28 September, 2017

Client-side, server-side and zero-knowledge end-to-end encryption in Nextcloud

End-to-end encryption in Android in action
Android encryption in action
Yesterday, Nextcloud published plans, designs and code for end-to-end encryption in the clients. A recent report from Forrester named data encryption as one of the top global Cybersecurity trends for 2017, so this is a big deal! I thought it'd be good to go over the differences between client-side, server-side and end-to-end encryption and position what we developed.

End-to-End Encryption

End-to-end encryption is usually associated with communication channels, think chat or video calls. Signal, Telegram and lately WhatsApp employ end-to-end encryption. So what does it mean?

The main property of end-to-end encryption is that the data is encrypted on the one end and decrypted on the other end, so only the sender and receiver can read it.

As an example, take the Nextcloud Video Calls app. When you share a link for a call and the other person joins, the Nextcloud Server essentially gives the other user the address of your computer and helps you connect to each other. It will also send signals when others join the call, when you mute and so on. But the actual call takes place between your system and that of your conversational partner, directly. And before it is sent out, your browser will encrypt the data for the other side to decrypt. This way, nobody in between, like your internet provider, can listen in!

The main downside of the term is that the definition of that 'end' can vary: you can say that normal https encryption is 'end-to-end', defining one end as the browser and the other end as the server. So this brings us to the difference between server-side and client-side encryption.

Server-side encryption

Server-side encryption serves to protect data on or going through a server: as soon as the data arrives, the server encrypts it. When you use a cloud storage like Amazon S3 or a Dropbox account or a FTP at another office with Nextcloud, our Server-side Encryption encrypts the data before it gets sent to the other storage and decrypt it only after it has been retrieved. Server-side encryption thus protects your data from access by a third party storage solution.

Note that encryption in the browser is essentially server-side encryption: the code that does the work comes from the server and thus the server controls what is going on. If a server is compromised, the attacker (or evil system administrator or government agency) can simply make a minor modification to that code so it gives them access to your private key!

When the data is on the server itself, however, the server admin has access to it as the keys are managed by the server. In case of Nextcloud, we encrypt that key with your login, making it impossible for the server to decrypt the files unless you are logged. That is called "protection of data at rest", but, of course, you log in all the time if you have the client running.

So the limitation of server-side encryption lies in what it does not protect you from: the server being compromised.

Client-side encryption

This is why server-side encryption is often contrasted with client-side encryption, which is what is employed by the end-to-end encryption Nextcloud introduced today. Where server-side encryption happens after transmission to the server, we encrypt the data on the Android, iOS or desktop client already. Then, only at the receiving end, it is decrypted again. That receiving end can be another device owned by the same user or a device owned by another user who has been given access to the data. But not anyone in between or otherwise not authorized! This is sometimes also called a zero-knowledge privacy: at no point in time can the server have any knowledge of the data.

The process of creating keys

A little bit about keys

Usually, public and private keys are used for the encryption and decryption. How does that work?

Everybody has a set of closely related keys, a 'public' and a 'private' key. They work a bit like a mail box works: anyone can throw a letter in the box, but only the mailman (or woman) can open and empty it. The public key is, as the name implies, public. Anyone can use it to encrypt something. But to decrypt the result, the private key is needed!

Nextcloud generates a public and private key pair the first time a user enables end-to-end encryption in their client. The public key gets signed by the server with 'certificate' to verify the user identity (our Cryptographic Identity Protection feature) and stored there for other users to encrypt files to that they wish to share. The private key gets encrypted with a locally, app-generated very secure and very long (12 word!) passcode which is displayed to the user and then the key gets stored on the server as well.

Another device owned by the user can download the private key, the user can enter the 12 word passcode to decrypt it, and this device will then also be able to encrypt and decrypt files. That is how you add your phone and desktop after you enabled end-to-end encryption on your laptop.

You can learn much more about exactly how the encryption and decryption work on the end-to-end encryption web page we made as well as the whitepaper you can download there.

Enterprise challenges

While consumers use end-to-end encryption for chat for years, larger organizations like companies and governments have struggled to find solutions that protect their sensitive data without disrupting productivity and legal requirements for audit logs.

Indeed, many solutions create a new layer over existing solutions like Box and Dropbox or have poor key management, making sharing cumbersome and less secure. A real enterprise solution needs to take the burden of complexity away from users and, if it needs to be anywhere, put it on the shoulders of the system administrators. Nextcloud has done exactly that, not even allowing users to create their own, potentially insecure password and making adding devices easy. The 12-word passcode can be recovered from any of the devices an user owns and it is possible to enable a system wide recovery key. If enabled, users will get warned of this and the system administrator gets to see and note down the key once and only once. After that, the code is destroyed and no attacker would be able to steal it, provided the server administrator puts it in a safe location: we'd recommend an actual safe.

Another important feature for enterprises is support for a Hardware Security Module which could be used to generate user certificates. Without it, our design does not allow users to switch identities (as this could be abused by an attacker with control over the server) but this restriction can be relaxed if a secure HSM is in the mix.

You can learn more on our webpage about end-to-end encryption!

01 August, 2017

Privacy, self-hosting, surveillance, security and open source in Berlin


August 22-29 we're organizing a conference to discuss and work on privacy, self-hosting, security and open source in Berlin: the Nextcloud Conference. We expect some 150-200 people to participate during a week of discussing and coding and, especially on the weekend, presenting and workshopping. So I thought I should blog about why should you be there and what can you expect?

If you care about protecting people from the all-pervasive surveillance, re-gain privacy and security of data and believe in self hosting and open source as solution for these issues, this is the place to be. Our event is special for two reasons:
The team that started ownCloud

We're doing it. And most of us have been, for a decade or more, in KDE, GNOME, SUSE, Ubuntu, phpBB and other earlier projects. The code we wrote has influenced millions of users already and we will go further and wider! Expect to meet people with a can-do attitude.

Second, Nextcloud has got a huge momentum, name recognition and has become one of the largest ecosystems in the open source privacy/self hosting area. It isn't just about us! Large companies, small startups and innovative individuals and small communities all over are building on and around Nextcloud. A few examples:

We are doers


So the Nextcloud conference is where you can find a wide range of individuals with interest, skills and ideas in the area of privacy and freedom activism, and they are doers! There is a reason we say "bring your laptop" on our conference page, though with that we don't mean we only want coders there!

Designers, activists and advocates are just as welcome. That is because Nextcloud is about more than technology. Frank is somebody who sometimes asks the hard questions and obviously it his vision is a strong diver, but we're all long time open source and/or privacy activists and deeply and personally motivated. Our entire community is built on drive, passion and a will to take on the challenges our society offers in the area of privacy, self determination, freedom.

That is the why you should be there. To help make a difference.

Now the what.

Getting Stuff Done

Our goal is to get work done; and facilitate communication and collaboration in our community. During the week, we simply provide space to talk and code (with wired and wireless network, Club Mate & other drinks, and free lunch). In the weekend, we have a program with talks & workshops. The setup is simple:

In the morning, everybody is in one room. First, we all hear from long time privacy activist and former Mozilla president Tristan Nitot. After that, community members working on a wide variety of interesting things around privacy/self hosting/open source and of course Nextcloud talk, shortly, about what they do. Just 3-8 minutes to give the audience an idea of their project, their plan, their idea, how to get involved, a call for action. Now again, everybody is in the room, so in the break, everybody has heard the same talks and has the same things to discuss! If you have something to add, be it about TOR, protests, encryption or anything else that is related: SUBMIT A TALK!

Collaboration & sharing ideas

Last year we announced the Nextcloud Box.
This year - be there and find out!
People can look up the speakers, join the meetings proposed and so on, in the afternoon. Because after lunch we have 2 (or more, not sure yet) tracks of workshops as well as hacking, coding and meetings in the coding rooms. Unconference style, so to say.

We now have several dozen talks and workshops already submitted and well over 100 people have registered but we are looking for more input in all areas so consider to be a part of this event!

It is free and open, supported by the TU Berlin which offers us a free location; and Nextcloud GmbH which sponsors drinks & practical stuff; and SUSE Linux which sponsors the Saturday evening party!

Learn more and register!

17 January, 2017

Happy Birthday ownCloud

Seven years ago at Camp KDE in San Diego, Frank announced a project to help people protect their privacy, building an alternative to Dropbox: ownCloud.

I was there, sharing a room with Frank at the infamous Banana Bungalow. Epic times, I can tell you that - there was lots of rum, lots of rain and loads of good conversations and making new friends.





Since then, a lot has changed. But the people who started building a self-hosted, privacy protecting alternative in 2010 and 2011 are still on it! In 2011, a first meetup was held, and the 5 participants at that meetup recently got on stage at the Nextcloud conference to recall some good memories:



Of course, today we continue the work at Nextcloud, that just yesterday published its latest bugfix- and security update. It is great to see so many people have stuck with us for all these years - just this month, the KDE sysadmins migrated their ownCloud instance to Nextcloud!

We'll keep up the good work and you're welcome to join, either if you're looking for a job or just want to code. In both cases I can promise you: working with such a motivated, dedicated, professional team is just plain amazing.

I also published a blog on our Nextcloud blog about this milestone.

EDIT: By the way - there's a meetup tonight in C-Base, B'lin, 19:00 - would be fun to drink a beer on ownCloud's birthday and talk about the future! Join! It will be at least until 10 or so, so if you can't be there before then - still come! ;-)

12 December, 2016

Wednesday: Release Party in Berlin!

On wednesday is our Nextcloud meetup and - Nextcloud 11 will be released, so let's make it a release party! Bring some snacks if you like, let's drink a beer or two, get our servers upgraded perhaps.
See and RSVP here:
When: Wednesday, December 14, 2016 7:00 PM
Where: C-Base, Rungestra├če 20, 10179 Berlin
We're in the main room. C-Base is at the river, all the way to the end from the street. You're there if you get geeky tingles from the murals :D
I look forward to seeing you there, everyone's invited! That includes KDE friends, by the way, would be fun to see the bunch of you! You can RSVP in the comments here or on meetup.com...

CU there!

25 November, 2016

3 alternative reasons why you should test Nextcloud 11 Beta

On the Nextcloud blog I just published about the beta for Nextcloud 11. The release will deliver many improvements and is worth checking out in itself, plus I put a nice clickbait-style title and gave three reasons to test it.

But I actually have some more reasons to test. You see, Nextcloud is one of the tools we need to keep our democracy working. As Frank notes on his home page:
"Privacy is the foundation of democracy"
And he is completely right. So, here are three different reasons why you should test (and help improve) Nextcloud:

1. The USA is making a massive swing towards even more spying

Obama has done nothing to curb the growth of the NSA and the scope of its operations. Secret laws spiked under his watch. Many of the folks about to be put in power by President-elect Trump favor more spying, including on US citizens, expansion of the NSA, a crackdown on whistleblowers and more. Trump's pick for CIA director calls for Snowden's execution. For what I can only guess must be giving proof of illegal government spying to dangerous terrorists like the Washington Post and the Guardian, who proceeded to win a Pulitzer prize by disclosing this information irresponsibly to the US public.

In general, as somebody who changes his stance on hugely important and complicated issues like torture in under an hour, it is impossible to predict what Trump will do with the most powerful spying agency in the world under his control, but his appreciation for dictatorial figures like Kim Jong Il and Putin gives plenty cause for concern.

2. Britain isn't doing much better

I wrote about the Snoopers' charter just some days ago - this piece of legislation goes further than any earlier piece of spying law. It allows not only passive spying but also actively hacking devices from citizens.

3. Nor is Europe

The UK is not alone. Since Snowden, Europe has complained a bit about the NSA but seems to simply follow suit, rather than doing anything about it. Germany is even introducing a bill that will allow spying on foreign journalists.

Help out!

So, how can you help? Well, test Nextcloud 11 Beta, obviously. Help others to use it, get them involved. But it goes beyond Nextcloud - promote the use of and help improve tools like Tor, Signal and others, or democracy is screwed.

Edit: updated the blog 

22 November, 2016

Brittain’s Snoopers charter threatens your privacy

pic from the ZDNet article
The United Kingdom this week passed the so called Snoopers Charter, a law which forces UK internet providers to store the browsing history of UK citizens for a full year. You, your family, visitors or any devices in your household which have been hacked (the government is now allowed to do that, by the way) better not visit anything bad as the government can get their hands on this data quite easily. What does this mean and what can you do?

An attack on privacy

There is a global siege on privacy. Governments all over the world have introduced legislation (sometimes secret) which forces email, internet or data storage providers to track what you do and make that data available to their governments. This, of course, also means third parties who gain access to the storage systems can see and abuse it. And because so many of us have put so much of our data at just a few providers, we're at great risk as events like last week's shutdown of hundreds of Google accounts did show.

While Google, Dropbox and others lure customers in with 'free' data storage and great online services, governments benefit from centralized data storages as it makes it easy for them to hack in or demand data from these companies.

Why this surveillance?

While governments usually claim they need access to this data to find terrorists or child pornography, experts point out that it will not be helpful at all. As multiple experts (even internally) put it, growing the haystack makes it harder to find the needle. Intelligence agencies are swamped with data and nearly every terrorist attack in western states over the last decade took place despite the agencies having all information they would have needed to prevent it. The Paris attackers, for example, coordinated their attack using plain SMS messages. The Guardian thus rightly points out that:
"Paris is being used to justify agendas that had nothing to do with the attack"
which has become a familiar refrain after nearly every terrorist attack.

Indeed, we all know the argument But you have nothing to hide, do you? and indeed, we probably don't. But some people do, so they'll try to avoid being seen. That being illegal won't change their behavior...

And as Phill Zimmermann, the inventor of the PGP encryption pointed out:
"When privacy is outlawed, only outlaws will have privacy"

So not terrorists. Then what?

Experts agree that the vast majority of these surveillance and anti-privacy laws have little or no effect on real criminals. The crime syndicates, corrupt politicians and large corporations evading taxes and anti-trust/health/environmental laws, they DO have something to hide, and thus they would use encryption or avoid surveilled communication methods even if it were outlawed.

However, ordinary citizens, including grass-roots local activists, charitable organizations, journalists and others, who DO have nothing to hide, would be surveilled closely. And with that information, the real criminals mentioned earlier - crime syndicates, corporations or corrupt politicians - would have weapons in hand to keep these citizens from bothering them. Whistle blowers can be found out and killed (like in Mexico), journalists can be harassed and charged for trivial transgressions (like was recently done at the US pipeline protest) and charities can be extorted.

What can we do?

Luckily, there are initiatives like the Stanford Law Schools' Crypto Policy Project which aim to train, for example, journalists in the use of encryption. Tools and initiatives like Signal, PGP email encryption, Let's Encrypt and Nextcloud provide the ability for users to protect themselves and their loved ones from surveillance. More importantly, these at the same time making it harder and more costly to conduct mass surveillance.

There is nothing wrong with governments targeting criminals with surveillance but just vacuuming up all data of all citizens that might, some day, be used is a massive risk for our democracy. We all have a responsibility to decentralize and use tools to protect our privacy so those who need it (press, activists and others) have a place to hide.

29 September, 2016

Get started with Nextcloud App development in 6 easy steps!

The brand new app scaffolding tool in our app store
Last night, Bernhard Posselt finished the app scaffold tool in the app store, making it easy to get up and running with app development. I was asked on twitter to blog about setting up a development environment, so... here goes.

What's simpler than downloading a zip file, extracting it and running a command in the resulting folder to get an Nextcloud server up on localhost for hacking?

Yes, it can be that simple, though it might require a few minor tweaks and you have to make sure to have all Nextcloud dependencies installed.

Note that this is useful if you want to develop an Nextcloud app. If you want to develop on the Nextcloud core, a git checkout is the way to go and you'll need some extra steps to get the dependencies in place, get started here. Feedback on this process is highly appreciated, especially if it comes with a pull request for our documentation of course ;-)

Step 1 and Two: Dependencies

  • Install PHP and the modules mentioned here
    Your distro should make the installation easy. Try these:
    • openSUSE: zypper in php5 php5-ctype php5-curl php5-dom php5-fileinfo php5-gd php5-iconv php5-json php5-ldap php5-mbstring php5-openssl php5-pdo php5-pear php5-posix php5-sqlite php5-tokenizer php5-xmlreader php5-xmlwriter php5-zip php5-zlib
    • Debian: apt-get install php5 php5-json php5-gd php5-sqlite curl libcurl3 libcurl3-dev php5-curl php5-common php-xml-parser php5-ldap bzip2
  • Make Nextcloud session management work under your own user account.
    Either change the path of php session files or chmod 777 the folder they are in, usually something like /var/lib/php (debian/SUSE) or /var/lib/php/session (Red Hat).

The Final Four Steps


Nextcloud should present you with its installation steps! Give your username and password and you're up and running with SQLite.

Start with the app

Now you create a subfolder in the nextcloud/apps with the name of your app and put in a skeleton. You can generate an app skeleton really easy: use the scaffolding tool, part of our new app store for Nextcloud 11!

It's probably wise to now get going with the app development tutorial here. This isn't updated for the scaffolding tool yet, so you'll have a head start here. Be sure to check out the changelog, we try to make sure the latest changes are noted there so even if we didn't manage to fully update the tutorial, you can find out what will and won't work in the changelog. Also, be sure to update the links to get the latest dev doc - this all links to 11, once that is out it is probably better to directly target 12 and so on.

Help and feedback

Your input is very much welcome! If you run through these steps and get stuck somewhere, let me know and I'll update the documentation. Or, of course better still, do a pull request on the documentation right in github. You don't even have to do a full checkout, smaller fixes can easily be done in the web interface on github.

Last but not least, ask questions on our forums in the app dev channel or on IRC. Here is the Nextloud development IRC chat channel on freenode.net, also accessible via webchat.

Thanks, good luck, and have fun building Nextcloud apps!