app.js

jQuery(function($) {
  function gotAssertion(assertion) {
    // got an assertion, now send it up to the server for verification  
    if (assertion !== null) {
      $.ajax({  
        type: 'POST',  
        url: '/auth/login',  
        data: { assertion: assertion },  
          success: function(res, status, xhr) {  
            window.location.reload();
          },  
          error: function(res, status, xhr) {
            alert("login failure" + res);
          }
        });
      }
    };

  $('#browserid').click(function() {
    navigator.id.get(gotAssertion);
  });
});

app.rb

require "rubygems"
require "haml"
require "sinatra"
require 'nestful'
require 'digest/md5'

enable :sessions

helpers do
  
  def login?
    return !session[:email].nil?
  end
  
  def getGravatarURL
    return "http://www.gravatar.com/avatar/#{Digest::MD5.hexdigest(session[:email].strip.downcase)}"
  end
   
end

get "/" do
  haml :index
end

post "/auth/login" do
  if params[:assertion]
    data = Nestful.post "https://browserid.org/verify", :format => :json, :params => { :assertion => "#{params[:assertion]}", :audience => "http://#{request.host}:#{request.port}" }
    if data["status"] == "okay"
      session[:email] = data["email"]
      return data.to_json
    end
  end
  return {:status => "error"}.to_json
end

get "/auth/logout" do
   session[:email] = nil
   redirect "/"
end
        

index.haml

-if login?
  %p="Welcome #{session[:email]}!"
  #avatar
    %img{:src => getGravatarURL, :alt => "Gravatar"}
  %a{:href => "/auth/logout", :title => "Sign-out"} Sign-out
-else
  %a#browserid{:href => "#", :title=>"Sign-in with BrowserID"}
    %img{:src=> "/images/sign_in_blue.png", :alt=>"Sign-in with BrowserID"}