1 files changed, 64 insertions, 0 deletions
diff --git a/crypto/src/util/BigIntegers.cs b/crypto/src/util/BigIntegers.cs
index d1b15f869..8c2068688 100644
--- a/crypto/src/util/BigIntegers.cs
+++ b/crypto/src/util/BigIntegers.cs
@@ -265,5 +265,69 @@ namespace Org.BouncyCastle.Utilities
                 return Nat.ToBigInteger(len, z);
             }
         }
+
+        public static bool ModOddIsCoprime(BigInteger M, BigInteger X)
+        {
+            if (!M.TestBit(0))
+                throw new ArgumentException("must be odd", nameof(M));
+            if (M.SignValue != 1)
+                throw new ArithmeticException("BigInteger: modulus not positive");
+            if (X.SignValue < 0 || X.CompareTo(M) >= 0)
+            {
+                X = X.Mod(M);
+            }
+
+            int bits = M.BitLength;
+
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+            if (bits <= 2048)
+            {
+                int len = Nat.GetLengthForBits(bits);
+                Span<uint> m = stackalloc uint[len];
+                Span<uint> x = stackalloc uint[len];
+                Nat.FromBigInteger(bits, M, m);
+                Nat.FromBigInteger(bits, X, x);
+                return 0 != Mod.ModOddIsCoprime(m, x);
+            }
+            else
+#endif
+            {
+                uint[] m = Nat.FromBigInteger(bits, M);
+                uint[] x = Nat.FromBigInteger(bits, X);
+                return 0 != Mod.ModOddIsCoprime(m, x);
+            }
+        }
+
+        public static bool ModOddIsCoprimeVar(BigInteger M, BigInteger X)
+        {
+            if (!M.TestBit(0))
+                throw new ArgumentException("must be odd", nameof(M));
+            if (M.SignValue != 1)
+                throw new ArithmeticException("BigInteger: modulus not positive");
+            if (X.SignValue < 0 || X.CompareTo(M) >= 0)
+            {
+                X = X.Mod(M);
+            }
+
+            int bits = M.BitLength;
+
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+            if (bits <= 2048)
+            {
+                int len = Nat.GetLengthForBits(bits);
+                Span<uint> m = stackalloc uint[len];
+                Span<uint> x = stackalloc uint[len];
+                Nat.FromBigInteger(bits, M, m);
+                Nat.FromBigInteger(bits, X, x);
+                return Mod.ModOddIsCoprimeVar(m, x);
+            }
+            else
+#endif
+            {
+                uint[] m = Nat.FromBigInteger(bits, M);
+                uint[] x = Nat.FromBigInteger(bits, X);
+                return Mod.ModOddIsCoprimeVar(m, x);
+            }
+        }
     }
 }