<PackageReference Include="BouncyCastle.Cryptography" Version="2.6.1" />

Org.BouncyCastle.Utilities.Encoders.UrlBase64

public class UrlBase64
namespace Org.BouncyCastle.Utilities.Encoders { public class UrlBase64 { public static byte[] Encode(byte[] data); public static int Encode(byte[] data, Stream outStr); public static byte[] Decode(byte[] data); public static int Decode(byte[] data, Stream outStr); public static byte[] Decode(string data); public static int Decode(string data, Stream outStr); public UrlBase64(); } }