Trying out Keybase blog

I was privileged enough to get access to the alpha preview of Keybase.io. Last year, the project raised 11M$ in venture capital and they seem to be attacking the hard problems, so it is a serious project, worth considering for any cryptography hacker like me. This was obviously discussed elsewhere previously but since Keybase has evolved a bit since then, I figured it would be worth adding my grain of salt.

The elite alpha problem

My first problem with Keybase was of course that I wasn't in the elite club of invited people. Somehow, I finally got in but the problem remains for the everyone else.

In my case, it was the Keybase filesystem announcement that brought my attention back to the project, although I have yet to test that itself - yet another invite-only problem (need to email chris@keybase.io to get access, I guess). Still, 10GB of storage might be interesting for some people, but considering the number of hurdles or "friction", as they say, that needs to be jumped over to get access, I am not sure how much traction this will get for now.

The project has been in alpha for a while now (more than a year) with no announced public beta just yet, which is way slower than similarly challenging projects with less capital. Let's encrypt, as a comparison, was publicly announced in 2014 and by the end of 2015, the public beta was opened.

Private key leakage

My second major concern is that Keybase does worrisome things to private key material. If you tell it to import your regular GPG keys, it will copy them into the keybase keyring, which is already a problem: now you have two places where you store sensitive secrets.

But worse, Keybase offers you to upload your private key material on the server, without clearly and explicitely exposing the potential risks that means to the user. The key, presumably, is encrypted (at least that is what I can parse from the Keybase privacy policy). Yet this is still a concern: a determined attacker (e.g. the government or another malicious entity) could force Keybase to give up the encrypted private key material and install sniffers that would reveal the passphrase that would allow decryption and impersonation of the related identity.

That is a huge deal. This is what caused Hushmail's demise in 2007: they had similar promises about how they had a "secure" email (in this case) service based on OpenPGP, but since they key was stored on the server, they only had to serve a malicious applet to victims and were able to give cleartext data to the US government (12 CDs!) under a Mutual Legal Assistance Treaty with Canada.

In Keybase, When I generate a new key, it asks me if I want to upload the key to their servers, and "Yes" is chosen as a default, so it is clearly a policy that is encouraged. This is presumably to enable browser-based crypto, yet this could be done by storing keys within the browser, not on the server.

The mere possibility that the client can meddle with secret key material in such a way is a problem. Even if uploading secret keys to the server is optional, the fact that it is a possibility widens the attack surface on the client significantly.

GPG has been working on isolating private key operations to a different process (gpg-agent) or smart cards, SSH has privilege seperation. The idea of uploading secret key material online is so beyond current practices that it should bring the project to a full stop already.

My private key material is pretty sensitive. I am a Debian developer: if someone gets access to that key, they can upload arbitrary code for thousands of packages, affecting thousands if not millions of users. That is a huge deal, and I am not ready to give that power to an arbitrary third party that I know little about.

Privacy policy issues

Furthermore, the Keybase privacy policy explicitely states that "Logs of this information may persist for an indefinite period", which include, and I quote:

Your computer’s IP address

Your preferences and settings (time zone, language, privacy preferences, application preferences, etc.)

The URL of the site that referred you to the Service

The buttons and controls you clicked on (if any) within the Service

How long you used the Service and which parts and features you used

Session times and lengths

For a company working to improve user's privacy, this is a pretty bad policy. It exposes Keybase users to undue surveillance, on a lot of private information that is not necessary to operate the service. I haven't actually read the remaining of the policy, as I was already scared as hell and figure I would just log off for now and try not to add any extra personal information in that already growing pile.

Let's mention, while I'm here, that the keybase commandline client has this odd way of working that it forks a daemon in the background all the time, even to run just keybase status . One has to wonder if this thing is included in the surveillance data above, which would make the keybase client an amazing surveillance device in itself. To stop all this, you need:

keybase logout keybase ctl stop

Not quite obvious...

Usability issues

Which brings me to a series of usability issues I have found while working with Keybase. Having worked on usability myself in the Monkeysphere project, I understand how hard those problems can be. But right now, the fact is that keybase is only a commandline client, with some web-based sugar sprinkled on top. I recognize the huge efforts that have been done to make the user experience (UX) as easy as possible through the commandline, but this is definitely not "grand public" material yet.

Even as a OpenPGP hacker, Keybase can get confusing. Since it has its own separate keyring from GPG, things that used to be obvious before are suddenly new things to learn. For example, I originally generated a key for anarcat@debian.org in keybase, thinking it would be a separate thing from my current GPG identity. Well, that ended up creating a new key in my GPG keyring, duplicating my existing identity, with no way for me to tell this was a Keybase copy. This could have ended up on the keyservers and confuse anyone looking for my PGP key.

Revoking keys

So I revoked that key, which, in itself, is not such an obvious process either. I first had to "drop" the key:

keybase pgp drop '010143572d4e438f457a7447c9758804cc7be44c1ee2b7915c3904567d0a3fb5cf590a'

To find that magic number, I had to go on the website and click through the PGP key to end up on the revoke link which told me which magic string to put. The web UI was telling me I could use keybase status to get that information, but I couldn't find that in the output here:

$ keybase status Username: anarcat Logged in: no Device: name: angela ID: 070f6a13f2a66afbb463f49dadfd4518 status: active Keybase keys: unlocked Session: anarcat [salt only] KBFS: status: not running version: log: /home/anarcat/.cache/keybase/keybase.kbfs.log Service: status: running version: 1.0.14-1 log: /home/anarcat/.cache/keybase/keybase.service.log Platform Information: OS: linux Runtime: go1.5.3 Arch: amd64 Client: version: 1.0.14-1 Desktop app: status: not running version: log: /home/anarcat/.cache/keybase/Keybase.app.log Config path: /home/anarcat/.config/keybase/config.json Default user: anarcat Other users: command-line client: keybase status [pid: 14562, version: 1.0.14-1]

So keybase drop "deletes" the key from the keybase client (and presumably the server). One problem here is that we have three different verbs to mean the same thing: in some places, the website says "deleted" (in the web graph), the commandline client uses "drop" and everyone else using PGP in the world uses "revoke". So what is it?

Also note that just dropping that key is not enough to eradicate that key: you still need to generate and import a revocation certificate on GPG's side as well, for that key. This makes sense, because you may have imported that key and you may not want to destroy it when you remove it from keybase, but there could be a little better guessing and UX here as well.

Password usage

Then another problem is that, when you signup on the commandline, it asks you to choose a passphrase. It's not clear at all from the UI what that passphrase is for. Is it to protect the private key material? To login the website? Both? It turns out it is actually to login to the website and the Keybase API. It could also be the key to the private key material, but I haven't quite figured that out yet.

Similarly, the "paper devices" are a little confusing to me as well. The registration process is fairly insistent that I need to write a series of secret words down on a piece of paper and put it my wallet. This is based on the idea that you can use that key to recover your account and setup new devices. However, it is not made clear at all how those credentials should be protected or used. What if I lose my wallet? What do I do then? Is it okay if i write it on the back of my laptop instead? I know it sounds like stupid questions to crypto geek, but it's definitely stuff people will do, and education, at all levels, is necessary here.

The existing web of trust

Finally, I found it surprisingly counter-intuitive to sign keys with keybase. I was assuming the whole point of the thing was to expand the web of trust, but it seems their mission lies somewhere else: there is no facility to sign keys directly in keybase. You sign statements on various social sites (Github, Twitter, Reddit...) but doing traditional key exchanges seems to be off limits.

My obvious use case was to sign my existing key material with my newly generated anarcat@keybase.io key, so that keybase would become another way of verifying my identity. Well, this is not possible with keybase directly - you still have to go through the regular:

gpg --sign-key DEADBEEF

Which is really unfortunate, because some craaaazy people like me insist on doing in person, actually secure key exchanges sometimes, and the tools to do this right now (mainly gpg, caff and monkeysign) really need a lot of love and help. Keybase could have helped a lot in pushing those initiatives forward and bring new ways of doing secure key exchanges, instead of only lowering the standards on cryptographic identity.

Usual proprietary startup rant

I can't help but finish by noticing that the whole basic problem with Keybase is more fundamental than a few usability issues, which can all be fixed fairly easily.

Keybase.IO is a web-based service that is entirely proprietary. The client is freely downloadable and free software - but the server side is not. This makes us rely on a central point of failure and the goodwill of those operators to not only keep the service running (for free?) indefinitely, but to protect us against all attackers, state-run or otherwise.

This is definitely against basic free software principles and the open architecture of the internet federation, well embodied in the Franklin street statement. Online services should be decentralized and open like the OpenPGP keyservers have always been, period.

Conclusion

I am curious to see where Keybase brings us, as a community. So far, I am concerned about centralization and devaluation of the web of trust as cryptographic system. I do not believe that trusting multiple corporate social networking sites bring much benefit to our security, although it does improve usability significantly and is certainly better than TOFU, so that part of the project is definitely interesting, especially since it allows leveraging classical internet protocols like DNS and HTTPS.

Key exchange is a critical problem that still hasn't properly been resolved in the cryptographic community. Most efforts at building communication tools (say like Signal or Telegram) mostly ignore the problem and expect people to read up strings of numbers or rely on synchronous communications (see the Axolotl rachet for Signal's take on it). Keybase's attempts at fixing this are great, but needs much more work to actually resolve the PKI issues in a significant way.

More fundamentally, the practice of storing keys on the servers should just stop: it is a definite no go for me, and a classic crypto mistake that has bitten way too many people. In my mind, it discredits the whole project. The point of OpenPGP is end to end encryption across devices: storing the keys on a server breaks that apart, and doesn't improve much on the existing HTTPS security systems already in place on the web.

It is especially a problem given the new waves of attacks on cryptography from western governments, from the UK to California... Until those issues are resolved, I can't get myself to recommend Keybase to anyone just yet.

Note to Keybase developers: I have considered filing issues regarding the above, but unfortunately, I was unable to filter through the gigantic github issues list for duplicates, and didn't have time to file detailed reports for everything. I apologize for bypassing those usual conventions.

If you want to try out Keybase to make your own opinion, I do have 4 invites I can give away, but I will do so only if you need to test specific issues. Otherwise, I note that there is a Request For Package for the Debian package to become official, that Debian developers (or Keybase developers!) may be interested in completing.