1 files changed, 21 insertions, 0 deletions
diff --git a/crypto/src/math/ec/rfc7748/X25519Field.cs b/crypto/src/math/ec/rfc7748/X25519Field.cs
index b4ea9a9ce..8365df03b 100644
--- a/crypto/src/math/ec/rfc7748/X25519Field.cs
+++ b/crypto/src/math/ec/rfc7748/X25519Field.cs
@@ -107,6 +107,20 @@ namespace Org.BouncyCastle.Math.EC.Rfc7748
             }
         }
 
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static void CMov(int cond, ReadOnlySpan<int> x, Span<int> z)
+        {
+            Debug.Assert(0 == cond || -1 == cond);
+
+            for (int i = 0; i < Size; ++i)
+            {
+                int z_i = z[i], diff = z_i ^ x[i];
+                z_i ^= (diff & cond);
+                z[i] = z_i;
+            }
+        }
+#endif
+
         public static void CNegate(int negate, int[] z)
         {
             Debug.Assert(negate >> 1 == 0);
@@ -126,6 +140,13 @@ namespace Org.BouncyCastle.Math.EC.Rfc7748
             }
         }
 
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static void Copy(ReadOnlySpan<int> x, Span<int> z)
+        {
+            x[..Size].CopyTo(z);
+        }
+#endif
+
         public static int[] Create()
         {
             return new int[Size];