“Online services should be allowed to report the exact number of government data requests received” — implying that Dropbox does receive such requests, obeys, and is not allowed to disclose them.
“Government data requests should be limited to specific people and investigations” — implying that Dropbox receives and obeys blanket requests.
“Governments should never install backdoors into online services or compromise infrastructure to obtain user data” — implying that Dropbox fears and cannot exclude this activity.
Dropbox says it will “work hard to reform these laws”. All of this basically tells us that our data is not safe there, and that this is not the fault of Dropbox.
Similar arguments apply to Google Drive.
Encrypted Cloud Storages
Enter encrypted cloud storages. Mind you, basically every cloud service encrypts the data on their servers. But here we talk about services that encrypt the data with a key that only the user knows. This means that even the service staff cannot access your data — even if they wanted to, and even if the government obliged them.
That sounds great, to be sure. But in all the hype about encryption, be aware what this entails: If you forget your password, there is no way to reset your password. This is because even the service staff does not know it, and without it the data is useless.
This so-called zero-knowledge policy also makes a number of other handy features of Dropbox very hard to implement:
Sharing How can you collaborate with others on a folder if only you know the password of the encrypted data? Your collaborators will each have their own passwords, and the service provider cannot mediate between them, because it is never allowed to see the data in clear.
Link sharing In Dropbox, you can send a link to a file to another person, who can then download the file from the cloud server even if he is not a Dropbox user. How could that be implemented when the server may never see the file in clear?
Web access Dropbox allows you to access your files from the Web. If this is to run under a zero-knowledge policy, then the entire decryption process has to happen in your browser.
Password changing If you change your password, then all data has to be re-encrypted on your computer, and sent again to the server.
Only very few services that advertise zero-knowledge cloud storage actually provide these features. The much-famed SpiderOak service, for example, provides a Web interface, but then the zero-knowledge model breaks.
Another thing you may want is infinite history of file versions. This is because if a malware should ever overwrite your data, you want to be able to go back to the originals. A finite number of versions is not sufficient, because if the cloud service stores the last n versions of files, the malware can simply overwrite the file n+1 times. A history of several days (as Dropbox provides) is acceptable for this scenario.
If you want two-factor authentication and client-side encryption, you find that Tresorit and Sync.com are nearly your only choices. We will now look at each of them.
Tresorit is a Swiss company that offers encrypted cloud storage. The servers and the data are physically in Europe, which means that European privacy laws apply, which are much stronger than the US laws.
In addition, Tresorit offers all of the above desiderata.
The following plans are available: the free plan (called Reader plan) is 1GB, other personal plans are €10 per month (200GB) and €25 (2TB) per month (with 20% discount when billed annually). There are also business plans available based on team size.
I have not tried out Tresorit personally, mainly because it is much more expensive than Sync.com.
Sync.com is a Canadian company with around 400,000 clients. Like Tresorit, it offers end-to-end encrypted cloud storage. Like Tresorit, it provides all of the above desiderata.
The plans currently (2018-02-20) offer 5 GB for free, and 500GB for 50 USD per year. Thus, the service is among the cheapest on the market.
Sync.com is located in Canada. This exempts the company from the US Patriot Act. However, Canada is still a member of the Five Eyes. As in nearly all countries, a Canadian company might be forced to hand over customer data by law. One may think that the encrypted data is safe. However, Sync.com could (be forced to) dish out a customized client software that sends the password back to the server. Then the server can decrypt all data. Something comparable has happened in the case of the Canadian email provider Hushmail, which provides encrypted email services.
I have brought this issue up with Sync.com's support, and they have replied in detail. Here are the main points:
Different from the US, Canada requires a court order before law enforcement can force a company to hand over data.
Different from the US, there are no National Security Letters in Canada. That means that the cloud storage company can inform the client if law enforcement requested the client’s data.
As for installing a backdoor in the software: Sync.com does not automatically update the client. As for the Web panel, it’s 100% open source. The Open Source principle is traditionally seen as the best (only?) protection against backdoors, because you could find the backdoor at least in principle.
I have been using Sync.com for 3 years now, and I am fully satisfied. I am mirroring my hard drive to Sync.com, I have my phone upload the pictures to it, and I synchronize two computers with it. Everything works fine. I am also impressed by the precise, informative, and fast support service.
Two desiderata remain:
Sync.com does not support Linux.
Sync.com does not offer a fallback-option for the two-factor authentication. A workaround is as follows: When you set up 2FA, scan the barcode not just with your own mobile, but also with the mobile of a trusted friend. Then, both mobiles will generate the same codes, and you have a fallback.
If you plan to try out Sync.com, please use the button below. It gives you and me each 1 extra GB for free (in addition to the 5 GB that are included for free). Thanks!