From 2e926396796aca084d61c85f554bedee577970d0 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Olivier=20Ch=C3=A9ron?= <olivier.cheron@gmail.com>
Date: Sat, 7 Oct 2017 15:16:53 +0200
Subject: [PATCH] Add P256.scalarMul

---
 Crypto/PubKey/ECC/P256.hs | 9 +++++++++
 tests/KAT_PubKey/P256.hs  | 4 ++++
 2 files changed, 13 insertions(+)

diff --git a/Crypto/PubKey/ECC/P256.hs b/Crypto/PubKey/ECC/P256.hs
index 3c350cd..7b8c7c1 100644
--- a/Crypto/PubKey/ECC/P256.hs
+++ b/Crypto/PubKey/ECC/P256.hs
@@ -34,6 +34,7 @@ module Crypto.PubKey.ECC.P256
     , scalarIsZero
     , scalarAdd
     , scalarSub
+    , scalarMul
     , scalarInv
     , scalarCmp
     , scalarFromBinary
@@ -237,6 +238,14 @@ scalarSub a b =
     withNewScalarFreeze $ \d -> withScalar a $ \pa -> withScalar b $ \pb ->
         ccryptonite_p256e_modsub ccryptonite_SECP256r1_n pa pb d
 
+-- | Perform multiplication between two scalars
+--
+-- > a * b
+scalarMul :: Scalar -> Scalar -> Scalar
+scalarMul a b =
+    withNewScalarFreeze $ \d -> withScalar a $ \pa -> withScalar b $ \pb ->
+         ccryptonite_p256_modmul ccryptonite_SECP256r1_n pa 0 pb d
+
 -- | Give the inverse of the scalar
 --
 -- > 1 / a
diff --git a/tests/KAT_PubKey/P256.hs b/tests/KAT_PubKey/P256.hs
index c570548..f038133 100644
--- a/tests/KAT_PubKey/P256.hs
+++ b/tests/KAT_PubKey/P256.hs
@@ -92,6 +92,10 @@ tests = testGroup "P256"
             let v = unP256 r `mod` curveN
                 v' = P256.scalarSub (unP256Scalar r) P256.scalarZero
              in v `propertyEq` p256ScalarToInteger v'
+        , testProperty "mul" $ \r1 r2 ->
+            let r = (unP256 r1 * unP256 r2) `mod` curveN
+                r' = P256.scalarMul (unP256Scalar r1) (unP256Scalar r2)
+             in r `propertyEq` p256ScalarToInteger r'
         , testProperty "inv" $ \r' ->
             let inv  = inverseCoprimes (unP256 r') curveN
                 inv' = P256.scalarInv (unP256Scalar r')