sprsn is an idea for a small piece of software which I think would do the world some good by existing, and which currently does not exist.

It’s a deeply technical project that I probably don’t have time to build (unless somebody wants to pay my rent for a few months while I take a shot at it with a helper or two! – I am not serious about this) but I can describe what’s needed and maybe it will inspire somebody, in whole or in part.

Synopsis: combine the new (telehash) with the old (SPKI) and get a Facebook-killer in the form of a command line utility that provides a decentralized social network. However, will Ethereum do this, and a ton more?

The dream

sprsn bob "hey when are you coming over?"

sprsn bob list friends
> leslie
> carol
> jake

sprsn bob add carol
> added bob's friend carol with key [a23fd61b7]
> you have no other routes to carol

sprsn jake
> use bob's key for jake?


Now imagine that sprsn also has a web interface mode: sprsn -d 9999

http://localhost:9999 mounts a web interface to your local sprsn instance. The sprsn instance connects to your (online) friends running sprsn using telehash (a persistant DHT tool) for web chat and for key management: click on your friend’s friends to acquire their keys, and multipath to people (“you have 9 friends in common”) to get more certainty about the keys.

Obviously this would be great: the best of SSH and Facebook in a single utility. It is now relatively easy to build.

Let me show you why it hasn’t happened already, and why we need it!

The Problem

GPG and HTTPS (X509) are broken in usability terms because the conceptual model of trust embedded in each network does not correspond to how people actually experience the world. As a result, there is a constant grind between people and these systems, mainly showing up as a series of user interface disasters. The GPG web of trust results in absurd social constructs like signing parties because it does not work and creating social constructs that weird to support it is a sign of that: stand in a line and show 50 strangers your government ID to prove you exist? Really? Likewise, anybody who’s tried to buy an X509 certificate (HTTPS cert) knows the process is absurd: anybody who’s really determined can probably figure out how to fake your details if they happen to be doing this before you do it for yourself, and of the 1500 or so Certificate Authorities issuing trust credentials at least one is weak or compromised by a State, and all your browser will tell you is “yes, I trust this credential absolutely.” You just don’t get any say in the matter at all.

The entirely manual, Byzantine process is broken, and so is the entirely invisible, automated one. It just doesn’t work. The process of mapping keys to people is just broken and nearly all the rest of the trouble emanates from this fact. A GPG key maps a person to an email address to a key, and leaves you to pick who you trust enough to prove the map is right. An HTTPS cert maps an organization to an IP address to a key, and asks you to trust one of 1500 organizations your browser vendor chose to trust. It’s not just the trust model that’s broken, it’s the binding of these various pieces of data together using cryptography. Gluing the wrong stuff to the wrong stuff produces constant security and reliability problems.

What’s the wrong stuff? Legacy delivery mechanisms like email and DNS. Mapping a person to an email address, and an email address to a key is two mappings. Same for HTTPS where we map an organization to an IP address to a key. Two mappings, one of which is essentially arbitrary: I care about identity and key. I should not have to worry about IP address or email address – that’s a minor technical detail. But these outmoded trust systems foreground it, much to our discomfort.

Telehash

Enter Telehash, an encrypted network stack in which you route messages directly to a public key. The code is pretty simple

expect(mesh).to.be.an('object');
mesh.receive(new Buffer("208cb2d0532f74acae82","hex"), pipe);

The cryptographic key is the routing address. So now we only have to accomplish one level of indirection: person to key.

Something old, something new, something borrowed, something blue. Enter SPKI and our old friend, the Granovetter diagram.

SPKI and trust in networks, not webs

Simple Public Key Infrastructure is what we should have deployed instead of X509/HTTPS and the GPG web of trust. There are two critical differences between SPKI and X509/GPG. They are:

1) SPKI gives users the ability to certify facts about other users, for example “bob is allowed to use my computer” can be expressed in a machine-readable fashion (s-expressions.) This lets users build their own trust architectures on an ad-hoc basis.

2) SPKI allows anybody to chain certificates of this type (“fred says that bob says that vinay says that bob is allowed to use his computer.”) This ability removes the centrality of the CA: anybody that I trust can give me a certificate stating “this is the key for amazon.com” and because of certificate chaining, I can see the line of authority down which that key passed.

These might sound like minor features, but they are not: these two features express the difference between trust-hierarchy (X509) and trust-soup (GPG), neither of which are productive, and the consumer-producer based trust-anarchy which SPKI permits and, indeed, requires.

The best explanation of this in more detail is the Ode to the Granovetter Diagram which shows how this different trust model maps cleanly to the networks of human communication found by Mark Granovetter in his sociological research. We’re talking about building trust systems which correspond to actual trust systems as they are found in the real world, not the broken military abstractions of X509 or the flawed cryptoanarchy of GPG.

Usable security is possible

Once you fix the trust model so that it works for humans, and use Telehash to reduce the number of mappings from three (person -> delivery mechanism -> key) to two (person -> key) it’s possible to imagine a secure system in which people actually understand what is happening well enough feel comfortable that they understand what is going on.

So let’s break this down into the desirable properties for the system we’d build using these primitives.

For ease, let’s consider realtime chat in the first instance – just pushing messages down telehash sockets. The only question we have to answer is which telehash socket corresponds to which person.

1) person = key
there’s no way to break the binding between a person and a key, because a person is a key, or multiple keys.

2) delivery = key
this is what we get from telehash – I don’t need to worry about how I’m sending you the message, it’s right there.

So I obtain a key for a friend of mine by, say, email. Once I’ve connected to them, I can then ask them to send me keys for our mutual friends.

3) keys carry the chain of referrers
“alice says this is her key”
“bob says that alice says that this is her key”
“fred says that bob says that alice says that this is her key”

What that looks like in practice is a social graph, like the one embedded in facebook. I click on you, my friend, and I click on alice, your friend, and the connection that forms is an SPKI key being transferred to my keyring. The key is its history – the path by which the key came to me is the trust chain. If I want to be more sure the key I have is Alice’s key (and not your sockpuppet) I need to find an independent route or two to Alice.

If Google and Dunn & Bradstreet both agree that this key is the key for the IRS, that’s good enough for me.

4) tools and affordances
So how would we actually build this? I would recommend a golang implementation for cross platform compatibility and ease of distribution. NaCl and Telehash both exist for golang, and the self-contained binaries which result are easy to spread around. A command line client would be easy to augment with a web interface in which the golang program running on localhost provides an HTTP interface for users that want graphics etc.

Basically you get a decentralized social network with secure chat pretty much out of the box, where “friending” somebody acquires their key, and the referral network through which keys propagate is a key social dynamic. This can work.

5) advanced topics
How do we message friends who aren’t online? Store and forwards seems to be the obvious approach. Suppose I create a certificate (“sign”) which lists a set of telehash keys that are my “store and forward” servers – if you try and chat to me and I’m not there, you can ping one of them and dump an (encrypted) message for me there and I’ll pick it up when I’m online again.

Same holds for large block transfer (i.e. dropbox) – I specify my choice of servers by issuing a digital certificate. Do we need a central store of those certificates? Maybe, or maybe it’s simply an addressing mechanism: every time we chat, I push over my updated delivery info, and you can ask your friends for my updated delivery info if you need to reach me.

In all probability, a decision has to be made about whether to keep the old SPKI s-expression format for certificates, or move to JSON. Good luck with that decision, it’s a hard one.

Conclusion

There’s no way to fix a broken conceptual model with a better user interface.

GPG does not work for ordinary users, and GPG cannot work: we’ve been trying to fix this for 20 years and it has not happened. The process by which humans communicate is not tractable using those trust primitives.

We are stuck with a mess, and X509 is not an answer either – it worked when only big orgs wanted to secure their email and web sites, but now everybody wants to do it and the certificate issuing mechanisms are becoming far too sloppy to trust.

We have to go back 20 years to the brilliant analysis of the people who did not ship a sloppy hack to quickly get to market but sat there and figured out the right thing to do, if we want to fix this mess in a durable way.

High roads and low roads

The high road on these issues is Ethereum.

Telehash takes the DHT and uses it for routing. Bitcoin takes the DHT and adds proof of work to generate a history.
Ethereum takes bitcoin and puts executable contracts into the history, plus protocols for chat and block transfer.

It’s entirely possible that SPKI-style user-generated certificates will make their way into Ethereum, either as part of the core spec or as a common class of DAAPs. “I have bought stuff from bob and would do so again” can be issues as a certificate, in a standardized format, and these certificates can be spidered out of the blockchain to generate trust metrics.

Likewise, if all your messaging is happening on the Ethereum protocol, you do not necessarily need telehash.

Here’s the question: is Ethereum’s “one ring to rule them all” approach feasible, or should we work closer to the Unix Philosophy and build smaller pieces, loosely joined. I can imagine a command line Telehash/SPKI client which is as commonly used as SSH is today, for slinging around chat and small data.

I can also imagine an operating-system like sea of executable contracts and helper functions in a densely knit global decentralized computational ecosystem providing all the same services and more.

I, personally, am in favor of a mixed strategy. I think the sheer naked moonshot ambition of Ethereum is extremely attractive, and part of the reason I joined the team (F.I.S.T.) was that I wanted to be part of such an ambitious vision.

But it’s an awful lot of bleeding edge tech, and with a project that large and complex, you can never be quite sure what will come out the other end. In particular, I have no idea whether the nuances of SPKI etc. which will enable a revolution in the way that ordinary users experience cryptography will show up in Ethereum in a usable way – the core smart contract etc. functions can work perfectly well without fixing the nuances that user-issued certificates will get.

So I’m writing this post for two reasons: to encourage the Telehash community to examine SPKI and look at it as a way of managing keys inside of their DHT routing paradigm, and to encourage the Ethereum community to look at SPKI and ask whether it might empower users within the larger Ethereum landscape. Either way, I would dearly love to see an SPKI revival so that, finally, at long last, pull the sword from the stone: Johnny can encrypt.