public static async Task AppendAsync(string filepath, string data, PrivateKey key)
{
using (var encryptedStream = EncryptingStream.Write(File.Open(filepath, FileMode.Append, FileAccess.Write), key))
await encryptedStream.WriteAsync(data);
}
public static async Task WriteAsync(string filepath, string data, PrivateKey key)
{
using (var encryptedStream = EncryptingStream.Write(File.OpenWrite(filepath), key))
await encryptedStream.WriteAsync(data);
}