diff --git a/Crypto/ECC.hs b/Crypto/ECC.hs
index e2897da..40092a0 100644
--- a/Crypto/ECC.hs
+++ b/Crypto/ECC.hs
@@ -100,8 +100,20 @@ instance EllipticCurve Curve_P256R1 where
     curveGenerateScalar _ = P256.scalarGenerate
     curveGenerateKeyPair _ = toKeyPair <$> P256.scalarGenerate
       where toKeyPair scalar = KeyPair (P256.toPoint scalar) scalar
-    encodePoint _ p = P256.pointToBinary p
-    decodePoint _ bs = P256.pointFromBinary bs
+    encodePoint _ p = mxy
+      where
+        mxy :: forall bs. ByteArray bs => bs
+        mxy = B.concat [uncompressed, xy]
+          where
+            uncompressed, xy :: bs
+            uncompressed = B.singleton 4
+            xy = P256.pointToBinary p
+    decodePoint _ mxy = case B.uncons mxy of
+        Nothing -> CryptoFailed $ CryptoError_PointSizeInvalid
+        Just (m,xy)
+            -- uncompressed
+            | m == 4 -> P256.pointFromBinary xy
+            | otherwise -> CryptoFailed $ CryptoError_PointFormatInvalid
 
 instance EllipticCurveArith Curve_P256R1 where
     pointAdd  _ a b = P256.pointAdd a b
diff --git a/Crypto/PubKey/ECC/P256.hs b/Crypto/PubKey/ECC/P256.hs
index 99ecbcc..e5a6e1d 100644
--- a/Crypto/PubKey/ECC/P256.hs
+++ b/Crypto/PubKey/ECC/P256.hs
@@ -49,7 +49,7 @@ import           Crypto.Internal.Compat
 import           Crypto.Internal.Imports
 import           Crypto.Internal.ByteArray
 import qualified Crypto.Internal.ByteArray as B
-import           Data.Memory.PtrMethods (memSet, memCopy)
+import           Data.Memory.PtrMethods (memSet)
 import           Crypto.Error
 import           Crypto.Random
 import           Crypto.Number.Serialize.Internal (os2ip, i2ospOf)
@@ -119,7 +119,7 @@ pointDh scalar p =
     B.unsafeCreate scalarSize $ \dst -> withTempPoint $ \dx dy -> do
         withScalar scalar $ \n -> withPoint p $ \px py -> withScalarZero $ \nzero ->
             ccryptonite_p256_points_mul_vartime nzero n px py dx dy
-        memCopy dst (castPtr dx) scalarSize
+        ccryptonite_p256_to_bin (castPtr dx) dst
 
 -- | multiply the point @p with @n2 and add a lifted to curve value @n1
 --