Related to #3508 (comment) (#3516)

Co-authored-by: Jimmy <[email protected]>

src/Neo.Cryptography.BLS12_381/ConstantTimeUtility.cs

@@ -11,23 +11,18 @@
 
 using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
+using System.Security.Cryptography;
 
 namespace Neo.Cryptography.BLS12_381;
 
 public static class ConstantTimeUtility
 {
     public static bool ConstantTimeEq<T>(in T a, in T b) where T : unmanaged
     {
-        ReadOnlySpan<byte> a_bytes = MemoryMarshal.AsBytes(MemoryMarshal.CreateReadOnlySpan(ref Unsafe.AsRef(in a), 1));
-        ReadOnlySpan<byte> b_bytes = MemoryMarshal.AsBytes(MemoryMarshal.CreateReadOnlySpan(ref Unsafe.AsRef(in b), 1));
-        ReadOnlySpan<ulong> a_u64 = MemoryMarshal.Cast<byte, ulong>(a_bytes);
-        ReadOnlySpan<ulong> b_u64 = MemoryMarshal.Cast<byte, ulong>(b_bytes);
-        ulong f = 0;
-        for (int i = 0; i < a_u64.Length; i++)
-            f |= a_u64[i] ^ b_u64[i];
-        for (int i = a_u64.Length * sizeof(ulong); i < a_bytes.Length; i++)
-            f |= (ulong)a_bytes[i] ^ b_bytes[i];
-        return f == 0;
+        var a_bytes = MemoryMarshal.AsBytes(MemoryMarshal.CreateReadOnlySpan(ref Unsafe.AsRef(in a), 1));
+        var b_bytes = MemoryMarshal.AsBytes(MemoryMarshal.CreateReadOnlySpan(ref Unsafe.AsRef(in b), 1));
+
+        return CryptographicOperations.FixedTimeEquals(a_bytes, b_bytes);
     }
 
     public static T ConditionalSelect<T>(in T a, in T b, bool choice) where T : unmanaged