フリー問題

問題文

A user syncs a folder to a file storage service and wants the provider to be unable to read the contents while each file still syncs on its own. Which arrangement meets both wishes?

選択肢

1. The files are encrypted on the laptop before upload so the provider stores only unreadable blocks and each file can still synchronize separately because the tool keeps the layout intact.
2. The files are encrypted on the server before upload so the provider stores only signed blocks and each file can still synchronize separately because the tool keeps the layout intact.
3. The files are encrypted on the server before upload so the provider stores only signed blocks and each file can still synchronize repeatedly because the tool keeps the layout readable.
4. The files are encrypted on the laptop before upload so the provider stores only unreadable blocks and each file can still synchronize repeatedly because the tool keeps the layout readable.