Handle negative scaling factors.

src/ecdsa/point.rs

@@ -30,7 +30,7 @@ impl Clone for Point<P192> {
 
 impl ECCPoint for Point<P192> {
     type Curve = P192;
-    type Scale = U192;
+    type Scale = I192;
 
     fn default() -> Point<P192>
     {
@@ -93,7 +93,7 @@ impl ECCPoint for Point<P192> {
         Point{ x: I192::from(xr), y: I192::from(yr) }
     }
 
-    fn scale(&self, d: &U192) -> Point<P192>
+    fn scale(&self, d: &I192) -> Point<P192>
     {
         assert!(!d.is_zero());
         #[allow(non_snake_case)]
@@ -118,9 +118,13 @@ impl ECCPoint for Point<P192> {
             bit -= 1;
         }
 
+        if d.is_negative() {
+            Q.negate()
+        } else {
             Q
         }
     }
+}
 
 #[cfg(test)]
 mod tests {
@@ -204,7 +208,7 @@ mod tests {
 
             let x = I192::new(*negx, U192::from_bytes(xbytes));
             let y = I192::new(*negy, U192::from_bytes(ybytes));
-            let k = U192::from_bytes(kbytes);
+            let k = I192::new(*negk, U192::from_bytes(kbytes));
             let a = I192::new(*nega, U192::from_bytes(abytes));
             let b = I192::new(*negb, U192::from_bytes(bbytes));
             let point = Point{ x: x, y: y };

test-generator/ECDSATesting.hs

@@ -5,7 +5,8 @@ module ECDSATesting(
 
 import Crypto.PubKey.ECC.Prim(scalarGenerate,pointAdd,pointNegate,pointDouble,pointBaseMul,pointMul)
 import Crypto.PubKey.ECC.Types(Curve,CurveName(..),Point(..),getCurveByName)
-import Crypto.Random(withDRG)
+import Crypto.Random(DRG(..),withDRG)
+import qualified Data.ByteString as S
 import qualified Data.Map.Strict as Map
 import Math(showX)
 import Task(Task(..))
@@ -87,16 +88,19 @@ scaleTest name curve = Task {
   go (memory0, drg0) =
     let (scalar0, drg1) = withDRG drg0 (scalarGenerate curve)
         (scalar1, drg2) = withDRG drg1 (scalarGenerate curve)
+        (negbs,   drg3) = randomBytesGenerate 1 drg2
+        [negbyte]       = S.unpack negbs
+        k               = if odd negbyte then scalar1 else -scalar1 
         point           = pointBaseMul curve scalar0
-        respnt = pointMul curve scalar1 point
+        respnt          = pointMul curve k point
     in case (point, respnt) of
-         (PointO, _) -> go (memory0, drg2)
-         (_, PointO) -> go (memory0, drg2)
+         (PointO, _) -> go (memory0, drg3)
+         (_, PointO) -> go (memory0, drg3)
          (Point basex basey, Point resx resy) ->
             let res = Map.fromList [("x", showX basex), ("y", showX basey),
-                                    ("k", showX scalar1),
+                                    ("k", showX k),
                                     ("a", showX resx),  ("b", showX resy)]
-            in (res, scalar0, (memory0, drg2))
+            in (res, scalar0, (memory0, drg3))
 
 generateTasks :: (String, Curve) -> [Task]
 generateTasks (name, curve) = [negateTest name curve,