Due to a weakness in OpenSSL's randon number generator, SSH keys have been removed on Alioth, and SSH logins through public-key authentication have been disabled. The latter will be restored when some safeguards have been set up so that insecure keys are not re-installed. Please upgrade your OpenSSL libraries as per the Debian Security Advisory #1571, then ensure your keys are safe (or, preferably, generate new keys), then install them on your account management page.