It sounds to me you will be sent to steemconnect for login and steemconnect will use your keys on behalf of utopian.io. Steemfiles.com, and busy.org do this also but only ask for your private posting key. Neither of these sites see your posting key but the software on busy.org can get steemconnect to vote on your behalf, and to post. That is how busy.org works. Steemconnect should give you a dialog of permissions. If you don't trust steemconnect with your active key, don't give it. If you do not trust utopia.app with your money don't give it permission.