What I’m Using for Privacy: Cloud

in privacy, security, Tools
January 9th, 2017

This post is part of a series on technologies that I’m currently using for privacy, and my reasons for them. You can see the entire list in the first post

tl;dr: I don’t trust anyone with my data except myself, and neither should you.

If you aren’t paying for it, you are the product

I think that trust is the single most important commodity on the internet, and the one that is least thought about. In the past four or five years the number of online file storage services (collectively ‘the cloud’) went from zero to more than I can name. All of them have the same business model: “Trust us with your data.”

But that’s not the pitch, which is, “Wouldn’t you like to have access to your files from any device?”

A large majority of my students use Google Docs for cloud storage. It’s free, easy to use, and well integrated into a lot of third-party tools. Google is a household name and most people trust them implicitly. However, as I point out to my students, if they bothered to read the terms of service when they signed up, they know that they are giving permission to Google to scan, index, compile, profile, and otherwise read through the documents that are stored on the Google cloud.

There’s nothing nefarious about this; Google is basically an ad agency, and well over half of their revenue is made by selling access to their profiles of each user, which are built by combining search history, emails, and the contents of our documents on their cloud. You agreed to this when you signed up for the service. It’s why you start seeing ads for vacations when you send your mom an email about an upcoming trip.

But isn’t my data encrypted?

Yes and no. Most cloud services will encrypt the transmission of your file from your computer to theirs, however when the file is at rest on their servers, it might or might not be encrypted, depending on the company. In most cases, if the file is encrypted, it is with the cloud service’s key, not yours. That means that if the key is compromised or a law-enforcement or spy agency wants to see what’s in the file, the cloud service will decrypt your file for them and turn it over. Warrants, in the form of National Security Letters, come with a gag order and so you will not be told when an agency has requested to see your files.

Some services are better than others about this; Apple says that files are encrypted in transit and at rest on their iCould servers. However, it’s my understanding that the files are currently encrypted with Apple’s keys, which are subject to FISA warrants. I believe that Apple is working on a solution in which they haven no knowledge of the encryption key.

You should assume that any file you store on someone else’s server can be read by someone else. 

Given that assumption, if you choose to use a commercial cloud service, the very least you should do is encrypt your files locally and only store the encrypted versions on the cloud.

And….they’re gone

Another trust issue that isn’t brought up much is whether or not the company you are using now to store your files will still be around in a few years. Odds are that Microsoft and Google and Apple will be in business (though we’ve seen large companies fail before), but what about Dropbox? Box? Evernote? When you store files on any company’s servers, you are trusting that they will still be in business in the future.

My personal solution

I don’t trust anyone with my data except myself. I do, though, want the convenience of cloud storage. My solution was to build my own personal cloud using Seafile, an open-source cloud server, running on my own Linux-based RAID storage system. My files are under my control, on a machine that I built, using software that I inspected, and encrypted with my own secure keys. The Seafile client runs on any platform, and so my files are always in sync no matter which device (desktop, phone, tablet) I pick up.

The network itself is as secure as I can manage, and I use several automated tools to monitor and manage security, especially around the cloud system.

I will admit that this isn’t a system that your grandmother could put together, however it isn’t as difficult as you might think; the pieces that you need (Linux server, firewall, RAID array) have become very easy for someone with just a little technical knowledge to set up. There’s a docker container for it, and I expect to see a Bitnami kit for it soon; both are one-button deployments.

Using my own cloud service solves all of my trust issues. If I don’t trust myself, I have bigger problems than someone reading through my files!

What about ‘personal’ clouds?

Several manufacturers sell personal cloud appliances, like this one from Western Digital. They all work pretty much the same way; your files are stored locally on the cloud appliance and available on your network to any device. My advice is to avoid appliances that have just one storage drive or use proprietary formats to store files…you are setting up a single point of failure with them.

If you want to access your files anywhere other than your house network, there’s a problem: The internet address of your home network isn’t readily available. The way that most home cloud appliances solve this is by having you set up an account on their server through which you can access your personal cloud. If you’re on the road, you open up the Western Digital cloud app, log on to their server, and through that account gain access to your files.

Well, here’s the trust problem again. You now are allowing a third party to keep track of your cloud server and possibly streaming your files through their network. Do you trust them? Worse, these appliances run closed-source, proprietary software and usually come out of the box with automatic updates enabled. If some three-letter agency wanted access to your files, they’d just push an update to your machine with a back door installed. And that’s assuming there isn’t one already installed…we don’t get to see the source code, so there’s no way to prove there isn’t one.

I would store my non-critical files on this kind of personal server but would assume that anything stored on it was compromised.

Paranoia, big destroyah

The assumption that third parties have access to your files in the cloud, and that you should assume that anything stored in the cloud is compromised, might seem like paranoia, but frankly this is how files should be treated. It’s your data, and no one should by default have any access to it whatsoever. We certainly have the technical capability to set up private cloud storage, but there apparently isn’t a huge market demand for it or it we’d see more companies step forward.

There are a few, though offering this level of service. Sync, a Canadian firm, looks promising. They seem to embrace zero-knowledge storage, which means that you hold the encryption keys, and they are not able to access your files in any way. They also seem to not store metadata about your files. Other services such as SpiderOak claim the same (in SpiderOak’s case only if you only use the desktop client and do not share files with others).

I say ‘seem to’ and ‘claim to’ because the commercial providers of zero-knowledge storage are closed-source…the only real evidence we have to back up their claims is that they say it is so. I would not trust these companies with any sensitive files, but I might use them for trivial data. I trust Seafile because I’ve personally examined the source code and compiled it on my own machines.

Bottom line

I can’t discount the convenience of storing data in the cloud. It’s become such a significant part of my own habits that I don’t even notice it any more…I take it for granted that I can walk up to any of my devices and everything I’m working on is just there, always. It would be a major adjustment for me to go back to pre-cloud work habits.

I have the advantage of having the technical skills and enough healthy skepticism to do all of this myself in a highly secure way. I understand that the average user doesn’t, and that this shouldn’t prevent them from embracing and using the cloud in their own lives.

To those I offer this advice: Be deliberate about what you store on commercial cloud services and appliances. Understand and act on the knowledge that once a file leaves your possession you lose control of it. Assume that it is being looked at. Use this knowledge to make an informed decision about what you will and will not store in the cloud.

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