Error connecting to people.ubuntu.com

Hi,

I'm trying to connecto to people.ubuntu.com: https://wiki.ubuntu.com/PeopleUbuntuCom

costales@T410:~$ sftp people.ubuntu.com
<email address hidden>: Permission denied (publickey).
Connection closed
costales@T410:~$ cat ~/.ssh/id_rsa.pub
ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQDdmdd6h54lu8RejL/j5CnG5ks6P6O7TTmGO19K/KqEHpBkthVtuNKtPhSLI9v0gPCzrcLiecX8TDFY6mRtab2oGTgWwnabKSSTumiWXpmUZvuDKW4wJ37/G9fbd5WoPZzh6O327YJLQDgmnhKpE/FgKTU2vFbYkFYYOgm8Vh4f8yd0ozprilRGSFUvtLz+Z06seci+gbMjPPUOs9B63VahbTifiVdExufmC83hypR1JrQ+TXIpWQoZKZ8tRqgOmZRZ4nv4hr+l4MWFQ8rlMg5bZoycd2lBuQH8bAzHNTqBYIdOX3MyXF58VCOCMEwPWvLBzYtSas2NDGAEA1A5RI3J costales@T410
costales@T410:~$

As you can see, the key is correct:
https://launchpad.net/~costales/+sshkeys

Am I missing something?

Thanks in advance.