Is it possible to allow key based authentication for sshd_cofnig chroot sftp users?

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http://serverfault.com – I'm running an Ubuntu 12.04.1 LTS (GNU/Linux 3.2.0-30-generic x86_64) Server, with OpenSSH_5.9p1 Debian-5ubuntu1, OpenSSL 1.0.1 14 Mar 2012. I'd like to configure chroot for sftp access using settings in /etc/ssh/sshd_config, with key based authentication. I've followed the tutorial here: http://www.thegeekstuff.com/2012/03/chroot-sftp-setup/ That tutorial helped me get sftp working with password authentication. I've modified the /etc/ssh/sshd_config file and copied the keys to try to get key based authentication working, but so far, no luck. Relevant parts of my /etc/ssh/sshd_config file (HowTos)