Can I noindex the HTTPS site?

For security purposes I access my blog (admin part) using HTTPS. But Google has indexed both versions of the site (HTTP and HTTPS). And it seems that this a duplicate content issue.

Is there a way to add “noindex” to the entire HTTPS site using WordPress SEO by Yoast?

If that is not possible, is there a way to have the rel=”canonical” pointing to the HTTP version of the site (even when a page is accesed over HTTPS)?

Thanks in adveance for your help.

PS: I don’t want to use 301 redirects, because I need to be able to access the admin part of the blog over HTTPS (don’t want to send the password unencrypted over the wire when traveling).

http://ww.wp.xz.cn/extend/plugins/wordpress-seo/