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diff --git a/_posts/2013-10-25-namecoind-ssl.md b/_posts/2013-10-25-namecoind-ssl.md new file mode 100644 index 0000000..ac700a3 --- /dev/null +++ b/_posts/2013-10-25-namecoind-ssl.md @@ -0,0 +1,217 @@ +--- +layout: post +title: Namecoin, A Replacement For SSL +--- + +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 |