Submitting form containing <keygen> using POST in AngularJS

Question

For the first time I have oi submit a form in AngularJS using POST Http Request, in particular this form contains a keygen element that generates a key as follows:

<keygen id="spkac" name="spkac" challenge="randomchars" keytype="rsa" hidden>

The spkac element gets to the server always empty, plus I think I am not passing the data from the form to the POST in the correct way, so my questions are:

1. How to set spkac as parameter part of the form?
2. Is this the correct way to pass the data to the POST in AngularJS?

EDIT Form:

    <form name="signupForm" id="signupForm" method="POST" ng-submit="create()">
                <input type="hidden" name="username" id="username" value="mtest">
                <input type="text" placeholder="Account name" name="webid" ng-model="account.webid" ng-focus="isFocused" ng-blur="isFocused = false"><br>
                <input type="text" placeholder="Full name" name="name" ng-model="account.name"><br>
                <input type="text" placeholder="Email" name="email" ng-model="account.email"><br>
                <input type="text" placeholder="Picture URL" name="pictureURL" ng-model="account.pictureURL"><br>

                <keygen id="spkac" name="spkac" challenge="randomchars" keytype="rsa" hidden>

                <input type="submit" id="submit" value="Submit">
            </form>

EDIT HTTP Request:

$scope.signupForm = {};
$scope.create = function () {
        document.getElementById("submit").value = "Creating...";
        var uri = "https://" + "...";
        //setting spkac part of the form's parameters
        $scope.account.spkac = document.getElementById("spkac");

        $http({
          method: 'POST', 
          url: uri,
          data: $.param($scope.account),
          headers: {
            'Content-Type': 'application/x-www-form-urlencoded',
            'Accept': 'application/x-x509-user-cert'
          },
          withCredentials: true
        }).
        success(function(data, status, headers) {
          if (status == 200 || status == 201) {
              //Account created 
          }
        }).

EDIT 2

Answer 1

Do not pass the entire form as data to post request. Instead you should pass the models associated with the field to data config of post request.

data : $.param({
  webid : webid,
  name : name,
  email : email
  ...
})

Since the Content-Type is application/x-www-form-urlencoded. You will get all the model values as form parameters in your back-end service.

Answer 2

Solved!

So preparing an HTTP Request to do that doesn't work for some reason. Instead the form action needs to be set and form submitted straight away in order to send the keygen with it. Here the solution:

in the Template the action is parametrical:

    <form name="signupForm" id="signupForm" method="POST" action="{{actionUrl}}">
     ...
    <input type="submit" id="btnSubmit" value="Submit" ng-click="completeForm()">

and the Controller sets the action and submits the form as follows:

$scope.completeForm = function () {
        $scope.actionUrl = "https://" + document.getElementById("username").value + "...";
        document.getElementById("signupForm").submit();     
};