Brian Picciano
11 years ago
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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 |
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first going to make a case for namecoins, explaining what they are and why |
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they're better than existing solutions. I'm then going to make a case for why |
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and how namecoins could be used to replace SSL (amongst other things). |
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# Bitcoins |
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This post is about namecoins. But namecoins are based on bitcoins, so you need |
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to know how those work first. |
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If you haven't yet checked out bitcoins, [I highly encourage you to do so][0]. |
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They're awesome, and I think they have a chance of really changing the way we |
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think of and use money in the future. At the moment they're still a bit of a |
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novelty in the tech realm, but they're growing in popularity. |
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The rest of this post assumes you know more or less what bitcoins are, and how |
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they work. |
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# Namecoins |
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Few people actually know about bitcoins. Even fewer know that there's other |
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cryptocurrencies besides bitcoins. Basically, developers of these alternative |
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currencies (altcoins, in the parlance of our times) took the original bitcoin |
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source code and modified it to produce a new, separate blockchain from the |
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original bitcoin one. The altcoins are based on the same idea as bitcoins |
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(namely, a chain of blocks representing all the transactions ever made), but |
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have slightly different characterstics. |
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One of these altcoins is called namecoin. Where other altcoins aim to be digital |
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currencies, and used as such (like bitcoins), namecoin has a different goal. The |
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point of namecoin is to create a global, distributed, secure key-value store. |
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You spend namecoins to claim arbitrary keys (once you've claimed it, you own it |
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for a set period of time) and to give those keys arbitrary values. Anyone else |
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with namecoind running can see these values. |
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|
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## Why use it? |
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A blockchain based on a digital currency seems like a weird idea at first. I |
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know when I first read about it I was less than thrilled. How is this better |
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than a DHT? It's a key-value store, why is there a currency involved? |
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|
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### DHT |
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DHT stands for Distributed Hash-Table. I'm not going to go too into how they |
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work, but suffice it to say that they are essentially a distributed key-value |
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store. Like namecoin. The difference is in the operation. DHTs operate by |
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spreading and replicating keys and their values across nodes in a P2P mesh. They |
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have [lots of issues][1] as far as security goes, the main one being that it's |
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fairly easy for an attacker to forge the value for a given key, and very |
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difficult to stop them from doing so or even to detect that it's happened. |
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Namecoins don't have this problem. To forge a particular key an attacker whould |
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essentially have to create a new blockchain from a certain point in the existing |
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chain, and then replicate all the work put into the existing chain into that new |
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compromised one so that the new one is longer and other clients in the network |
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will except it. This is extremely non-trivial. |
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|
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### Why a currency? |
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To answer why a currency needs to be involved, we need to first look at how |
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bitcoin/namecoin work. When you take an action (send someone money, set a value |
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to a key) that action gets broadcast to the network. Nodes on the network |
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collect these actions into a block, which is just a collection of multiple |
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actions. Their goal is to find a hash of this new block, combined with some data |
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from the top-most block in the existing chain, combined with some arbitrary |
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data, such that the first n characters in the resulting hash are zeros (with n |
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constantly increasing). When they find one they broadcast it out on the network. |
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Assuming the block is legitimate they receive some number of coins as |
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compensation. |
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This last step is the crucial piece. Receiving compensation for doing the work |
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of putting a block onto the chain is what keeps the bitcoin style of |
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crypto-currency going. If there were no compensation there would be no reason to |
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mine except out of goodwill, so far fewer people would do it. Since the chain |
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can be compromised if a malicious group has more computing power then all |
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legitimate miners combined, having few legitimate miners is a serious problem. |
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In the case of namecoins, there's even more reason to involve a currency. Since |
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you have to spend money to make changes to the chain there's a disincentive for |
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attackers (read: idiots) to spam the chain with frivolous changes to keys. |
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### Why a new currency? |
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I'll admit, it's a bit annoying to see all these altcoins popping up. I'm sure |
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many of them have some solid ideas backing them, but it also makes things |
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confusing for newcomers and dilutes the "market" of cryptocoin users; the more |
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users a particular chain has, the stronger it is. If we have many chains, all we |
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have are a bunch of weak chains. |
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The exception to this gripe, for me, is namecoin. When I was first thinking |
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about this problem my instinct was to just use the existing bitcoin blockchain |
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as a key-value storage. However, the maintainers of the bitcoin clients |
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(who are, in effect, the maintainers of the chain) don't want the bitcoin |
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blockchain polluted with non-commerce related data. At first I disagreed; it's a |
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P2P network, no-one gets to say what I can or can't use the chain for, and they |
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can't stop me! And that's true. But things work out better for everyone involved |
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if there's two chains. |
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Bitcoin is a currency. Namecoin is a key-value store (with a currency as its |
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driving force). Those are two completely different use-cases, with two |
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completely difference usage characteristics. And we don't know yet what those |
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characteristics are, or if they'll change. If the chain-maintainers have to deal |
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with a mingled chain we could very well be tying their hands with regards to |
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what they can or can't change with regards to the behavior of the chain, since |
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improving performance for one use-case may hurt the performance of the other. |
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With two separate chains the maintainers of each are free to do what they see |
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fit to keep their respective chains operating as smoothly as possible. |
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Additionally, if for some reason bitcoins fall out of favor and fall by the |
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wayside, namecoin will still have a shot at continuing operation since it isn't |
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tied to the former. Tldr: separation of concerns. |
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# SSL |
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Time to switch gears. SSL is the mechanism by which web-browsers establish an |
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encrypted connection to web-servers. The goal of this connection is that only |
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the destination web-browser and the server know what data is passing between |
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them. Anyone spying on the connection would only see gibberish. To do this a |
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secret key is first established between the client and the server, and used to |
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encrypt/decrypt all data. As long as no-one but those parties knows that key, |
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that data will never be decrypted by anyone else. |
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SSL is what's used to establish that secret key on a per-session basis, so that |
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a key isn't ever re-used and so only the client and the server know it. |
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## Public-Private Key Cryptography |
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There exists something called public-private key cryptography. In this system |
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person A has a public and a private key. They can give the public key to anyone |
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at all that they want to talk with, doing so can't hurt them. They must keep the |
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private key secure from everyone but themselves. If they give their public key |
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to person B, then person B can use it to create a message that can only be |
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decrypted by the private key. Additionaly, person A can sign messages with their |
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private key, so that anyone with the public key can verify that the message came |
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from person A and that the contents of the message haven't been tampered with. |
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There are two problems with public-private key cryptography. First, it's slower |
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then normal cryptography where both parties simply share the same key. Second, |
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it assumes that the public key given to person B hasn't been tampered with. If |
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person C intercepted A's message to B and instead gave B a different public key, |
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then when B encrypted a message with that key C would be able to read it instead |
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of A. |
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## How does SSL work? |
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SSL is at its heart a public-private key system. The client uses the server's |
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public key to send the server an encrypted message with the symmetric key it |
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wants to use. Since it's only used in the initial setup of the connection to |
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negotiate a symmetric key the speed isn't as much of a factor. But getting the |
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client the server's public key is. |
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SSL uses a trust-chain to verify that a public key is the intended one. Your web |
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browser has a built-in set of public keys, called the root certificates, that it |
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implicitly trusts. These root certificates are managed by a small number of |
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companies designated by some agency who decides on these things. These companies |
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sign intermediate certificates for intermediary companies. These intermediary |
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companies then sign certificates for websites to serve with SSL. So when you get |
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a servers SSL certificate (its public key) you also get the signing chain. Your |
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browser sees that the server's key is signed by an intermediate public key, and |
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that that intermediate public key is signed by one of the root public keys. As |
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long as all signatures check out, the public key for the server you're talking |
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to also checks out. |
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## How SSL doesn't work |
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SSL has a few glaring problems. One, it implies we trust the companies holding |
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the root certificates to not be compromised. If some malicious agency was to get |
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ahold of a root certificate they could man-in-the-middle any connection on the |
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internet they came across. They could trivially steal any data we send on the |
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internet. Alternatively, the NSA could, [theoretically][2], get ahold of a root |
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certificate and do the same. |
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The second problem is that it's expensive. Really expensive. If you're running a |
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business you'll have to shell out about $200 a year to keep your SSL certificate |
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signed (those signatures have an expiration date attached, of course). Since |
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there's very few root authorities there's an effective monopoly on signatures, |
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and there's nothing we can do about it. For 200 bucks I know most people simply |
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say "no thanks" and go unencrypted. The solution is causing the problem. |
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# Namecoin as an alternative to SSL |
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There are already a number of proposed formats for standardizing how we store |
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data on the namecoin chain so that we can start building tools around it. I'm |
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not hugely concerned with the particulars of those standards, only that we can, |
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in some way, standardize on attaching a public key (or a fingerprint of one) to |
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some key on the namecoin blockchain. When you visit a website, the server |
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would then send both its public key and the namecoin chain key to be checked |
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against to the browser, and the browser would validate that the public key it |
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received is the same as the one on the namecoin chain. |
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The main issue with this is that it requires another round-trip when visiting a |
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website: One for DNS, and one to check the namecoin chain. And where would this |
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chain even be hosted? |
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My proposition is there would exist a number of publicly available servers |
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hosting a namecoind process that anyone in the world could send requests for |
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values on the chain. Browsers could then be made with a couple of these |
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hardwired in. ISPs could also run their own copies at various points in their |
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network to improve response-rates and decrease load on the globally public |
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servers. Furthermore, the paranoid could host their own and be absolutely sure |
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that the data they're receiving is valid. |
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If the above scheme sounds a lot like what we currently use for DNS, that's |
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because it is. In fact, one of namecoin's major goals is that it be used as a |
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replacement for DNS, and most of the talk around it is focused on this subject. |
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DNS has many of the same problems as SSL, namely single-point-of-failure and |
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that it's run by a centralized agency that we have to pay arbitrarily high fees |
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to. By switching our DNS and SSL infrastructure to use namecoin we could kill |
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two horribly annoying, monopolized, expensive birds with a single stone. |
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[0]: http://vimeo.com/63502573 |
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[1]: http://www.globule.org/publi/SDST_acmcs2009.pdf |
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[2]: https://www.schneier.com/blog/archives/2013/09/new_nsa_leak_sh.html |
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