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diff --git a/static/src/_posts/2013-10-25-namecoind-ssl.md b/static/src/_posts/2013-10-25-namecoind-ssl.md new file mode 100644 index 0000000..deded79 --- /dev/null +++ b/static/src/_posts/2013-10-25-namecoind-ssl.md @@ -0,0 +1,249 @@ +--- +title: Namecoin, A Replacement For SSL +description: >- + If we use the namecoin chain as a DNS service we get security almost for + free, along with lots of other benefits. +tags: tech crypto +--- + +At [cryptic.io][cryptic] we are creating a client-side, in-browser encryption +system where a user can upload their already encrypted content to our storage +system and be 100% confident that their data can never be decrypted by anyone +but them. + +One of the main problems with this approach is that the client has to be sure +that the code that's being run in their browser is the correct code; that is, +that they aren't the subject of a man-in-the-middle attack where an attacker is +turning our strong encryption into weak encryption that they could later break. + +A component of our current solution is to deliver the site's javascript (and all +other assets, for that matter) using SSL encryption. This protects the files +from tampering in-between leaving our servers and being received by the client. +Unfortunately, SSL isn't 100% foolproof. This post aims to show why SSL is +faulty, and propose a solution. + +## SSL + +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 + +SSL is based around public-private key cryptography. In a public-private key +system, you have both a public key which is generated from a private key. The +public key can be given to anyone, but the private key must remain hidden. There +are two main uses for these two keys: + +* Someone can encrypt a message with your public key, and only you (with the + private key) can decrypt it. + +* You can sign a message with your private key, and anyone with your public key + can verify that it was you and not someone else who signed it. + +These are both extremely useful functions, not just for internet traffic but for +any kind of communication form. Unfortunately, there remains a fundamental flaw. +At some point you must give your public key to the other person in an insecure +way. If an attacker was to intercept your message containing your public key and +swap it for their own, then all future communications could be compromised. That +attacker could create messages the other person would think are from you, and +the other person would encrypt messages meant for you but which would be +decrypt-able by the attacker. + +### How does SSL work? + +SSL is at its heart a public-private key system, but its aim is to be more +secure against the attack described above. + +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. + +When you receive a server's SSL certificate (its public key) that certificate +will be signed by a root certificate. You can verify that signature since you +have the root certificate's public key built into your browser. If the signature +checks out then you know a certificate authority trusts the public key the site +gave you, which means you can trust it too. + +There's a bit (a lot!) more to SSL than this, but this is enough to understand +the fundamental problems with it. + +### 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 listen in on any connection on the +internet by swapping a site's real certificate with one they generate on the +fly. They could trivially steal any data we send on the internet. + +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). 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 creating a bigger problem. + +## Bitcoins + +Time to switch gears, and propose a solution to the above issues: namecoins. I'm +going to first talk about what namecoins are, how they work, and why we need +them. To start with, namecoins are based on bitcoins. + +If you haven't yet checked out bitcoins, [I highly encourage you to do +so][bitcoins]. 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 +crypto-currencies 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][dht] 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 would +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. + +That compensation is what keeps a blockchain based 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 than 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 +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 by the wayside, namecoin will +still have a shot at continuing operation since it isn't tied to the former. +Tldr: separation of concerns. + +## Namecoin as an alternative to SSL + +And now to tie it all together. + +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. + +That's it. If we use the namecoin chain as a DNS service we get security almost +for free, along with lots of other benefits. To make this happen we need +cooperation from browser makers, and to standardize on a simple way of +retrieving DNS information from the chain that the browsers can use. The +protocol doesn't need to be very complex, I think HTTP/REST should suffice, +since the meat of the data will be embedded in the JSON value on the namecoin +chain. + +If you want to contribute or learn more please check out [namecoin][nmc] and +specifically the [d namespace proposal][dns] for it. + +[cryptic]: http://cryptic.io +[bitcoins]: http://vimeo.com/63502573 +[dht]: http://www.globule.org/publi/SDST_acmcs2009.pdf +[nsa]: https://www.schneier.com/blog/archives/2013/09/new_nsa_leak_sh.html +[nmc]: http://dot-bit.org/Main_Page +[dns]: http://dot-bit.org/Namespace:Domain_names_v2.0 |