On 9 August 2013 13:43, Mike Hearn <mike@plan99.net> wrote:
This is just me making notes for myself, I'm not seriously suggesting this be implemented any time soon.

Mozilla Persona is an infrastructure for web based single sign on. It works by having email providers sign temporary certificates for their users, whose browsers then sign server-provided challenges to prove their email address.

Because an SSO system is a classic chicken/egg setup, they run various fallback services that allow anyone with an email address to take part. They also integrate with the Google/Yahoo SSO systems as well. The intention being that they do this until Persona becomes big enough to matter, and then they can remove the centralised struts and the system becomes transparently decentralised.

In other words, they seem to do a lot of things right.

Of course you can already sign payments using an X.509 cert issued to an email address with v1 of the payment protocol, so technically no new PKI is needed. But the benefit of leveraging Persona would be convenience - you can get yourself a Persona cert and use it to sign in to websites with a single click, and the user experience is smart and professional. CAs in contrast are designed for web site admins really so the experience of getting a cert for an email address is rather variable and more heavyweight.

Unfortunately Persona does not use X.509. It uses a custom thing based on JSON. However, under the hood it's just assertions signed by RSA keys, so an implementation is likely to be quite easy. From the users perspective, their wallet app would embed a browser and drive it as if it were signing into a website, but stop after the user is signed into Persona and a user cert has been provisioned. It can then sign payment requests automatically. For many users, it'd be just one click, which is pretty neat.

Persona, in it's current state, is the exact opposite of the principle behind of bitcoin. 

Bitcoin sought to reduce dependence on trusted third parties, where as, persona is increasing the reach of trusted third parties.  The keys and passwords are stored on mozilla's servers, sometimes on your email providers.  Persona, is however, a progression and will hopefully improve its security and decentralization as it goes along.

A (client or server side) X.509 cert can be issued to any address, be it email, telephone, webpage, *or* to a bitcoin address, it allows any URI in he subjectAlternativeName field.  This is much more of bitcoin like model where the private key sits on your client and the public key is in discoverable by the other end.

Most enterprises (including Mozilla) take the stance that key management on the client is beyond the average user.  The notable exception is twitter who are rolling out 2 factor auth based on PKI.

If you're interested in signing stuff with RSA (or other) keys, the web payments and payswarm guys have done a ton of work on this, including implementations, which you may be able to reuse ...
 



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