Posts Tagged ‘ DNS ’

Web-of-Trust DNS

Originally published here, copied below (edits and references coming later): http://www.reddit.com/r/Meshnet/comments/o3wex/wotdns_web_of_trust_based_domain_name_system

Previously mentioned on my blog here: https://roamingaroundatrandom.wordpress.com/2010/12/06/my-ideas-for-dns-p2p/

WoT-DNS – Description

Link: https://en.wikipedia.org/wiki/Web_of_trust

TL;DR: A system for deciding where domain names should go based on who you trust.

WoT-DNS is my proposal for a new P2P based DNS system.

This system decides where a domain name like reddit.wot should go based on your trust, as an invidividual; it does not care about the opinion of random strangers. You are the one who choose who’s trusted and who’s not, since it’s using WoT (web of trust). Also, domain names are intentionally NOT globally unique, since the only way to achieve that is with a centralized service or a first-come, first-serve system like Namecoin, and I dislike both those solutions. This means that if you would ask for a sitename like reddit.wot, you could get many results instead of going straight to one site. But whenever one site is trusted (for you) much more than the rest (like reddit’s official site would be), that’s where you’ll go.

Basic idea: Gather site registrations for a domain name from the network and from friends -> calculate your WoT metrics for each of the results -> pick the top site if one stands out at the top as most trusted -> let the application go to that site.

Basics

Every participant runs a WoT-DNS client. There are several ways to enable browsers and IM clients, etc, to use this system. One is to run a local proxy where only .wot domains are intercepted, and normal traffic are untouched. When connecting, it would start by asking the WoT-DNS network about who has registered their site with that domain name.

Every client has a unique asymmetric keypair, both regular users and servers have them. Servers additionally generate one unique keypair per registered domain. Registered .wot domains are identified by their key. Each registered domain has at least two addresses: The readable one, such as example-domain.wot, and one that contains it’s public key hash (like I2P, [the 52 base32 characters of the SHA256 hashed public key].key.wot, so “key.wot” are one of those domains you can’t register). That means you can always go directly to a particular site by entering it’s key hash.

A domain registration has to contain at least this: The domain name, the server’s public key, addresses (yes, more than one if you like, useful for load balancing and to additionally specify I2P/Tor addresses along with regular-internet IP addresses). Additionally, you can add all the data that ordinary DNS servers can hold for a domain. Also, it can hold a site name and a description of the site, which is useful for telling sites with the same domain name apart. All registrations are also timestamped. I would also like to see a trusted timestamping system built in, to ensure that nobody claims that their domain registrations are older than they are, and the point is to prevent phishing by faking a site’s age.

Domain registrations are stored in a distributed database. This means that every node keeps local copies of plenty of registrations. Updates will be continously added to the distributed database (such as when IP addresses change), and the old registrations are then replaced (but only if the keys and signature match). I suggest that we use some DHT system (“distributed hash table”) like Kademelia for the database, or something similiar that provides the features we need.

The Web of Trust part:

The keypairs make this possible. Since everybody has a unique key pair that consists of a public key and a secret one (using asymmetric cryptography, public key encryption), PGP makes it possible to create signatures of data that likely can’t be forged in our lifetimes. 2048 & 4096 bit keys using RSA are highly secure (while I prefer larger and safer 4096 bit keys, they’re unfortunately also about 5-6 times slower). Keypairs are both used by the site owners for signing their domain registrations, as well as by users that additionally sign them as a means to show that they trust that that site. You can also sign a site as untrusted.

WoT details: You have a list of trusted people and organizations, including their public keys. Organizations like Verisign (SSL certificate authority) could be predefined for the sake of newcomers, this will make it like SSL out of the box. If a site has been signed by a friend or by a trusted organization your client will detect that and calculate what level of trust (trust metric) that site gets based on it. Since there can be several sites for a domain name, the site with the highest trust metric are the site your client chooses to go to. If both Microsoft and a spammer registered microsoft.wot and only MS has a signature from Verisign, then Microsoft’s site will be more trusted so your client will prefer to go to Microsoft’s site if your client is set to trust Verisign.

If the site in the top don’t have a trust metric that’s high enough (not enough trusted signatures or less than around 30% higher trust than the runner-up) it triggers some an alert (some spam/scam detection should also be built in), then you won’t be sent to the top site right away – instead you get a list of the matching sites, ranked by the trust metrics.

So, how are trust metrics calculated? There are PLENTY of ways. One is to assign various levels of trust to your friends, and then simply take a look at how trusted a site is by the people in your web of trust, such as your friends friend. If it’s fully trusted by somebody you fully trust, then you fully trust the site. If it’s a bit trusted by somebody you trust a bit, it’s just a little bit trusted by you. And that’s just the short version!

Note that a signature of a domain from a user or organization as Verisign aren’t intended as a method to indicate how trustable the site owner is, it’s primarily a means of voting in this case (choosing who gets what domain name). The trust part is secondary, but necessary to make sure that scammers and spammers won’t be able to take over popular domain names to trick people.

So how do you get started? If you want to clear out Verisign and those from the predefined list because you don’t trust them, how do you add people you trust? Well, one way is to “bootstrap” using social networks. Let your client announce on Facebook, Twitter or Google+ that you now are using WoT-DNS with a message that contains the key. When your friends start using WoT-DNS, their clients will automatically find your key and connect to you (if they choose to connect to the same social network). Then you’ll have a list of your friends in your client, and can set the trust levels there. And we don’t need to limit it to social networks.

For site admins: While sites will have one keypair, it’s not the only one. Your client also have your personal (or corporate) keypair that your site’s key will be signed with. This “master keypair” for that site can be kept away from your servers, so you can keep it encrypted on a drive in a safe (obviously you can have multiple separate keypairs, so you don’t need that level of security for the rest). If the server is hacked and somebody get your site key, you can issue a revokation signature with your master key pair, which will tell everybody that the site’s old keys now are revoked.

Then you can restore the servers and generate a new site key, and all the old trust signatures can be “moved over”. This won’t be automatic, but everybody who has signed the site key will get notified about the replacement key pair so that they can sign it.

Problems

  • Vulnerable to targeted social engineering. A scammer could try to trick several close friends of some CEO to sign his site, in order to convince the CEO that his site is legitimate.
  • Trust metrics. How do we calculate them? How do we make them hard to “game”/mess with?
  • Evaluating trust. How do you know if your friend can judge if a site is legitimate? How do you yourself know if a site is legitimate?

NON-issues

  • Botnets/spammers that mass-sign phishing sites’ keys. This is only a problem if a significant part of YOUR Web of Trust (your friends) sign the site’s public key and it hasn’t been flagged yet by somebody like Microsoft or Google (they keep their own blacklists already for spam domains for use in Chrome and IE).
  • A bunch of strangers or Group X or Group Y signing the key for a site that’s in conflict with the one you want to go to from Group Z. This will NOT prevent you from getting to the site you want. Just don’t set your client to trust X or Y. But yes, this means that followers of different groups can end up on different sites for the same domain name. This is by design, as I can’t come up with any other solution that isn’t first come, first serve, and that would make domain names globally unique. So I’m allowing domain name conflicts and letting different people get to different sites for them. I do not see this as an issue.
  • Non-static URL:s. We can have those too, but you need to use the key hash domain names. A static URL could look like this: abcdef0123456789abcdef0123456789abcdef0123456789abcd.key.wot/news/global/reddit-is-awesome.php
  • Single point of failures/hacked Certificate Authorities. Remember that we are computing a site’s trust based on what ALL of the nodes that WE trust think of it. A single flag from somebody you trust could alert you about a malicious site. If Verisign were to be hacked, it could be a flag from StartSSL. Or from somebody else. Doesn’t matter. All it needs is one warning. But the scammer has to trick almost everybody you trust into trusting him.

Feedback and questions, please! Please contribute by giving me feature suggestions, or by pointing out possible problems, or by just telling me about any useful idea you might have. All feedback is welcome! If you don’t like my idea, tell me why!

[This is not finished yet, it’s a work in progress…]

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My ideas for DNS-P2P

First of all, see my previous post on dynamic DNS using DHT and asymmetric crypto keys. I am going to reuse ideas from there.

Basic idea: We want a way to have static and globally unique names for web sites and servers. We want to avoid centralization, so no single organization like ICANN will exist for it.
This Domain Naming System will ask peers instead of a single server for IP addresses, thus P2P in the name.

So here it goes:
Every site has a master key pair. This is important. This key should be large, maybe a 16 kb RSA key.
Every host (individual computer that acts as server on a domain) has a key pair of it’s own. The host’s public keys are signed by the master key for the domain.

All these public keys are stored in the peer network using DHT. The IP adressess and all the DNS data is also stored using DHT, and it’s signed.
To access a site, you ask for the public key by it’s checksum. Then you verifiy the DNS data that comes back by checking the signatures and time stamps.

The checksum based domain names would be in hexadecimal format, like this (but random instead): 0123456789abcdef0123456789abcdef.pkh.p2p
Pkh stands for “Public key hash”, and “hash” is another name for checksums. I would prefer something else, but I don’t know what would be better.

The readable domain names, like website.p2p, would be “mapped” to the hash based ones. That means that when you ask for website.p2p, you get the hash based domain name.
When you ask for the hash, you get the public master key, host keys, and the DNS data such as IP addresses.

The real issue that still has to be solved is how we can make the readable domain names globally unique and secure…
I guess we have to go for “majority-unique”, such that website-a.p2p will point to the same site for most users. We probably have to accept “subscriptions” or “moderation services” that will manage situations where several people want the same domain name, and they would be optional to use as well as decentralized.

I will write more about this in the future.

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