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author | elijah <elijah@riseup.net> | 2013-04-04 00:40:55 -0700 |
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committer | elijah <elijah@riseup.net> | 2013-04-04 00:40:55 -0700 |
commit | 0c8a49ce32bfd2b1ebd0496fac1e9cfeb7cfc7de (patch) | |
tree | 1fc56d2d28daa3f679d41a01196db7d61143e2f4 /pages/services/technology/nickid | |
parent | 19362e0cc60e8b5ba2b592836a1459271e89e1e6 (diff) |
s/nickid/nicknym
Diffstat (limited to 'pages/services/technology/nickid')
-rw-r--r-- | pages/services/technology/nickid/en.md | 66 |
1 files changed, 0 insertions, 66 deletions
diff --git a/pages/services/technology/nickid/en.md b/pages/services/technology/nickid/en.md deleted file mode 100644 index f763af1..0000000 --- a/pages/services/technology/nickid/en.md +++ /dev/null @@ -1,66 +0,0 @@ -@title = 'NickID' -@toc = true - -The sad, sorry state of cryptographic identity -============================== - -Existing forms of secure identity are deeply flawed. These systems rely on either a single trusted entity (e.g. Skype), a vulnerable Certificate Authority system (e.g. S/MIME), or keys that cannot be made human memorable (e.g. OpenPGP, OTR). When an identity system is hard to use, it is effectively compromised because too few people take the time to use it properly. - -The broken nature of existing identities systems (either in security or in usability) is especially troubling because identity remains a bedrock precondition for any message security: you cannot ensure confidentiality or integrity without confirming the authenticity of the other party. - -NickID -============================ - -The cornerstone of the LEAP design is a system to make digital identity for messaging both secure and easy to use. We call this system NickID, since the goal is for the individual to be able to think of cryptographic identity in terms of a domain qualified nickname just as they do with email addresses. - -With NickID, we want to be backward compatible with existing public key infrastructures, like OpenPGP and OTR, but also add additional support for automatic validation that happens invisibly in the background without the need for user intervention. NickID does this with three levels of automatic validation: - -**Level 1 — TOFU of user keys:** The first and lowest level of validation is to naively accept the key of another user when you first encounter it. This is often called "trust on first use" or TOFU and is used commonly by SSH (and, in common practice, how many people use OTR and OpenPGP). This level of validation is backwards compatible with existing infrastructure, but has many obvious flaws. When you TOFU a user key, you are making a bet that possible attackers against you did not have the foresight to specifically target you with a false key during discovery. TOFU of user keys can be considerably strengthened by using network perspective and by anonymizing the discovery process, but you still have problems with key expiration, ambiguous mapping between email and keys, and with attackers flooding the discovery process (for example, by filling keyservers with bogus keys). - -**Level 2 — TOFU of provider keys:** We can improve considerably on Level 1 with a single addition: if a service provider signs the keys of it's users, then we do not need to TOFU user keys for that provider, we just need to TOFU the provider's key. Once we have trusted the provider's key, we know to always choose the key for a user that was most recently signed by the provider. If the provider publishes their key using webfinger or DNS, then we can also piggyback (temporarily) on the X.509 Certificate Authority system to validate the provider's key. A service provider is also much less likely to lose their private key, a significant problem with TOFU of user keys. - -**Level 3 — Federated Web of Trust:** Although Level 2 is pretty good, we can do better by adding a Federated Web of Trust (FWOT). The system works like this: each service provider is responsible for the due diligence of properly signing the keys of a few other providers, akin to the distributed web of trust model of OpenPGP, but with all the hard work of proper signature validation placed upon the service provider. When a user communicates with another party who happens to use a service provider that participates in the FWOT, the user's software will automatically trace a chain of signature from the other party's key, to their service provider, to the user's own service provider (with some possible intermediary signatures). This allows for identity that is verified through an end-to-end trust path from any user to any other user in a way that can be automated and is human memorable. Unlike Level 2, a FWOT does not rely, even temporarily, on the X.509 infrastructure. Also, FWOT can include better mechanisms for dealing with revocation of bad actors, renewal of keys, and emergency re-key events if a provider's keys are lost. On the down side, FWOT is more complicated and would need to deploy specific countermeasures to keep an attacker from abusing the system (see below). - -The service provider determines what level of automatic validation is possible. If the service provider does nothing, then only Level 1 is possible. If the service provider signs user keys, then Level 2 is possible. If the service provider signs other providers' keys, then Level 3 is possible. - -Discovery mechanisms -================================== - -It is important to not collapse concept of discovery with the concept validation. Although there is some overlap, they should be thought of as entirely distinct. - -Currently, no single discovery mechanism has emerged as a dominant method for key discovery. There are several proposed standards, but few people are using any of them. NickID will take an agnostic approach by allowing providers to use whichever standard they choose. - -To discover a key, a NickID agent will try these methods, in this order: - -* **Webfinger**: Webfinger includes a standard mechanism for distributing a user's public key via a simple HTTP request. This is very easy to implement on the server, and very easy to consume on the client side. -* **DNS**: There are multiple competing standards for key discovery via DNS. When and if one of these emerges predominate, NickID should attempt to use this method when available. DNS discovery, however, has some problems. DNS discovery of keys is much harder to implement, because the service provider must run their own customized authoritative nameserver. Also, since keys can be too big for domain UDP packets, any future-proof DNS method relies on an HTTP request, thus undermining the potential benefit of decentralization you might get from using DNS rather than webfinger. -* **Keyservers**: As a fallback, NickID agents will try the existing keyservers when other mechanisms are not supported. This should be avoided when possible, because current keyservers are vulnerable to be flooded with bogus keys. This can be improved by prioritizing responses from keyservers that add mailback verification during key registration (currently not supported by many, but easy to add). - - -Users are not websites -============================== - -What about WebID or BrowserID (Mozilla Personas)? These are both interesting cryptographic identity standards that are gaining support and implementations. So why do we need something new? - -These protocols, and the poorly conceived OpenID Connect, are designed to address a fundamentally different problem: authenticating a user to a website. The problem of authenticating users to one another requires a different architecture entirely. There are some similarities, however, and in the long run a Federated Web of Trust could be combined with something like BrowserID/Personas. - -FWOT attacks and countermeasures -========================================== - -Most attacks on a FWOT can be mitigated with a simple "network perspectives" approach that keeps each service provider honest. Let's enumerate the attacks and how to prevent them. Suppose two providers, A and B. - -**Attack 1 - Intercept Outgoing:** provider A signs an impostor key for provider B and distributes it to users of A (in order to intercept outgoing messages sent to B). - -**Attack 2 - Intercept Incoming:** provider A signs an impostor key for one of its own users, and distributes to users of B (in order to intercept incoming messages). - -**Attack 3 - Association Mapping:** A provider tracks all the requests for key discovery in order to build a map of association. - -To prevent these attacks, NickID will support independent notaries who sole purpose is to answer a single question: "Do you see the same key that I see?" - -In order to prevent attack 1, the user's client software will not blindly trust that it has encountered the correct provider key for B. Instead, it will get confirmation from the notaries that they also received the same key (or a key signed by the same key). - -In order to prevent attack 2, the user's client software will regularly query the notaries for their own key. If the notaries see a different key, the user is alerted that their provider is attempting to intercept their messages. - -In order to prevent attack 3, the user's client software will be able to use the response of a notary as the initial key discovery, and to proxy a request to one notary through another. Each notary request will be encrypted to the public key of that notary. - -For this to work, client software that supports FWOT will come pre-seeded with a list of some of the notaries and their public keys. New notaries are then discovered and validated using consensus of these root notaries. |