path: root/_posts/2013-10-25-namecoind-ssl.md

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layout: post
title: Namecoin, A Replacement For SSL
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This is a long post, and it could very well be two posts disguised as one. I'm
first going to make a case for namecoins, explaining what they are and why
they're better than existing solutions. I'm then going to make a case for why
and how namecoins could be used to replace SSL (amongst other things).

# Bitcoins

This post is about namecoins. But namecoins are based on bitcoins, so you need
to know how those work first.

If you haven't yet checked out bitcoins, [I highly encourage you to do so][0].
They're awesome, and I think they have a chance of really changing the way we
think of and use money in the future. At the moment they're still a bit of a
novelty in the tech realm, but they're growing in popularity.

The rest of this post assumes you know more or less what bitcoins are, and how
they work.

# Namecoins

Few people actually know about bitcoins. Even fewer know that there's other
cryptocurrencies besides bitcoins. Basically, developers of these alternative
currencies (altcoins, in the parlance of our times) took the original bitcoin
source code and modified it to produce a new, separate blockchain from the
original bitcoin one. The altcoins are based on the same idea as bitcoins
(namely, a chain of blocks representing all the transactions ever made), but
have slightly different characterstics.

One of these altcoins is called namecoin. Where other altcoins aim to be digital
currencies, and used as such (like bitcoins), namecoin has a different goal. The
point of namecoin is to create a global, distributed, secure key-value store.
You spend namecoins to claim arbitrary keys (once you've claimed it, you own it
for a set period of time) and to give those keys arbitrary values. Anyone else
with namecoind running can see these values.

## Why use it?

A blockchain based on a digital currency seems like a weird idea at first. I
know when I first read about it I was less than thrilled. How is this better
than a DHT? It's a key-value store, why is there a currency involved?

### DHT

DHT stands for Distributed Hash-Table. I'm not going to go too into how they
work, but suffice it to say that they are essentially a distributed key-value
store. Like namecoin. The difference is in the operation. DHTs operate by
spreading and replicating keys and their values across nodes in a P2P mesh. They
have [lots of issues][1] as far as security goes, the main one being that it's
fairly easy for an attacker to forge the value for a given key, and very
difficult to stop them from doing so or even to detect that it's happened.

Namecoins don't have this problem. To forge a particular key an attacker whould
essentially have to create a new blockchain from a certain point in the existing
chain, and then replicate all the work put into the existing chain into that new
compromised one so that the new one is longer and other clients in the network
will except it. This is extremely non-trivial.

### Why a currency?

To answer why a currency needs to be involved, we need to first look at how
bitcoin/namecoin work. When you take an action (send someone money, set a value
to a key) that action gets broadcast to the network. Nodes on the network
collect these actions into a block, which is just a collection of multiple
actions. Their goal is to find a hash of this new block, combined with some data
from the top-most block in the existing chain, combined with some arbitrary
data, such that the first n characters in the resulting hash are zeros (with n
constantly increasing). When they find one they broadcast it out on the network.
Assuming the block is legitimate they receive some number of coins as
compensation.

This last step is the crucial piece. Receiving compensation for doing the work
of putting a block onto the chain is what keeps the bitcoin style of
crypto-currency going. If there were no compensation there would be no reason to
mine except out of goodwill, so far fewer people would do it. Since the chain
can be compromised if a malicious group has more computing power then all
legitimate miners combined, having few legitimate miners is a serious problem.

In the case of namecoins, there's even more reason to involve a currency. Since
you have to spend money to make changes to the chain there's a disincentive for
attackers (read: idiots) to spam the chain with frivolous changes to keys.

### Why a new currency?

I'll admit, it's a bit annoying to see all these altcoins popping up. I'm sure
many of them have some solid ideas backing them, but it also makes things
confusing for newcomers and dilutes the "market" of cryptocoin users; the more
users a particular chain has, the stronger it is. If we have many chains, all we
have are a bunch of weak chains.

The exception to this gripe, for me, is namecoin. When I was first thinking
about this problem my instinct was to just use the existing bitcoin blockchain
as a key-value storage. However, the maintainers of the bitcoin clients
(who are, in effect, the maintainers of the chain) don't want the bitcoin
blockchain polluted with non-commerce related data. At first I disagreed; it's a
P2P network, no-one gets to say what I can or can't use the chain for, and they
can't stop me! And that's true. But things work out better for everyone involved
if there's two chains.

Bitcoin is a currency. Namecoin is a key-value store (with a currency as its
driving force). Those are two completely different use-cases, with two
completely difference usage characteristics. And we don't know yet what those
characteristics are, or if they'll change. If the chain-maintainers have to deal
with a mingled chain we could very well be tying their hands with regards to
what they can or can't change with regards to the behavior of the chain, since
improving performance for one use-case may hurt the performance of the other.
With two separate chains the maintainers of each are free to do what they see
fit to keep their respective chains operating as smoothly as possible.
Additionally, if for some reason bitcoins fall out of favor and fall by the
wayside, namecoin will still have a shot at continuing operation since it isn't
tied to the former. Tldr: separation of concerns.

# SSL

Time to switch gears. SSL is the mechanism by which web-browsers establish an
encrypted connection to web-servers. The goal of this connection is that only
the destination web-browser and the server know what data is passing between
them. Anyone spying on the connection would only see gibberish. To do this a
secret key is first established between the client and the server, and used to
encrypt/decrypt all data. As long as no-one but those parties knows that key,
that data will never be decrypted by anyone else.

SSL is what's used to establish that secret key on a per-session basis, so that
a key isn't ever re-used and so only the client and the server know it.

## Public-Private Key Cryptography

There exists something called public-private key cryptography. In this system
person A has a public and a private key. They can give the public key to anyone
at all that they want to talk with, doing so can't hurt them. They must keep the
private key secure from everyone but themselves. If they give their public key
to person B, then person B can use it to create a message that can only be
decrypted by the private key. Additionaly, person A can sign messages with their
private key, so that anyone with the public key can verify that the message came
from person A and that the contents of the message haven't been tampered with.

There are two problems with public-private key cryptography. First, it's slower
then normal cryptography where both parties simply share the same key. Second,
it assumes that the public key given to person B hasn't been tampered with. If
person C intercepted A's message to B and instead gave B a different public key,
then when B encrypted a message with that key C would be able to read it instead
of A.

## How does SSL work?

SSL is at its heart a public-private key system. The client uses the server's
public key to send the server an encrypted message with the symmetric key it
wants to use. Since it's only used in the initial setup of the connection to
negotiate a symmetric key the speed isn't as much of a factor. But getting the
client the server's public key is.

SSL uses a trust-chain to verify that a public key is the intended one. Your web
browser has a built-in set of public keys, called the root certificates, that it
implicitly trusts. These root certificates are managed by a small number of
companies designated by some agency who decides on these things. These companies
sign intermediate certificates for intermediary companies. These intermediary
companies then sign certificates for websites to serve with SSL. So when you get
a servers SSL certificate (its public key) you also get the signing chain. Your
browser sees that the server's key is signed by an intermediate public key, and
that that intermediate public key is signed by one of the root public keys. As
long as all signatures check out, the public key for the server you're talking
to also checks out.

## How SSL doesn't work

SSL has a few glaring problems. One, it implies we trust the companies holding
the root certificates to not be compromised. If some malicious agency was to get
ahold of a root certificate they could man-in-the-middle any connection on the
internet they came across. They could trivially steal any data we send on the
internet. Alternatively, the NSA could, [theoretically][2], get ahold of a root
certificate and do the same.

The second problem is that it's expensive. Really expensive. If you're running a
business you'll have to shell out about $200 a year to keep your SSL certificate
signed (those signatures have an expiration date attached, of course). Since
there's very few root authorities there's an effective monopoly on signatures,
and there's nothing we can do about it. For 200 bucks I know most people simply
say "no thanks" and go unencrypted. The solution is causing the problem.

# Namecoin as an alternative to SSL

There are already a number of proposed formats for standardizing how we store
data on the namecoin chain so that we can start building tools around it. I'm
not hugely concerned with the particulars of those standards, only that we can,
in some way, standardize on attaching a public key (or a fingerprint of one) to
some key on the namecoin blockchain. When you visit a website, the server
would then send both its public key and the namecoin chain key to be checked
against to the browser, and the browser would validate that the public key it
received is the same as the one on the namecoin chain.

The main issue with this is that it requires another round-trip when visiting a
website: One for DNS, and one to check the namecoin chain. And where would this
chain even be hosted?

My proposition is there would exist a number of publicly available servers
hosting a namecoind process that anyone in the world could send requests for
values on the chain. Browsers could then be made with a couple of these
hardwired in. ISPs could also run their own copies at various points in their
network to improve response-rates and decrease load on the globally public
servers. Furthermore, the paranoid could host their own and be absolutely sure
that the data they're receiving is valid.

If the above scheme sounds a lot like what we currently use for DNS, that's
because it is. In fact, one of namecoin's major goals is that it be used as a
replacement for DNS, and most of the talk around it is focused on this subject.
DNS has many of the same problems as SSL, namely single-point-of-failure and
that it's run by a centralized agency that we have to pay arbitrarily high fees
to. By switching our DNS and SSL infrastructure to use namecoin we could kill
two horribly annoying, monopolized, expensive birds with a single stone.

[0]: http://vimeo.com/63502573
[1]: http://www.globule.org/publi/SDST_acmcs2009.pdf
[2]: https://www.schneier.com/blog/archives/2013/09/new_nsa_leak_sh.html