +16,9 @@ point_t *point_new(void) {
 	return result;
 }
 
+/**
+ * Creates a copy of a point.
+ */
 point_t *point_copy(const point_t *from) {
 	point_t *result = point_new();
 	point_set(from, result);