Encrypting it with a random key that doesn't get sent to the server, but is in the URI that the user sends to the receiver means that only the sender and receiv

Encrypting it with a random key that doesn't get sent to the server, but is in the URI that the user sends to the receiver means that only the sender and receiver know what the file actually contains. Means neither you nor law enforcement can know what you are storing unless the URI is captured.