THIS ARTICLE WILL HELP YOU:
Understand Tracking Security
By default, convert cookies that are set under your domain will be set with the "secure" flag false. If you want to change that you can place the following JS code before the main Convert Experiments tracking code on the page:
<script>
window._conv_q = window._conv_q || [];
window._conv_q.push(['forceCookieSecure',true]);
</script>