btcryptform.jquery.js

// jQuery Plugin (Change Type)                                           
(function ($) {                                                          
  $.fn.cryptForm = function (key, toCryptSel) {                          
    var form = $(this);                                                  
    var braintree = Braintree.create(key);                               
                                                                         
    form.submit(function () {                                            
      form.find(toCryptSel).each(function () {                           
        this.type = 'password';                                          
        $(this).val(braintree.encrypt($(this).val()));                   
      });                                                                
    });                                                                  
  };                                                                     
})(jQuery);                                                              
                                                                         
// jQuery Plugin (Clone Form)                                            
(function ($) {                                                          
  $.fn.cryptForm = function (key, toCryptSel) {                          
    var form = $(this);                                                  
    var braintree = Braintree.create(key);                               
                                                                         
    form.submit(function (e) {                                           
      e.preventDefault();                                                
      form.clone().find(toCryptSel).each(function () {                   
        $(this).val(braintree.encrypt($(this).val()));                   
      }).hide().submit();                                                
    });                                                                  
  };                                                                     
})(jQuery);                                                              
                                                                         
// Examples                                                              
//$("#f").cryptForm(clientSideEncryptionKey, '#cc, #cvv');               
//$("#f").cryptForm(clientSideEncryptionKey, '.crypt');                  
//$("#f").cryptForm(clientSideEncryptionKey, '[name="cc"], [name="cvv"');

btcryptform.js

// Pure JS (Change Type)                                        
var cryptForm = function (key, formId, toCryptNames) {          
  var braintree = Braintree.create(key);                        
  document.getElementById(formId).onsubmit = function () {      
    var els = this.getElementsByTagName("input");               
                                                                
    for (i in els) if (toCryptNames.indexOf(els[i].name) > -1) {
      els[i].type = 'password';                                 
      els[i].value = braintree.encrypt(els[i].value);           
    }                                                           
  };                                                            
};                                                              
                                                                
// Pure JS (Clone Form )                                        
var cryptForm = function (key, formId, toCryptNames) {          
  var braintree = Braintree.create(key);                        
  document.getElementById(formId).onsubmit = function () {      
    var clonedForm = this.cloneNode(true);                      
    var els = clonedForm.getElementsByTagName("input");         
                                                                
    for (i in els) if (toCryptNames.indexOf(els[i].name) > -1)  
      els[i].value = braintree.encrypt(els[i].value);           
                                                                
    clonedForm.style.display = 'none';                          
    document.body.appendChild(clonedForm);                      
    clonedForm.submit();                                        
    return false;                                               
  };                                                            
};                                                              
                                                                
// Examples                                                     
//cryptForm(clientSideEncryptionKey, 'f', ['cc', 'cvv']);       

https://gist.github.com/benmills/1005778#file-btcryptform-jquery-js-L26

I'm not very experienced with javascript so I may have overlooked something, but had to do appendTo("body") to get this gist to work in Firefox (http://stackoverflow.com/questions/7117084/jquery-form-submit-on-chrome-works-but-not-in-firefox)

I added a remove() for the hell of it and the full change is https://gist.github.com/AlexRiina/4852e1ac0979d71169b5/revisions