<apex:page sidebar="false" controller="demo2Controller" action="{!directlogin}" showheader="false" standardStylesheets="false">

function submitbtn(){
      var username = $("[id$='username']").val();
      var password = $("[id$='password']").val();
      if($("[id$='UserPass']").is(":checked")){
            $.cookie('apex__username', username, { expires: 14 });
            $.cookie('apex__password', password, { expires: 14 });
            $.cookie('apex__remember', true, { expires: 14 });
        }
        else  if($("[id$='directlogin']").is(":checked"))
        {

            $.cookie('apex__username', username, { expires: 14 });
            $.cookie('apex__password', password, { expires: 14 });
            $.cookie('apex__directlogin', true, { expires: 14 });
        }
      console.log($.cookie("apex__password"));
      console.log(CryptoJS.MD5(password));
     //here we have to encrypt the password.
      $.cookie('apex__encryptpassword', CryptoJS.MD5(password), { expires: 14 });

     controllerMethod();
}

public PageReference directlogin(){
Cookie getPass = ApexPages.currentPage().getCookies().get('encryptpassword');
          password =  getPass.getValue();
//here we have to decrypt the password.
}