Span usage in Math.Raw

1 files changed, 999 insertions, 81 deletions

diff --git a/crypto/src/math/raw/Nat.cs b/crypto/src/math/raw/Nat.cs
index 4065c82c2..09c263f4d 100644
--- a/crypto/src/math/raw/Nat.cs
+++ b/crypto/src/math/raw/Nat.cs
@@ -21,6 +21,20 @@ namespace Org.BouncyCastle.Math.Raw
             return (uint)c;
         }
 
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static uint Add(int len, ReadOnlySpan<uint> x, ReadOnlySpan<uint> y, Span<uint> z)
+        {
+            ulong c = 0;
+            for (int i = 0; i < len; ++i)
+            {
+                c += (ulong)x[i] + y[i];
+                z[i] = (uint)c;
+                c >>= 32;
+            }
+            return (uint)c;
+        }
+#endif
+
         public static uint Add33At(int len, uint x, uint[] z, int zPos)
         {
             Debug.Assert(zPos <= (len - 2));
@@ -45,6 +59,20 @@ namespace Org.BouncyCastle.Math.Raw
             return c == 0 ? 0 : IncAt(len, z, zOff, zPos + 2);
         }
 
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static uint Add33At(int len, uint x, Span<uint> z, int zPos)
+        {
+            Debug.Assert(zPos <= (len - 2));
+            ulong c = (ulong)z[zPos + 0] + x;
+            z[zPos + 0] = (uint)c;
+            c >>= 32;
+            c += (ulong)z[zPos + 1] + 1;
+            z[zPos + 1] = (uint)c;
+            c >>= 32;
+            return c == 0 ? 0 : IncAt(len, z, zPos + 2);
+        }
+#endif
+
         public static uint Add33To(int len, uint x, uint[] z)
         {
             ulong c = (ulong)z[0] + x;
@@ -67,6 +95,19 @@ namespace Org.BouncyCastle.Math.Raw
             return c == 0 ? 0 : IncAt(len, z, zOff, 2);
         }
 
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static uint Add33To(int len, uint x, Span<uint> z)
+        {
+            ulong c = (ulong)z[0] + x;
+            z[0] = (uint)c;
+            c >>= 32;
+            c += (ulong)z[1] + 1;
+            z[1] = (uint)c;
+            c >>= 32;
+            return c == 0 ? 0 : IncAt(len, z, 2);
+        }
+#endif
+
         public static uint AddBothTo(int len, uint[] x, uint[] y, uint[] z)
         {
             ulong c = 0;
@@ -91,13 +132,27 @@ namespace Org.BouncyCastle.Math.Raw
             return (uint)c;
         }
 
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static uint AddBothTo(int len, ReadOnlySpan<uint> x, ReadOnlySpan<uint> y, Span<uint> z)
+        {
+            ulong c = 0;
+            for (int i = 0; i < len; ++i)
+            {
+                c += (ulong)x[i] + y[i] + z[i];
+                z[i] = (uint)c;
+                c >>= 32;
+            }
+            return (uint)c;
+        }
+#endif
+
         public static uint AddDWordAt(int len, ulong x, uint[] z, int zPos)
         {
             Debug.Assert(zPos <= (len - 2));
-            ulong c = (ulong)z[zPos + 0] + (x & M);
+            ulong c = z[zPos + 0] + (x & M);
             z[zPos + 0] = (uint)c;
             c >>= 32;
-            c += (ulong)z[zPos + 1] + (x >> 32);
+            c += z[zPos + 1] + (x >> 32);
             z[zPos + 1] = (uint)c;
             c >>= 32;
             return c == 0 ? 0 : IncAt(len, z, zPos + 2);
@@ -106,15 +161,29 @@ namespace Org.BouncyCastle.Math.Raw
         public static uint AddDWordAt(int len, ulong x, uint[] z, int zOff, int zPos)
         {
             Debug.Assert(zPos <= (len - 2));
-            ulong c = (ulong)z[zOff + zPos] + (x & M);
+            ulong c = z[zOff + zPos] + (x & M);
             z[zOff + zPos] = (uint)c;
             c >>= 32;
-            c += (ulong)z[zOff + zPos + 1] + (x >> 32);
+            c += z[zOff + zPos + 1] + (x >> 32);
             z[zOff + zPos + 1] = (uint)c;
             c >>= 32;
             return c == 0 ? 0 : IncAt(len, z, zOff, zPos + 2);
         }
 
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static uint AddDWordAt(int len, ulong x, Span<uint> z, int zPos)
+        {
+            Debug.Assert(zPos <= (len - 2));
+            ulong c = z[zPos + 0] + (x & M);
+            z[zPos + 0] = (uint)c;
+            c >>= 32;
+            c += z[zPos + 1] + (x >> 32);
+            z[zPos + 1] = (uint)c;
+            c >>= 32;
+            return c == 0 ? 0 : IncAt(len, z, zPos + 2);
+        }
+#endif
+
         public static uint AddDWordTo(int len, ulong x, uint[] z)
         {
             ulong c = (ulong)z[0] + (x & M);
@@ -137,6 +206,19 @@ namespace Org.BouncyCastle.Math.Raw
             return c == 0 ? 0 : IncAt(len, z, zOff, 2);
         }
 
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static uint AddDWordTo(int len, ulong x, Span<uint> z)
+        {
+            ulong c = z[0] + (x & M);
+            z[0] = (uint)c;
+            c >>= 32;
+            c += z[1] + (x >> 32);
+            z[1] = (uint)c;
+            c >>= 32;
+            return c == 0 ? 0 : IncAt(len, z, 2);
+        }
+#endif
+
         public static uint AddTo(int len, uint[] x, uint[] z)
         {
             ulong c = 0;
@@ -161,6 +243,20 @@ namespace Org.BouncyCastle.Math.Raw
             return (uint)c;
         }
 
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static uint AddTo(int len, ReadOnlySpan<uint> x, Span<uint> z)
+        {
+            ulong c = 0;
+            for (int i = 0; i < len; ++i)
+            {
+                c += (ulong)x[i] + z[i];
+                z[i] = (uint)c;
+                c >>= 32;
+            }
+            return (uint)c;
+        }
+#endif
+
         public static uint AddTo(int len, uint[] x, int xOff, uint[] z, int zOff, uint cIn)
         {
             ulong c = cIn;
@@ -173,6 +269,20 @@ namespace Org.BouncyCastle.Math.Raw
             return (uint)c;
         }
 
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static uint AddTo(int len, ReadOnlySpan<uint> x, Span<uint> z, uint cIn)
+        {
+            ulong c = cIn;
+            for (int i = 0; i < len; ++i)
+            {
+                c += (ulong)x[i] + z[i];
+                z[i] = (uint)c;
+                c >>= 32;
+            }
+            return (uint)c;
+        }
+#endif
+
         public static uint AddToEachOther(int len, uint[] u, int uOff, uint[] v, int vOff)
         {
             ulong c = 0;
@@ -186,6 +296,21 @@ namespace Org.BouncyCastle.Math.Raw
             return (uint)c;
         }
 
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static uint AddToEachOther(int len, Span<uint> u, Span<uint> v)
+        {
+            ulong c = 0;
+            for (int i = 0; i < len; ++i)
+            {
+                c += (ulong)u[i] + v[i];
+                u[i] = (uint)c;
+                v[i] = (uint)c;
+                c >>= 32;
+            }
+            return (uint)c;
+        }
+#endif
+
         public static uint AddWordAt(int len, uint x, uint[] z, int zPos)
         {
             Debug.Assert(zPos <= (len - 1));
@@ -204,6 +329,17 @@ namespace Org.BouncyCastle.Math.Raw
             return c == 0 ? 0 : IncAt(len, z, zOff, zPos + 1);
         }
 
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static uint AddWordAt(int len, uint x, Span<uint> z, int zPos)
+        {
+            Debug.Assert(zPos <= (len - 1));
+            ulong c = (ulong)x + z[zPos];
+            z[zPos] = (uint)c;
+            c >>= 32;
+            return c == 0 ? 0 : IncAt(len, z, zPos + 1);
+        }
+#endif
+
         public static uint AddWordTo(int len, uint x, uint[] z)
         {
             ulong c = (ulong)x + z[0];
@@ -220,6 +356,16 @@ namespace Org.BouncyCastle.Math.Raw
             return c == 0 ? 0 : IncAt(len, z, zOff, 1);
         }
 
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static uint AddWordTo(int len, uint x, Span<uint> z)
+        {
+            ulong c = (ulong)x + z[0];
+            z[0] = (uint)c;
+            c >>= 32;
+            return c == 0 ? 0 : IncAt(len, z, 1);
+        }
+#endif
+
         public static uint CAdd(int len, int mask, uint[] x, uint[] y, uint[] z)
         {
             uint MASK = (uint)-(mask & 1);
@@ -257,7 +403,7 @@ namespace Org.BouncyCastle.Math.Raw
             for (int i = 0; i < len; ++i)
             {
                 uint z_i = z[zOff + i], diff = z_i ^ x[xOff + i];
-                z_i ^= (diff & MASK);
+                z_i ^= diff & MASK;
                 z[zOff + i] = z_i;
             }
 
@@ -272,27 +418,29 @@ namespace Org.BouncyCastle.Math.Raw
             //}
         }
 
-        public static void CMov(int len, int mask, int[] x, int xOff, int[] z, int zOff)
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static void CMov(int len, int mask, ReadOnlySpan<uint> x, Span<uint> z)
         {
-            mask = -(mask & 1);
+            uint MASK = (uint)-(mask & 1);
 
             for (int i = 0; i < len; ++i)
             {
-                int z_i = z[zOff + i], diff = z_i ^ x[xOff + i];
-                z_i ^= (diff & mask);
-                z[zOff + i] = z_i;
+                uint z_i = z[i], diff = z_i ^ x[i];
+                z_i ^= diff & MASK;
+                z[i] = z_i;
             }
 
-            //int half = 0x55555555, rest = half << (-mask);
+            //uint half = 0x55555555U, rest = half << (-(int)MASK);
 
             //for (int i = 0; i < len; ++i)
             //{
-            //    int z_i = z[zOff + i], diff = z_i ^ x[xOff + i];
+            //    uint z_i = z[i], diff = z_i ^ x[i];
             //    z_i ^= (diff & half);
             //    z_i ^= (diff & rest);
-            //    z[zOff + i] = z_i;
+            //    z[i] = z_i;
             //}
         }
+#endif
 
         public static int Compare(int len, uint[] x, uint[] y)
         {
@@ -322,10 +470,21 @@ namespace Org.BouncyCastle.Math.Raw
             return 0;
         }
 
-        public static void Copy(int len, uint[] x, uint[] z)
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static int Compare(int len, ReadOnlySpan<uint> x, ReadOnlySpan<uint> y)
         {
-            Array.Copy(x, 0, z, 0, len);
+            for (int i = len - 1; i >= 0; --i)
+            {
+                uint x_i = x[i];
+                uint y_i = y[i];
+                if (x_i < y_i)
+                    return -1;
+                if (x_i > y_i)
+                    return 1;
+            }
+            return 0;
         }
+#endif
 
         public static uint[] Copy(int len, uint[] x)
         {
@@ -334,11 +493,23 @@ namespace Org.BouncyCastle.Math.Raw
             return z;
         }
 
+        public static void Copy(int len, uint[] x, uint[] z)
+        {
+            Array.Copy(x, 0, z, 0, len);
+        }
+
         public static void Copy(int len, uint[] x, int xOff, uint[] z, int zOff)
         {
             Array.Copy(x, xOff, z, zOff, len);
         }
 
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static void Copy(int len, ReadOnlySpan<uint> x, Span<uint> z)
+        {
+            x[..len].CopyTo(z);
+        }
+#endif
+
         public static ulong[] Copy64(int len, ulong[] x)
         {
             ulong[] z = new ulong[len];
@@ -356,6 +527,13 @@ namespace Org.BouncyCastle.Math.Raw
             Array.Copy(x, xOff, z, zOff, len);
         }
 
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static void Copy64(int len, ReadOnlySpan<ulong> x, Span<ulong> z)
+        {
+            x[..len].CopyTo(z);
+        }
+#endif
+
         public static uint[] Create(int len)
         {
             return new uint[len];
@@ -372,7 +550,7 @@ namespace Org.BouncyCastle.Math.Raw
             long c = 0;
             for (int i = 0; i < len; ++i)
             {
-                c += (long)x[i] - (y[i] & MASK);
+                c += x[i] - (y[i] & MASK);
                 z[i] = (uint)c;
                 c >>= 32;
             }
@@ -385,26 +563,73 @@ namespace Org.BouncyCastle.Math.Raw
             long c = 0;
             for (int i = 0; i < len; ++i)
             {
-                c += (long)x[xOff + i] - (y[yOff + i] & MASK);
+                c += x[xOff + i] - (y[yOff + i] & MASK);
                 z[zOff + i] = (uint)c;
                 c >>= 32;
             }
             return (int)c;
         }
 
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static int CSub(int len, int mask, ReadOnlySpan<uint> x, ReadOnlySpan<uint> y, Span<uint> z)
+        {
+            long MASK = (uint)-(mask & 1);
+            long c = 0;
+            for (int i = 0; i < len; ++i)
+            {
+                c += x[i] - (y[i] & MASK);
+                z[i] = (uint)c;
+                c >>= 32;
+            }
+            return (int)c;
+        }
+#endif
+
         public static int Dec(int len, uint[] z)
         {
             for (int i = 0; i < len; ++i)
             {
                 if (--z[i] != uint.MaxValue)
+                    return 0;
+            }
+            return -1;
+        }
+
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static int Dec(int len, Span<uint> z)
+        {
+            for (int i = 0; i < len; ++i)
+            {
+                if (--z[i] != uint.MaxValue)
+                    return 0;
+            }
+            return -1;
+        }
+#endif
+
+        public static int Dec(int len, uint[] x, uint[] z)
+        {
+            int i = 0;
+            while (i < len)
+            {
+                uint c = x[i] - 1;
+                z[i] = c;
+                ++i;
+                if (c != uint.MaxValue)
                 {
+                    while (i < len)
+                    {
+                        z[i] = x[i];
+                        ++i;
+                    }
                     return 0;
                 }
             }
             return -1;
         }
 
-        public static int Dec(int len, uint[] x, uint[] z)
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static int Dec(int len, ReadOnlySpan<uint> x, Span<uint> z)
         {
             int i = 0;
             while (i < len)
@@ -424,6 +649,7 @@ namespace Org.BouncyCastle.Math.Raw
             }
             return -1;
         }
+#endif
 
         public static int DecAt(int len, uint[] z, int zPos)
         {
@@ -431,9 +657,7 @@ namespace Org.BouncyCastle.Math.Raw
             for (int i = zPos; i < len; ++i)
             {
                 if (--z[i] != uint.MaxValue)
-                {
                     return 0;
-                }
             }
             return -1;
         }
@@ -444,25 +668,46 @@ namespace Org.BouncyCastle.Math.Raw
             for (int i = zPos; i < len; ++i)
             {
                 if (--z[zOff + i] != uint.MaxValue)
-                {
                     return 0;
-                }
             }
             return -1;
         }
 
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static int DecAt(int len, Span<uint> z, int zPos)
+        {
+            Debug.Assert(zPos <= len);
+            for (int i = zPos; i < len; ++i)
+            {
+                if (--z[i] != uint.MaxValue)
+                    return 0;
+            }
+            return -1;
+        }
+#endif
+
         public static bool Eq(int len, uint[] x, uint[] y)
         {
             for (int i = len - 1; i >= 0; --i)
             {
                 if (x[i] != y[i])
-                {
                     return false;
-                }
             }
             return true;
         }
 
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static bool Eq(int len, ReadOnlySpan<uint> x, ReadOnlySpan<uint> y)
+        {
+            for (int i = len - 1; i >= 0; --i)
+            {
+                if (x[i] != y[i])
+                    return false;
+            }
+            return true;
+        }
+#endif
+
         public static uint EqualTo(int len, uint[] x, uint y)
         {
             uint d = x[0] ^ y;
@@ -485,6 +730,19 @@ namespace Org.BouncyCastle.Math.Raw
             return (uint)(((int)d - 1) >> 31);
         }
 
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static uint EqualTo(int len, ReadOnlySpan<uint> x, uint y)
+        {
+            uint d = x[0] ^ y;
+            for (int i = 1; i < len; ++i)
+            {
+                d |= x[i];
+            }
+            d = (d >> 1) | (d & 1);
+            return (uint)(((int)d - 1) >> 31);
+        }
+#endif
+
         public static uint EqualTo(int len, uint[] x, uint[] y)
         {
             uint d = 0;
@@ -507,6 +765,19 @@ namespace Org.BouncyCastle.Math.Raw
             return (uint)(((int)d - 1) >> 31);
         }
 
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static uint EqualTo(int len, ReadOnlySpan<uint> x, ReadOnlySpan<uint> y)
+        {
+            uint d = 0;
+            for (int i = 0; i < len; ++i)
+            {
+                d |= x[i] ^ y[i];
+            }
+            d = (d >> 1) | (d & 1);
+            return (uint)(((int)d - 1) >> 31);
+        }
+#endif
+
         public static uint EqualToZero(int len, uint[] x)
         {
             uint d = 0;
@@ -529,15 +800,26 @@ namespace Org.BouncyCastle.Math.Raw
             return (uint)(((int)d - 1) >> 31);
         }
 
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static uint EqualToZero(int len, ReadOnlySpan<uint> x)
+        {
+            uint d = 0;
+            for (int i = 0; i < len; ++i)
+            {
+                d |= x[i];
+            }
+            d = (d >> 1) | (d & 1);
+            return (uint)(((int)d - 1) >> 31);
+        }
+#endif
+
         public static uint[] FromBigInteger(int bits, BigInteger x)
         {
-            if (bits < 1)
-                throw new ArgumentException();
+            int len = GetLengthForBits(bits);
+
             if (x.SignValue < 0 || x.BitLength > bits)
                 throw new ArgumentException();
 
-            int len = (bits + 31) >> 5;
-            Debug.Assert(len > 0);
             uint[] z = Create(len);
 
             // NOTE: Use a fixed number of loop iterations
@@ -550,15 +832,33 @@ namespace Org.BouncyCastle.Math.Raw
             return z;
         }
 
-        public static ulong[] FromBigInteger64(int bits, BigInteger x)
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static void FromBigInteger(int bits, BigInteger x, Span<uint> z)
         {
-            if (bits < 1)
+            int len = GetLengthForBits(bits);
+
+            if (x.SignValue < 0 || x.BitLength > bits)
+                throw new ArgumentException();
+            if (z.Length < len)
                 throw new ArgumentException();
+
+            // NOTE: Use a fixed number of loop iterations
+            z[0] = (uint)x.IntValue;
+            for (int i = 1; i < len; ++i)
+            {
+                x = x.ShiftRight(32);
+                z[i] = (uint)x.IntValue;
+            }
+        }
+#endif
+
+        public static ulong[] FromBigInteger64(int bits, BigInteger x)
+        {
+            int len = GetLengthForBits64(bits);
+
             if (x.SignValue < 0 || x.BitLength > bits)
                 throw new ArgumentException();
 
-            int len = (bits + 63) >> 6;
-            Debug.Assert(len > 0);
             ulong[] z = Create64(len);
 
             // NOTE: Use a fixed number of loop iterations
@@ -571,21 +871,70 @@ namespace Org.BouncyCastle.Math.Raw
             return z;
         }
 
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static void FromBigInteger64(int bits, BigInteger x, Span<ulong> z)
+        {
+            int len = GetLengthForBits64(bits);
+
+            if (x.SignValue < 0 || x.BitLength > bits)
+                throw new ArgumentException();
+            if (z.Length < len)
+                throw new ArgumentException();
+
+            // NOTE: Use a fixed number of loop iterations
+            z[0] = (ulong)x.LongValue;
+            for (int i = 1; i < len; ++i)
+            {
+                x = x.ShiftRight(64);
+                z[i] = (ulong)x.LongValue;
+            }
+        }
+#endif
+
         public static uint GetBit(uint[] x, int bit)
         {
             if (bit == 0)
-            {
                 return x[0] & 1;
-            }
+
             int w = bit >> 5;
             if (w < 0 || w >= x.Length)
-            {
                 return 0;
-            }
+
             int b = bit & 31;
             return (x[w] >> b) & 1;
         }
 
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static uint GetBit(ReadOnlySpan<uint> x, int bit)
+        {
+            if (bit == 0)
+                return x[0] & 1;
+
+            int w = bit >> 5;
+            if (w < 0 || w >= x.Length)
+                return 0;
+
+            int b = bit & 31;
+            return (x[w] >> b) & 1;
+        }
+#endif
+
+        public static int GetLengthForBits(int bits)
+        {
+            if (bits < 1)
+                throw new ArgumentException();
+
+            return (int)(((uint)bits + 31) >> 5);
+        }
+
+        public static int GetLengthForBits64(int bits)
+        {
+            if (bits < 1)
+                throw new ArgumentException();
+
+            return (int)(((uint)bits + 63) >> 6);
+        }
+
         public static bool Gte(int len, uint[] x, uint[] y)
         {
             for (int i = len - 1; i >= 0; --i)
@@ -619,14 +968,46 @@ namespace Org.BouncyCastle.Math.Raw
             for (int i = 0; i < len; ++i)
             {
                 if (++z[i] != uint.MinValue)
+                    return 0;
+            }
+            return 1;
+        }
+
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static uint Inc(int len, Span<uint> z)
+        {
+            for (int i = 0; i < len; ++i)
+            {
+                if (++z[i] != uint.MinValue)
+                    return 0;
+            }
+            return 1;
+        }
+#endif
+
+        public static uint Inc(int len, uint[] x, uint[] z)
+        {
+            int i = 0;
+            while (i < len)
+            {
+                uint c = x[i] + 1;
+                z[i] = c;
+                ++i;
+                if (c != 0)
                 {
+                    while (i < len)
+                    {
+                        z[i] = x[i];
+                        ++i;
+                    }
                     return 0;
                 }
             }
             return 1;
         }
 
-        public static uint Inc(int len, uint[] x, uint[] z)
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static uint Inc(int len, ReadOnlySpan<uint> x, Span<uint> z)
         {
             int i = 0;
             while (i < len)
@@ -646,6 +1027,7 @@ namespace Org.BouncyCastle.Math.Raw
             }
             return 1;
         }
+#endif
 
         public static uint IncAt(int len, uint[] z, int zPos)
         {
@@ -653,9 +1035,7 @@ namespace Org.BouncyCastle.Math.Raw
             for (int i = zPos; i < len; ++i)
             {
                 if (++z[i] != uint.MinValue)
-                {
                     return 0;
-                }
             }
             return 1;
         }
@@ -666,44 +1046,79 @@ namespace Org.BouncyCastle.Math.Raw
             for (int i = zPos; i < len; ++i)
             {
                 if (++z[zOff + i] != uint.MinValue)
-                {
                     return 0;
-                }
             }
             return 1;
         }
 
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static uint IncAt(int len, Span<uint> z, int zPos)
+        {
+            Debug.Assert(zPos <= len);
+            for (int i = zPos; i < len; ++i)
+            {
+                if (++z[i] != uint.MinValue)
+                    return 0;
+            }
+            return 1;
+        }
+#endif
+
         public static bool IsOne(int len, uint[] x)
         {
             if (x[0] != 1)
-            {
                 return false;
+
+            for (int i = 1; i < len; ++i)
+            {
+                if (x[i] != 0)
+                    return false;
             }
+            return true;
+        }
+
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static bool IsOne(int len, ReadOnlySpan<uint> x)
+        {
+            if (x[0] != 1)
+                return false;
+
             for (int i = 1; i < len; ++i)
             {
                 if (x[i] != 0)
-                {
                     return false;
-                }
             }
             return true;
         }
+#endif
 
         public static bool IsZero(int len, uint[] x)
         {
             if (x[0] != 0)
-            {
                 return false;
+
+            for (int i = 1; i < len; ++i)
+            {
+                if (x[i] != 0)
+                    return false;
             }
+            return true;
+        }
+
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static bool IsZero(int len, ReadOnlySpan<uint> x)
+        {
+            if (x[0] != 0)
+                return false;
+
             for (int i = 1; i < len; ++i)
             {
                 if (x[i] != 0)
-                {
                     return false;
-                }
             }
             return true;
         }
+#endif
 
         public static int LessThan(int len, uint[] x, uint[] y)
         {
@@ -763,6 +1178,18 @@ namespace Org.BouncyCastle.Math.Raw
             }
         }
 
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static void Mul(int len, ReadOnlySpan<uint> x, ReadOnlySpan<uint> y, Span<uint> zz)
+        {
+            zz[len] = MulWord(len, x[0], y, zz);
+
+            for (int i = 1; i < len; ++i)
+            {
+                zz[i + len] = MulWordAddTo(len, x[i], y, zz[i..]);
+            }
+        }
+#endif
+
         public static void Mul(uint[] x, int xOff, int xLen, uint[] y, int yOff, int yLen, uint[] zz, int zzOff)
         {
             zz[zzOff + yLen] = MulWord(yLen, x[xOff], y, yOff, zz, zzOff);
@@ -773,6 +1200,19 @@ namespace Org.BouncyCastle.Math.Raw
             }
         }
 
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static void Mul(ReadOnlySpan<uint> x, ReadOnlySpan<uint> y, Span<uint> zz)
+        {
+            int xLen = x.Length, yLen = y.Length;
+            zz[yLen] = MulWord(yLen, x[0], y, zz);
+
+            for (int i = 1; i < xLen; ++i)
+            {
+                zz[i + yLen] = MulWordAddTo(yLen, x[i], y, zz[i..]);
+            }
+        }
+#endif
+
         public static uint MulAddTo(int len, uint[] x, uint[] y, uint[] zz)
         {
             ulong zc = 0;
@@ -800,9 +1240,24 @@ namespace Org.BouncyCastle.Math.Raw
             return (uint)zc;
         }
 
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static uint MulAddTo(int len, ReadOnlySpan<uint> x, ReadOnlySpan<uint> y, Span<uint> zz)
+        {
+            ulong zc = 0;
+            for (int i = 0; i < len; ++i)
+            {
+                zc += MulWordAddTo(len, x[i], y, zz[i..]) & M;
+                zc += zz[i + len] & M;
+                zz[i + len] = (uint)zc;
+                zc >>= 32;
+            }
+            return (uint)zc;
+        }
+#endif
+
         public static uint Mul31BothAdd(int len, uint a, uint[] x, uint b, uint[] y, uint[] z, int zOff)
         {
-            ulong c = 0, aVal = (ulong)a, bVal = (ulong)b;
+            ulong c = 0, aVal = a, bVal = b;
             int i = 0;
             do
             {
@@ -814,9 +1269,26 @@ namespace Org.BouncyCastle.Math.Raw
             return (uint)c;
         }
 
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static uint Mul31BothAdd(int len, uint a, ReadOnlySpan<uint> x, uint b, ReadOnlySpan<uint> y,
+            Span<uint> z)
+        {
+            ulong c = 0, aVal = a, bVal = b;
+            int i = 0;
+            do
+            {
+                c += aVal * x[i] + bVal * y[i] + z[i];
+                z[i] = (uint)c;
+                c >>= 32;
+            }
+            while (++i < len);
+            return (uint)c;
+        }
+#endif
+
         public static uint MulWord(int len, uint x, uint[] y, uint[] z)
         {
-            ulong c = 0, xVal = (ulong)x;
+            ulong c = 0, xVal = x;
             int i = 0;
             do
             {
@@ -830,7 +1302,7 @@ namespace Org.BouncyCastle.Math.Raw
 
         public static uint MulWord(int len, uint x, uint[] y, int yOff, uint[] z, int zOff)
         {
-            ulong c = 0, xVal = (ulong)x;
+            ulong c = 0, xVal = x;
             int i = 0;
             do
             {
@@ -842,9 +1314,25 @@ namespace Org.BouncyCastle.Math.Raw
             return (uint)c;
         }
 
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static uint MulWord(int len, uint x, ReadOnlySpan<uint> y, Span<uint> z)
+        {
+            ulong c = 0, xVal = x;
+            int i = 0;
+            do
+            {
+                c += xVal * y[i];
+                z[i] = (uint)c;
+                c >>= 32;
+            }
+            while (++i < len);
+            return (uint)c;
+        }
+#endif
+
         public static uint MulWordAddTo(int len, uint x, uint[] y, int yOff, uint[] z, int zOff)
         {
-            ulong c = 0, xVal = (ulong)x;
+            ulong c = 0, xVal = x;
             int i = 0;
             do
             {
@@ -856,22 +1344,56 @@ namespace Org.BouncyCastle.Math.Raw
             return (uint)c;
         }
 
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static uint MulWordAddTo(int len, uint x, ReadOnlySpan<uint> y, Span<uint> z)
+        {
+            ulong c = 0, xVal = x;
+            int i = 0;
+            do
+            {
+                c += xVal * y[i] + z[i];
+                z[i] = (uint)c;
+                c >>= 32;
+            }
+            while (++i < len);
+            return (uint)c;
+        }
+#endif
+
         public static uint MulWordDwordAddAt(int len, uint x, ulong y, uint[] z, int zPos)
         {
             Debug.Assert(zPos <= (len - 3));
-            ulong c = 0, xVal = (ulong)x;
+            ulong c = 0, xVal = x;
             c += xVal * (uint)y + z[zPos + 0];
             z[zPos + 0] = (uint)c;
             c >>= 32;
             c += xVal * (y >> 32) + z[zPos + 1];
             z[zPos + 1] = (uint)c;
             c >>= 32;
-            c += (ulong)z[zPos + 2];
+            c += z[zPos + 2];
             z[zPos + 2] = (uint)c;
             c >>= 32;
             return c == 0 ? 0 : IncAt(len, z, zPos + 3);
         }
 
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static uint MulWordDwordAddAt(int len, uint x, ulong y, Span<uint> z, int zPos)
+        {
+            Debug.Assert(zPos <= (len - 3));
+            ulong c = 0, xVal = x;
+            c += xVal * (uint)y + z[zPos + 0];
+            z[zPos + 0] = (uint)c;
+            c >>= 32;
+            c += xVal * (y >> 32) + z[zPos + 1];
+            z[zPos + 1] = (uint)c;
+            c >>= 32;
+            c += z[zPos + 2];
+            z[zPos + 2] = (uint)c;
+            c >>= 32;
+            return c == 0 ? 0 : IncAt(len, z, zPos + 3);
+        }
+#endif
+
         public static uint ShiftDownBit(int len, uint[] z, uint c)
         {
             int i = len;
@@ -884,31 +1406,31 @@ namespace Org.BouncyCastle.Math.Raw
             return c << 31;
         }
 
-#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
-        public static uint ShiftDownBit(int len, Span<uint> z, uint c)
+        public static uint ShiftDownBit(int len, uint[] z, int zOff, uint c)
         {
             int i = len;
             while (--i >= 0)
             {
-                uint next = z[i];
-                z[i] = (next >> 1) | (c << 31);
+                uint next = z[zOff + i];
+                z[zOff + i] = (next >> 1) | (c << 31);
                 c = next;
             }
             return c << 31;
         }
-#endif
 
-        public static uint ShiftDownBit(int len, uint[] z, int zOff, uint c)
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static uint ShiftDownBit(int len, Span<uint> z, uint c)
         {
             int i = len;
             while (--i >= 0)
             {
-                uint next = z[zOff + i];
-                z[zOff + i] = (next >> 1) | (c << 31);
+                uint next = z[i];
+                z[i] = (next >> 1) | (c << 31);
                 c = next;
             }
             return c << 31;
         }
+#endif
 
         public static uint ShiftDownBit(int len, uint[] x, uint c, uint[] z)
         {
@@ -934,6 +1456,20 @@ namespace Org.BouncyCastle.Math.Raw
             return c << 31;
         }
 
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static uint ShiftDownBit(int len, ReadOnlySpan<uint> x, uint c, Span<uint> z)
+        {
+            int i = len;
+            while (--i >= 0)
+            {
+                uint next = x[i];
+                z[i] = (next >> 1) | (c << 31);
+                c = next;
+            }
+            return c << 31;
+        }
+#endif
+
         public static uint ShiftDownBits(int len, uint[] z, int bits, uint c)
         {
             Debug.Assert(bits > 0 && bits < 32);
@@ -960,6 +1496,21 @@ namespace Org.BouncyCastle.Math.Raw
             return c << -bits;
         }
 
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static uint ShiftDownBits(int len, Span<uint> z, int bits, uint c)
+        {
+            Debug.Assert(bits > 0 && bits < 32);
+            int i = len;
+            while (--i >= 0)
+            {
+                uint next = z[i];
+                z[i] = (next >> bits) | (c << -bits);
+                c = next;
+            }
+            return c << -bits;
+        }
+#endif
+
         public static uint ShiftDownBits(int len, uint[] x, int bits, uint c, uint[] z)
         {
             Debug.Assert(bits > 0 && bits < 32);
@@ -986,6 +1537,21 @@ namespace Org.BouncyCastle.Math.Raw
             return c << -bits;
         }
 
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static uint ShiftDownBits(int len, ReadOnlySpan<uint> x, int bits, uint c, Span<uint> z)
+        {
+            Debug.Assert(bits > 0 && bits < 32);
+            int i = len;
+            while (--i >= 0)
+            {
+                uint next = x[i];
+                z[i] = (next >> bits) | (c << -bits);
+                c = next;
+            }
+            return c << -bits;
+        }
+#endif
+
         public static uint ShiftDownWord(int len, uint[] z, uint c)
         {
             int i = len;
@@ -998,6 +1564,20 @@ namespace Org.BouncyCastle.Math.Raw
             return c;
         }
 
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static uint ShiftDownWord(int len, Span<uint> z, uint c)
+        {
+            int i = len;
+            while (--i >= 0)
+            {
+                uint next = z[i];
+                z[i] = c;
+                c = next;
+            }
+            return c;
+        }
+#endif
+
         public static uint ShiftUpBit(int len, uint[] z, uint c)
         {
             for (int i = 0; i < len; ++i)
@@ -1020,6 +1600,19 @@ namespace Org.BouncyCastle.Math.Raw
             return c >> 31;
         }
 
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static uint ShiftUpBit(int len, Span<uint> z, uint c)
+        {
+            for (int i = 0; i < len; ++i)
+            {
+                uint next = z[i];
+                z[i] = (next << 1) | (c >> 31);
+                c = next;
+            }
+            return c >> 31;
+        }
+#endif
+
         public static uint ShiftUpBit(int len, uint[] x, uint c, uint[] z)
         {
             for (int i = 0; i < len; ++i)
@@ -1042,6 +1635,30 @@ namespace Org.BouncyCastle.Math.Raw
             return c >> 31;
         }
 
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static uint ShiftUpBit(int len, ReadOnlySpan<uint> x, uint c, Span<uint> z)
+        {
+            for (int i = 0; i < len; ++i)
+            {
+                uint next = x[i];
+                z[i] = (next << 1) | (c >> 31);
+                c = next;
+            }
+            return c >> 31;
+        }
+#endif
+
+        public static ulong ShiftUpBit64(int len, ulong[] x, ulong c, ulong[] z)
+        {
+            for (int i = 0; i < len; ++i)
+            {
+                ulong next = x[i];
+                z[i] = (next << 1) | (c >> 63);
+                c = next;
+            }
+            return c >> 63;
+        }
+
         public static ulong ShiftUpBit64(int len, ulong[] x, int xOff, ulong c, ulong[] z, int zOff)
         {
             for (int i = 0; i < len; ++i)
@@ -1053,6 +1670,19 @@ namespace Org.BouncyCastle.Math.Raw
             return c >> 63;
         }
 
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static ulong ShiftUpBit64(int len, ReadOnlySpan<ulong> x, ulong c, Span<ulong> z)
+        {
+            for (int i = 0; i < len; ++i)
+            {
+                ulong next = x[i];
+                z[i] = (next << 1) | (c >> 63);
+                c = next;
+            }
+            return c >> 63;
+        }
+#endif
+
         public static uint ShiftUpBits(int len, uint[] z, int bits, uint c)
         {
             Debug.Assert(bits > 0 && bits < 32);
@@ -1077,17 +1707,19 @@ namespace Org.BouncyCastle.Math.Raw
             return c >> -bits;
         }
 
-        public static ulong ShiftUpBits64(int len, ulong[] z, int zOff, int bits, ulong c)
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static uint ShiftUpBits(int len, Span<uint> z, int bits, uint c)
         {
-            Debug.Assert(bits > 0 && bits < 64);
+            Debug.Assert(bits > 0 && bits < 32);
             for (int i = 0; i < len; ++i)
             {
-                ulong next = z[zOff + i];
-                z[zOff + i] = (next << bits) | (c >> -bits);
+                uint next = z[i];
+                z[i] = (next << bits) | (c >> -bits);
                 c = next;
             }
             return c >> -bits;
         }
+#endif
 
         public static uint ShiftUpBits(int len, uint[] x, int bits, uint c, uint[] z)
         {
@@ -1113,6 +1745,70 @@ namespace Org.BouncyCastle.Math.Raw
             return c >> -bits;
         }
 
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static uint ShiftUpBits(int len, ReadOnlySpan<uint> x, int bits, uint c, Span<uint> z)
+        {
+            Debug.Assert(bits > 0 && bits < 32);
+            for (int i = 0; i < len; ++i)
+            {
+                uint next = x[i];
+                z[i] = (next << bits) | (c >> -bits);
+                c = next;
+            }
+            return c >> -bits;
+        }
+#endif
+
+        public static ulong ShiftUpBits64(int len, ulong[] z, int bits, ulong c)
+        {
+            Debug.Assert(bits > 0 && bits < 64);
+            for (int i = 0; i < len; ++i)
+            {
+                ulong next = z[i];
+                z[i] = (next << bits) | (c >> -bits);
+                c = next;
+            }
+            return c >> -bits;
+        }
+
+        public static ulong ShiftUpBits64(int len, ulong[] z, int zOff, int bits, ulong c)
+        {
+            Debug.Assert(bits > 0 && bits < 64);
+            for (int i = 0; i < len; ++i)
+            {
+                ulong next = z[zOff + i];
+                z[zOff + i] = (next << bits) | (c >> -bits);
+                c = next;
+            }
+            return c >> -bits;
+        }
+
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static ulong ShiftUpBits64(int len, Span<ulong> z, int bits, ulong c)
+        {
+            Debug.Assert(bits > 0 && bits < 64);
+            for (int i = 0; i < len; ++i)
+            {
+                ulong next = z[i];
+                z[i] = (next << bits) | (c >> -bits);
+                c = next;
+            }
+            return c >> -bits;
+        }
+#endif
+
+        public static ulong ShiftUpBits64(int len, ulong[] x, int bits, ulong c, ulong[] z)
+        {
+            Debug.Assert(bits > 0 && bits < 64);
+            for (int i = 0; i < len; ++i)
+            {
+                ulong next = x[i];
+                z[i] = (next << bits) | (c >> -bits);
+                c = next;
+            }
+            return c >> -bits;
+        }
+
         public static ulong ShiftUpBits64(int len, ulong[] x, int xOff, int bits, ulong c, ulong[] z, int zOff)
         {
             Debug.Assert(bits > 0 && bits < 64);
@@ -1125,6 +1821,20 @@ namespace Org.BouncyCastle.Math.Raw
             return c >> -bits;
         }
 
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static ulong ShiftUpBits64(int len, ReadOnlySpan<ulong> x, int bits, ulong c, Span<ulong> z)
+        {
+            Debug.Assert(bits > 0 && bits < 64);
+            for (int i = 0; i < len; ++i)
+            {
+                ulong next = x[i];
+                z[i] = (next << bits) | (c >> -bits);
+                c = next;
+            }
+            return c >> -bits;
+        }
+#endif
+
         public static void Square(int len, uint[] x, uint[] zz)
         {
             int extLen = len << 1;
@@ -1187,6 +1897,39 @@ namespace Org.BouncyCastle.Math.Raw
             ShiftUpBit(extLen, zz, zzOff, x[xOff] << 31);
         }
 
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static void Square(int len, ReadOnlySpan<uint> x, Span<uint> zz)
+        {
+            int extLen = len << 1;
+            uint c = 0;
+            int j = len, k = extLen;
+            do
+            {
+                ulong xVal = (ulong)x[--j];
+                ulong p = xVal * xVal;
+                zz[--k] = (c << 31) | (uint)(p >> 33);
+                zz[--k] = (uint)(p >> 1);
+                c = (uint)p;
+            }
+            while (j > 0);
+
+            ulong d = 0UL;
+            int zzPos = 2;
+
+            for (int i = 1; i < len; ++i)
+            {
+                d += SquareWordAddTo(x, i, zz);
+                d += zz[zzPos];
+                zz[zzPos++] = (uint)d; d >>= 32;
+                d += zz[zzPos];
+                zz[zzPos++] = (uint)d; d >>= 32;
+            }
+            Debug.Assert(0UL == d);
+
+            ShiftUpBit(extLen, zz, x[0] << 31);
+        }
+#endif
+
         public static uint SquareWordAddTo(uint[] x, int xPos, uint[] z)
         {
             ulong c = 0, xVal = (ulong)x[xPos];
@@ -1216,6 +1959,22 @@ namespace Org.BouncyCastle.Math.Raw
             return (uint)c;
         }
 
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static uint SquareWordAddTo(ReadOnlySpan<uint> x, int xPos, Span<uint> z)
+        {
+            ulong c = 0, xVal = x[xPos];
+            int i = 0;
+            do
+            {
+                c += xVal * x[i] + z[xPos + i];
+                z[xPos + i] = (uint)c;
+                c >>= 32;
+            }
+            while (++i < xPos);
+            return (uint)c;
+        }
+#endif
+
         public static int Sub(int len, uint[] x, uint[] y, uint[] z)
         {
             long c = 0;
@@ -1239,6 +1998,21 @@ namespace Org.BouncyCastle.Math.Raw
             }
             return (int)c;
         }
+
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static int Sub(int len, ReadOnlySpan<uint> x, ReadOnlySpan<uint> y, Span<uint> z)
+        {
+            long c = 0;
+            for (int i = 0; i < len; ++i)
+            {
+                c += (long)x[i] - y[i];
+                z[i] = (uint)c;
+                c >>= 32;
+            }
+            return (int)c;
+        }
+#endif
+
         public static int Sub33At(int len, uint x, uint[] z, int zPos)
         {
             Debug.Assert(zPos <= (len - 2));
@@ -1263,6 +2037,20 @@ namespace Org.BouncyCastle.Math.Raw
             return c == 0 ? 0 : DecAt(len, z, zOff, zPos + 2);
         }
 
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static int Sub33At(int len, uint x, Span<uint> z, int zPos)
+        {
+            Debug.Assert(zPos <= (len - 2));
+            long c = (long)z[zPos + 0] - x;
+            z[zPos + 0] = (uint)c;
+            c >>= 32;
+            c += (long)z[zPos + 1] - 1;
+            z[zPos + 1] = (uint)c;
+            c >>= 32;
+            return c == 0 ? 0 : DecAt(len, z, zPos + 2);
+        }
+#endif
+
         public static int Sub33From(int len, uint x, uint[] z)
         {
             long c = (long)z[0] - x;
@@ -1285,6 +2073,19 @@ namespace Org.BouncyCastle.Math.Raw
             return c == 0 ? 0 : DecAt(len, z, zOff, 2);
         }
 
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static int Sub33From(int len, uint x, Span<uint> z)
+        {
+            long c = (long)z[0] - x;
+            z[0] = (uint)c;
+            c >>= 32;
+            c += (long)z[1] - 1;
+            z[1] = (uint)c;
+            c >>= 32;
+            return c == 0 ? 0 : DecAt(len, z, 2);
+        }
+#endif
+
         public static int SubBothFrom(int len, uint[] x, uint[] y, uint[] z)
         {
             long c = 0;
@@ -1309,13 +2110,27 @@ namespace Org.BouncyCastle.Math.Raw
             return (int)c;
         }
 
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static int SubBothFrom(int len, ReadOnlySpan<uint> x, ReadOnlySpan<uint> y, Span<uint> z)
+        {
+            long c = 0;
+            for (int i = 0; i < len; ++i)
+            {
+                c += (long)z[i] - x[i] - y[i];
+                z[i] = (uint)c;
+                c >>= 32;
+            }
+            return (int)c;
+        }
+#endif
+
         public static int SubDWordAt(int len, ulong x, uint[] z, int zPos)
         {
             Debug.Assert(zPos <= (len - 2));
-            long c = (long)z[zPos + 0] - (long)(x & M);
+            long c = z[zPos + 0] - (long)(x & M);
             z[zPos + 0] = (uint)c;
             c >>= 32;
-            c += (long)z[zPos + 1] - (long)(x >> 32);
+            c += z[zPos + 1] - (long)(x >> 32);
             z[zPos + 1] = (uint)c;
             c >>= 32;
             return c == 0 ? 0 : DecAt(len, z, zPos + 2);
@@ -1324,21 +2139,35 @@ namespace Org.BouncyCastle.Math.Raw
         public static int SubDWordAt(int len, ulong x, uint[] z, int zOff, int zPos)
         {
             Debug.Assert(zPos <= (len - 2));
-            long c = (long)z[zOff + zPos] - (long)(x & M);
+            long c = z[zOff + zPos] - (long)(x & M);
             z[zOff + zPos] = (uint)c;
             c >>= 32;
-            c += (long)z[zOff + zPos + 1] - (long)(x >> 32);
+            c += z[zOff + zPos + 1] - (long)(x >> 32);
             z[zOff + zPos + 1] = (uint)c;
             c >>= 32;
-            return c == 0 ? 0 : DecAt(len, z,  zOff, zPos + 2);
+            return c == 0 ? 0 : DecAt(len, z, zOff, zPos + 2);
+        }
+
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static int SubDWordAt(int len, ulong x, Span<uint> z, int zPos)
+        {
+            Debug.Assert(zPos <= (len - 2));
+            long c = z[zPos + 0] - (long)(x & M);
+            z[zPos + 0] = (uint)c;
+            c >>= 32;
+            c += z[zPos + 1] - (long)(x >> 32);
+            z[zPos + 1] = (uint)c;
+            c >>= 32;
+            return c == 0 ? 0 : DecAt(len, z, zPos + 2);
         }
+#endif
 
         public static int SubDWordFrom(int len, ulong x, uint[] z)
         {
-            long c = (long)z[0] - (long)(x & M);
+            long c = z[0] - (long)(x & M);
             z[0] = (uint)c;
             c >>= 32;
-            c += (long)z[1] - (long)(x >> 32);
+            c += z[1] - (long)(x >> 32);
             z[1] = (uint)c;
             c >>= 32;
             return c == 0 ? 0 : DecAt(len, z, 2);
@@ -1346,15 +2175,28 @@ namespace Org.BouncyCastle.Math.Raw
 
         public static int SubDWordFrom(int len, ulong x, uint[] z, int zOff)
         {
-            long c = (long)z[zOff + 0] - (long)(x & M);
+            long c = z[zOff + 0] - (long)(x & M);
             z[zOff + 0] = (uint)c;
             c >>= 32;
-            c += (long)z[zOff + 1] - (long)(x >> 32);
+            c += z[zOff + 1] - (long)(x >> 32);
             z[zOff + 1] = (uint)c;
             c >>= 32;
             return c == 0 ? 0 : DecAt(len, z, zOff, 2);
         }
 
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static int SubDWordFrom(int len, ulong x, Span<uint> z)
+        {
+            long c = z[0] - (long)(x & M);
+            z[0] = (uint)c;
+            c >>= 32;
+            c += z[1] - (long)(x >> 32);
+            z[1] = (uint)c;
+            c >>= 32;
+            return c == 0 ? 0 : DecAt(len, z, 2);
+        }
+#endif
+
         public static int SubFrom(int len, uint[] x, uint[] z)
         {
             long c = 0;
@@ -1379,6 +2221,20 @@ namespace Org.BouncyCastle.Math.Raw
             return (int)c;
         }
 
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static int SubFrom(int len, ReadOnlySpan<uint> x, Span<uint> z)
+        {
+            long c = 0;
+            for (int i = 0; i < len; ++i)
+            {
+                c += (long)z[i] - x[i];
+                z[i] = (uint)c;
+                c >>= 32;
+            }
+            return (int)c;
+        }
+#endif
+
         public static int SubWordAt(int len, uint x, uint[] z, int zPos)
         {
             Debug.Assert(zPos <= (len - 1));
@@ -1397,6 +2253,17 @@ namespace Org.BouncyCastle.Math.Raw
             return c == 0 ? 0 : DecAt(len, z, zOff, zPos + 1);
         }
 
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static int SubWordAt(int len, uint x, Span<uint> z, int zPos)
+        {
+            Debug.Assert(zPos <= (len - 1));
+            long c = (long)z[zPos] - x;
+            z[zPos] = (uint)c;
+            c >>= 32;
+            return c == 0 ? 0 : DecAt(len, z, zPos + 1);
+        }
+#endif
+
         public static int SubWordFrom(int len, uint x, uint[] z)
         {
             long c = (long)z[0] - x;
@@ -1413,28 +2280,69 @@ namespace Org.BouncyCastle.Math.Raw
             return c == 0 ? 0 : DecAt(len, z, zOff, 1);
         }
 
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static int SubWordFrom(int len, uint x, Span<uint> z)
+        {
+            long c = (long)z[0] - x;
+            z[0] = (uint)c;
+            c >>= 32;
+            return c == 0 ? 0 : DecAt(len, z, 1);
+        }
+#endif
+
         public static BigInteger ToBigInteger(int len, uint[] x)
         {
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+            return ToBigInteger(len, x.AsSpan());
+#else
             byte[] bs = new byte[len << 2];
-            for (int i = 0; i < len; ++i)
+            int xPos = len, bsPos = 0;
+            while (--xPos >= 0)
             {
-                uint x_i = x[i];
-                if (x_i != 0)
-                {
-                    Pack.UInt32_To_BE(x_i, bs, (len - 1 - i) << 2);
-                }
+                Pack.UInt32_To_BE(x[xPos], bs, bsPos);
+                bsPos += 4;
+            }
+            return new BigInteger(1, bs);
+#endif
+        }
+
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static BigInteger ToBigInteger(int len, ReadOnlySpan<uint> x)
+        {
+            int bsLen = len << 2;
+            Span<byte> bs = bsLen <= 512
+                ? stackalloc byte[bsLen]
+                : new byte[bsLen];
+
+            int xPos = len;
+            Span<byte> t = bs;
+            while (--xPos >= 0)
+            {
+                Pack.UInt32_To_BE(x[xPos], t);
+                t = t[4..];
             }
             return new BigInteger(1, bs);
         }
+#endif
 
         public static void Zero(int len, uint[] z)
         {
             for (int i = 0; i < len; ++i)
             {
-                z[i] = 0;
+                z[i] = 0U;
             }
         }
 
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static void Zero(int len, Span<uint> z)
+        {
+            for (int i = 0; i < len; ++i)
+            {
+                z[i] = 0U;
+            }
+        }
+#endif
+
         public static void Zero64(int len, ulong[] z)
         {
             for (int i = 0; i < len; ++i)
@@ -1442,5 +2350,15 @@ namespace Org.BouncyCastle.Math.Raw
                 z[i] = 0UL;
             }
         }
+
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public static void Zero64(int len, Span<ulong> z)
+        {
+            for (int i = 0; i < len; ++i)
+            {
+                z[i] = 0UL;
+            }
+        }
+#endif
     }
 }