Add automatic EC point validation for decoded points and for multiplier outputs

2 files changed, 8 insertions, 28 deletions

diff --git a/crypto/src/math/ec/multiplier/AbstractECMultiplier.cs b/crypto/src/math/ec/multiplier/AbstractECMultiplier.cs
index fe683726f..517881323 100644
--- a/crypto/src/math/ec/multiplier/AbstractECMultiplier.cs
+++ b/crypto/src/math/ec/multiplier/AbstractECMultiplier.cs
@@ -10,7 +10,13 @@
                 return p.Curve.Infinity;
 
             ECPoint positive = MultiplyPositive(p, k.Abs());
-            return sign > 0 ? positive : positive.Negate();
+            ECPoint result = sign > 0 ? positive : positive.Negate();
+
+            /*
+             * Although the various multipliers ought not to produce invalid output under normal
+             * circumstances, a final check here is advised to guard against fault attacks.
+             */
+            return ECAlgorithms.ValidatePoint(result);
         }
 
         protected abstract ECPoint MultiplyPositive(ECPoint p, BigInteger k);
diff --git a/crypto/src/math/ec/multiplier/ReferenceMultiplier.cs b/crypto/src/math/ec/multiplier/ReferenceMultiplier.cs
index 832fd7be4..4848ada39 100644
--- a/crypto/src/math/ec/multiplier/ReferenceMultiplier.cs
+++ b/crypto/src/math/ec/multiplier/ReferenceMultiplier.cs
@@ -3,35 +3,9 @@ namespace Org.BouncyCastle.Math.EC.Multiplier
     public class ReferenceMultiplier
         : AbstractECMultiplier
     {
-        /**
-         * Simple shift-and-add multiplication. Serves as reference implementation
-         * to verify (possibly faster) implementations in
-         * {@link org.bouncycastle.math.ec.ECPoint ECPoint}.
-         * 
-         * @param p The point to multiply.
-         * @param k The factor by which to multiply.
-         * @return The result of the point multiplication <code>k * p</code>.
-         */
         protected override ECPoint MultiplyPositive(ECPoint p, BigInteger k)
         {
-            ECPoint q = p.Curve.Infinity;
-            int t = k.BitLength;
-            if (t > 0)
-            {
-                if (k.TestBit(0))
-                {
-                    q = p;
-                }
-                for (int i = 1; i < t; i++)
-                {
-                    p = p.Twice();
-                    if (k.TestBit(i))
-                    {
-                        q = q.Add(p);
-                    }
-                }
-            }
-            return q;
+            return ECAlgorithms.ReferenceMultiply(p, k);
         }
     }
 }