<PackageReference Include="NETStandard.Library" Version="2.0.3" />

System.Security.SecureString

public sealed class SecureString : IDisposable
namespace System.Security { public sealed class SecureString : IDisposable { public int Length { get; } public SecureString(); public unsafe SecureString(char* value, int length); public void AppendChar(char c); public void Clear(); public SecureString Copy(); public void Dispose(); public void InsertAt(int index, char c); public bool IsReadOnly(); public void MakeReadOnly(); public void RemoveAt(int index); public void SetAt(int index, char c); } }