How can I pass TraditionalDecrypter to rubyzip file from buffer

Question

I'm trying to expand zip file included in raw mail message. My code is like

Zip::File.open_buffer(attachment.data) do |zip|
  zip.each do |entry|
    # bellow works file
    puts entry.name 

    # bellow cause Zlib::DataError: invalid block type
    # because zip file is encrypted by password I guess 
    puts entry.get_input_stream.read 
  end
end

How can I pass Zip::TraditionalDecrypter to Decompressor?